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1. Photon Intermediate Direct Energy Conversion Using a Sr 90 Beta Source A Dissertation Presented to the Faculty of the Graduate School University of Missouri Columbia In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy by Robert J Schott Nuclear Science and Engineering Institute December 2012 The undersigned appointed by the dean of the Graduate School have examined the dissertation entitled PHOTON INTERMEDIATE DIRECT ENERGY CONVERSION USING A SR 90 BETA SOURCE presented by Robert Schott a candidate for the degree of Doctor of Philosophy and hereby certify that in their opinion it is worthy of acceptance Dr Mark Prelas Dr Tushar Ghosh Dr Robert Tompson Dr Sudarshan Loyalka Dr Dabir Viswanath ACKNOWLEDGEMENTS would like to express my gratitude and appreciation for all of the help and support have been given during my time here The faculty and my fellow students have been very helpful along the way The program and support have been incredible While many have helped me or been friends along the way there are a few would like to call out specifically There are many others but these helped me the most along the way Dr Mark Prelas was always ready to give advice on any problems He was always friendly regardless of the issues that arose Without his help neither this thesis nor the paper would have
2. PRESSURE PSIG CURRNENT A AFTER DELAY 0 0 111683189 600 0 141127162 1100 0 15493095 1400 0 19358316 1900 0 176318268 2400 0 244693866 69 DAC WW Ww LINSE AAR AA WA AA NM GM MR AA AA AA AUA AUA AA AA AA AN AA Nag 70 Figure 27 High Pressure Vessel top view 71 4 i Figure 29 Looking Down the Mirror Chamber 72 73 Appendix 4 Paper submitted to Nuclear Technology Photon Intermediate Direct Energy Conversion Using a Sr 90 Beta Source Robert J Schott Charles L Weaver Mark A Prelas Kyuhak Oh Jason B Rothenberger R V Tompson Denis A Wisniewski Nuclear Science and Engineering Institute E2433 Lafferre Hall University of Missouri Columbia MO 65211 E mail rjs01a O mail missouri edu Proofs and page charge invoice to Mark A Prelas Nuclear Science and Engineering Institute E2433 Lafferre Hall University of Missouri Columbia MO 65211 Total pages 15 total tables 0 total figures 4 74 Abstract The use of a Photon Intermediate Direct Energy Conversion PIDEC process to develop a proof of concept of a long lived and efficient nuclear battery powered by a radioactive beta source is discussed Fundamentally PIDEC is a means of matching the scale length of the range of radiation to the scale length of the transducer The device uses a photovoltaic cell and excimer gas based photon source In this work argon was used to
3. 1equirements of RWP Page 2 of 6 59 H H D RADIATION Radiation Work Permit 2009 10 sen S FAX 573 882 7940 1 7 H Gi d H ENVIRONMENTAL MANAGEMENT 882 7018 10 mCi Strontium 90 SOBICE handling requirements INDUSTRIAL HYGIBNE OCCUPATIONAL SAFETY 882 7018 t RADIATION SAFETY 882 7018 Environmental Health amp Safety University of Missouri Columbia Research Park Development Building Columbia MO 65211 3050 b RSO staff present to coordinate and inspect 6 Expect dose rates greater than background a Beta dose rates i The beta dose rate is 1400 R hr 2 cm unshielded ii The beta dose rate is 37 R hr at 15 cm unshielded 7 Staff Requirements a Staff will maintain a logbook that will include i Time staff entered the lab to begin research ii Time source was removed fiom the safe iii Time source was placed into experimental chamber iy Time source was removed from experimental chamber v Time source was secured inside safe vi Time of meter survey to verify source is secured in the safe vii Check yes or no to indicate dosimetry is present and is being worn properly viii Check yes or no that required access restrictions are in place to prevent other staff from entering the work area when source is removed from safe ix Check yes or no that ALARA was maintained during source handling x Time staff concluded use with the source and left the lab b Staff shall i Set out physical barriers to establish wo
4. Al and 0 03 g of Met 2 Cleaning the glass surface removed any contaminants 3 4 5 6 a Analcohol bath with low particulate and non residue wipes removed gross contaminants b De ionized water and non residue soap Alconox and the same wipes were then used to remove anything that remained c Regent grade acetone was then poured over them to dry them quickly without leaving anything behind The glass was then immediately placed onto a rotary rack and held in place with screwed down metal bands at each end of the glass This assembly was then set into the evaporation chamber The evaporation chamber was pumped down to remove any oxygen Typically this took several hours and the empty slide was used to heat the chamber expediting the process In order to help ensure even coatings the rotary rack was turned on to about one revolution per second Aluminum was then flash evaporated Typically this was a slow ramping up in power until the aluminum would start to visibly change moving or melting and then a quick ramp in power high enough to flash it out This allowed for the greatest amount of aluminum to be evaporated before it crept out of the boat Often less than half of the Al was actually evaporated 17 7 The MgF was then evaporated by increasing the power slowly until it all disappeared from the boat it was much easier to work with than the aluminum 8 Once this was all completed the rotation was turned off
5. c Went to Add Ins gt ExceLINX gt Configure Meter to open up that worksheet d Went to Add Ins gt ExceLINX gt Scan Meter to open up that worksheet e On the Configure Meter sheet made sure that the proper device was selected KESCPI GPIB 14 f Under the Status Cmds tab selected Detect Device g The device was then ready to interface from the Meter Scan page h On the Meter Scan page under Data Location changed which worksheet column and row the data would be saved under to the desired location 34 Under Sample Trigger on the Meter Scan page found the listing Count Selected the number of counts for the run This was a number up to 2048 the maximum it would allow for selected counts or infinite which would have to be stopped manually The computer system was then ready for testing Starting the run then only took looking under Task for Status Cmds and using the Start option 3 Checked mirror chamber Unpacked it from its protective wrapping Made sure that the mirrors were set into place properly and were not dirty If they were dirty canned air was used to remove particulates anything that this could not solve likely meant that the mirror would need to be replaced Made sure that the holding rods and end caps were properly aligned Tested the photovoltaic with the DMM to make sure it was still connected properly and was functioning Reconnected wires or reset the photovolta
6. Lab Book Page 1184 16 Medical Imaging Laboratory industrial Gauging Laboratory 24937 Avenue Tibbitts Valencia California 91355 1800 North Keystone Street Burbank California 01504 Figure 4 Strontium 90 Source Data Sheet 13 APR 24 2006 81 46 FM mu NSE 1 STs wes seer ISOTOPE PRODUCTS LABORATORIES 24937 Avenue Tibbetts Valencia CA 91355 U S A Tel 1 661 309 1010 Fax 1 661 257 8305 e mail rhunter isotopeproducts com Quotation Number 7303 Rev 1 ISSUE DATE 21 April 2006 ATTN Mr Tushar K Ghosh COMPANY Nuclear Science amp Engineering Institute University of Missouri Columbia Terms Net 30 Delivery 30 days ARO F O B Burbank CA USA All payments to be in US Dollars Quotation Valld for 12 Months Sr 90 source 1mC nominal activity A3203 2 460 00 2 450 00 capsule ga x 0 312 OD SS with 0 002 thick r 90 source ImCi nominal activity 2 460 00 capsule 0 200 x 0 312 OD r r ET Olik SS window 1 Sr 90 source SmCi nominal activity 450 00 2 460 capsule 0 200 x 0 312 OD Teun with ry 002 thick SS window pm Sr 80 source 10mCi inal activity A3203 2 450 00 2 450 00 capsule 0 200 x 0 OD SS with 0 002 thick SS window NOTE Customer is responsible for freight handling and Insurance charges CALIBRATION AN sources are manufactured to a precision of 215 with respect to the customer s specified activity This Quotation is valid for acceptance within 30
7. The safe is stored inside a locked room in Lafferre Hall room W0030 Sr 90 has a 29 1 year half life it emits a Beta particle with Emax 0 546 MeV and Eaye 0 196 MeV At this time the Sr 90 source is in secular equilibrium with Yttrium 90 Y 90 Y 90 has a 64 1 hour half life and emits a Beta particle with Ema 2 284 MeV and Bag 935 MeV The beta emissions from this source present a shallow dose external hazard to the skin and eye The A side of the source holder indicates the hot side on the source holder Beta dose tates The beta dose rate is 1400 R ht 2 cm unshielded The beta dose rate is 37 R hr at 15 cm unshielded Sr 90 handling considerations a Source handling is restricted to authorized radiation workers listed on Dr Ghosh s authorization dosimetry is required to handle the source Page 1 of 6 58 I i PV Environmental Health amp Safety Research Park Development Building 18 University of Missouri Columbia Columbia MO 65211 3050 RADIATION SAFETY Radiation Work Permit 2009 10 oe ge FAX 573 882 7940 i H 5 i i ENVIRONMENTAL MANAGEMENT 882 7018 10 mCi St ontum 90 SONKO handling requirements INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 b Source storage is restricted to the safe in W0030 and its use restricted to that of an irradiation source for various materials in room W0030 c Authorized staff will perform documented radiati
8. s range in the gas becoming an important contributor to photon production As pressure continues to increase beyond this point current again follows an upward trend Based on beta ranges in slab materials 6 it is assumed that there is a transition point at some argon density in that pressure range where the lower energy and subsequently shorter range Sr 90 betas are depositing their energy inside of the mirror chamber and the higher energy longer range betas from Y 90 are beginning to be collected after this point CH N CH LA LO CH LA N Ca lt x So T ei E kg Les OU Bn Sm 5 0 11 0 0E 00 2 0E 06 4 0E 06 6 0E 06 8 0E 06 1 0E 07 1 2E 07 1 4E 07 1 6E 07 Pressure Pa 81 Figure 3 A typical data set for the PIDEC cell s current output as a function of argon pressure The PIDEC cell uses an argon excimer flourescer spectral peak at 129 nm for the photon source Calculated efficiency The primary factors in determining the conversion efficiency of this system are energy deposition in the excimer gas excimer gas fluorescence efficiency photovoltaic photon conversion efficiency and finally photon reflection efficiency Using the MCNPX 2 6 0 14 model 6 the percentage of energy released by the source that was deposited into the gas was 3 47 This value is the energy transport efficiency a from the source to the gas plenum This energy was deposited between the center rod and the gla
9. Argon was used as the excimer gas It has an excimer wavelength of 129 nm and its pressure was varied between 7x10 to 1 4x10 Pa 10 to 2100 psig By using an excimer gas like argon photons of a known wavelength are repeatedly and non destructively generated without the need for the beta particles to impinge on the photovoltaic Excimer formation is discussed in great detail in Birks 8 and argon more specifically in Wieme 11 By varying the gas pressure it can be seen that increasing gas pressure captures a larger amount of beta energy in the gas plenum Over a broad enough pressure range an optimal transport scale length could be found for future system designs A mirror chamber was made to house the source and photovoltaic cell High efficiency mirrors gt 80 15 for argon excimers were fabricated by evaporating aluminum using a thermal resistive evaporator onto pre treated glass and then sealed with a thin coating of MgF gt to prevent aluminum oxidation 15 However due to the limited space in the pressure vessel the configuration of the source and lead plug radiation shield placement severely limited the photon transport efficiency to the photovoltaic cell The Si photovoltaic cell used in this experiment was manufactured by International Radiation Detectors serial number 01 527 and was calibrated by the National Institute of Standards and Technology NIST This photovoltaic cell is not radiation hardened 79 1 Outsid
