CA1202787A - Apparatus and method for reprocessing and separating spent nuclear fuels - Google Patents
Apparatus and method for reprocessing and separating spent nuclear fuelsInfo
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- CA1202787A CA1202787A CA000418317A CA418317A CA1202787A CA 1202787 A CA1202787 A CA 1202787A CA 000418317 A CA000418317 A CA 000418317A CA 418317 A CA418317 A CA 418317A CA 1202787 A CA1202787 A CA 1202787A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/0615—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with transition metals other than titanium, zirconium or hafnium
- C01B21/063—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with transition metals other than titanium, zirconium or hafnium with one or more actinides, e.g. UN, PuN
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
- G21C19/42—Reprocessing of irradiated fuel
- G21C19/44—Reprocessing of irradiated fuel of irradiated solid fuel
- G21C19/48—Non-aqueous processes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
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- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
APPARATUS AND METHOD FOR REPROCESSING AND SEPARATING
SPENT NUCLEAR FUELS
Abstract A method and apparatus for separating and reprocessing spent nuclear fuels includes a separation vessel housing a molten metal solvent in a reaction region, a reflux region positioned above and adjacent to the reaction region, and a porous filter member defining the bottom of the separation vessel in a supporting relationship with the metal solvent. Spent fuels are added to the metal solvent. A
non-oxidizing nitrogen-containing gas is introduced into the separation vessel, forming solid actinide nitrides in the metal solvent from actinide fuels, while leaving other fission products in solution. A
pressure of about 1.1 to 1.2 atm is applied in the reflux region, forcing the molten metal solvent and soluble fission products out of the vessel, while leaving the solid actinide nitrides in the separation vessel.
SPENT NUCLEAR FUELS
Abstract A method and apparatus for separating and reprocessing spent nuclear fuels includes a separation vessel housing a molten metal solvent in a reaction region, a reflux region positioned above and adjacent to the reaction region, and a porous filter member defining the bottom of the separation vessel in a supporting relationship with the metal solvent. Spent fuels are added to the metal solvent. A
non-oxidizing nitrogen-containing gas is introduced into the separation vessel, forming solid actinide nitrides in the metal solvent from actinide fuels, while leaving other fission products in solution. A
pressure of about 1.1 to 1.2 atm is applied in the reflux region, forcing the molten metal solvent and soluble fission products out of the vessel, while leaving the solid actinide nitrides in the separation vessel.
Description
7~7 , APPARATUS AND METHOD FOR REPROCESSING AND SEPARATING
SPENT NUCLEAR FUFLS
Background of the Invention The present invention relates generally to a method and apparatus for the reprocessing and separating of spent nuclear fuels contaminated with fission products in a molten metal solvent. More particularly, the present invention is directed to a method and apparatus for reprocessing and separating spent fuel,elements in a separation apparatus housing a molten metal solvent~ and including a porous filter member to remove the molten solvent and compounds soluble therein from the separation apparatus.
A molten metal sol:vent, usu~lly tin, has been used as the solvent and reaction medium in the reprocessing and separation of spent nuclear fuel elements~ including actinide fuels, e.g., the removal of fission products and other impur;ties from spent uranium-plutonium and thorium-uranium (plutonium) fuels in oxide, metal, or carbide form.
Initially, the spent fuel is declad9 if necessary, then put ;nto a ~solution of mol~en tin maintained at a temperature of about 1600C.
If the fuel ;s an oxide a carbothermic reduct10n process is necessary.
20 For this purpose, the separat~on vessel housing the molten tin is comprised of a material which is a source of carbon, preferably graphite. Carbon dissolves in the molten tin and reacts with the actinide and fissio~ product oxides3 converting them to a metallic solution and generating CO gas. For a uranium-plutoniu~ fuel the principal reaction is represented as:
7~'7
SPENT NUCLEAR FUFLS
Background of the Invention The present invention relates generally to a method and apparatus for the reprocessing and separating of spent nuclear fuels contaminated with fission products in a molten metal solvent. More particularly, the present invention is directed to a method and apparatus for reprocessing and separating spent fuel,elements in a separation apparatus housing a molten metal solvent~ and including a porous filter member to remove the molten solvent and compounds soluble therein from the separation apparatus.
A molten metal sol:vent, usu~lly tin, has been used as the solvent and reaction medium in the reprocessing and separation of spent nuclear fuel elements~ including actinide fuels, e.g., the removal of fission products and other impur;ties from spent uranium-plutonium and thorium-uranium (plutonium) fuels in oxide, metal, or carbide form.
Initially, the spent fuel is declad9 if necessary, then put ;nto a ~solution of mol~en tin maintained at a temperature of about 1600C.
If the fuel ;s an oxide a carbothermic reduct10n process is necessary.
20 For this purpose, the separat~on vessel housing the molten tin is comprised of a material which is a source of carbon, preferably graphite. Carbon dissolves in the molten tin and reacts with the actinide and fissio~ product oxides3 converting them to a metallic solution and generating CO gas. For a uranium-plutoniu~ fuel the principal reaction is represented as:
7~'7
2 -(U,Pu)02(s) ~ 2 C(jn Sn solution) (U,Pu)(jn Sn SOlution) ~ 2 ~0(9) During dissolut;on of the fuel, volat~le f;sslon products are released and swep~ out of the separation vessel by the CO, while the more refractory fiss;on products remain behind in the molten tln solvent. Although the volatile fission products have varying volatilities in the molten tin9 they are all removed in one step~
Along with the volatile fission products a significant portion of the molten tin solvent also evaporates and is removed from the vessel.
Thereafter, the actinides (in solution) are separated from the majority of the fission products remaining in the molten tin in a nitriding reaotion. A non-oxidizing nitrogen containing atmosphere is introduced into the vessel, resulting in the formation of actinide nitrides in the molten tin. For a uranium-plutonium fuel the reaction lS is represented by the ~ollowing equation:
(U'Pu)~in Sn solution) ~ N(2)(9~ ~ (U,Pu)N(s) (2) During the nitriding process, molten tin may also evaporate and escape from the separation vessel. Once nitriding is oomplete, the solid actinide nitrides are separated from the molten tin and the fission products remaining in the tin solvent.
