Simulated sources containing $sup 252$Cf equivalents of 0.1 to 1.0 milligrams were prepared. Samarium was used as the simulant in a modified chemical plating technique similar to that used to prepare palladium-californium oxide cermet for industrial applications. The length of the platinum-10 percent iridium doubly encapsulated source with its protective sheath is 0.545 in. (14.1 mm). Outside dia of the source, including its sheath, is 0.109 in. (2.8 mm). Existing ''Brachytrons'' can accommodate this source form. This capsule system will withstand internal gas pressures from helium due to alpha decay and fission gases from a 1 mg $sup 252$Cf source after ten years if the source is subjected to a maximum temperature of 800$sup 0$C, the theoretical temperature of an accidental fire. Under these conditions the safety factor is 3. The capsule system is being tested with tracer amounts of $sup 252$Cf to ensure that it will withstand adverse service conditions as well as tests specified for Special Form Materials. (auth

Boulogne, A.R.

Walker, V.W.

UNT Digital Library

FABRICATION OF INTENSE NEUTRON SOURCES FOR MEDICAL APPLICATIONS by A. R. Boulogne and V. W. Walker Savannah River Laboratory E. I. du Pont de Nemours & Company Aiken, South Carolina 29801 For presentation at the Californium-252 Utilization Meeting San Diego, California November 4-6, 1975 " .. . ' Q7-76-1!1i/- 3 DP-MS-75-103 r-----NOTICE----~ This rcporl was prep11ed as an account or work sponsor~ by the United Sta tes Government. Neither the United States nor the United States Ener ~:arch and Development Administration, nor any ~ bco empk>yees, nor any of their contractors su ntracton:, or t~eir employees, makes an~ ~nty, express or implied, or assumes any legal liabili ty or rcsponsibi:'.ity for the accuracy, completeness or usefu l~ess of any tnformation, appantus, product or prof ?C" d~osed, or represents that ils use wouJd not in nnge pnvately o wned rights. This paper was prepared in connec.~ion with work under Contract No. AT(07- 2)-l with the U.S. Energy Research and Development Admi nistration. By acceptance of this paper, the publisher and/or recipient acknowledges the U.S. Government's right to retain a nonexclusive, royalty-free license in and to any copy-right covering this paper, along with the right to reproduce and t o author i ze other s to reproduce all or part of the copy-righted paper. I . ~ DISTRIBUTION OF THIS DOCUMH T IS UNLIMlTEil DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. FABRICATION OF INTENSE NEUTRON SOURCES FOR MEDICAL APPLICATIONS A. R. Boulogne and V. W. Walker Savannah River Laboratory E. I. du Pont de Nemours & Company Aiken, SC 29801 ABSTRACT DP-MS-75-103 Simulated sources containing 252 Cf equivalents of 0.1 to 1.0 milligrams were prepared. Samarium was used as the simulant in a modified chemical plating technique similar to ~hat used to prepare palladium-californium oxide cermet for industrial appli-cations .1 The length of the platinum-10% iridium doubly encapsu-lated source with its protective sheath is 0.545 in. (14.1 !lllll). Outside diameter of the source, including its sheath, is 0.109 in. (2. 8 mm). Existing "Brachytrons" can accommodate this source form. This capsule system will withstand internal gas pressures from helium due to alpha decay and fission gases from a 1 milligram 252 Cf source after ten years if the source is subjected to a maximum temperature of 800°C, the theoretical temperature of an accidental fire. Under these conditions the safety factor is 3. The capsule system is being tested with tracer amol..ll'lts of 252 Cf to ensure that it will withstand adverse service conditions as well as tests specified for Special Form Materials. The information contained in this articie was developed during the course of work under Contract No. AT(07-2)-l with the U. S. Energy Resear~h and Development Administration. - 1 -INTRODUCTION . The first 252Cf sources for radiotherapy research were pre-pared at the Savannah River Laboratory about ten years ago. 2 ' 3 Initially, these sources resembled the classical radium needles familiar in clinical radiotherapy. Eventually, afterloading cells and applicator tubes were supplied to medical evaluators, and all medical sources were improved by the use of californium-palladium cermet wire sheathed in precious metal alloy as source material.