US3873651A - Freeze drying method for preparing radiation source material - Google Patents

Freeze drying method for preparing radiation source material Download PDF

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Publication number
US3873651A
US3873651A US252643A US25264372A US3873651A US 3873651 A US3873651 A US 3873651A US 252643 A US252643 A US 252643A US 25264372 A US25264372 A US 25264372A US 3873651 A US3873651 A US 3873651A
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californium
palladium
crystals
refractory
temperature
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US252643A
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English (en)
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Jr Wilbur C Mosley
Paul K Smith
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US Atomic Energy Commission (AEC)
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US Atomic Energy Commission (AEC)
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Priority to US252643A priority Critical patent/US3873651A/en
Priority to CA168,037A priority patent/CA994999A/en
Priority to GB1650573A priority patent/GB1413712A/en
Priority to JP48052074A priority patent/JPS4947797A/ja
Priority to FR7316987A priority patent/FR2184691B1/fr
Priority to BE131022A priority patent/BE799424A/xx
Priority to IT24014/73A priority patent/IT987289B/it
Priority to DE2323865A priority patent/DE2323865A1/de
Priority to SE7306667A priority patent/SE385783B/xx
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Publication of US3873651A publication Critical patent/US3873651A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • F26B5/06—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum the process involving freezing
    • F26B5/065—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum the process involving freezing the product to be freeze-dried being sprayed, dispersed or pulverised
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
    • G21G4/00—Radioactive sources
    • G21G4/02—Neutron sources