U.S. Patents No. 3,843,765 dated October 22, 1974 to Anderson et al, and 3,843,766 dated October 22, 1974 to Anderson et al. are illustrative of such molten tin separation methods and apparatus~
The above-cited patents disclose that the actinide nitrides are separated from fission product impurities in the separation vessel by including mechanical means to physically move one from the otherr However9 the necessary hardware to aohieve this kind o~ physioal separation is cumbersome to incorporate in with a separation system operating at liquid tin temperatures. Additionally9 the hardware is very costly.
1~2~7~7 Summary of the Invention Accordingly, and object of the invention is to provide an apparatus and method for reprocessing and separating spent nuclear fuels inclu~ing actinide fuels and fission products, wherein actinide fuels are separated from fission products at eleYated temperatures.
Another object of the invention is to provide an apparatus and method for separating and reprocessing spent nuclear fuels, wherein actinide fuels are separated from fission products without the use of mechanical means to separate the ~wo.
Yet another obje~t of the invention is to provide an apparatus and method for separating and reprocessing spent nuclear fuels, wherein a transport system to physically move the actinides from the fission products is unnecessary.
Additional sbjects, advantages and novel features of the invention wlll be set forth in part in the descript;on which follows7 and in part will become apparent to those skilled in the art upon examination of the following3 or may be learned by practice o~ the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects~ and in accordance with the purpose of the present invention as embodied and broadly described herein, the apparatus ~or reprocessing and separa~ing spent nuclear fuels employs a molten metal solvent. A separation vessel is provided which includes a reaction region to house the metal solvent, and a reflux region positioned above and adjacent to the reaction region. The two regions are temperature-independent~ capable of operating at different temperatures Disposed within a separation vessel wall member, in a position adjacent to the re~lux region~ is an aperture. A porous filter member is disposed within a separation vessel wall member, de~ining the bottom of the separat;on vessel in support;ng relationship to the metal solvent. Means for varying the temperature of the separation vessel are included. Additionally, means for evacuating the separation vessel and means ~or introducing various atmospheres into the vessel are provided.
In a further aspect of the present invention, in accordance with its objects and purposes~ the method for reprocessing and separating spent nuclear fuels including actinide fuels, volatile and non-volatile fission products, utilizes a molten metal solvent. A
separation vessel is provided which includes a reaction region housing the metal solvent, and a reflux region positioned above and adjacent to the reaction region. The separation vessel further includes an aperture disposed within a vessel wll member in a position adjacent to the reflux region, and a porous filter member disposed wi~hin a vessel wall member de~ining the bottom of the vessel in supporting relationship to the metal solvent. Spent nuclear ~uels are introduced into the separation vessel, followed by the introduction of a non-oxidizing ni~rogen-containing atmosphere. Solid actinide nitrides are formed within the metal solvent, while the non-volatile fission products remain in solution. The reflux region is subsequently pressurized sufficiently to force the molten metal solvent through the porous filter, leaving the actinide nitrides behind in the reaction region of the separation vessel.
Inclusion of the porous filter member enables the separation of the solidified actinide nitrides from the molten metal solvent and the non-volatile fission products remaining in solution without the need to provide a transport system to collect the solid actinide nitrides, and then physically transport them away from the molten solution.
Additionally, substantial cost savings are realized by elimina$ing the expensive mechanical transport system. The separation of the present invention proceeds successfully at temperatures required to maintain the metal solvent in a molten state.
Descript;on of the Drawing The accompanying drawing, which is i ncorporated and forms a part of the specification~ illustrates an embodiment of the invention9 and, together with the Description, serves to explain the principles of the invention.
7~7 Figure 1 ;s a schematic diagram of a spent nuclear fuel reprocessing and separation apparatus.
Description Spent nuclear fuels; including actinide fuels in oxide, carbide or metal form, and volatile and non-volatile fission products are successfully reprocessed and separated utilizing a separation vessel housing a liquid metal solvent in a reaction region of the vessel, and a reflux region positioned above the reaction region. One embodiment of such a separation apparatus is illustrated in Fig. 1. Separation vessel lO is formed from wall members 12 made of a carbon~containing material.
Preferably~ vessel walls 12 should: (1) be refractory and capable of containing the system at temperatures well above reaction temperatures;
(2) inert to actinides at the reaction temperatures and solvent conditions employed9 (3~ possess low neutron absorption characteristics;
and (4) be a source of carbon for the carbothermic reduckion oF actinide oxides. Exemplary carbon-containing materials include carbides, hydrocarbons and graphite~ Graphite is the preferred material.
Separation vessel lO defines var;ous distinct regions: a reaction region 14 housing a molten metal solvent 16; a reflux region 18 positioned immedia~ely adjacent to and above reaction region 14, and a condensation region l9 positioned adjacent to and immediately on top of reflux region 18. Condensation region l9 is a dome~like structure, removable from the remainder of vessel 10, deFining the top of the vessel. A reservoir 20 is formed within condensation region l9 at its intersection witl re~lux region 18. Reservoir 20 is defined by a wall of insulation 22 and vessel wall member 12, Es~ablishment of different regions within vessel lO permits the formation of a thermal gradient therein. Regions 14~ 18 and l9 are all temperature independent. Generally reaction region 14 is maintained ak a higher temperature than regions 18 and 19. When reflux region 18 and condensation region l9 are maintained at lower temperatures, evaporated metal from solvent 16 enters reflux region 18, condenses therein with the aid of a series of baffles 249 preferably formed of graphite, and '7~7 returns to the solvent in reaction region 14. Regions 14 and 18 can be maintained at the same temperature, while condensation region 19 is maintained at a lower temperature. In this event, evaporated metal solvent continues through region 18 and into reg;on 19. The evaporated solvent condenses therein and is collected in reservoir 20 as a liquid.
For purposes of the present invention, the metal solvent should have good solubility for uranium and o~her actinide metals; possess a vapor pressure suitably low ~o allow condensation of the solvent in the reflux region; not readily form nitrides; and have a suitably low neutron oross section. Suitable solvents include lead, zinc~ bismuth, and tin, as well as combinations thereof. The preferred solvent is tin.