~,s The most recent medical source form produced in quantity for therapy research was described in a previous presen-tation at this meeting. 6 The purpose of my presentation is to describe our progress in the preparation of physically small, intense 252Cf sources for remote afterioading. Remote after-loading is used by many hospitals in the U.S. and abroad to avoid radiation exposure to personnel caring for patients. 7 At least five· designs of remote afterloaders are available - the "Curietron" in France, the "Cervitron-11" in Switzerland, the "Cathetron" in England, the "Hicesitron" in U.S., and the "Brachytron" in Canada. The afterloading sources described in this paper were designed specificially for the "Brachytron," manufactured by AECL, Ottawa. SLIDE l (REMOTE AFTERLOADER) The first remote afterloader in the United States to use cycling sources was installed for clinical use at Memorial Hospital, New York in 1967. Traditionally, the remote afterloader has physically small, intense 6 °Co sources attached to the ends of - 2 -long cables which pass through the wall of the shielded cell or treatment room, With the patient in the treatment room and the shielded-room door closed, the sources are advanced to the treat-ment positio~ in previously installed applicators by means of th~ cables and a mechanism in the control system outside the treatment-room wall. Patient control is maintained by means of an interco~ and closed-circuit television system. Source position control is achi~ved by a system of count rate meters, lights, and buttons and visually through a shielding window. Source-cycling control is maintained visually and manually or automatically through ·a system of pre-set stops and friction roller~ which is controlled by a scaled oscillating device. Our goal is to adapt 2 5_2Cf sources containing between 0.1 and 1 milligram 252Cf to use in remote after loaders in the United States and Japan. SLIDE 2 (6 °Co SOURCES AND CATHETERS) Hardware for the "Brachytron" was designed for use with 6 °Co sources. Straight or curved catheters are available. The "st;i.ff length" of the source is dictated by the minin)l,lm ct.n:-vature radius through which the source must travel during cycling. T~is slide · shows that catheters exist which will accept sources whose "stiff length" is less than 0. 600 in. (15. 24 mm) . Catheters exist which will accept 60 co sources containing up to 10 6 °Co pellets. The "stiff length" of such a source -is 0 .960 in. (24. 38 mm). Our goal has been to prepare a 1 milligram 252Cf source with the shortest possible "stiff length" and the greatest possible integrity. - 3 -·SLIDE 3 (252Cf 11 BRACHYTRON" SOURCE) We have prepared simulated 2 52Cf "Brachytron" sources con-taining up to 1 milligram 252Cf equivalents using samarium as the 252Cf stand-in. This design consists of a double encapsulation in platinum-10% iridium alloy which is protected by a sheath crimped to the 1/16-inch diameter of a 304L stainless steel, 7 x 7-strand cable. This connection withstood the required 100 pounds of tensile force. "Stiff length" of this assembly is 'Vl.4 mm; diameter is 2 .8 mm. The assembled source will pass through existing catheters. Inner and outer capsules have been fabricated from Pt-10% Ir tubing and by machining swaged Pt-10% Ir rod. The encapsulated source was welded with a Linde PWM-4 Plasma Needle Arc Welder fitted with a PT-10 Plasma Needle Arc Torch. Pr~paration of the 252Cf source pellet and integrity tests of the encapsulation will be described in subsequent slides. SLIDE 4 (252 Cf JAPANESE REMOTE AFTERLOADING SOURCE) Neutron sources for 252 Cf research in Japan can be slightly larger in physical size and must contain ap~roximately 100 to ·200 micrograms 252Cf. The source carrier that is provided to us will accept a doubly encapsulated source 11 mm long by 4.7 mm in diameter. The. double encapsulation is made of platinum-10% iridium alloy and is plasma arc-welded. We have prepared ten of these sources for physical testing, which is in progress. - 4 -SLIDE 5 (252 Cf203 -Pd