Definitions

  • a solution containing radioisotope and palladium values is atomized into an air flow entering a cryogenically cooled chamber where the solution is deposited on the chamber walls as a thin layer of frozen material.
  • the solvent portion of the frozen material is sublimated into a cold trap by elevating the temperature within the chamber while withdrawing solvent vapors.
  • the residual crystals are heated to provide a uniformly mixed powder of palladium metal and a refractory radioisotope compound.
  • the powder is thereafter consolidated into a pellet and further shaped into rod. wire or sheet form for easy apportionment into individual radiation sources.
  • the present invention relates to radiation source materials, particularly those including rare and expensive radioisotopes.
  • the spontaneous fission of californium-252 provides a substantial neutron flux but this element is extremely difficult and expensive to produce and fabricate.
  • This element is produced by the long and costly procedure of successive neutron capture in nuclear reactors, beginning with, for instance, uranium-238. Handling this radioisotope is both difficult and hazardous due to neutron fission fragments and alpha emissions. Consequently, californium-252 must be provided in a material form that can be conveniently and safely allotted into precise microgram and milligram quantities for encapsulation as a neutron source with a minimum of process loss. In respect to safety. this isotope must be contained in a refractory and stable form to prevent its escape should the encapsulation fail during use or storage.
  • Actinides such as actinium-227, plutonium-238, curium-242 or 244, americium-24l or 243 as well as other transplutonium isotopes have potential as heat, gamma, beta and alpha sources. Like californium-252 these isotopes are produced by the costly process of neutron capture in a nuclear reactor. Other useful radiation source isotopes such as polonium-ZlO and cobalt-6O are similarly produced.
  • Fission and decay products including cesium-137, strontium-90, thulium-l70 or 171 and promethium- I47 also have use as radiation sources and like the above-mentioned isotopes, are difficult to separate, handle and contain safely.
  • Prior radiation source materials have included salts of radioisotopes in solution, in precipitate or oxide form.
  • Californium-252 can be transferred or stored in an acidic aqueous solution of californium nitrate, as a californium oxalate precipitate, perhaps including a carrier metal oxalate, or as californium oxide or oxysulfate obtained by incinerating an ion exchange resin containing californium ions.
  • the allocation ofa californium material in any of these forms into precise quantities followed by encapuslation to a form usable as neutron sources can be a difficult process if losses are held to an extremely small level as required.
  • a liquid solution containing a uniform mixture of pallidium and californium isotope values is atomized into a liquid mist entrained within an air flow.
  • the mist is sprayed into a vessel cooled to a sufficiently low temperature to freeze a thin layer of solid crystals onto the inside vessel walls.
  • a substantial portion of the solvent is sublimated from the crystals by withdrawing solvent vapors from the vessel while maintaining the crystals at a temperature below their melting point.
  • the residual crystals are then heated to remove the solvent associated with crystalization and to dissociate the califorium isotope and palladium values to refractory and elemental forms.
  • the resulting powder comprising a uniform dispersion of the refractory californium isotope throughout the palladium metal, can be consolidated into an integral form and further shaped into a rod, wire or sheet for convenient apportionment into individual radiation sources.
  • FIG. 1 is a schematic showing of one apparatus that can be employed in practicing the present invention.
  • FIG. 2 is an illustration of one form of radiation source material that can be produced by the method of the present invention.
  • FIG. 1 the apparatus is shown with an assembly 11, including a first vessel 13 removably disposed within a cooling device 15 and a second vessel 17 partially submerged in a container 19 of refrigerant 21.
  • This particular arrangement of the apparatus is employed in performing one of the several steps of the present method which will be described hereinafter.
  • a furnace 23, adapted to receive and heat vessel 13 is shown for use in a subsequent step.
  • Assembly 11 includes an injection tube 25 having manifold inlets 27 and 29 for gas and liquid feed solutions.
  • Tube 25 is directed to discharge towards the lower wall surfaces of vessel 13, but extends only part way down the vessel to a point sufficiently spaced from the bottom to avoid splattering.
  • An outlet tube 31 communicates with the top portion of vessel 13 and branches into a valved vent outlet 33 and a valved inlet tube 37 extending into second vessel 17.
  • Inlet tube 37 is directed to discharge towards and near the lower. cold surfaces of vessel 17 to freeze and trap condensible material as a deposit of ice.
  • a vacuum source 39 is connected through a valved conduit 35 to the inner volume of vessel 17 to evacuate noncondensible gases from within the assembly during sublimation.
  • assembly 11 can be laboratory type implements as illustrated.
  • Vessel 13 can be adapted for positioning within cooling device as shown. within furnace 23 or refrigerant container 19 for performing the several process steps.
  • Refrigerant 21 within container 19 is one that is capable of maintaining a very low cryogenic temperature such as liquid nitrogen or dry ice and acetone.
  • Cooling device 15 can be a more moderate source of refrigeration such as a thermoelectric cooler or a liquid ammonia or freon cooled device. It is sufficient for device 15 to maintain a cold temperature that is several degrees Centigrade below the melting point of the material to be freeze dried.
  • Furnace 23 can be a conventional electric or other type furnace that can produce temperatures of several hundred degrees Centigrade.
  • vessel 13 is placed within container 19 in contact with refrigerant 21 maintained at a cryogenie temperature.
  • a solution or slurry containing palladium valves. and a dissolved or colloidally dispersed californium isotope salt. such as californium nitrate or oxalate. is introduced into inlet 29 of injection tube 25.
  • the solution can include water, an alcohol or some other suitable liquid substance as a solvent.
  • An inert gas or air is simultaneously introduced into inlet 27 to atomize the solution into a mist as it is sprayed from tube towards the lower walls of vessel 13.
  • the walls of vessel 13 are maintained at a temperature substantially below the freezing point of the solution to effect rapid and complete freezing of the solution as a thin layer of frozen crystals on the vessel walls.
  • the frozen crystals include dissociable salts of the californium isotope and palladium. as well as the solvent from the original solution.
  • the dry inert gas flow is continuously withdrawn through vent outlet 33 with valved inlet tube 37 closed while the freezing operation is being performed.
  • thin frozen layers e.g.. about 0.1 to 0.5 millimeters, are preferred to allow removal of the heat generated in radioisotope disintegration before the central portion of the layer remelts.
  • the relatively large exposed surface of the thin layer of frozen solution is beneficial in performing the following vacuum drying step.
  • vessel 13 is disposed in cooling device 15 and the second or trap vessel 17 is par tially submerged in refrigerant 21 as is shown in FIG. 1.
  • the temperature of vessel 13 is elevated to a level just several degrees Centigrade below the melting point of the solution.
  • Valved inlet tube 37 is opened with vent outlet 33 closed to draw solvent vapors from vessel 13 into trap vessel 17.
  • Vacuum source 39 is engaged to evacuate the assembly to a few millimeters of mercury absolute pressure. Solvent vapors discharged from inlet 37 will contact the cold lower surfaces oftrap vessel 17 and freeze. thus capturing any of the radioi' sotope that may be entrained with the vapors.