In order to effect the thermal gradient within vessel 10, a first induction heater 26, connected to a suitable power source, is dis-posed at the exterior of the vessel in surrounding relationship with reaction region 14. A second induction heater 28, also connected to a suitable power source, is disposed at the exterior of the vessel in sur~
rounding relationship with reflux region 18. Each induction heater is independent of the other, permitting the formation o-f the thermal gradi-ent within vessel 10. Okher heating and cooling means can be employed to establish the temperature gradient. Such means include~ bu~ are not limited to, radiation heating with resistance heaters, electron impact heating of the vessel, and direct electrical resistance heating applied to the vessel. A plurality of cooling coils 30 are disposed at the ex-terior of condensation section 19 in surrounding relationship thereto.
25 r~ circulating medium such as water, steam, air, helium and the like flows through coils 30 to cool $he condensation section of vessel 10.
Separation vessel 10~ induction heaters 26) 28J and cooling coils 30 are all housed within a metal vacuum tank 32. Tank 32 can alternatively be an inert gas chamber. The tank serves as a secondary containment vessel for the spent nuclear fuels and provides additional safety in the event of a spill. Top lid 34 of tank 32 is removable, providing a means for introducing spent fuel into vessel 10. To this end, a flange 36 joining the vessel wall members whioh define reflux region 18 and ~ondensation region 19, is removed from condensation i'Zl~Z'7~
region l9, e.g.; the dome is separated from the remaining sections of vessel lO. Spent fuel is then added mechanically or in batch~style to the vessel. A removable graph1te liner 38 may optionally be included and disposed within the interior of vessel lO. Before each new batch of spent fuel is reprocessed, a new graphite liner is placed within vessel lO. This reduces wear on the interior walls of vessel lO.
A conduit 40 pierces bottom wall 42 of tank 32 and wall member 12 of vessel 10. A valve 43 is disposed within conduit 40. Conduit 40 is in communication with pump and vacuum systems (not shown), various collection vessels (not shown) to coll~ct and hold C0, volatile fission products, etc. removed from vessel lO, and also a containment vessel (not shown) housing a non-oxidizing nitrogen-containing gas such as N2. Electrical leads for induction heaters 26 and 28, piping for coils 30, and other required auxiliaries are also provided through bottom wall 42.
Disposed within separation vessel wall member 12 in a position defining the bottom of vessel lO, and speciFically the bottom of reaction region 14, is a porous filter member 46 which is in a supporting relationship with metal solvent 16. Filter 46 can vary in size, and may extend to the full width of the bottom of vessel lO. The porosity of filter 46 must be sufficient to provide support for molten metal solvent 16 when a pressure of about l atm is appliPd to reflux region lO and condensation region l9, but yet permit the flow of the solvent and any compositions soluble therein when a pressure of about l.l to 1.2 atm is applied to the reflux region. Preferably; the pore size of the filter material should be about lO to lO0 microns.
If graphite liner 38 is included in separation vessel lO, the bottom of liner 38 is of a porous nature similar to filter 46.
Preferred filter materials include graphite, stainless steel9 and other materials which may be used to form separation vessel lO. The preferred material is graphite. When a pressure of about 1~1 to 1.2 atm of the non-oxidizing nitrogen-containing gas~ or an inert gas such as argon~ is applied to separation vessel lO above m~tal solvent 16, the solvent is caused to flow from the vessel and into a recycle chamber 48 positioned 7~3~7 under vessel 10. Recycle chamber 48 is cooled by the circulation of a cooling medium such as water through its chamber walls. Me~al solvent 16 as well as the non-Yola~ile fission products are collected in recycle chamber 48, cooled, and ~herea~ter removed ~herefrom. A drainage tube 49 is removably attached to separation vessel 10, and also removably attached to recycle chamber 48. Inclusion of drainage tube 49 is hecessary to separate the cooler recycle chamber from the much hotter separation vessel.
Metal solvent 16, as well as reaction region 14, are maintained at a temperature sufficient to solubilize the actinlde fuels, e.g~9 the reaction region temperature. Preferably3 the reaction region temperature is abcut 1450 to 1800~C. More preferably~ ~he temperature is from 1550 to 1700C~ and most preferably it is about 1630C.
Reflux reg~on 18 is înitially maintained at a lower tempera~ure than the lS reaction region e~9~9 the reflux temperature. This reflux temperature must be low enough to effect the refluxing of the metal solvent. When tin is employed as the solvent, a temperature of aboyt 800 to 1200C
is maintained. Preferably, the temperature range is about 950 to 1050C. The temperature of condensation region 19 is lower than reflux region 18, but above the melting point of the metal solvent. A
temperature range of about 232 to about 1050C is suitableO At these lower temperatures~ residual metal solvent or volatile fission products that pass through reflux region 18 are trapped and collected.
The rate of carbothenmic reduction of aotin~de oxides is dependent on the amount cf ava~lable carbon within the metal solvent of choice. Carbon ~s only very sl~ghtly soluble in the metals of choice, especially in tin. However~ w~th the additlon of a first catalyst to the metal to increase rarbon solubility and permeabilik the carbotherm~c reduction rate is greatly increasedO To be effective, the eatalyst must increase carbon solubility in the metal and not readily form stable carbides~ Suitable catalysts ~nclude cobalt, nickel~ ~ron, and oombinatisns thereof. The preferred catalyst ~s cobalt. These elements ~e also part~cularly useful . . . ~. .
because they are relatfvely non-volattle and do not evapora~e from the molten tin sol Yent~ For example, kl n is more than one thousand times as volatile as cobalt. The catalyst ~s present in an amount wherein the weigh~ percentage of catalyst in molten metal so1vent is in khe range of from about 0.1 to 20. Preferably, the percentage is from about 1 ~o 20. Most preferably, ~he percen~age is about 5 to lO.
Prior to introducing the spent nuclear fuel in~o vessel lO, it may be necessary to declad the fuel, either mechanically or chemically.
The spent ~uel is broken up ~o relatively small pieces (3mm or less~ and then introduced into vessel lO with a mechanical feeder or in batch style.
Once the spent nuclear fuels have been added to solvent 16 at the appropriate temperature, carbon from graphite wall 12, dispenser 52 and liner 38 reduces the actinide oxides, evolving CO. As the spent lS fuels dissolve in the metal solvent, volatile fission products are released, while non-volat~le fission products remain in solution. At the reac~ion reg;on ~emperature, a significant amount of solvent from molten solvent 16 in reaction region 14 is evaporated and enters reflux region 18 along with the volatile fission products and CO. Within reflux region 18 the evaporated solvent is caused to condense,.due to the lower temperature, and is returned ~o reaction region 14. YPry little of the evaporated solvent reaches condensation region l9.