POWDER BY CHEMICAL PLATING) A chemical plating technique has been used for about 3 years to prepare palladium-californium oxide cermet powder from which industrial 252Cf neutron sources are made. Since "Brachytron" sources are much smaller and contain more 2 5 2Cf than other sources for medical or industrial applications, we modified our chemical plating technique used to prepare industrial cermet pellet$ and wire to produce smaller batches of powder -containing more 252Cf in greater yield. A synthetic feed solution containing samarium nitrate plus typical oxalate-forming impurities found in 252Cf feed stocks is added to the small glass reaction vessel. The volume of solution is chosen so as to provide up to 1 milligram 252Cf equivalents. Approximately 40 milligrams oxalic acid in solution is added. The mixture is sparged with air through a hypodermic needle immersed in the solution. After californium oxalate has precipitated, 1 ml of 85% hydrazine hydrate is adde~ and the mixture is again sparged with air. Air sparging promotes mixing and the formation of finely divided oxalate particles when the hydrazine hydrate is added. This dispersion promotes uniform coating, or plating, of the oxalate particles during subsequent reduction of palladium ion to metal and precipitation of the metal around the oxalate particles, Finally, 45 milligrams of palladium nre introduced as a solution of palladium tetramine dinitrate while the oxalate - 5 particles are kept suspended by air sparging. When the reduction of palladium ion to palladium metal by the hydrazine hydrate is complete, the oxalate particles have been coated with palladium metal. The metal-coated precipitate is permitted to settle under an argon atmosphere. The supernate is aspira~ed to a recovery vessel. The reaction vessel is lowered into the furnace and valved to the argon gas line, and the precipitate is dried under argon at 100°C. The dried powder is calcined under a 96% helium·~ 4% hydrogen gas mixture for approximately 30 minutes. The calcined powder is then cooled from approximately 200°C to room temperature in an argon atmosphere. SLIDE 6 (252Cf20rPd CERMET PELLET FABRICATION) The glass reaction vessel containing the powder is designed to be mated and sealed to a polished metal funnel so the entire charge of metal powder can be transferred through the funnel to a compaction die. A vibrator is used if necessary to aid in transferring the small powder batch. The compaction die has an inside diameter of only 0.050 in. (1.27 mm), so the ram is 0.0495 in. (1.21 mm) x 2 in. (50.8 mm) long and must be supported throughout its travel in the die. Ram support bushings are assembled on top of the die after the powder charge has been transferred. · As the powder is pressed into a pellet, ram support bushings are removed sequentially until the pellet is formed. This "green" pellet is pressed at approximatdy 12,500 psi. The pellet is next transferred to a combustion tube - 6 -and sintered. Sintering takes .place under 96% helium - 4% hydrogen up to 1000°C and under argon at 1050°C for two hours. The sintered pellet is coined in a special die to a 1.17-nnn diameter. Coining is performed at approximately 15,600 psi. Average length of 10 coined pellets was 0.070 in. (1.8 mm). SLIDE 7 (CAPSULE INTERNAL GAS PRESSURES) Maximum permissible internal. gas pressures at 25°C and 80Q°C in platinum-10~6 iridium capsules of the "Brachytron" design were calculated using the latest published data available for tensile strengths at elevated temperatures. Internal gas pressure~ from helium due to alpha deyay and from the fission gases was calculated using currently accepted nuclear data for half-life and spo~taneous fission decay of 252Cf. These data are summarized in the s~ide. At the theoretical fire temperature of 800°C, the pri~ary capsule can accommodate a !