  • the solvent within the frozen solution is sublimated into trap vessel 17 leaving crystals of hydrated salts 41 having a uniform distribution of dissociable californium isotope salt and palladium salt within vessel 13.
  • Drying of crystals 41 is completed by transferring vessel 13 to furnace 23 and slowly warming to a temperature of between about to 300C. A flowing inert gas is introduced into inlet 27 and discharged through vent outlet 33 to remove solvent vapors from the assembly. During this drying step at elevated temperature, the water or solvent bound within the hydrated salt crystals is removed to leave a dry salt residue of powder consistency.
  • the gas flow is changed to a slightly reducing composition. for instance 4% H 967( He gas. and the temperature elevated to a sufficient level to dissociate the palladium salt to the elemental state and the californium isotope salt to a refractory form such as an oxide.
  • the volatile portions of the salt or salts are discharged with the gas flow through outlet 33 as this step is performed.
  • the powder from the above dissociation step is shaped by metallurgical processes to form a pellet. rod. wire or sheet.
  • the powder is compacted into a pellet and heated to a temperature just below where significant sintering begins in a slightly reducing atmosphere. This heating step ensures that all of the salt has dissociated to refractory and elemental form before the palladium metal matrix is closed by sintering.
  • the pellet is then heated to a sufficient sintering temperature in an inert gas atmosphere to fuse the palladium metal particles together in an integral matrix.
  • the completed pellet will contain a uniform dispersion of the californium isotope sealed within the palladium metal matrix and can be encapsulated either along or with other pellets for use as a radiation source. If desired.
  • the pellet or pellets can be enclosed within a tubular sheath of noble metal and elongated by rolling, swaging, drawing or other shaping processes into a rod or wire form with a noble metal cladding.
  • Various cross sectional configurations such as circular, square. rectangular. etc., can be adopted for the pellet, rod or wire members.
  • Sheets of radiation source material can be provided by suitable rolling or pressing processes.
  • FIG. 2 illustrates a rod or wire form of the radiation source material.
  • An outer cladding 45 of noble metal protects and contains an inner core 47 of palladium metal matrix and refractory californium isotope material. Small particles 49 of the californium isotope in refractory form are shown uniformly dispersed throughout the palladium metal matrix.
  • a measured length of this wire can be removed with a conventional pinch cutting tool having rounded edges such as one used in pinch welding.
  • a sealed end portion as shown at 51 can thereby be provided both on the severed length and the remainder of the wire.
  • the severed length of wire can be encapsulated to provide a radiation source of predictable strength.
  • EXAMPLE I A solution containing 10 grams of palladium tetramine dinitrate, 10 milligrams of samarium nitrate and 5 nanograms of californium-252 in about 50 cc water was prepared and atomized into a mist within a flowing air stream. The mist was rapidly frozen into a thin solid layer on the lower portion of a vessel cooled by liquid nitrogen at about -l96C. The resulting frozen crystals were allowed to warm to -lC and maintained at this temperature for about 10 hours while withdrawing solvent vapors from the vessel at an absolute pressure of less than 2 mm. mercury. The solvent vapors were passed into contact with cold surfaces of a water trap vessel submerged in liquid nitrogen at about l96C.
  • the resulting powder was pressed at 15,000 psi to form a cylindrical pellet, heated to lO0OC in 4% H He gas and sintered on an alumina setter at 1300C in argon for 30 minutes.
  • the sintered pellet was enclosed in a palladium metal sheath and swaged into a 25 cm. long wire of about 1 millimeter square cross section in several reduction steps interspersed with annealing at 800C in argon.
  • the wire was found to have both samarium and californium distributed along its length to within less than 5 percent deviation from uniformity. Moreover. substantially I00 percent of the californium and samarium within the feed solution was detected within the final wire product.
  • EXAMPLE II A similar procedure to that of Example I is performed with about 1 gram of palladium as nitrate, 5 milligrams of californium-252 in nitrate solution and no samarium in the feed solution. An approximately centimeter long palladium clad wire is produced having a substantially uniform distribution of californium along its length.
  • a low intensity neutron source material is provided without introducing a carrier element in addition to the californium and palladium.
  • a slurry containing about 5 grams of palladium nitrate and less than 10 nanograms of californium nitrate is prepared and processed as in Example I.
  • a palladium clad wire having a uniform neutron emission of about 10 neutrons/cm-sec throughout its length is produced.
  • isotopes of elements other than californium and samarium have not been tried in this process, it is reasonable to assume that a large number of other radioisotopes could be processed by the present method. Any radioisotope which forms a refractory compound on the decomposition of a dissociable salt could most probably be employed. Most lanthanides and actinides, as well as other metallic cations, form soluble nitrate solutions and nitrate salts crystalized from these solutions can be dissociated to refractory oxides. Salts other than nitrates such as carbonates, and phosphates might also be used in some instances.
  • a colloidal dispersion in solution of cesium, noble metal and uranyl carbonates could be frozen to form crystals which could then be thermally dissociated into water, carbon dioxide gas and powder particles having a uniform distribution of Cs U O within palladium metal.
  • Noble metal cations other than palladium for instance platinum, ruthenium, rhodium, silver, osmium, iridium, and gold can be crystallized from solution along with the radioisotope salt in practicing the present invention.
  • palladium has been found to be a preferred matrix material for use in a radiation source after consideration of numerous properties of this noble metal.
  • palladium resists oxidation has a high melting point (l552C), alloys readily with californium and other elements, is ductile, dissolves in concentrated nitric acid for recovery of the radioisotope, gives little gamma interference on neutron activation, and is less expensive than many other noble metals.
  • the method of the present inven tion can be used to prepare radiation source materials of uniform intensity including neutron, gamma, beta, alpha, heat or a combination of various type sources.
  • the method reduces the risk of contamination associated with other methods employing the blending of dry powders or of blending powders with solutions.
  • a high yield of the radioisotope from feed to product is obtained even in the preparation of low intensity sources due to the complete freezing of substantially all of the feed solution and the gentle process of removing the solvent therefrom by sublimation.
  • the radiation source material produced by the present method will include a radioisotope in refractory form uniformly dispersed and sealed within a stable noble metal matrix material.
  • a measured portion of the material can be subdivided and encapuslated for use in an individual radiation source of predictable strength.
  • the source will in most instances safely contain the radioisotope even if the encapsulation should fail since the radioisotope is in the form ofa refractory compound trapped within an inert noble metal matrix.
  • a method of preparing radioisotopic source material comprising:
  • said mist is performed at a first temperature substantially below the melting point of said crystals and the step of withdrawing solvent vapors is performed while maintaining said crystals at a second temperature between said first temperature and the melting point of said crystals.