Volatlle fission products9 as de~ined hereln, ~nclude those ~ission products l~ste~ in Table I which have very high, moderate, or low volatilities. Volatil1ties of the vola~ile fiss~on products within reflux region 18 vary tremendously. At the reflux region temperature the less vola~ile fission products condense and return ~o molten t~n solvent 16. These volatile fiss~on products are defined as condensable fission products. The more vola~ile fission products do not condense in reflux region 18 or condensation region 19. Instead) they flow from the vessel through conduit 40 and are separately collected in a collection vessel. By definition herein, the more volatile fission products are called non-condensable fission products.
Table I lists the estimated volatilities of fission products at about 1 627C .
Table I
15Volatilities of Fission Products A. ~ery high (10 3 tn 1 atm) I, Br, Cd, Cs, Rb, and Se B. Moderate (10 6 to 10 4 atm) Sb and Te 20C. Low (10 8 to 10 6 atm) Ba9 Eu9 Sm9 and Sr D~ Very low (less than 10 9 atm~
Ce, Gd~ La, Mo, Nd, Pd, Pm, Pr, Rh, Ru, Tcg Y9 and ~r . .
During the removal of C0 and the non-condensable vola~le ~ission products, a sp~rglng gas is introd~ced into vessel 10 through conduit S0 to accelerate carbothermic reduc~ion~ An inert gas such ~s argon is suitable for this purpose. After the non-condensable volatile fission products have been removed from Yessel 10, the temperature of re~lux region 18 is increased from its reflux temperature, eOg., 9S0 to 1050C, ~o ~he ~empera~ure of the reaction region. However, condensation region 19 is mainta~ned by cooling as necessary at a ~emperature within the range of 232 to 1050C. At the elevated reaction region temperature, the condensable volatile fission products will yenerally not condense in reflux region 180 Essentially~ the condensable volatile fission products, as well as some evaporated tin9 are distilled, condensed and collected in condensation region 19 at reservoir 20. Althnugh some tin ~s lost ~n this distillation process, far less is lost than if the removal of all volatile fission produ~ts occurred without the existence of reflux and condensatiDn regions which establish the temperature gradient. Add~tionally9 the temperature gradient permits selective separation oi the volatile fission products based on their different ~olatilities7 e.g.~ condensable and non-condensable volatile fission products are separatedO
When d~stillat~on ~5 camplete~ the temperature of re~lux region 18 is decreased back to the defined reflux temperature of about 95~ to 1050C. Therea~ter, a non-oxidiz~ng nitrogen contain~ng atmosphere is introdueed into vessel 10. An example o~ such an atmosphere is pure nitrogenJ The nitrogen atmosphere enters metal solvent 16 and is dispersed there~n wlth the aid of dispenser 52.
Additionally, the nitrogen containing atmosphere may also be introduced through conduit 40. A nitrogen pressure of about 1 atm is preferred~
Within solvent 16, solid actinide nitr~des ~ncluding UN, U2N3~ PuN, 3n Pu2N3, ThN and the llke, are formedO The orlginal soluble f~ssion products remain in solution.
To separate the sol~d actinide nitrides from the malten solvent and soluble fission products, reflux and condensation regions 18 and 19 are pressured with a gas sueh as nitrogen, and ~ntroduced through csndult 4a at a pressure of about 1.1 to 1.2 atm. The h~
~2 ~ressurizing effec~ forces the molten solvent and solubl~ fission products to flow from react~on reg~on 14, through filter 46 and ~nto recycle chamber 48~ Vessel 10 is then cooled and dismantled e.g., a separation of the vessel at flange 36 occurs. The remaining sol1d actinide nitrides Are taken from vessel 10 and processed to yield usable fuels, e.g., ignited in the presence of oxygen to produce actin~de oxid sO
~ o accelerate the nitriding process, a second catalyst is included. The second catalyst chosen must ~ncrease the affinity of nitrogen in the metal solvent, but not form stable nitrides. Suitable catalysts ~nclude magnesium, calcium9 strontium, barium, aluminum, manganese~ vanadium, chrom~um, and m1xturPs thereof. The pref2rred se~ond catalyst is calcium. Depending on the choice of second catalyst, it may be added to the metal solvent initially as part of ~he solvent" or ~ust prior to the nitridiny process. This is due to varying volatil~t~es of the catalysts and the potential loss of the more volatile seeond catalysts during the carbothermis reduction process. The weight percentage of second catalyst to metal solvent is about 1.0 to 1030~ Preferably, the weight percentage is about 1~8 to 2.S. Most preferably, it is about 1Ø By including the second oatalyst, an approximate threefold rate incre~se in nitriding is observed.
The following examples are illustrative of the process ~nd appar~tus of the present invent~on~ and are not to be regarded as limiting its scope.
Example 1 509 nf reagent grade shot tin~ 109 of U02 (depleted~ and lg of cobalt ~re added to the separation vessel shown in Fig. 1~ Cobalt is added as a catalyst otherwlse the carbothermic reduction w~ll take about 20~30 hours. The reaction re~on of the vessel and the tin are then heated and maintained at a temperature of about 1600OCD creating a ~olten tln solvent. ~he re~lux region of the vessel ~s ~ain~ained ~t lz~7~
, a temperature of about 1000C. 10 grams of U0z (depleted) are ~dded to the molten t~n solvent. Argon ~s then bubbled through the molten tin as a sparg~ng gas for two hours: Non-condensable volatile fission products are collected ~n s~itable cold traps, C0 ~s oxidized to C02 and trapped ~n an alkaline matrix such as ghe commercial product Ascarite. The ~emperature of the reflux region is then ~ncreased to about 1600~C. vaporated ~in and the previously condensable volatlle fission products are collected ~n a collection vessel. After about 1~ minutes, the temperature of the reflux region is decreased to about 1000C. N2 (at 1 atm) is introduc~d into ~he vessel through the porous filter, forming actinide nitridesO After a~out one hour~ the ~low of N2 through the filter is discont~nued while N2 is in~roduced into the reflux region at about 1.2 atm. The molten tin dnd the non-volatile fiss~on products in the molt~n ~in flow out of the Yessel through the porous filter and collected in a recycle chamber, leaving the solid actini~e nitrides behind.