10. B atom molec phys 1975 8 Oh K et al Theoretical Maximum Efficiencies of Optimized Slab and Spherical Betavoltaic Systems Utilizing S 35 Sr 90 and Y 90 Nuclear Technology August 2012 not yet published as of this writing Steinfelds E V et al Development of Radioisotope Energy Conversion Systems Efficient Radioisotopic Power 2003 Proceedings of ICAPP Birks J B Excimers Reports on Progress in Physics 1975 38 8 p 72 McCusker M The Rare Gas Excimers Excimer Lasers 1984 30 p 40 Prelas M A et al Nuclear driven flashlamps Laser and Particle Beams 1988 6 1 p 38 Wieme W and J Lenaerts Excimer formation in argon krypton and xenon discharge afterglows between 200 and 400 K Journal of Chemical Physics 1981 74 1 p 11 Keto J W J R E Gleason and G K Walters Production Mechanisms and Radiative Lifetimes of Argon and Xenon Molecules Emitting in the Ultraviolet Physical Review Letters 1974 33 23 p 4 Petzenhauser l et al Comparison between the ultraviolet emission from pulsed microhollow cathode discharges in xenon and argon Applied Physics Letters 2003 83 21 p 3 Pelowitz D B MCNPX User s Manual in LA CP 07 14732008 Los Alamos National Laboratory Canfield L R G Hass and J E Waylonis Further Studies on MgF2 Overcoated Aluminum Mirrors with Highest Reflectance in the Vacuum Ultraviolet Applied Optics 1966 5 1 p 5 Javedani J B Optical Concentration
11. Radiation Work Permit 2009 10 10 mCi Strontium 90 source handling requirements ii Adequate and quality surveys Research Park Development Building Columbia MO 65211 3050 RADIATION SAFETY PHONE 573 882 7018 FAX 573 882 7940 ENVIRONMENTAL MANAGEMENT 882 7018 INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 iii Proper source handling to include time and distance iv Regular surveys v Frequent checks 16 Conclusion The work is not outside the scope of AU or staff abilities lt a ZEKA Date di 23 e 5 Date D 3 9 Signatories for Work to begin Originator Reviewer Ss K CR RSO Page 5 of 6 62 FYR Environmental Health amp Safety KR University of Missouri Columbia Radiation Work Permit 2009 10 10 mCi Strontium 90 source handling requirements TEMPLATE FOR DAILY SOURCE USE CHECKLIST Research Park Development Building Columbia MO 65211 3050 RADIATION SAFETY PHONE 573 882 7018 FAX 573 882 7940 ENVIRONMENIAL MANAGEMENT 882 7018 INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 382 7018 Time staff entered the lab to begin research Time source was removed fiom the safe Time source was placed into experimental chamber Time source was removed from experimental chamber Time source was secured inside safe Time of meter survey to verify source is secured in the safe
12. 13 highpressure com 60 23HF6 High Pressure Tee 3 highpressure com Nipples 60 HM6 3 3 Nipple 10 highpressure com 60 HM6 6 6 Nipple 4 highpressure com 60 HM6 8 8 Nipple 4 highpressure com 60 HM6 12 12 Nipple 4 highpressure com Ball Check 60 41HF6 Unidirectional flow valve 4 highpressure com Valve Wire HPPL14 AM3 S316 4 24 AWG Alumel wires 1 conaxbuffalo com Feedthrough B 24 4AL 1K 1 24 AWG type K T C pair A S316B 6 CGL 24 24 Vacuum Pump Trivac D16B Rated 10 psi Picoammeter Keithly 6487 Pressure PG5000 0 to 5000 psi www swagelok com Gauge Power Supply PS 21KX Input 115V AC 60 Hz 450 W 1 Pyramid regulated Output 13 8VDC 20 amp power supply Power PW1100 12 1100 Watt 12V 1 PowerBright Inverter Transformer GIS 500 1115V 50 60Hz Stancor AC Power SA 20 120V AC 20 amps 50 60Hz SurgeX Conditioner Faraday Cage 1 DESIGN PRESSURE 60 000 PSI APPROXIMATE ASSEMBLY WEIGHT 270 LB NOTE 1 THE COVER WEIGHT IS APPROXIMATELY 10 LB THIS WEIGHT MUST BE OFFSET NEUTRALIZED PRIOR TO ASSEMBY OR DISASSEMBLY 2 THREAD LUBRICANT MUST BE APPLIED TO THE BODY THREADS PRIOR TO EACH RE ASSEMBLY BILL OF MATERIALS ITEM QTY DESCRIPTION PARTNO DRAWINGNO MATERIAL HYDROSTATIC TEST PRESSURE 80 000 PSI 1 1 COVER 602713 602713 4340 2 1 Booy 801911 801911 4340 3 1 BACK
13. 60 Hz Figure 16 Solar Cell No Light No Source Pre exposure Voltage V Solar Cell Box closed source 0 0031 0 200 400 60Q 800 1000 1200 1400 1600 1800 T NE A ER EA T SEAT 0 0032 0 0033 0 0034 0 0035 0 0036 0 0037 Data Points 60 Hz Figure 17 Solar Cell No Light Source 40 Solar Cell Box open no source post 5 min exposure 2 00E 05 Voltage V 1 30E 04 1 80E 04 Data Points 60 Hz Figure 18 Solar Cell Light No Source Post exposure Log Plot of Average Voltage 1 Light Pre exposure No Light Pre exposure During Exposure H un D gt H un Ben S lt Light Post exposure 0 00001 0 000001 Figure 19 Log Plot of Average Voltage for Solar Cell Tests 41 With less than 5 minutes of exposure all of the photovoltaics tested were rendered effectively inoperable PIDEC System Data sets of average values are in tabulated format in Appendix 2 Argon Figure 20 below shows a typical test using argon It ranges from vacuum pressure roughly 10 6 psi up to 2200 psig 42 ee N pay a LO N a UT lt ES x lt del E K ka fan Q 1000 Pressure psi Figure 20 PIDEC Argon Result At the low end there is a current that is likely due to bremsstrahlung radiation from beta particles interacting with the steel and lead of the source hold
14. Check yes or no to indicate dosimetry is present and is being worn properly Check yes or no that required access testrictions are in place to prevent other staff from entering the work area when source is removed from safe Check yes or no that ALARA was maintained during source handling Time staff concluded use with the source and left the lab Time Page 6 of 6 Figure 24 Radiation Work Permit 2009 10 63 University of Missouri Columbia Loi Environmental Health amp Safety Research Park Development Building Columbia MO 65211 3050 H H D f RADIATION SAFETY Radiation Work Permit 2011 06 sa DEEN FAX 573 882 7940 10 mCi Strontium 90 source handling requirements ENE ET STONE INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 Subject 1 Statement of Problem Issue Dr Ghosh is authorized to possess a Sr 90 9 9 mCi on reference date 5 22 06 which has a 29 1 year half life it emits a Beta particle with Emax 0 546 MeV and Eayg 0 196 MeV At this time the Sr 90 source is in secular equilibrium with Yttrium 90 Y 90 Y 90 has a 64 1 hour half life and emits a Beta particle with Ema 2 284 MeV and Eaye 935 Mey The beta emissions from this source present a shallow dose external hazard to the skin and eye Because of the strong energetic beta EHS has drafted RWP s for previous uses of the source 2 General Discussion Recent use of the Sr 90 source as
15. experiment These silicon solar cells were purchased from RadioShack Model amp Catalog 276 124 0 3 amps at 0 55 VDC in full sunlight 0 8 x1 6 Figure 9 ADAQ board and computer were used for data collection A black box was used that could either be closed off completely from ambient light or left open to allow light from a fluorescent light in Each solar cell went through an initial test to make sure that they were functioning properly 22 Figure 9 RadioShack solar cell The procedure for bare chips was as follows 1 2 3 4 5 6 7 8 Wires were attached to the front and back at connection sites using silver solder being careful not to let the photovoltaic get too hot Tested the resistance of connections from one point on the surface to the end of the wire If there was a problem try step one again Mounted the photovoltaic in the black box making certain that the light was at the correct position The connections were then tested The box was then closed and a test was taken in the dark Voltage data was then recorded The box was then reopened and a test was taken in the light Voltage data was then recorded Radiation badges were then put into place and the radiation area was secured with signs Placed the source on the center of the photovoltaic with the hot side facing it The box was then closed and a test was taken in the dark with the source Voltage data was then r
16. gt 150 of use the photovoltaic cell exhibited no measurable damage While this device did have an inherently low photon transport efficiency it was sufficient to provide a proof of concept with future work focusing on photon transport improvements thus reinforcing similar work 7 19 77 Methods The experimental setup consisted of the following a picoammeter Keithley Model 6487 a computer used to operate the picoammeter a pressure vessel High Pressure Equipment Company R2 10 40 high pressure pipes valves and fittings High Pressure Equipment Company all rated to 4 1x10 Pa 60 000 psi a UPC 5 5 argon gas tank a 10 mCi Sr 90 source a Trivac D16B vacuum pump rated to 7x10 gt Pa 10 psi a mirror chamber and a Si photovoltaic cell described below A basic diagram of the system is given below in Fig 1 Computer system Ar source Pressure vessel Pressure guage Vacuum Figure 1 A system diagram of the experimental setup for the PIDEC cell Sr 90 makes an excellent source for this experiment due to two main factors First Sr 90 has a half life of 28 78 years allowing for many years of use without significant reduction in power output Second Sr 90 is a pure beta source and its daughter Y 90 is nearly a pure beta source with a very low frequency gamma lt 0 001 20 This choice allows for the long lifetime that is desired and the lack of gammas makes shielding the photovoltaic cell easier 78
17. made it to completion Dr s Lynn and Annie Tipton helped a great deal in the early portion of the project with guidance and moral support They left long before my graduation but their influence was felt throughout my entire time in the nuclear engineering program Dr Eric Lukosi helped me work through a few difficulties by talking things through and with a helpful bit of code His dedication and drive were always an inspiration TABLE OF CONTENTS ACKNOWLEDGEMENTS se eege verde En ii SER v LIST OF EIGURES vi PS og EG SE ee EE NE viii INTRODUCTION ee 1 LITERATURE REVIEW ennnnnronnonnrrnnnennrrnnnennrrnnnsnnnrnnesennrrnnsennrrnnsennnrnnssennrnnssennrrnnsennrrnnssnnnrnnesennrnneeennrnee 3 MATERIALS AND EXPERIMENTAL DESIGN sannrnnnnnnnrnnnnennrrnnnrnnvrnnnennnrnnnnennrnnnsennrnnesennnrneseennrnessennrneesennvnne 8 Primary System GCOMPONENKS 2ovseic cave scseeers casdeess vavesess doves endrar ranerne eide adresse 8 lee Cl et 12 case 16 MIRROR e DEI 19 MEN DIONE 22 Brea 22 Radiation Zone and Procedures AA 25 NOISE ISSUES se 27 Argon Gas DET aS 30 lee E EE 31 RE gid Lt ee 31 erre So PE 32 Experimental Procedure Argon cccccccccccceceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeenss 33 Experimental Procedure XENON ccccccccccceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeseneess 38 RESULTS eee 39 Solar cell photovoltaic rrrnrnrnnrrnnnnnnnnnrrrnnvrnnnnnnnnsrrnnsrn
18. match the transport scale length of the radiation to that of the transducer 6 The PIDEC process begins by stopping the radiation in a gas plenum This gas is chosen to produce specific fluorescence with known fluorescence efficiency 10 Once these photons are produced they must be transported to the photovoltaic cell which will in turn produce an electrical current through the photovoltaic effect Matching the photon transport photovoltaic band gap and the photon energy are the keys to maximizing the efficiency of a PIDEC system This device was built to demonstrate that the transducer damage could be reduced or eliminated entirely while some of the beta particles energy was deposited into the gas plenum The optical waveguide was not designed to maximize transport efficiency and the highest gas pressure achieved was not intended to capture all of the beta particles energy In direct beta energy conversion systems beta particles directly impinge on the photovoltaic surface 3 This process physically damages the photovoltaic cell by creating knock on dislocations in the device which renders it inoperable in a short period of time when under a sufficient beta fluence to produce power Using an intermediate material that cannot be damaged by the beta particles protects the photovoltaic cell In addition the excimer gas photons are of a known wavelength which makes it possible to choose a photovoltaic material that is specifically optimized to conv