-.milligram source with a safety factor of approximately 1.5. The secondary capsule, ~der the same conditions, will provide an additional safety factor of approxi-ma.tely 3. SLIDE 8 (CAPSULE SAFETY TESTS) Using tracer amounts of 2 52Cf, the capsule system will be subjected t:o .tests to simulatt:l expected .a.dvers~ service cqndi tiqns. four tests (impact, percussion, heating, and immersic:m) are specified in ERDA Manual Chaptei• 0529-05, "Safety Standards .for the Packaging of Radioactive and Fissile ~aterials, Annex 4, .Tests - 7 -' for Special Forl!l Materials." Four other tests (steri 1i zation, pinching, crushi.ng, and abrasion), though not spec,if,ied in the ERDA Manua~ will be conducted to demonstrate th~ s~fety of ti!~ capsule system tmder conditions which might be expected during service. These tests will also satisfy reql.iirements of the Nuclear Regulatory Commission's Regulatory Guides 6.1 ("Leak Testing Radioact~ ve Brachytherapy Sources") and 6; 2 ("Integrity and Test Sp~cifications for Selected Br~chytherapy Source~") ho.th dated Februa+:y 1974. - 8 .. REFERENCES 1. A, R. Boulogne .. "Californium-252 Encapsulation and Shipping at Savannah River Laboratory." Proc. ANS Topical Mee.ting, Austin, Texas. September 11-13, 1972. USAEC Report CONF-720902, p 51 (1972). · 2, A. R. Boulogne and A. G. Evans. "Ca,lifornium-252 Neutron Sources for Medical Applicati0ns." Int. J, Appl. Radiat. Iao. 20, 453 (1969). 3, C. N. Wright, A. R. Boulogne, W. C. Reinig, and A. G. Evans. "Implantable Californium-25~ Neutron Sources for Radiotherapy." Radiology 89, (No, 2) 337 (1967). 4. W, C. Mosley, Jr., P. K. Smith, and P. E. McBeath. "Neutron Sources of Palladium-Californium-252 Ox~de Cermet Wire." ANS Topical Meeting, Austin, Te~as, September 11-13, 1972. USAEC Report CONF-720902, p 51 (1972). 5. V. W. Walker. "Equipment and Operations for Preparing 252cf · Neutron Sources·for Interstitial Cancer Radiotherapy Research." Accepted for presentation at the Remote Systems Te~hnology Conference of the American Nuclear Society - November 16, 1975 at San Francisco, California, and for publication in the con-ference proceedings. 6. P. H. Permar. "Manufacture of 252 Cf Seed Assemblies for Int~r­stitial Implants." Ca.li:fornium-252 Utilization Meeti.ng, Nov~m­b~r 4-6, 1975, San Diego, California. 7. Basil S. Hilaris, M.D. "A Manual for Brachytherapy," pp 75-81. Memorial Hospital, New York, Department of Radiation Therapy, Second Edition (1970). - 9 -SLlDE l Remote Afterloader - 10 -A No. of Pellets Two Ten 0.393 in. SLIDE 2 B c Source length "Stiff" length inch mm ~ mm 0.350 8.89 0.600 15.24 0.710 18.03 0.960 24.38 6°Co SOURCE (B) /: '· R =Minimum Curvature Radius inch .!!!!!!. 2.00 50.8 5.00 127.0 ~~~~~~~~~ -...,~-- ----------------J,Q:===i 262.3 mm 6 °Co Sources and Catheters - 11 -~--· __ . ___ 0.545 Inch __ I 14.1 mm Stainless Steel Cable Protective Sheath Pd- ~ 52Cf203 Pellet SLIDE 3 2 s 2 cf 11 Brc3,chytron 11 Source - 12 -0.109 inch 3.77mm Pt.,.10% Ir Capsule rlm(]j ~I Pt-10%Ir End Plug~ ·SLIDE 4 ~0.436in.~ I II.Imm I --0-4·.~r-~~· Doubly - Encapsulated Neutron . Source .. ,..,.,_ Pd - 252Cf 20 3 Pt-10% Ir · . Pel let Capsules Japanese 252 Cf Afterloading Source ~ 13 -,, Trap 8 ~ Bubbler Hypodermic Needle -~ Precipitator Vessel Air Argon ·96°/o He -4°/o H2 ,.- Furnoce SLIDE 5 252 Cf20rPd Powder by Chemical Plating - 14 -1. Hydraulic Press 2 . Prnr.ipitator Vessel 3. Powder Funnel 4 . Compaction Die 5. Ram 6. Ram Support Bushings 7. A3seml.Jly Clamps 2 ~, \ 4 5 6 WQ@#h! "WI@"' f.I rsa. B 7 ; SLIDE 6 252Cf203-Pd Cennet Pellet Fabrication - 15 -.-- . Press!Cl'e resi) at 25°C Pr>ess!Cl'e resi) at 8.00°~ A[ter 1 o u.r Deaau A[ter 1 O '.fl' DeC!ait Capsul.e 0,2 1.0 2.0 o, 2 1,0 2.0 Desaription Permissible (milligrams) Permissible (miUigrams) Primarl 8,500 155 715 1,430 4,500· 605 2, 780 5,560 Secondary b 10,445 lio 500 1,000 5,610 420 1,940 3,875 a. Theoretical temperature during an accidental fire. b. Platinum - 10% Iridium alloy. SLIDE 7 Capsule Internal Gas Pressures "· ... · - 16 -•. Impact - free drop Sterilization Percussion Pinching Heating - Crushing Immersion Abrasion a. Specified and described in AEC Manuq.l Chapter 0529-05, "Safety Standards for the Packaging of Radioactive and FissPe Materials, Annex 4, Tests for Special Form Materials." · SLIDE 8 Capsule Safety Tests - 17 -

Fabrication of intense neutron sources for medical applications

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Fabrication of intense neutron sources for medical applications

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