Example ~
lOg of ThO2 is separated frQm other spent nuclear fuels under the same cond~tions as in Example 1.
Example 3 lOg of ~U,Pu~02, i.e.~ a mixture of U02 and Pu02, is separated from other spent nuclear fuels under the same conditions as xampl~ 1 . ' ~he ~oregoing descript1On of ~ preferred emhodiment Df the 2~ lnvent~on has been presented for purposes of ~llustratlon ~nd descr~ption~ It ~s ~ntended that the ScopP of the invent~on be defin2d by the cla~ms appended hereto.
~ ~ ~~- r, . ........ _.. ,,,. _
Along with the volatile fission products a significant portion of the molten tin solvent also evaporates and is removed from the vessel.
Thereafter, the actinides (in solution) are separated from the majority of the fission products remaining in the molten tin in a nitriding reaotion. A non-oxidizing nitrogen containing atmosphere is introduced into the vessel, resulting in the formation of actinide nitrides in the molten tin. For a uranium-plutonium fuel the reaction lS is represented by the ~ollowing equation:
(U'Pu)~in Sn solution) ~ N(2)(9~ ~ (U,Pu)N(s) (2) During the nitriding process, molten tin may also evaporate and escape from the separation vessel. Once nitriding is oomplete, the solid actinide nitrides are separated from the molten tin and the fission products remaining in the tin solvent.
U.S. Patents No. 3,843,765 dated October 22, 1974 to Anderson et al, and 3,843,766 dated October 22, 1974 to Anderson et al. are illustrative of such molten tin separation methods and apparatus~
The above-cited patents disclose that the actinide nitrides are separated from fission product impurities in the separation vessel by including mechanical means to physically move one from the otherr However9 the necessary hardware to aohieve this kind o~ physioal separation is cumbersome to incorporate in with a separation system operating at liquid tin temperatures. Additionally9 the hardware is very costly.
1~2~7~7 Summary of the Invention Accordingly, and object of the invention is to provide an apparatus and method for reprocessing and separating spent nuclear fuels inclu~ing actinide fuels and fission products, wherein actinide fuels are separated from fission products at eleYated temperatures.
Another object of the invention is to provide an apparatus and method for separating and reprocessing spent nuclear fuels, wherein actinide fuels are separated from fission products without the use of mechanical means to separate the ~wo.
Yet another obje~t of the invention is to provide an apparatus and method for separating and reprocessing spent nuclear fuels, wherein a transport system to physically move the actinides from the fission products is unnecessary.
Additional sbjects, advantages and novel features of the invention wlll be set forth in part in the descript;on which follows7 and in part will become apparent to those skilled in the art upon examination of the following3 or may be learned by practice o~ the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects~ and in accordance with the purpose of the present invention as embodied and broadly described herein, the apparatus ~or reprocessing and separa~ing spent nuclear fuels employs a molten metal solvent. A separation vessel is provided which includes a reaction region to house the metal solvent, and a reflux region positioned above and adjacent to the reaction region. The two regions are temperature-independent~ capable of operating at different temperatures Disposed within a separation vessel wall member, in a position adjacent to the re~lux region~ is an aperture. A porous filter member is disposed within a separation vessel wall member, de~ining the bottom of the separat;on vessel in support;ng relationship to the metal solvent. Means for varying the temperature of the separation vessel are included. Additionally, means for evacuating the separation vessel and means ~or introducing various atmospheres into the vessel are provided.
In a further aspect of the present invention, in accordance with its objects and purposes~ the method for reprocessing and separating spent nuclear fuels including actinide fuels, volatile and non-volatile fission products, utilizes a molten metal solvent. A
separation vessel is provided which includes a reaction region housing the metal solvent, and a reflux region positioned above and adjacent to the reaction region. The separation vessel further includes an aperture disposed within a vessel wll member in a position adjacent to the reflux region, and a porous filter member disposed wi~hin a vessel wall member de~ining the bottom of the vessel in supporting relationship to the metal solvent. Spent nuclear ~uels are introduced into the separation vessel, followed by the introduction of a non-oxidizing ni~rogen-containing atmosphere. Solid actinide nitrides are formed within the metal solvent, while the non-volatile fission products remain in solution. The reflux region is subsequently pressurized sufficiently to force the molten metal solvent through the porous filter, leaving the actinide nitrides behind in the reaction region of the separation vessel.
Inclusion of the porous filter member enables the separation of the solidified actinide nitrides from the molten metal solvent and the non-volatile fission products remaining in solution without the need to provide a transport system to collect the solid actinide nitrides, and then physically transport them away from the molten solution.
Additionally, substantial cost savings are realized by elimina$ing the expensive mechanical transport system. The separation of the present invention proceeds successfully at temperatures required to maintain the metal solvent in a molten state.
Descript;on of the Drawing The accompanying drawing, which is i ncorporated and forms a part of the specification~ illustrates an embodiment of the invention9 and, together with the Description, serves to explain the principles of the invention.
7~7 Figure 1 ;s a schematic diagram of a spent nuclear fuel reprocessing and separation apparatus.
Description Spent nuclear fuels; including actinide fuels in oxide, carbide or metal form, and volatile and non-volatile fission products are successfully reprocessed and separated utilizing a separation vessel housing a liquid metal solvent in a reaction region of the vessel, and a reflux region positioned above the reaction region. One embodiment of such a separation apparatus is illustrated in Fig. 1. Separation vessel lO is formed from wall members 12 made of a carbon~containing material.
Preferably~ vessel walls 12 should: (1) be refractory and capable of containing the system at temperatures well above reaction temperatures;
(2) inert to actinides at the reaction temperatures and solvent conditions employed9 (3~ possess low neutron absorption characteristics;
and (4) be a source of carbon for the carbothermic reduckion oF actinide oxides. Exemplary carbon-containing materials include carbides, hydrocarbons and graphite~ Graphite is the preferred material.