19. normal tank pressure was used maximum test pressure was 2400 psi as that was determined to be sufficient to test the concept Inside of the pressure vessel a source holder photovoltaic mount and waveguide was needed to safely convert the beta energy into useable current For this a mirror chamber was made which is described in detail in the materials design section below Once the system was complete tests were run using excimer forming gasses Argon and Xenon one at a time These both showed a general trend upwards in current being generated as the pressure was increased The overall efficiency of the system was very low primarily due to a loss efficiency of 0 23 from such things as energy escaping the system photon absorption and other factors but it was still sufficient to demonstrate that a PIDEC system is viable LITERATURE REVIEW Here is a brief discussion of previous work that has gone into direct energy conversion and how PIDEC adds an extra step that solves long term viability issues Direct energy conversion systems place a source either in direct contact with a semiconductor p n junction or using a beam of electrons or other charged particles 2 3 4 5 Beta particles enter the semiconductor and its energy is deposited directly into the material During this step if energy is deposited the semiconductor may be damaged reducing its ability to generate a useable current or the energy could be put in a place where it m
20. of Isotropic Light in Nuclear Science and Engineering Institute1985 University of Missouri Columbia Javedani J B and M A Prelas Concetrating Properties of Simple Two Dimensional Geometries for Isotropic Light Laser Interactions and Related Plasma Phenomena 1986 7 p 12 Boody F P and M A Prelas Efficient Light Transport using Large Diameter to Length Ratio Hollow Lightpipes in Proceedings of Specialist Conference on Physics of Nuclear Induced Plasmas and Problems of Nuclear Pumped Lasers 1992 Obninsk USSR Institute of Physics and Power Engineering Steinfelds E V et al A Comparison of the Performance Capabilities of Radioisotope Energy Conversion Systems Betavoltaic Cells and other Nuclear Batteries 2006 Nuclides and Isotopes 16th edition2002 88 REFERENCES 10 11 12 13 14 15 16 17 18 PRELAS M A ET AL TWO STEP PHOTON INTERMEDIATE TECHNIQUE FOR THE PRODUCTION OF ELECTRICITY CHEMICALS OR LASERS IN NUCLEAR ENERGY CONVERSION PROGRESS IN NUCLEAR ENERGY 1990 23 3 P 223 240 RAPPAPORT P THE ELECTRON VOLTAIC EFFECT IN P N JUNCTIONS INDUCED BY BETA PARTICLE BOMBARDMENT PHYSICAL REVIEW 1954 93 P 2 WINDLE W F PM 147 SILICON BETAVOLTAIC BATTERY FEASIBILITY IN REPORT SANDIA CORPORATION SC RR 65 6711966 P 25 UEHARA Y ET AL HIGH POWER ARGON EXCIMER LASER AT 126 NM PUMPED BY AN ELECTRON BEAM OPTICS LETTERS 1984 9 12 BARBET A N SADEGHI AND J
21. pair reactions will be minimal As the gas pressure increases and the gas density along with it the path length of the beta particles will decrease putting more of their energy into the gas 6 In order to have a process that can excite the excimer gas without needing excessive shielding a radioactive source is needed that has sufficiently energetic particles without unwanted radiation primarily in the form of gammas It was decided to use a beta source in this experiment with others doing an alpha experiment The table below has a number of potentially suitable candidates Parent nuclides are on the left while all subsequent daughters are on the right Table 1 Potential Beta Nuclides Nuclide Decay Energy MeV Half Life yr Comments Parent Daughter H 3 0 019 12 3 He 3 Ar 42 0 6 32 9 K 42 3 525 0 0014 Ca 42 Co 60 2 824 5 2713 Strong Gamma Ni 60 Kr 85 0 687 10 755 Gamma Rb 85 Sr 90 0 546 28 77 Y 90 2 280 0 0073 Zr 90 Ru 106 0 039 1 0234 Rh 106 3 541 9E 7 Gammas Pd 106 Sb 125 0 767 2 73 Gammas Te 125 Cs 137 1 175 30 10 Gammas Ba 137 Sm 151 0 076 90 Eu 151 Eu 155 0 253 4 67 Gammas Gd 155 Tm 171 0 096 1 92 Yb 171 Os 194 0 097 6 00 Ir 194 2 247 2 437 0 0022 0 468 Gammas Pt 194 The most desirable radioi
22. performed after the experiment The results of each are given in Fig 4 From Fig 4 it can be seen that most of the quantum efficiencies remained the same The only significant differences show an increase in quantum efficiency rather than a loss in the range of 116 4 to 135 4 nm However the most extreme differences fall within two or three standard deviations of NIST s calibration experimental error These results show that the photovoltaic was not damaged by the bremsstrahlung or high energy betas during the course of this experiment 85 e Pre Exposure Post Exposure E e Oo lt Q gt E D H 2 v gt H E Qu 2 Eff IG OO Mm O st Ou B NN ti eil vi ei ei Wavelength nm Figure 4 Measurements taken by NIST before dashed line and after dotted line the experiment The vertical bars are for one standard deviation Conclusions A PIDEC experiment was created and tested using Sr 90 as a radioactive source argon as an excimer producing gas a photon waveguide mirror chamber and a Si photovoltaic Experimental data shows current production that generally increases with increasing pressure over the ranges tested Unlike direct energy conversion wherein the beta particles would impinge directly onto the photovoltaic this process is non destructive and may be used over extended periods of time without loss of efficiency The ma
23. produce the excimer photon source argon excimer at 129 nm with a pressure range from 7x10 gt to 1 4x10 Pa 10 to 2100 psig The beta source used in this study was a strontium 90 Sr 90 source which has a daughter yttrium 90 Y 90 that then decays to stable zirconium 90 Intermediate shielding from lead and an argon gas plenum were used to prevent damage to the photovoltaic cell This battery demonstrated power variations with gas pressure as expected and no radiation damage to the photovoltaic cell was observed over a period in excess of 150 hours Such a long exposure period demonstrates the desired tolerance of the device to the direct radiation damage that would otherwise be sustained in normal semiconductor based energy conversion systems Keywords Betavoltaic PIDEC Nuclear Battery Introduction Long lifetime stable power systems batteries are very desirable for use in a number of fields where it is currently impossible or very difficult to replace and maintain power sources For example in deep space or in the deep ocean it is problematic to replace a depleted battery 75 and solar power may not be available in sufficient strength In addition hand held military devices would benefit from rugged long lived batteries Photon Intermediate Direct Energy Conversion PIDEC is a means of achieving two critical goals in nuclear battery design The first is to eliminate radiation damage in the transducer The second is to
24. w E v ki VI 1 5E 12 Counts Figure 10 Noise 1 28 KA Qa E lt w E v de den ki Oo 40 60 80 100 120 Counts Figure 11 Noise 2 1 35E 10 1 3E 10 1 25E 10 1 2E 10 Current Amps 1 15E 10 1 1E 10 0 500 1000 1500 2000 Counts Figure 12 Noise 3 29 Argon Gas Density Argon Gas 2000 4000 6000 8000 10000 12000 14000 Pressure psi Figure 13 Argon Gas Density This graph shows the density of Argon as pressure increases Near the beginning it is close to the ideal gas but by the end it diverges by a large amount The vertical line represents the highest pressure reached in this experiment with a density of 0 27 g cm With increasing density more of the beta particles energy can be captured over a smaller distance However it takes a greater and greater amount of pressure to achieve significant gains while at the same time the housing material must be further reinforced 30 PIDEC System Description A rough basic diagram of the system is given in Figure 14 below This experimental setup consisted of the following components a picoammeter Keithley Model 6487 and a computer used to operate and record data from the picoammeter are listed as Computer system high pressure pipes valves and fittings High Pressure Equipment Company all rated to 60 000 psi a UPC 5 5 argon gas tank or a combination of tanks for Xeno
25. well as use of the Po 210 source indicates the lab staff are using safe handling procedures Refer to RWP 2009 10 Sr 90 rev 2 docx for a history of the first Sr 90 source experiment 3 Proposed Basic Work scope of support organizations and offsite Vendors and Associated Cost The Sr 90 source is a button source It is routinely stored in a Lucite pig with lid that is in turn stored inside a large lead pig with lid When not in use the source is stored in a locked safe inside both pigs in Lafferre Hall room W0030 The proposed work is as follows The Sr 90 is placed in a face up or active side up and kept inside the lucite lead nested pig configuration e The entire assembly is placed in a Lucite enclosure Above the source is a lens and a fiber optic cable The fiber optic cable feeds through a hole in the Lucite enclosure and is connected to a PMT The shielding of the source holder nested Lucite and lead pigs and the Lucite enclosure are sufficient to reduce radiation levels to background levels with the exceptiom of the access door and the cable port In these areas radiation levels are below 0 5 mR hr Page 1 of 5 64 Environmental Health amp Safety Research Park Development Building University of Missouri Columbia Columbia MO 65211 3050 RADIATION Radiation Work Permit 2011 06 oe payaan FAX 573 882 7940 10 mCi Strontium 90 source handling requirements EN VIRONMENTAL MANAGEMENT e EN INDUSTRIAL HYGIENE OCCUPAT
26. ACUUM ULTRAVIOLET APPLIED OPTICS 1966 5 1 P 5 JAVEDANI J B OPTICAL CONCENTRATION OF ISOTROPIC LIGHT IN NUCLEAR SCIENCE AND ENGINEERING INSTITUTE1985 UNIVERSITY OF MISSOURI COLUMBIA JAVEDANI J B AND M A PRELAS CONCETRATING PROPERTIES OF SIMPLE TWO DIMENSIONAL GEOMETRIES FOR ISOTROPIC LIGHT LASER INTERACTIONS AND RELATED PLASMA PHENOMENA 1986 7 P 12 Booby F P AND M A PRELAS EFFICIENT LIGHT TRANSPORT USING LARGE DIAMETER TO LENGTH RATIO HOLLOW LIGHTPIPES IN PROCEEDINGS OF SPECIALIST CONFERENCE ON PHYSICS OF NUCLEAR INDUCED PLASMAS AND PROBLEMS OF NUCLEAR PUMPED LASERS 1992 OBNINSK USSR INSTITUTE OF PHYSICS AND POWER ENGINEERING 89 19 STEINFELDS E V ET AL A COMPARISON OF THE PERFORMANCE CAPABILITIES OF RADIOISOTOPE ENERGY CONVERSION SYSTEMS BETAVOLTAIC CELLS AND OTHER NUCLEAR BATTERIES2006 20 NUCLIDES AND ISOTOPES 16TH EDITION2002 90 VITA Robert Schott received his undergraduate degree in Physics from the University of Missouri Rolla in 2003 After that he went to the University of Missouri Columbia for a Masters in Biophysics received in 2005 followed by a Ph D in Nuclear Engineering Medical Physics emphasis and received in 2012 91
27. C PEBAY PEYROULA DECAY OF METASTABLE XENON ATOMS XE CR IN A XENON AFTERGLOW J PHYS B ATOM MOLEC PHYS 1975 8 OH K ET AL THEORETICAL MAXIMUM EFFICIENCIES OF OPTIMIZED SLAB AND SPHERICAL BETAVOLTAIC SYSTEMS UTILIZING S 35 SR 90 AND Y 90 NUCLEAR TECHNOLOGY AUGUST 2012 NOT YET PUBLISHED AS OF THIS WRITING STEINFELDS E V ET AL DEVELOPMENT OF RADIOISOTOPE ENERGY CONVERSION SYSTEMS EFFICIENT RADIOISOTOPIC POWER 2003 PROCEEDINGS OF ICAPP BIRKS J B EXCIMERS REPORTS ON PROGRESS IN PHYSICS 1975 38 8 P 72 MCCUSKER M THE RARE GAS EXCIMERS EXCIMER LASERS 1984 30 P 40 PRELAS M A ET AL NUCLEAR DRIVEN FLASHLAMPS LASER AND PARTICLE BEAMS 1988 6 1 P 38 WIEME W AND J LENAERTS EXCIMER FORMATION IN ARGON KRYPTON AND XENON DISCHARGE AFTERGLOWS BETWEEN 200 AND 400 K JOURNAL OF CHEMICAL PHYSICS 1981 74 1 P 11 KETO J W J R E GLEASON AND G K WALTERS PRODUCTION MECHANISMS AND RADIATIVE LIFETIMES OF ARGON AND XENON MOLECULES EMITTING IN THE ULTRAVIOLET PHYSICAL REVIEW LETTERS 1974 33 23 P 4 PETZENHAUSER I ET AL COMPARISON BETWEEN THE ULTRAVIOLET EMISSION FROM PULSED MICROHOLLOW CATHODE DISCHARGES IN XENON AND ARGON APPLIED PHYSICS LETTERS 2003 83 21 P 3 PELOWITZ D B MCNPX USER S MANUAL IN LA CP 07 14732008 Los ALAMOS NATIONAL LABORATORY CANFIELD L R G HASS AND J E WAYLONIS FURTHER STUDIES ON MGF2 OVERCOATED ALUMINUM MIRRORS WITH HIGHEST REFLECTANCE IN THE V
28. IONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 Sr 90 handling considerations for this experimental set up are Source handling is restricted to authorized radiation workers listed on Dr Ghosh s authorization dosimetry is required to handle the source Source storage is restricted to the safe in W0030 and its use restricted to that of an irradiation source for various materials in room W0030 Authorized staff will perform documented radiation level measurements on contact and at 30 cm of the source storage location safe or experimental setup Surveys will be performed following each source move from safe to setup from setup to safe or monthly whichever is more frequent Staff will restrict access to the workbench experimental area when source is being used and is out of the storage safe Contact Information email aldrichm missouri edu ghosht missouri edu Organization Vendors Contact Person Basic Work Scope Phone RSS Mary Aldrich Research 882 5024 Tushar Ghosh Research 882 9736 4 Time Lines with Milestones a This RWP was discussed reviewed with Charles Weaver and Robert Schott on July 29 2011 5 Practice run a Dry runs have been conducted and dose rates were taken during a practice runs No further practice runs will be performed 6 Expect dose rates greater than background 7 Staff Requirements a Staff will maintain a logbook that wil