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  • General Engineering & Computer Science (AREA)
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US252643A 1972-05-12 1972-05-12 Freeze drying method for preparing radiation source material Expired - Lifetime US3873651A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US252643A US3873651A (en) 1972-05-12 1972-05-12 Freeze drying method for preparing radiation source material
CA168,037A CA994999A (en) 1972-05-12 1973-04-05 Freeze drying method for preparing radiation source material
GB1650573A GB1413712A (en) 1972-05-12 1973-04-06 Freeze drying method for preparing radiation source material
FR7316987A FR2184691B1 (enrdf_load_stackoverflow) 1972-05-12 1973-05-10
JP48052074A JPS4947797A (enrdf_load_stackoverflow) 1972-05-12 1973-05-10
BE131022A BE799424A (fr) 1972-05-12 1973-05-11 Procede pour former une source de radiations avec sechage par congelation,
IT24014/73A IT987289B (it) 1972-05-12 1973-05-11 Procedimento per preparare un materiale che funge da sorgente di radiazioni
DE2323865A DE2323865A1 (de) 1972-05-12 1973-05-11 Verfahren zur herstellung eines strahlungsquellenmaterials
SE7306667A SE385783B (sv) 1972-05-12 1973-05-11 Frystorkforfarande for framstellning av stralkellmaterial