Separation vessel lO defines var;ous distinct regions: a reaction region 14 housing a molten metal solvent 16; a reflux region 18 positioned immedia~ely adjacent to and above reaction region 14, and a condensation region l9 positioned adjacent to and immediately on top of reflux region 18. Condensation region l9 is a dome~like structure, removable from the remainder of vessel 10, deFining the top of the vessel. A reservoir 20 is formed within condensation region l9 at its intersection witl re~lux region 18. Reservoir 20 is defined by a wall of insulation 22 and vessel wall member 12, Es~ablishment of different regions within vessel lO permits the formation of a thermal gradient therein. Regions 14~ 18 and l9 are all temperature independent. Generally reaction region 14 is maintained ak a higher temperature than regions 18 and 19. When reflux region 18 and condensation region l9 are maintained at lower temperatures, evaporated metal from solvent 16 enters reflux region 18, condenses therein with the aid of a series of baffles 249 preferably formed of graphite, and '7~7 returns to the solvent in reaction region 14. Regions 14 and 18 can be maintained at the same temperature, while condensation region 19 is maintained at a lower temperature. In this event, evaporated metal solvent continues through region 18 and into reg;on 19. The evaporated solvent condenses therein and is collected in reservoir 20 as a liquid.
For purposes of the present invention, the metal solvent should have good solubility for uranium and o~her actinide metals; possess a vapor pressure suitably low ~o allow condensation of the solvent in the reflux region; not readily form nitrides; and have a suitably low neutron oross section. Suitable solvents include lead, zinc~ bismuth, and tin, as well as combinations thereof. The preferred solvent is tin.
In order to effect the thermal gradient within vessel 10, a first induction heater 26, connected to a suitable power source, is dis-posed at the exterior of the vessel in surrounding relationship with reaction region 14. A second induction heater 28, also connected to a suitable power source, is disposed at the exterior of the vessel in sur~
rounding relationship with reflux region 18. Each induction heater is independent of the other, permitting the formation o-f the thermal gradi-ent within vessel 10. Okher heating and cooling means can be employed to establish the temperature gradient. Such means include~ bu~ are not limited to, radiation heating with resistance heaters, electron impact heating of the vessel, and direct electrical resistance heating applied to the vessel. A plurality of cooling coils 30 are disposed at the ex-terior of condensation section 19 in surrounding relationship thereto.
25 r~ circulating medium such as water, steam, air, helium and the like flows through coils 30 to cool $he condensation section of vessel 10.
Separation vessel 10~ induction heaters 26) 28J and cooling coils 30 are all housed within a metal vacuum tank 32. Tank 32 can alternatively be an inert gas chamber. The tank serves as a secondary containment vessel for the spent nuclear fuels and provides additional safety in the event of a spill. Top lid 34 of tank 32 is removable, providing a means for introducing spent fuel into vessel 10. To this end, a flange 36 joining the vessel wall members whioh define reflux region 18 and ~ondensation region 19, is removed from condensation i'Zl~Z'7~
region l9, e.g.; the dome is separated from the remaining sections of vessel lO. Spent fuel is then added mechanically or in batch~style to the vessel. A removable graph1te liner 38 may optionally be included and disposed within the interior of vessel lO. Before each new batch of spent fuel is reprocessed, a new graphite liner is placed within vessel lO. This reduces wear on the interior walls of vessel lO.
A conduit 40 pierces bottom wall 42 of tank 32 and wall member 12 of vessel 10. A valve 43 is disposed within conduit 40. Conduit 40 is in communication with pump and vacuum systems (not shown), various collection vessels (not shown) to coll~ct and hold C0, volatile fission products, etc. removed from vessel lO, and also a containment vessel (not shown) housing a non-oxidizing nitrogen-containing gas such as N2. Electrical leads for induction heaters 26 and 28, piping for coils 30, and other required auxiliaries are also provided through bottom wall 42.
Disposed within separation vessel wall member 12 in a position defining the bottom of vessel lO, and speciFically the bottom of reaction region 14, is a porous filter member 46 which is in a supporting relationship with metal solvent 16. Filter 46 can vary in size, and may extend to the full width of the bottom of vessel lO. The porosity of filter 46 must be sufficient to provide support for molten metal solvent 16 when a pressure of about l atm is appliPd to reflux region lO and condensation region l9, but yet permit the flow of the solvent and any compositions soluble therein when a pressure of about l.l to 1.2 atm is applied to the reflux region. Preferably; the pore size of the filter material should be about lO to lO0 microns.
If graphite liner 38 is included in separation vessel lO, the bottom of liner 38 is of a porous nature similar to filter 46.
Preferred filter materials include graphite, stainless steel9 and other materials which may be used to form separation vessel lO. The preferred material is graphite. When a pressure of about 1~1 to 1.2 atm of the non-oxidizing nitrogen-containing gas~ or an inert gas such as argon~ is applied to separation vessel lO above m~tal solvent 16, the solvent is caused to flow from the vessel and into a recycle chamber 48 positioned 7~3~7 under vessel 10. Recycle chamber 48 is cooled by the circulation of a cooling medium such as water through its chamber walls. Me~al solvent 16 as well as the non-Yola~ile fission products are collected in recycle chamber 48, cooled, and ~herea~ter removed ~herefrom. A drainage tube 49 is removably attached to separation vessel 10, and also removably attached to recycle chamber 48. Inclusion of drainage tube 49 is hecessary to separate the cooler recycle chamber from the much hotter separation vessel.
Metal solvent 16, as well as reaction region 14, are maintained at a temperature sufficient to solubilize the actinlde fuels, e.g~9 the reaction region temperature. Preferably3 the reaction region temperature is abcut 1450 to 1800~C. More preferably~ ~he temperature is from 1550 to 1700C~ and most preferably it is about 1630C.
Reflux reg~on 18 is înitially maintained at a lower tempera~ure than the lS reaction region e~9~9 the reflux temperature. This reflux temperature must be low enough to effect the refluxing of the metal solvent. When tin is employed as the solvent, a temperature of aboyt 800 to 1200C
is maintained. Preferably, the temperature range is about 950 to 1050C. The temperature of condensation region 19 is lower than reflux region 18, but above the melting point of the metal solvent. A
temperature range of about 232 to about 1050C is suitableO At these lower temperatures~ residual metal solvent or volatile fission products that pass through reflux region 18 are trapped and collected.