29. UPRING 205693 205693 STEEL 4 1 O RING UNIF 29 800127 BUNAN 5 3 COLAR 60 2H6 316 6 3 GLAND 60 2HM6 316 7 1 TONYBAR B00469 STEEL 8 2 12 13 EYE BOLT 801405 STEEL 18 25 a 17 00 10 00 i fe o des se HF6 CONN E 3 16 THRU Py ND i ka 548 AE ei i j CH N Ww Ka NE NN HF6 CONN K K N XQ e3 3 16 THRU i OG NHFS CONN i 3 16 THRU D GO NO REVISION DATE DISTRIBUTION OR REPRODUCTION OF THIS DOCUMENT IS HIGH PRESSURE EQUIPMENT COMPANY ERIE PENNSYLVANIA USA PROHIBITED WITHOUT WRITTEN R2 REACTOR PERMISSION FROM HIGH PRESSURE 801910 By EQUIPMENTCOMPANY Du SS Figure 1 Pressure Vessel Schematic Table 3 Mirror Chamber System Component List STD TOLERANCES AND MFG PRACTICES ES 002 Type Serial Model Description Amount Glass 1 Custom 1 x3 16 x9 12 www qsiquartz com Glass 29 custom 1 x3 16 x8 12 www qsiquartz com Steel rod inner 8890K451 12 used 4 rod www mcmaster com Steel rods outer 9120K9 3 3 8 rods www mcmaster com Aluminum end 88685K73 1100 2 x2 2 end www mcmaster com caps caps Teflon end caps 8545K18 6 x6 x3 8 2 end 1 www mcmaster com caps Photovoltaic 01 527 Si photovoltaic 1 www ird inc com Le
30. ad Plug Shaped lead fishing weight 1 Source Figure 4 Figure 5 Figure 6 10 Keithley 6487 picoammeter www keithley com Computer by 0 200 or 0 200 H M Ge S 8 io Senge mea La P oa 8 0 200 F 0 020 Pr 0 413 b Q a t 0455 0 500 Figure 2 Source Rod Schematic 1 626 0 020 1 000 0 453 E Figure 3 Source Rod Photo 11 Source Information 10 mCi Strontium 90 Sr 90 Table 4 Strontium 90 Decay Parent Daughter Strontium 90 Sr90 Yttrium 90 Y 90 Zirconium 90 Zr 90 Half life 28 78 years 64 hours Decay Type Beta Beta Energy 0 546 MeV max 2 280 MeV max 0 18 MeV avg 0 92 MeV avg Gamma N A lt 0 001 2 186 MeV Daughter Yttrium 90 Zirconium 90 Stable 12 D S Isotope Products PRATS gum 0933 7 Laboratories Tel 661 309 1010 An Eckert amp Ziegler Company Fax 661 257 8303 NOMINAL SOURCE DATA SHEET Catalog No R032030010M Date 15 May 06 Capsule Type a3203 3 Quantity 1 Nature of Active Deposit stontum 90 in Ceramic Matrix Active Diameter Weight 0 212 5 38 mm Backing Stainless Steel Cover Stainless Steel Nuclide Source No Activity Ref Date Sr 90 B5 773 10 mCi 370 MBq 15 May 06 Leak Test Information is on the reverse side Impurities None Detected Remarks None
31. and the system was repressurized 9 Mirrors were then checked for any obvious issues These are generally either small particulates that adhered to the surface after the last rinse or streaking due to residues that remained Generally mirrors with these issues would have the Al and MgF2 removed and then be cleaned again so that they could be put through the process again Example evaporation Boat pre mass g Sample mass g Boat after evap g Wire boat Al 2 757 0 980 3 235 Boat MgF gt 6 580 0 032 6 576 18 MIRROR CHAMBER A waveguide was made that would help excimer photons reach the photovoltaic while limiting radiation damage that would occur from the beta and bremsstrahlung radiation In Figure 7 below each component can be seen This is the first version used The later version used Teflon end caps instead of Al in order to limit conduction paths that might have been causing problems In the end there was no noticeable change between the two versions As mentioned in the section on mirror creation two different lengths of mirrors were used The first length used was 9 but it was found that at this length the pressure vessel was unable to fully close before the mirror chamber itself would be compressed by the plug Sometimes this contact would pull the wires out causing a need to stop the experiment and set it up again while other times the pressure vesse
32. ar atmospheric Repeated steps f and g at least 2 more times each then finished with doing step f again 36 The faraday cage was then closed the vacuum pump was unplugged to reduce noise that could come from the power line it was on and all safety connections were double checked to make sure they were in place Took a reading at vacuum pressure immediately and then another after waiting at least 10 minutes If on the second check there was still a noticeable amount of charge discharge in the measured response then another 10 minutes was waited before taking another reading This was repeated until a sufficiently steady result is returned Increased the pressure to the next desired amount Step j was then repeated with the new pressure in place of vacuum Step k was then repeated until the desired maximum pressure had been recorded Closed the valve to pressure tank and opened the pressure relief valve until the pressure in the vessel was close to atmospheric pressure Opened up the pressure vessel and removed the mirror chamber The source was then put away into the safe Wrapped the mirror chamber in a protective wrapping Made sure the wires were not in the way in the pressure vessel and that the o ring was in place It was then resealed Vacuumed out the system as stated before pressurized up to 200 psig of Argon and then opened relief valve to bring pressure back down to near 37 atmospheric This step was repeated 1 m
33. at the Xenon highest current is at a slightly higher pressure than the Argon the two numbers are not directly comparable as to which is more efficient However it is clear that both have similar responses over the range that they were tested in Also since the decrease in responsivity going from Argon to Xenon is roughly the same percentage change as the increase in intrinsic photovoltaic efficiency going from a 129 nm photon to a 172 nm photon the final results being similar numbers at similar pressures shows a consistent result in this chamber Photovoltaic Damage Over the course of the experiment the photovoltaic was in close proximity for more than 150 hours Based on the tests done with the solar cells any amount of time beyond a few minutes should have shown a large amount of degradation in the photovoltaics ability to generate current 50 In Figure 22 below two calibration curves are shown One was taken before any experimentation was done and the other after e Pre Exposure Post Exposure PE ae aio E Oo Oo x a E D oO E v mm gt H E Ki SS E Lu E 3 E 53 O 9 DOG st un RN ri vi Wavelength nm Figure 22 NIST Calibration and Recalibration It is clear that there was no appreciable damage to the photovoltaic over the course of the experiment The only significant differences show an increase in quantum efficiency rath
34. ay dissociated and so do not normally form molecules When for example an Argon atom is impinged upon by in the case presented here a beta particle there is at most a 50 10 probability that an excitation will occur that will allow for the formation of an excimer Once formed this unstable molecule breaks apart rapidly 8 12 The primary influences on this process are the temperature the level of impurities and the pressure of the gas Gas temperature influences two body reaction rates in Argon and Xenon strongly at high temperature but has a slow drop off for low temperature 11 Impurity levels impact the formation of desired excimers by either forming other non preferred excimers such as if there is a different noble gas in the mixture or through quenching such as when oxygen 12 13 is in the system which will interact with the Argon or Xenon atom without forming the desired photon Finally pressure the variable which will be changed in this experiment increases the rate of two body reactions asymptotically up to a maximum after a few atmospheres while three body reaction rates continue to increase 12 In this experiment pressure will be changed while holding temperature constant and using a highly pure Argon source for one test and a combination of Xenon and Helium for another Over the pressure ranges to be used from vacuum up to normal tank pressure of around 2200 psig reaction rates should be high enough that excited
35. d checking the mirror chamber 1 Checked and prepared system a Made sure it was still under pressure from last use If it was then these steps would continue If the pressure had fallen significantly then the system would have to be systematically pressurized until the leak was found and fixed then the steps would continue b The relief valve was opened until the pressure inside of the system was near atmospheric and then it was closed High pressure from the system was not allowed to enter the vacuum pump c The vacuum pump was then turned on and the system was opened to it After at least 15 minutes of pumping it was sealed off from the rest of the system and then it was turned off 33 d The system was pressurized up to 500 psig argon and checked for leaks If there were any they were fixed and the process was restarted from 1b e The relief valve was then opened until the system was at around 100 psig Argon It was then closed and the piping leading to the gas was sealed off f The relief valve was again opened until the system was near atmospheric pressure and then closed again g The system was then ready to be opened and have the mirror chamber placed inside 2 Checked computer system a In order to assure that the Keithley was warmed up properly it was turned on and plugged into the computer at least an hour before it was to be used in an experiment b Opened excel in a new sheet or continued on an old as desired
36. days and is valid for deliveries made within 12 months from the date of issue To place an order please contact Industrial Products Customer Service at 661 309 1010 Richard Hunter Director Global Industrial Sales Direct Tel Fax 1 781 373 1610 Figure 5 Strontium 90 Quote 14 S Laboratories Meet ISOTOPE Sr 90 ACTIVITY 40 mCi ACTIVITY 370 MBq REF DATE 15 May 06 SOURCE B5 773 NOT FOR DRUG USE 5049 Hey F Figure 6 Strontium 90 Container and Button Picture 15 Crafting Mirrors Polished quartz glass 1 x 3 16 x 9 and 1 x 3 16 x 8 was used as a base upon which Aluminum Al and Magnesium Flouride MgF2 were evaporated to form mirrors Met was needed as Al oxidizes quickly to a state with poor reflective qualities for ultraviolet photons The steps used to create the mirrors were as follows 1 The evaporation chamber was prepared a Two tungsten boats and one tungsten wire boat were taken b One boat was used as a blank to heat the chamber This sped up desorption from the walls c The other boat had an amount of MgF gt placed on it while the wire boat was used for Al Using the density of each 3 15 g cm3 and 2 70 g cm3 respectively and the equation below the desired thickness was reached mass g Me ee a 10 77 x 2963cm density 2 i nm cm 16 d In order to have sufficiently thick Al and sufficiently thin Met we used 1 g of
37. e air 2 Pressure vessel not to scale 3 Gas volume outside of mirror chamber 4 Aluminum end caps for structure top holds photovoltaic while bottom holds the source rod 5 Gas plenum inside of mirror chamber 6 Mirror walls 4 total 2 are illustrated here 7 Lead plug 8 Below the 8 is the hole for the source with two smaller holes cut out of the rod to minimize beta loss in the holding rod 9 Iron source holding rod Figure 2 Scale diagram of the mirror chamber inside of the pressure vessel Results Figure 3 shows a typical PIDEC nuclear battery experimental result A small amount of current compared to the currents generated at the highest pressures tested is measured at vacuum pressure 7x10 gt Pa 10 psi This is due to a small amount of bremsstrahlung radiation impinging on the photovoltaic cell A decrease in measured current output is observed as pressure increases to approximately 6 9 x 10 Pa 100 psi which shields the bremsstrahlung radiation Subsequent increase in chamber pressure results in a general upward trend in measured current due to the increased stopping power of the gas and subsequent excimer production 80 Generally between 6 9x10 and 1 1x10 Pa 1000 and 1600 psig there is a reduction in current observed This is due to the lower energy beta of the Sr 90 reaching its peak geometrical optimum range in the gas for photon collection and a transition to the higher energy Y 90 beta