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US252643A US3873651A (en) 1972-05-12 1972-05-12 Freeze drying method for preparing radiation source material

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JP (1) JPS4947797A (enrdf_load_stackoverflow)
BE (1) BE799424A (enrdf_load_stackoverflow)
CA (1) CA994999A (enrdf_load_stackoverflow)
DE (1) DE2323865A1 (enrdf_load_stackoverflow)
FR (1) FR2184691B1 (enrdf_load_stackoverflow)
GB (1) GB1413712A (enrdf_load_stackoverflow)
IT (1) IT987289B (enrdf_load_stackoverflow)
SE (1) SE385783B (enrdf_load_stackoverflow)

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US20020193290A1 (en) * 1999-04-05 2002-12-19 Pharmaceutical Discovery Corporation Methods for fine powder formation
WO2004114324A3 (en) * 2003-06-19 2005-02-24 Hiroaki Mitsugashira Method for producing a sealed 210 pb- 210 po alpha source (alpha particle emitter) and apparatus thereof
US20050163915A1 (en) * 2003-04-23 2005-07-28 Baumann Robert C. High activity, spatially distributed radiation source for accurately simulating semiconductor device radiation environments
US9339615B2 (en) 2008-06-13 2016-05-17 Mannkind Corporation Dry powder inhaler and system for drug delivery
US9346766B2 (en) 2004-08-20 2016-05-24 Mannkind Corporation Catalysis of diketopiperazine synthesis
US9364436B2 (en) 2011-06-17 2016-06-14 Mannkind Corporation High capacity diketopiperazine microparticles and methods
US9446001B2 (en) 2005-09-14 2016-09-20 Mannkind Corporation Increasing drug affinity for crystalline microparticle surfaces
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US9675674B2 (en) 2004-08-23 2017-06-13 Mannkind Corporation Diketopiperazine salts for drug delivery and related methods
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US9802012B2 (en) 2012-07-12 2017-10-31 Mannkind Corporation Dry powder drug delivery system and methods
US9801925B2 (en) 1999-06-29 2017-10-31 Mannkind Corporation Potentiation of glucose elimination
US9925144B2 (en) 2013-07-18 2018-03-27 Mannkind Corporation Heat-stable dry powder pharmaceutical compositions and methods
US9943571B2 (en) 2008-08-11 2018-04-17 Mannkind Corporation Use of ultrarapid acting insulin
US9983108B2 (en) 2009-03-11 2018-05-29 Mannkind Corporation Apparatus, system and method for measuring resistance of an inhaler
US10130581B2 (en) 2006-02-22 2018-11-20 Mannkind Corporation Method for improving the pharmaceutic properties of microparticles comprising diketopiperazine and an active agent
US10159644B2 (en) 2012-10-26 2018-12-25 Mannkind Corporation Inhalable vaccine compositions and methods
CN109827384A (zh) * 2019-03-09 2019-05-31 深圳市信宇人科技股份有限公司 真空烤箱
US10307464B2 (en) 2014-03-28 2019-06-04 Mannkind Corporation Use of ultrarapid acting insulin
US10342938B2 (en) 2008-06-13 2019-07-09 Mannkind Corporation Dry powder drug delivery system
US10421729B2 (en) 2013-03-15 2019-09-24 Mannkind Corporation Microcrystalline diketopiperazine compositions and methods
US10561806B2 (en) 2014-10-02 2020-02-18 Mannkind Corporation Mouthpiece cover for an inhaler
US10625034B2 (en) 2011-04-01 2020-04-21 Mannkind Corporation Blister package for pharmaceutical cartridges
US10675421B2 (en) 2008-06-20 2020-06-09 Mannkind Corporation Interactive apparatus and method for real-time profiling of inhalation efforts
US11446127B2 (en) 2013-08-05 2022-09-20 Mannkind Corporation Insufflation apparatus and methods