The rate of carbothenmic reduction of aotin~de oxides is dependent on the amount cf ava~lable carbon within the metal solvent of choice. Carbon ~s only very sl~ghtly soluble in the metals of choice, especially in tin. However~ w~th the additlon of a first catalyst to the metal to increase rarbon solubility and permeabilik the carbotherm~c reduction rate is greatly increasedO To be effective, the eatalyst must increase carbon solubility in the metal and not readily form stable carbides~ Suitable catalysts ~nclude cobalt, nickel~ ~ron, and oombinatisns thereof. The preferred catalyst ~s cobalt. These elements ~e also part~cularly useful . . . ~. .
because they are relatfvely non-volattle and do not evapora~e from the molten tin sol Yent~ For example, kl n is more than one thousand times as volatile as cobalt. The catalyst ~s present in an amount wherein the weigh~ percentage of catalyst in molten metal so1vent is in khe range of from about 0.1 to 20. Preferably, the percentage is from about 1 ~o 20. Most preferably, ~he percen~age is about 5 to lO.
Prior to introducing the spent nuclear fuel in~o vessel lO, it may be necessary to declad the fuel, either mechanically or chemically.
The spent ~uel is broken up ~o relatively small pieces (3mm or less~ and then introduced into vessel lO with a mechanical feeder or in batch style.
Once the spent nuclear fuels have been added to solvent 16 at the appropriate temperature, carbon from graphite wall 12, dispenser 52 and liner 38 reduces the actinide oxides, evolving CO. As the spent lS fuels dissolve in the metal solvent, volatile fission products are released, while non-volat~le fission products remain in solution. At the reac~ion reg;on ~emperature, a significant amount of solvent from molten solvent 16 in reaction region 14 is evaporated and enters reflux region 18 along with the volatile fission products and CO. Within reflux region 18 the evaporated solvent is caused to condense,.due to the lower temperature, and is returned ~o reaction region 14. YPry little of the evaporated solvent reaches condensation region l9.
Volatlle fission products9 as de~ined hereln, ~nclude those ~ission products l~ste~ in Table I which have very high, moderate, or low volatilities. Volatil1ties of the vola~ile fiss~on products within reflux region 18 vary tremendously. At the reflux region temperature the less vola~ile fission products condense and return ~o molten t~n solvent 16. These volatile fiss~on products are defined as condensable fission products. The more vola~ile fission products do not condense in reflux region 18 or condensation region 19. Instead) they flow from the vessel through conduit 40 and are separately collected in a collection vessel. By definition herein, the more volatile fission products are called non-condensable fission products.
Table I lists the estimated volatilities of fission products at about 1 627C .
Table I
15Volatilities of Fission Products A. ~ery high (10 3 tn 1 atm) I, Br, Cd, Cs, Rb, and Se B. Moderate (10 6 to 10 4 atm) Sb and Te 20C. Low (10 8 to 10 6 atm) Ba9 Eu9 Sm9 and Sr D~ Very low (less than 10 9 atm~
Ce, Gd~ La, Mo, Nd, Pd, Pm, Pr, Rh, Ru, Tcg Y9 and ~r . .
During the removal of C0 and the non-condensable vola~le ~ission products, a sp~rglng gas is introd~ced into vessel 10 through conduit S0 to accelerate carbothermic reduc~ion~ An inert gas such ~s argon is suitable for this purpose. After the non-condensable volatile fission products have been removed from Yessel 10, the temperature of re~lux region 18 is increased from its reflux temperature, eOg., 9S0 to 1050C, ~o ~he ~empera~ure of the reaction region. However, condensation region 19 is mainta~ned by cooling as necessary at a ~emperature within the range of 232 to 1050C. At the elevated reaction region temperature, the condensable volatile fission products will yenerally not condense in reflux region 180 Essentially~ the condensable volatile fission products, as well as some evaporated tin9 are distilled, condensed and collected in condensation region 19 at reservoir 20. Althnugh some tin ~s lost ~n this distillation process, far less is lost than if the removal of all volatile fission produ~ts occurred without the existence of reflux and condensatiDn regions which establish the temperature gradient. Add~tionally9 the temperature gradient permits selective separation oi the volatile fission products based on their different ~olatilities7 e.g.~ condensable and non-condensable volatile fission products are separatedO
When d~stillat~on ~5 camplete~ the temperature of re~lux region 18 is decreased back to the defined reflux temperature of about 95~ to 1050C. Therea~ter, a non-oxidiz~ng nitrogen contain~ng atmosphere is introdueed into vessel 10. An example o~ such an atmosphere is pure nitrogenJ The nitrogen atmosphere enters metal solvent 16 and is dispersed there~n wlth the aid of dispenser 52.
Additionally, the nitrogen containing atmosphere may also be introduced through conduit 40. A nitrogen pressure of about 1 atm is preferred~
Within solvent 16, solid actinide nitr~des ~ncluding UN, U2N3~ PuN, 3n Pu2N3, ThN and the llke, are formedO The orlginal soluble f~ssion products remain in solution.
To separate the sol~d actinide nitrides from the malten solvent and soluble fission products, reflux and condensation regions 18 and 19 are pressured with a gas sueh as nitrogen, and ~ntroduced through csndult 4a at a pressure of about 1.1 to 1.2 atm. The h~
~2 ~ressurizing effec~ forces the molten solvent and solubl~ fission products to flow from react~on reg~on 14, through filter 46 and ~nto recycle chamber 48~ Vessel 10 is then cooled and dismantled e.g., a separation of the vessel at flange 36 occurs. The remaining sol1d actinide nitrides Are taken from vessel 10 and processed to yield usable fuels, e.g., ignited in the presence of oxygen to produce actin~de oxid sO
~ o accelerate the nitriding process, a second catalyst is included. The second catalyst chosen must ~ncrease the affinity of nitrogen in the metal solvent, but not form stable nitrides. Suitable catalysts ~nclude magnesium, calcium9 strontium, barium, aluminum, manganese~ vanadium, chrom~um, and m1xturPs thereof. The pref2rred se~ond catalyst is calcium. Depending on the choice of second catalyst, it may be added to the metal solvent initially as part of ~he solvent" or ~ust prior to the nitridiny process. This is due to varying volatil~t~es of the catalysts and the potential loss of the more volatile seeond catalysts during the carbothermis reduction process. The weight percentage of second catalyst to metal solvent is about 1.0 to 1030~ Preferably, the weight percentage is about 1~8 to 2.S. Most preferably, it is about 1Ø By including the second oatalyst, an approximate threefold rate incre~se in nitriding is observed.