38. ecorded 23 9 The source was then put away along with the badges The radiation area signs were taken down 10 With the box already open a test was taken in the light for a post exposure reading Voltage data was then recorded Further tests were run using glass slides and stacking photovoltaics to try to limit damage over time without success Enough shielding to extend the lifetime of the photovoltaics was also enough for the voltage response to be indistinguishable from the normal dark measurements 24 Radiation Zone and Procedures Working with EHS specifically Mary Aldrich aldrichm missouri edu the Sr 90 source radiation zone was established along with a procedure for safe handling The specific paperwork from EHS is in Appendix 1 The procedure used was simple 1 The radiation work permit Figure 25 and radiation survey Figure 23 forms were taken out and the initial sections were filled 2 Badges were retrieved from their locked cabinet and put into place on all personnel who would be entering the radiation zone for the experiment 3 The Ludlum model 3 radiation survey meter was then tested to ensure that it remained within calibration range This information was recorded on its own notebook 4 Prepared the experimental area including putting up the temporary radiation warning signs and getting the mirror chamber ready 5 Following ALARA the source was then removed from the safe and placed into the mirr
39. ely secure the source form further exposing RW s and others and notify AU and RSO office b An ALARA overexposure investigation will be conducted by the Health Physics office upon notification or upon elevated results from quarterly dosimetry 13 Overnight Storage Contingency Plans a The facility is secure against unauthorized entry 14 Ancillary Staff Needs a All staff with access to W0030 must be radiation workers op ancillary workers with training provided and documented by the AU b Other students conducting research in W0030 need to be informed when work is going to begin c Other students conducting research in W0030 must be informed and understand not to enter work area when source handling is conducted d Other students while source is in experiment and are they are in the room they must wear their own whole body dosimtery e Absolutely no visitors allowed when source is not in safe 15 Pertinent Questions to ask Pre Job Brief a Have we done this before and how i Yes and no b What are the Critical Steps i Pre Job analysis c What Mistakes might be made i Potential for over exposure to staff ii Potential for over exposure to other students conducting research in the lab d What is the worst that could happen i Dose to members of the public e What are our defenses i Adequate pre job briefs Page 4 of 6 61 University of Missouri Columbia M Environmental Health amp Safety
40. enon which made hitting pressures much more difficult this also accounts for the data point spread Secondly because of the method used the ratio of Xenon to pressure was much more poorly controlled at that extreme end so the measurements taken there would have little meaning when compared to the other points plotted However the general trend seen in the Argon tests still holds There is a general trend upwards in current as pressure increases except for a brief dip The dip appears to have moved slightly towards a higher pressure range as well Efficiency The primary factors in determining the conversion efficiency of this system are energy deposition in the excimer gas excimer gas fluorescence efficiency photovoltaic photon conversion efficiency and finally photon reflection efficiency Using the MCNPX 2 6 0 14 1 14 14 14 13 12 11 10 9 8 7 6 model 6 6 6 6 7 the percentage of energy released by the source that was deposited into the gas was 3 47 This value is the 45 energy transport efficiency 14 from the source to the gas plenum This energy was deposited between the center rod and the glass mirrors which is illustrated by region 5 in Figure 7 Mirror Chamber Schematic Any energy deposited elsewhere was considered lost Idealized numbers were used for fluorescence and photon conversion efficiencies Excimer gases and fluorescence emission have been extensively studied and the maximum fluorescence effic
41. er than a loss in the range of 116 4 to 135 4 nm However the most extreme differences fall within two or three standard deviations of NIST s calibration experimental error 51 CONCLUSION A PIDEC experiment was created and tested using Sr 90 as a radioactive source both Argon and Xenon as excimer producing gases a photon waveguide mirror chamber and a Si photovoltaic Experimental data shows current production that generally increases with increasing pressure over the ranges tested in each experiment These experiments also showed a consistency between using Argon and Xenon as excimer gases The matching of range of the radiation with the scale of the transducer and the basic principles of PIDEC were demonstrated Unlike direct energy conversion wherein the beta particles would impinge directly onto the photovoltaic this process is non destructive and may be used over extended periods of time without loss of efficiency Here after more than 150 hours of exposure the photovoltaic showed no sign of degradation at all as the NIST calibration tests showed The efficiency of the system was very low due to losses in beta energy outside of the gas plenum and photon absorption Both of these factors may be improved Increasing the size and pressure of the gas plenum will increase the fraction of beta energy absorbed by the gas Mirroring the source holding rod and lead shield plug will be critical in the improvement of photon transport effic
42. er than the half life of the parent Sr 90 these two beta decays are assumed to be in secular equilibrium and so both are assumed to occur simultaneously Sr 90 decays into Y 90 by emitting a beta particle that has a maximum energy of 0 546 MeV and an average of 0 18 MeV Y 90 then also undergoes beta decay forming stable zirconium 90 with a beta that has a maximum energy of 2 28 MeV and an average of 0 92 MeV Using these average beta energies of 0 18 MeV and 0 92 MeV for Sr 90 and Y 90 respectively total power output of the source P ource IS Energy per complete decay 0 18 MeV 0 92 MeV 1 1 MeV 4 decays Sr 90 source activity 10 mCi 3 7 x 108 L 5 second 6 47 MeV decays 1 6022 x 107 Joule 1 1 x 3 7 x 10 x decay second 1 MeV oules 6 5 Xx 107 J Watts second Prource 6 5 X 1075W Taking the highest value reached in Figure 20 0 24 x 10719A photodiode current eg P hotovoltaic qa 1 5 x 10 W p A 0 16 W responsivity Gives an absolute efficiency of P i 1 5 x 1070W _ photovoltaic _ 4 __ Xx 100 2 3 x 10740 aS E D EE 6 5 x 105W A A 7 8 Using the above efficiencies we define the absolute uncertainty as all others multiplied together Nabs NaN FN PV NTR 48 9 Where Naps is defined above as 2 3 x 10 na is the energy transport efficiency from the source to the gas plenum given above as 3 47 npr is the fluo
43. ert those photons into current thereby maximizing power output of the battery system 76 Also important are the relative efficiencies of the energy conversion processes that occur in direct beta energy conversion systems versus PIDEC based systems Even when ignoring the radiation damage that a photovoltaic cell would experience in a direct system the maximum theoretical efficiency with Sr 90 and a SiC photovoltaic cell is lt 0 25 6 while the maximum theoretical efficiency of the PIDEC system using SiC is 8 8 4 25 for Si 17 6 for diamond 10 These theoretical maximum system efficiencies are products of the maximum efficiency of the following energy deposition to the gas from the radiation source the fluorescence the photon transport and for the conversion of fluorescence to electricity in the photovoltaic cell Using a 10 mCi Sr 90 beta source an excimer gas a waveguide and a Si photovoltaic cell a current source was made The Sr 90 source was in the form of a cylindrical button 5 mm x 8 mm OD 0 200 in x 0 312 in OD and was held in place with a rod mounted inside a mirror chamber waveguide Argon was used as an excimer forming gas with beta particles used to excite it in a process that could be repeated indefinitely without suffering damage As an excimer fluorescer argon is optically thin to the photons it produces because the ground state is unbound It is also otherwise chemically inert in the system After many hours
44. his and the frequency of photon put out by other excimer 53 gases it would be possible to find a photon wavelength with high quantum efficiency for a given photovoltaic that was also in a better range for highly reflective mirrors Working on a similar type of project some preliminary work has already been done using direct energy conversion where a beta particle directly impinges on a wide band gap material and releases a characteristic photon Since it is not a photovoltaic and does not rely ona depletion zone a much larger volume may convert the energy Also wide band gap materials are harder to damage with this radiation with any displaced areas potentially being fixed through self annealing or simply being filled after capturing enough electrons after which they would pose less of a problem Some preliminary work with GaP using the above method is shown below These were done with a Po 210 source Test Voltage Current x10 gt Notes 1 600 0 00 No source No filter 600 0 02 Source No filter 600 0 00 Source Filter 2 700 0 01 No source No filter 700 0 19 Source No filter 700 0 11 Source Filter 3 750 0 15 No source No filter 750 0 26 Source No filter 750 0 14 Source Filter 54 There is a very definite response shown by the PMT when the source is put below the GaP However when a band pass filter is applied around the wavelength that it is believed to be what photons
45. ic as needed The mirror chamber was then set near the radiation safe for quick placement of source 4 Ran experiment Opened up the top of the pressure vessel and made sure that there was a clear path for the mirror chamber to fit in and that the o ring was in place If it was out of place or a wire was trapped under it a tool was used to resettle it properly 35 The source rod was then placed into mirror chamber The mirror chamber was then slid into pressure vessel and the internal wires were attached to it Each connection was then tested to ensure proper functionality and reset if needed Screwed down pressure vessel lid until chamber was sealed Typically all but the last revolution or so was easy Made sure that the wires were still attached on the inside If they were not then the Keithly would be giving either too high of a result wires touching or too low displaced contact If either of these happened or there was continual charging and discharging showing up then the pressure vessel was reopened and the connections were redone The vacuum pump was then turned on and the valves between the vacuum and the system were opened The vacuum was run for at least 15 minutes after which the valves between the vacuum pump and system were closed The vacuum pump was then turned off Pressurized the system to 200 psig of Argon Sealed off the tank from the pressure vessel Used the pressure relief valve to get back down to ne
46. iencies as it is currently part of the largest loss factor Decreasing the size of both the steel rod and the lead plug will limit loss of energy inside of the system as well 52 ADVANCED PIDEC CONCEPTS FUTURE WORK While this project dealt primarily with changing pressure of a system with a fixed source and only two gases future work could expand in a number of areas The most important of these areas is the mirror chamber waveguide itself In designing the one used for this experiment longevity of the photovoltaic was the highest priority With no appreciable damage over the course of this experiment and seeing how much of the beta energy gets stopped by the gas plenum under sufficient pressure it would be possible to design a new chamber This new chamber would be able to have less shielding that hindered the process and work more with having a higher pressure of gas to stop the radiation from impinging on the photovoltaic With the current design only a small window is available to capture the energy of the betas nearly all of the energy escapes outside of the narrow mirror chamber Shaping this differently so that the betas must pass through more gas before leaving the system would greatly increase the efficiency Modifying the chamber to a cone structure would also allow for a more directed guide of photons Argon and Xenon both behaved in similar ways it would be expected that other excimer gases would do the same Knowing t