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DE2655354C2 (de) * 1976-12-07 1986-04-17 Kernforschungszentrum Karlsruhe Gmbh, 7500 Karlsruhe Bestrahlungsanlage zur Aktivierung von Kalzium und Phosphor
JPS5673998U (enrdf_load_stackoverflow) * 1979-11-12 1981-06-17
JP2818533B2 (ja) * 1993-08-10 1998-10-30 動力炉・核燃料開発事業団 核燃料サイクルから発生する使用済溶媒の分離精製方法
RU2235377C2 (ru) * 2002-07-10 2004-08-27 Федеральное государственное унитарное предприятие Государственный научный центр РФ - научно-исследовательский институт атомных реакторов Источник нейтронов на основе калифорния-252 для контроля работы атомного реактора
DE102017105266B4 (de) * 2017-03-13 2023-08-31 Hach Lange Gmbh Verfahren zur Bestimmung oxidierbarer Stoffe

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US7794754B2 (en) 1999-04-05 2010-09-14 Mannkind Corporation Methods for fine powder formation
US20060191375A1 (en) * 1999-04-05 2006-08-31 Mannkind Corporation Methods for fine powder formation
US7278843B2 (en) * 1999-04-05 2007-10-09 Mannkind Corporation Methods for fine powder formation
US20020193290A1 (en) * 1999-04-05 2002-12-19 Pharmaceutical Discovery Corporation Methods for fine powder formation
US9801925B2 (en) 1999-06-29 2017-10-31 Mannkind Corporation Potentiation of glucose elimination
US9700690B2 (en) 2002-03-20 2017-07-11 Mannkind Corporation Inhalation apparatus
US20050163915A1 (en) * 2003-04-23 2005-07-28 Baumann Robert C. High activity, spatially distributed radiation source for accurately simulating semiconductor device radiation environments
US20070098606A1 (en) * 2003-06-19 2007-05-03 Hiroaki Mitsugashira Method for producing a sealed 210pb-210po alpha source (alpha particle emitter) and apparatus thereof
US7476370B2 (en) 2003-06-19 2009-01-13 Hiroaki Mitsugashira Method for producing a sealed 210Pb—210Po alpha particle emitter
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WO2004114324A3 (en) * 2003-06-19 2005-02-24 Hiroaki Mitsugashira Method for producing a sealed 210 pb- 210 po alpha source (alpha particle emitter) and apparatus thereof
US9346766B2 (en) 2004-08-20 2016-05-24 Mannkind Corporation Catalysis of diketopiperazine synthesis
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CA994999A (en) 1976-08-17
FR2184691B1 (enrdf_load_stackoverflow) 1976-09-17
GB1413712A (en) 1975-11-12
IT987289B (it) 1975-02-20
FR2184691A1 (enrdf_load_stackoverflow) 1973-12-28
BE799424A (fr) 1973-08-31
JPS4947797A (enrdf_load_stackoverflow) 1974-05-09
DE2323865A1 (de) 1973-11-22
SE385783B (sv) 1976-07-26

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