47. iency np for argon is 50 1 The photovoltaic energy conversion efficiency npy for a Si cell using the 129 nm excimer photon has a theoretical maximum of 5 7 10 10 10 10 11 9 8 This is shown in equations 2 and 3 Driving potential efficiency and fill factor were assumed to be ideal 0 5 and 1 respectively and are defined in more detail in Oh s paper 6 6 6 6 7 E Npy F x Driving Potential Ef ficiency x Fill Factor 2 si lt x 0 5 x1 0 057 3 Npy Si eech 5X1 0 The greatest loss in efficiency for this system occurs with reflections due primarily to the unoptimized design of the waveguide Aluminum was used as it has a gt 80 reflectivity 15 for the deep ultraviolet photons of the Argon excimers but the number of reflections any photon may undergo is highly variable In addition the rod used to hold the source and the lead plug that topped it were not reflective A coating of aluminum and Met was deposited on each but 46 resulted in a milky and dull appearance due to the incompatibility of the surface for mirror finishes It was assumed that all photons striking either the rod or lead plug were lost With these two factors the vast majority of photons created were not in the narrow window where they could be collected by the photovoltaic making this factor the greatest loss in efficiency Each Sr 90 decay eventually produces two betas As the half life of the daughter product Y 90 is much short
48. ight be useful the depletion layer When energy is deposited in the depletion layer of the junction it may create a hole ion pair which can then migrate to create a current across the photovoltaic 6 Energy deposited outside of this region is typically considered lost While under bombardment the physical structure of the semiconductor will be changed This change could cause defects to form in the semiconductor limiting its ability to transfer charge properly eventually this damage cumulates enough to render the photovoltaic useless Because of this damage an alternative method of utilizing the beta particle s energy is needed A PIDEC system as mentioned earlier uses an indirect method of power conversion through excimer formation 1 7 Excimer formation is the most important aspect of this system and it has undergone a great deal of study 8 9 10 11 An excimer gas may undergo excitation and decay without suffering from damage or reduction in efficiency an unlimited amount of times This allows for its time frame of use to greatly exceed that of an application where radiation impinges directly onto a photovoltaic The word excimer itself comes from excited dimer where a dimer is simply two identical atoms or molecules In the case presented here two noble gases Argon and Xenon will be used as the excimer forming gas one at a time While in its ground state these noble gases interact in a repulsive manner they st
49. ing requirements TEMPLATE FOR DAILY SOURCE USE CHECKLIST Staff Name Date Time staff entered the lab to begin research Time E Time source was removed from the safe Time Time source was placed into experimental chamber Time source was removed from experimental chamber Time source was secured inside safe Time of meter survey to verify source is secured in the safe Check yes or no to indicate dosimetry is present and is being worn properly Check yes or no that required access restrictions are in el place to prevent other staff from entering the work area when source is removed from safe Check yes or no that ALARA was maintained during source handlin Time staff concluded use with the source and left the lab Time DN SE GE BE Page 5 of 5 Figure 25 Radiation Work Permit 2011 06 68 Appendix 2 Tabulated Results Table 5 Figure 20 Argon Tabulation PRESSURE PSIG CURRENT x10 A IMMEDIATE CURRNENT A AFTER DELAY Vacuum 0 16 0 14 100 0 11 0 125 250 0 138 0 133 400 0 147 0 146 500 0 15 0 150 600 0 16 0 146 700 0 16 0 148 800 0 16 0 163 900 0 17 0 162 1000 0 17 0 166 1200 0 19 0 195 1300 0 2 0 201 1400 0 21 0 211 1500 0 22 0 215 1600 0 228 0 212 1650 0 21 0 210 1900 0 23 0 224 2100 0 25 0 239 Table 6 Figure 21 Xenon Tabulation
50. ing rod from the glass of the mirror chamber and from the pressure vessel itself As the pressure increases the current from that process dies away as more of the beta energy is being captured by the gas and the bremsstrahlung radiation is damped by the gas both inside and outside of the mirror chamber After the initial dip the current steadily increases with increasing pressure Between 1000 psig and 1600 psig there is another slight reduction in current occurs This is due to the lower energy beta of the Sr 90 reaching its peak geometrical optimum range in the gas for photon collection followed by a transition wherein the Y 90 s higher energy betas start 43 increasing their contribution to photon production The range over which it occurs has to do with a combination of uncertainty in the pressure being measured and the orientation of the rod When the rod is screwed into the base the exact placement of the hot cold sides of the source was not well controlled It was only recorded that the screwed section was roughly flush with the end cap Xenon N o N p 00 LA a pr lt lt E OM Som Q o LA CH gt LA N o KA 1000 1500 Pressure psi Figure 21 PIDEC Xenon Result 44 Figure 21 above shows a representative Xenon run The lower end of the pressure does not show the normal bump for two reasons First the procedure had to be changed in order to use X
51. l include i Time staff entered the lab to begin research ii Time source was removed from the safe iii Time source was placed into experimental chamber iv Time source was removed from experimental chamber v Time source was secured inside safe vi Time of meter survey to verify source is secured in the safe vii Check yes or no to indicate dosimetry is present and is being worn properly viii Check yes or no that required access restrictions are in place to prevent other staff from entering the work area when source is removed from safe Page 2 of 5 65 5 Radiation Work Permit 2011 06 2257 10 mCi Strontium 90 source handling requirements ENS CREE OSEN 10 nls 12 IS 14 Environmental Health amp Safety Research Park Development Building University of Missouri Columbia Columbia MO 65211 3050 PHONE 573 882 7018 FAX 573 882 7940 INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 ix Check yes or no that ALARA was maintained during source handling x Time staff concluded use with the source and left the lab b Staff shall i Set out physical barriers to establish work area ii Mark boundaries with radiation area signs iii Use remote handling tools when at all possible c Staff shall contact EHS prior to i Removing or replacing the source orientation in the jig holder ii Loading the source into a new jig holder Dosimetry requirements a Whole body dosimeters worn
52. l would release prematurely which would not allow for a full test to be completed This lead to the use of 8 long glass instead which alleviated these problems 19 1 Outside air 2 Pressure vessel not to scale 3 Gas volume outside of mirror chamber 4 Aluminum end caps for structure top holds photovoltaic while bottom holds the source rod 5 Gas plenum inside of mirror chamber 6 Mirror walls 4 total 2 are illustrated here 7 Lead plug 8 Below the 8 is the hole for the source with two smaller holes cut out of the rod to minimize beta loss m the holding rod 9 Iron source holding rod Figure 7 Mirror Chamber Schematic Not shown in Figure 7 above are wires that come out of the top from the photovoltaic and three rods that connect each of the bases together 20 Figure 8 Aluminum end cap with mounted photovoltaic In Figure 8 the holes where the rods would touch can be seen Running through the holes are screws that thread into each end of the rod such that it is possible to tighten both ends simultaneously 21 METHODOLOGY Preparation Work In preparation for testing PIDEC a simple experiment was performed on several silicon photovoltaics solar cells These tests were performed to determine the rate at which radiation from the Sr 90 source would cause degradation in the photovoltaic as a baseline for what a similar test would do to the calibrated source used in the PIDEC
53. ltiplied together Nabs NaNeNpvNrr 8 Where naps is defined above as 2 3 x 10 ng is the energy transport efficiency from the source to the gas plenum given above as 3 47 nr is the fluorescence efficiency of argon 50 1 Npyis 5 7 for a Si photovoltaic 10 and n pis the unknown loss coefficient due to photon absorption energy deposited outside of the gas plenum and all other losses Solving for nrp n IS 100 0 23 9 _ eX 0 TR nanriev 0 0347 0 5 0 057 oy The photon transport efficiency 7p is an area where substantial improvement can be made by using different reflective waveguide designs to shield the photovoltaic Theoretical studies have been done for such configurations and nrg could approach 70 16 17 18 84 Another improvement would be with the use of excimer gases with lower energy photon emission such as Xe 172 nm These photons would be in a range where reflection efficiencies for mirrors can be gt 90 This reflectance efficiency is important because a photon could undergo many reflections before encountering the photovoltaic cell Photovoltaic exposure Over the course of this experiment the photovoltaic had been exposed to over 150 hours of time near the source In our experiment it had been shielded from direct radiation damage through use of a lead plug and an intervening gas NIST prepared a calibration report before the photovoltaic was used and another calibration was
54. n and a Helium fill gas listed as Ar source a pressure vessel R2 10 40 a vacuum pump Trivac D16B rated to 10 6 psi a mirror chamber and a Si photovoltaic Manufactured by International Radiation Detectors IRD Serial Number 01 527 calibrated by the National Institute of Standards and Technology NIST 31 Computer system Ar source Pressure vessel Pressure guage Vacuum Figure 14 Rough PIDEC System Schematic Outgassing In order to ensure that the system was as free of contaminants as possible before tests an outgassing procedure was performed before each new run of several experiments This process involved using heating tape to heat the system and then cycle the system through vacuum and argon flushes As the system takes quite some time to heat up and cool down this process typically took around 3 days One day to heat up one day to perform the flushes and then another day to cool down During heat up and cool down the vacuum pump was run continuously 32 Between uses where a thorough outgassing should not be required the system was put under vacuum and then 200 psig of argon pressure Any loss in this pressure between runs would call for testing of all seals to make sure that they were in working order Experimental Procedure Argon This procedure is extended from the radiation zone procedures above It is expanding on step 8 The experiment for the day would then be performed an
55. n brief the PIDEC system tested for this thesis used two excimer gasses Argon and Xenon to produce photons These gasses were excited into excimer production using a 10 mCi Sr 90 source and held in place at pressures ranging from 10 to 2400 psi by a pressure vessel Photons produced were guided towards a photovoltaic by a mirror chamber lined with high efficiency aluminum mirrors Outside of the pressure vessel a picoammeter read the current off of the photovoltaic and sent the current to a computer for data processing Of primary interest was how the current changed based on the amount of energy captured by the gas plenum which was related to the pressure of the system The overall efficiency of this system was low due to a non optimized waveguide much of the beta energy being lost beyond the gas plenum and other factors However viii the results were sufficient to show that the process was successfully completed and making a new system to optimize for these features is warranted INTRODUCTION The goal of a Photon Intermediate Direct Energy Conversion PIDEC system is simply to match the scale length of the radiation range to the scale length of the transducer for a long lifetime maintenance free power source a nuclear battery 1 This battery would be capable of supplying electrical current to devices in any setting where replacement of the battery would be problematic such as in the depths of the ocean or
56. nnnnnnnsssnnsrnnnnnnsnsssrnnsrnnnnnnnnsennnnnnnnnnssee 39 PIDEC SYSTEM ee A R E E A E AE 42 PAS OND Pe e EEE E E E E E E E E E an 42 KNM eebe 44 Efflclency 45 Photovoltaic Damage cccccccsssssssseeceececcaueeseeecceeeessaaeueeeeceeeessauauseeeeeeessssuaaseeeeeeseesaaagaess 50 CONCLUSION EE 52 ADVANCED PIDEC CONCEPTS FUTURE WORK sccsssceesseeeseseeeeeneeceseeceeaeecseaeeceaeeseaeeeseaeesenaeensneeneas 53 APDENGICES EE 56 Appendix 1 Radiation Work Paperwork ssssesssssssseeresssssssesrressssssserrressssnsserrressssnsssereens 56 Appendix 2 Tabulated Results 69 Appendix 3 Pictures Of Setup 70 Appendix 4 Paper submitted to Nuclear Technology rrvrrrnnnnnnnnvnnnnrrrrnnnnnnnrnnnnnrrrnnneresvrnnnnnn 74 REFERENGES EET 89 VITA cicccecatecessvacenrcssaceunestadeupesapounteavosnseseaunstonavunsysutvaustausveveeeateuuneee aeons taaguessacgusensnapee tent EES 91 LIST OF TABLES Tables Page Table 1 Potential Beta NUCH SS vsusascsnciveuvanenensedavevanesevienivestvaysvessensvaenssavandexaneuerentnane 5 Table 2 Pressure System Component List 8 Table 3 Mirror Chamber System Component List rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrsrrrnnnnn 10 Table A Strontium 90 Decay Parent Daughter cccscccccccecesessssssseeeceeeeeessssseeeeeeers 12 Table 5 Figure 20 Argon Tablet een avsatte 69 Table 6 Figure 21 Xenon Tabulation 69 LIST OF FIGURES Figure
57. nown issues such as the building power being unstable possibly due to a large amount of computers on the system along with other equipment along with unknown ambient issues In order to deal with the building power being disruptive a transformer GIS 500 Stancor and an AC power conditioner SA 20 SurgeX were installed This helped but did not eliminate all of the noise especially during peak usage hours of the rest of the building After trying those two extra steps were put into place These were taking the partially cleaned power and running it through an AC to DC power supply PS 21KX Pyramid and then running that through a DC to AC power inverter PW1100 12 PowerBright This process cleaned the power sufficiently The other noise issue was some unknown ambient It was almost always there in some form but it changed in frequency magnitude and function often In order to help eliminate this problem a faraday cage was brought in all wires were shortened and wrapped in an extra layer of protection and all of it was grounded on a dedicated ground separate from the building s normal ground This was sufficient only to eliminate some of the ambient noise but it was 27 reduced enough to be able to take measurements again It did get rid of the long charge discharge cycles most of the time and turning the room lighting on and off no longer changed the signal Examples of noise problems resolved KA a E lt
58. on level measurements on contact and at 30 cm of the source storage location safe or experimental setup Surveys will be performed following each source move from safe to setup from setup to safe or monthly whichever is more frequent d The sealed source is constructed of S1 90 in a ceramic matrix with a stainless steel cover and backing and active diameter is 5 38 mm It should be able to withstand the rigors of the experiment where it will be under pressure vacuum Staff will ensure the source is inspected for undue wear at each use e Staff will restrict access to the workbench experimental area when source is being loaded into experimental mirrored source holder and experimental chamber and again upon removal of source from experimental chamber and experimental mirrored source holder and back into safe Contact Information anization Vendors Contact rasa Basic Work Scope Mary Aldrich Research 882 5024 aldrichm missouri edu Tushar Ghosh Research 882 9736 ghosht missouri edu 4 Time Lines with Milestones a Two Milestones i New RWP requirements will be discussed on July 20 ii Source will be returned upon understanding of new RWP requirements on July 20 b July 23 i RWP requirements briefed posting requirements received ii Access use log received c July 23 i Source returned 5 Date of Practice run a Practice Run will be performed to ensure AU and staff understand and demonstrate new
59. on the torso of the body b Ring dosimeter worn on the hand that is handling the source Monitoring Instrument needs a Ludlum model 3 and pancake GM or equivalent Surveys conducted during use and when source returned to storage a Performed each day of use and at least once monthly if not used Area measurements will be established with survey meters prior to work beginning to confirm that ambient radiation levels are consistent with background Over Exposures Plan a If overexposure is suspected by staff during source handling immediately secure the source form further exposing RW s and others and notify AU and RSO office b An ALARA overexposure investigation will be conducted by the Health Physics office upon notification or upon elevated results from quarterly dosimetry Overnight Storage Contingency Plans a The facility is secure against unauthorized entry Ancillary Staff Needs a All staff with access to W0030 must be radiation workers or ancillary workers with training provided and documented by the AU b Other students conducting research in W0030 need to be informed when work is going to begin c Other students conducting research in W0030 must be informed and understand not to enter work area when source handling is conducted Page 3 of 5 66 882 7018 Environmental Health amp Safety Research Park Development Building University of Missouri Columbia Columbia MO 65211 3050 Radiation Work Permit 2011 06 e
60. or chamber which was then installed into the pressure vessel 25 6 If working with a second person the times would be recorded for each step above as they happened If only one person was working then the source handling steps would be completed and then the times would be filled out in order to minimize source exposure 7 With the source in the pressure vessel the radiation survey of the experimental setup would be taken and recorded on the radiation survey form Note On the radiation survey form the Storage survey and the Experimental setup survey are listed in the opposite order in which they are taken First the experimental setup was done as shown here Later the storage survey is performed 8 The experiment for the day would then be performed Greater detail of this step is given in the PIDEC section below 9 The mirror chamber was then removed from the pressure vessel the source was removed from the mirror chamber and the source was returned to the safe 10 On the radiation survey form the Storage survey is now performed along with the times on the radiation work permit 11 The paperwork was then double checked for accuracy and filed away in its drawer 12 The temporary radiation warning signs were then taken down and the badges were locked in their cabinet 26 Noise Issues During the experiment increasing noise issues led to using a number of noise dampening solutions This noise came from k
61. ore time and then the vessel was pressurized up to 200 psig before being sealed to wait for the next test Experimental Procedure Xenon This follows the same procedure as for Argon in every way except that instead of performing step 4j and on as written after the last vacuuming 200 psig of Xenon is put into the system and then Helium fill gas is put in until the system is at the top pressure desired After that the readings proceed with decreasing pressure rather than increasing but the wait and recording times are all the same This was done as the Xenon acquired was under too low of a pressure to hit the proper final pressure desired This process kept the ratio of Xenon in the chamber roughly equal over the course of the experiment 38 RESULTS Solar cell photovoltaic Over 20 photovoltaics were tested as described in the methodology above Below are several figures representing typical solar cell tests The results of each were all similar to these Solar Cell Fluorescent Light Box open no source NAA A A a A LEI rer Lele cd Al el eZ VUE UT PE Uu Vy Wee ye ye ue ie yee N VY Vy VV Vy pV V VV yy Data Points 60 Hz OO Oo gt Figure 15 Solar Cell Room Light No Source Pre exposure 39 Voltage V Solar Cell Dark Current 6 50E 05 Box closed no source 4 50E 05 if 2 50E 05 5 00E 06 1 50E 05 3 50E 05 5 50E 05 7 50E 05 9 50E 05 1 15E 04 Data Points
62. rescence efficiency of argon 50 1 1 1 1 npyis 5 7 for a Si photovoltaic 10 and n7ris the unknown loss coefficient due to photon absorption energy deposited outside of the gas plenum and all other losses Solving for rp MEL ER Ko x 100 0 23 TR menpy 0 0347 00 5 0 057 AR The photon transport efficiency Nrg Is an area where substantial improvement can be made by using different reflective waveguide designs to shield the photovoltaic Theoretical studies have been done for such configurations and Nrg could approach 70 16 17 18 The same experiment was then run with Xenon as the excimer gas rather than Argon Xenon has a lower energy photon emission with a wavelength of 172 nm 7 2 eV and so falls under a slightly better reflectance range gt 90 possible than the Argon eximer Assuming all else to be equal except for the new photon wavelength using the current from the Xenon test Figure 21 and the new responsivity 0 11 A W the following efficiencies are calculated E Npy T x Driving Potential Ef ficiency x Fill Factor 2 49 1 1 eV Npy Si 75 ov x05x1 0 076 11 0 245 x 10719A photodiode current 12 Ponotovottate 4 2 2 x 107W 0 1177 responsivity P ic 22x107W 13 __ photovoltaic _ 4 r 100 3 4 x 10749 labs P urce 6 5 x 105W A A Nabs 3 4 x 1076 14 EA NIATI N EMO ATE 0 NTR Manene 0 0347 0 5 0 076 x 100 0 26 Given th
63. rk area ii Mark boundaries with radiation area signs iii Use remote handling tools when at all possible iv Handle source only at the ends of the source jig holder c Staff are prohibited from i Removing the source from the current jig holder ii Handling the source directly see b iv above d Staff shall contact EHS prior to i Removing or replacing the source orientation in the jig holder ii Loading the source into a new jig holder 8 Dosimetry requirements a Whole body OSL dosimeter worn on the torso of the body b Ring dosimeter worn on the hand that is handling the source 9 Monitoring Instrument needs a Ludlum model 3 and pancake GM or equivalent Page 3 of 6 60 t Environmental Health amp Safety Research Park Development Building University of Missouri Columbia Columbia MO 65211 3050 Radiation Work Permit 2009 10 Sey FAX 373 882 7940 ENVIRONMENTAL MANAGEMENT 882 7018 INDUSTRIAL HYGIBNE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 10 mCi Strontium 90 source handling requirements 10 Surveys before and after source is removed from safe and used a Meter surveys i Each day of use ii Monthly on a pre established schedule 11 Area measurements will be established with survey meters prior to work beginning to confirm that ambient radiation levels are consistent with background 12 Over Exposures Plan a If overexposure is suspected by staff during source handling immediat
64. s Page Figure 1 Pressure Vessel Schemati AAA 10 Figure Source el dE 11 Figure 3 Source Rod Photo 11 Figure 4 Strontium 90 Source Data Sheet AAA 13 Figure 5 Strontium 90 Quote irisan AREENA EE EERTE 14 Figure 6 Strontium 90 Container and Button Picture rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrnnnenn 15 Figure 7 Mirror Chamber Schematic AAA 20 Figure 8 Aluminum end cap with mounted photovoltaic ensssssnneenenosssssnnereresssesne 21 Figure 9 RadioShack solar cell guung eegene eegene AE Ehe ebe 23 Figure 10 NOISE Luuanehar aner veaywedd ee eegen ege ee ed 28 Figure 11 NOISE en Egide Seege EE EE EE dE degen 29 Figure 12 NOISE TEEN 29 Figure 13 Argon Gas Density rmnrannorvorannonvenrennevenrenvavnernavevrernennerernavnernenennevvennennuvensen 30 Figure 14 Rough PIDEC System Schemat 32 Figure 15 Solar Cell Room Light No Source Pre exposure ssssssssssssssssssssssssssssse 39 Figure 16 Solar Cell No Light No Source Pre expoSure rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrnnnnn 40 Figure 17 Solar Cell No Light SOuUrce sagen ege gege 40 Figure 18 Solar Cell Light No Source Post evposure 41 Figure 19 Log Plot of Average Voltage for Solar Cell Tests 41 vi Figure 20 gt PIDEE Areon Results ie siniri tess eee saan eee uted eaten ee 43 Figure 21 PIDEC Xenon Result rrrnnnnnnrrnnnnnnnnnnrrnnnrrrnnnnnnnnnsrnnnrrnnnnnnnnnassnnnnrnnnnn
65. should be coming out band pass 550 nm 10 nm the signal drops to background Further testing needs to be done to resolve this issue 55 Appendices Appendix 1 Radiation Work Paperwork The radiation survey sheet Figure 23 below shows the radiation zone and is filled out whenever the source is removed from and put back into the safe 56 DOCUMENTED RADIATION SURVEY UNIVERSITY OF MISSOURI COLUMBIA 4 List all locarlons where the survey data exces the levels listel below il mene indicate None When laboratory ALARA or Survey Procedure actiou levels are exceeded tbe activas takeun must be documented in the comment section below Instone Ertzienz Lamm Lalm MK Ek Cre Canadon Cale pa alten Cute Rsmavahle Contaminanon locannos Swipefap a raam ams greater Ia Solace Cyntsminatice lususans eatk tndevue 202 dpms 106 em hae of 1 van us imlicuned Seles Safe at contact Safe at 32 cm mR hr Experimental setup Housing at contact He Housing at 29 cm Camas eren Sr 99 Fu suures horse HO MEF Zut ier User L Gah Roum sik Die T ginsering Fam vost Dots F Dabo By JE NE Figure 23 Radiation Survey 57 Columbia MO 65211 3050 kd Environmental Health amp Safety Research Park Development Building University of Missouri Columbia H RADIATION Radiation Work Permit 2009 10 s r E FAX 573 882 7940 4 Ps a A Ee ENVIRONMENIAL MANAGEMENT 82 7018 10 mCi St ontium 90 so
66. snnnssssnnnn 44 Figure 22 NIST Calibration and Recalibration ccccccccccccsssssssseeeeceeeeseeeeseeeeeeeeeeeaas 51 Figure 23 Radiation SUrvey cccccccccssssssseeceeceeeceseeeseeeceeeeeeesseeasseeeeeeeesssueaaseeeeeeeeeseaaa 57 Figure 24 Radiation Work Permit 20009 10 63 Figure 25 Radiation Work Permit 2011 06 rrrrrrnnrrrnnnnnnnnnrrrnnrrrnnnnnnnnnrrnnnrrnnnnnnnnnnssrnnnn 68 Figure 26 High Pressure Connections and Valves Safety Forms s s 70 Figure 27 High Pressure Vessel top view 71 Figure 28 Photovoltaic in Packaging ccccccccsssssseeeceeceeeeeeseeseeeeeeeeeessaeeaeeeeeeeeeeeeaaa 72 Figure 29 Looking Down the Mirror Chamber 72 Figure 30 Badge Cabinet and Radiation Safety Sheet ccccecccceceeeeesessseeeeeeeeeeeaes 73 Figure 31 Faraday Cage Pressure Vessel Tubing and Valves Heating Tape Pressure Gauge and Vacuum PUMP muse 73 vii ABSTRACT This thesis covers an examination of a need for a compact long lived power source and a proof of concept for one such design To begin tests were done dealing with photovoltaics and their lifetime while undergoing radiation damage from the source of interest Strontium 90 Sr 90 After completing these tests a system was designed built and ultimately tested over a range of pressures in order to test if a Photon Intermediate Direct Energy Conversion PIDEC system would be potentially viable I
67. sotope would have the following qualities Few to no gammas a half life of at least 10 years generate at least one sufficiently energetic beta particle and be readily available It was decided to use Sr 90 with its highly energetic beta producing daughter Y 90 as the radioisotope for this experiment Sr 90 is readily available from distributers a 10 mCi source was obtained from Isotope Products Laboratories With a half life of almost 30 years it would work well in a long duration battery and would allow for a large amount of fairly steady state testing The Y 90 daughter does have a small abundance lt 1 0E 3 of a gamma but this was deemed to be sufficiently low enough to ignore MATERIALS AND EXPERIMENTAL DESIGN Detailed below are the components used in making the system along with how key components were crafted Primary System Components Table 2 Pressure System Component List Type Serial Model Description Amount Pressure R2 10 40 8 O D 40 000 psi 1 highpressure com Vessel 10 Inside Depth 4340 alloy steel 160 lbs 3 pressure tubing ports Coupling 30 21HF6NMB 3 8 High Pressure to 4 highpressure com Adapter Female NPT Pipe 30 21HM6NMB 3 8 High Pressure to 4 highpressure com Male NPT Pipe High Pressure 60 11HF6 2 Way Straight Valve 3 highpressure com Valves 60 15HF6 3 Way 2 Stem Connection 8 highpressure com Valve Elbows Tees 60 22HF6 High Pressure Elbow
68. ss mirrors which is illustrated by region 5 in Fig 2 Any energy deposited elsewhere was considered lost Idealized numbers were used for fluorescence and photon conversion efficiencies Excimer gases and fluorescence emission have been extensively studied and the maximum fluorescence efficiency 7 for argon is 50 1 The photovoltaic energy conversion efficiency Npy for a Si cell using the 129 nm excimer photon has a theoretical maximum of 5 7 10 This is shown in equations I and 2 Driving potential efficiency and fill factor were assumed to be ideal 0 5 and 1 respectively and are defined in more detail in Oh s paper 6 E Npy S x Driving Potential Ef ficiency x Fill Factor 1 R 0 5 x 1 0 057 2 Npy l GET xX U 2 82 The greatest loss in efficiency for this system occurs with reflections due primarily to the unoptimized design of the waveguide Aluminum was used as it has a gt 80 reflectivity 15 for the deep ultraviolet photons of the argon excimers but the number of reflections any photon may undergo is highly variable In addition the rod used to hold the source and the lead plug that topped it were not reflective A coating of aluminum and MgF was deposited on each but resulted in a milky and dull in appearance due to the incompatibility of the surface for mirror finishes It was assumed that all photons striking either the rod or lead plug were lost With these two factors the vast majority of photons crea
69. t FAX 573 882 7940 10 mCi Strontium 90 source handling requirements ERR NEA sin INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 d Other students while source is in experiment and are they are in the room they must wear their own whole body dosimtery e Absolutely no visitors allowed when source is not in safe 15 Pertinent Questions to ask Pre Job Brief a Have we done this before and how i Yesandno gt gt b What are the Critical Steps i Pre Job analysis c What Mistakes might be made i Potential for over exposure to staff ii Potential for over exposure to other students conducting research in the lab d What is the worst that could happen i Dose to members of the public e What are our defenses i Adequate pre job briefs ii Adequate and quality surveys iii Proper source handling to include time and distance iv Regular surveys v Frequent checks 16 Conclusion The work is not outside the scope of AU or staff abilities Signatories for Work to begin Date Ailu Date amp Til Date Originator Reviewer RSO Page 4 of 5 67 Environmental Health amp Safety Research Park Development Building University of Missouri Columbia Columbia MO 65211 3050 Radiation Work Permit 2011 06 aon FAX 573 882 7940 ENVIRONMENTAL MANAGEMENT 882 7018 INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 10 mCi Strontium 90 source handl
70. tching of range of the radiation with the scale of the transducer and the basic principles of PIDEC were demonstrated 86 The efficiency of the system was very low due to losses in beta energy outside of the gas plenum and photon absorption Both of these factors may be improved Increasing the size and pressure of the gas plenum will increase the fraction of beta energy absorbed by the gas Mirroring the source holding rod and lead shield plug will be critical in the improvement of photon transport efficiencies as it is currently part of the largest loss factor Decreasing the size of both the steel rod and the lead plug will limit loss of energy inside of the system as well 87 REFERENCES 10 11 12 13 14 15 16 17 18 19 20 Prelas M A et al A two step photon intermediate technique for the production of electricity chemicals or lasers in nuclear energy conversion Progress in Nuclear Energy 1990 23 3 p 223 240 Rappaport P The Electron Voltaic Effect in p n Junctions Induced by Beta Particle Bombardment Physical Review 1954 93 p 2 Windle W F Pm 147 Silicon Betavoltaic Battery Feasibility in Report Sandia Corporation SC RR 65 6711966 p 25 Uehara Y et al High power argon excimer laser at 126 nm pumped by an electron beam Optics Letters 1984 9 12 Barbet A N Sadeghi and J C Pebay Peyroula Decay of metastable xenon atoms Xe P3 in a xenon afterglow J Phys
71. ted were not in the narrow window where they could be collected by the photovoltaic making this factor the greatest loss in efficiency Each Sr 90 decay eventually produces two betas As the half life of the daughter product Y 90 is much shorter than the half life of the parent Sr 90 these two betas are assumed to be in secular equilibrium and so both are assumed to occur simultaneously Sr 90 decays into Y 90 by emitting a beta particle that has a maximum energy of 0 546 MeV and an average of 0 18 MeV Y 90 then also undergoes beta decay forming stable zirconium 90 with a beta that has a maximum energy of 2 28 MeV and an average of 0 92 MeV Using these average beta energies of 0 18 MeV and 0 92 MeV for Sr 90 and Y 90 respectively total power output of the source Pogurce 18 Energy per complete decay 0 18 MeV 0 92 MeV 1 1 MeV 3 decays Sr 90 source activity 10 mCi 3 7 x 103 SE 4 second MeV decays 1 6022 x 10713 Joule 1 1 x 3 7 x 108 x _____ _ decay second 1 MeV ou 6 5 x 107 J se Jones Watts 5 cond SES 83 Piource 6 5 xX 1075W Taking the highest value reached in Fig 3 0 24 x 10710A photodiode current E P hotovoltaic Io mm 1 5 x 10 W 6 P A 0 16 W responsivity Gives an absolute efficiency of photovoltaic 0 40 Nabs eee x 100 Ur 2 3 x 10 0 7 Ee 6 5 x 10 5W Using the above efficiencies we define the absolute uncertainty as all others mu
72. the remote reaches of space Even more ordinary hand held devices would benefit from a battery that would not need to be replaced for the lifetime of the device Here a proof of concept is demonstrated for a PIDEC system using Strontium 90 Sr 90 that shows no damage to the photovoltaic over more than 150 hours of exposure time and with a half life of 28 78 years it would out last chemical batteries Radiation damage is prevented by both a lead shield and by the intermediary used to generate the photons that are used for power This device was built to test various pressures in order to show increasing energy capture by the gas plenum as the pressure increased and thereby improving the scale length Testing the fundamentals involved testing the Sr 90 source with conventional photovoltaics to see how long they would last before being rendered inoperable This gave a baseline amount of time expected for other similar photovoltaics without needing to destroy expensive equipment These tests showed that with the high energy betas coming out of the source a photovoltaic would lose functionality rapidly and be inoperable in less than 5 minutes Radiation hardened photovoltaics undergoing bombardment by beta particles with less energy are able to last much longer but they do so at reduced efficiency With that completed a high pressure system was built that allowed for pressures ranging from vacuum up through 60 000 psi However for this test only
73. urce handling requirements INDUSTRIAL HYGIENE OCCUPATIONAL SAFETY 882 7018 RADIATION SAFETY 882 7018 Subject 1 Statement of Problem Issue Inform the staff under Dr Tushar Ghosh s authorization number 00933 of the hazards presented when using the 10 milliCurie mCi Strontium 90 source in Lafferre Hall room W0030 This will be done prior to the return of the source to the user by the health physics office This training is done to inform the user s of the potential hazards associated with the use of the source 2 General Discussion In order to continue use of the 10 milliCurie mCi Strontium 90 source in Lafferre Hall room W0030 an initial ALARA training for the user s will be conducted to inform them of the hazards presented by the source handling requirements inclusion of dose 1ate s from the source in various configurations dosimetry requirements storage requirements and an understanding of how to limit dose to workers This training should be reinforced annually and at any time deemed necessary by the Radiation Safety Officer or Health Physics Office personnel 3 Proposed Basic Work scope of support organizations and offsite Vendors and Associated Cost The Sr 90 source is stored inside a steel source holder that is then placed inside a lead lined syringe holder that screws together and is then locked inside a safe that requires a key and an access code This is the required storage configuration when source is not in use

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