The following examples are illustrative of the process ~nd appar~tus of the present invent~on~ and are not to be regarded as limiting its scope.
Example 1 509 nf reagent grade shot tin~ 109 of U02 (depleted~ and lg of cobalt ~re added to the separation vessel shown in Fig. 1~ Cobalt is added as a catalyst otherwlse the carbothermic reduction w~ll take about 20~30 hours. The reaction re~on of the vessel and the tin are then heated and maintained at a temperature of about 1600OCD creating a ~olten tln solvent. ~he re~lux region of the vessel ~s ~ain~ained ~t lz~7~
, a temperature of about 1000C. 10 grams of U0z (depleted) are ~dded to the molten t~n solvent. Argon ~s then bubbled through the molten tin as a sparg~ng gas for two hours: Non-condensable volatile fission products are collected ~n s~itable cold traps, C0 ~s oxidized to C02 and trapped ~n an alkaline matrix such as ghe commercial product Ascarite. The ~emperature of the reflux region is then ~ncreased to about 1600~C. vaporated ~in and the previously condensable volatlle fission products are collected ~n a collection vessel. After about 1~ minutes, the temperature of the reflux region is decreased to about 1000C. N2 (at 1 atm) is introduc~d into ~he vessel through the porous filter, forming actinide nitridesO After a~out one hour~ the ~low of N2 through the filter is discont~nued while N2 is in~roduced into the reflux region at about 1.2 atm. The molten tin dnd the non-volatile fiss~on products in the molt~n ~in flow out of the Yessel through the porous filter and collected in a recycle chamber, leaving the solid actini~e nitrides behind.
Example ~
lOg of ThO2 is separated frQm other spent nuclear fuels under the same cond~tions as in Example 1.
Example 3 lOg of ~U,Pu~02, i.e.~ a mixture of U02 and Pu02, is separated from other spent nuclear fuels under the same conditions as xampl~ 1 . ' ~he ~oregoing descript1On of ~ preferred emhodiment Df the 2~ lnvent~on has been presented for purposes of ~llustratlon ~nd descr~ption~ It ~s ~ntended that the ScopP of the invent~on be defin2d by the cla~ms appended hereto.
~ ~ ~~- r, . ........ _.. ,,,. _
Claims (12)
1. An apparatus for reprocessing and separating spent nuclear fuels including actinide fuels and fission products, in a molten metal solvent, comprising:
a vessel having a reaction region housing said molten metal solvent, and a reflux region positioned above said reaction region, said reflux region being capable of operating at a different temperature than said reaction region, said vessel including an aperture disposed within a wall member of said vessel in a position adjacent said reflux region;
means for heating said vessel;
means for evacuating said vessel; and means for introducing a non-oxidizing nitrogen containing atmosphere into said vessel, to form actinide nitrides within said molten metal solvent.
a vessel having a reaction region housing said molten metal solvent, and a reflux region positioned above said reaction region, said reflux region being capable of operating at a different temperature than said reaction region, said vessel including an aperture disposed within a wall member of said vessel in a position adjacent said reflux region;
means for heating said vessel;
means for evacuating said vessel; and means for introducing a non-oxidizing nitrogen containing atmosphere into said vessel, to form actinide nitrides within said molten metal solvent.
2. The apparatus according to Claim 1 wherein said vessel further comprises a condensation region positioned above and adjacent said reflux region, said condensation region being capable of operating at a different temperature than said reflux and reaction regions.
3. The apparatus according to Claim 1 further comprising a liner disposed within said vessel.
4. The apparatus according to Claim 1 wherein said vessel is substantially formed of graphite.
5. The apparatus according to Claim 1, wherein a porous filter member is disposed within a separation vessel wall member defining the bottom of said separation vessel in supporting relation-ship to said metal solvent.
6. The apparatus according to Claim 1, wherein said filter member has a pore size of about 10 to 100 microns.
7. A method for reprocessing and separating spent nuclear fuels including actinide fuels, volatile and non-volatile fission products, comprising:
providing a separation vessel formed of a carbon-containing material, and a molten metal solvent disposed within said separation vessel, said separation vessel including an aperture disposed within a vessel wall member;
adding a first catalyst to said metal solvent which increases the solubility of carbon in said solvent;
introducing spent nuclear fuels into said separation vessel; and forming CO within said molten metal solvent from actinide fuels which are oxides.
providing a separation vessel formed of a carbon-containing material, and a molten metal solvent disposed within said separation vessel, said separation vessel including an aperture disposed within a vessel wall member;
adding a first catalyst to said metal solvent which increases the solubility of carbon in said solvent;
introducing spent nuclear fuels into said separation vessel; and forming CO within said molten metal solvent from actinide fuels which are oxides.
8. The method according to Claim 7, further comprising removing said volatile fission products and CO from said reaction vessel.
9. The method according to Claim 8, further comprising:
introducing a non-oxidizing nitrogen-containing atmosphere into said separation vessel after said volatile fission products and CO have been removed therefrom;
forming solid nitrides from said actinide fuels within said molten metal solvent; and separating said solid actinide nitrides from said molten metal solvent and non-volatile fission products.
introducing a non-oxidizing nitrogen-containing atmosphere into said separation vessel after said volatile fission products and CO have been removed therefrom;
forming solid nitrides from said actinide fuels within said molten metal solvent; and separating said solid actinide nitrides from said molten metal solvent and non-volatile fission products.
10. A method for reprocessing and separating spent nuclear fuels including actinide fuels, volatile and non-volatile fission products, in a molten tin solvent, comprising:
providing a separation vessel formed of a carbon-containing material, said separation vessel defining a reaction region housing said molten tin solvent and a reflux region positioned adjacent to and above said reaction region, said separation vessel including an aperture disposed within a vessel wall member in a position adjacent said reflux region;
adding a first catalyst to said tin solvent which increases the solubility of carbon in said solvent;
maintaining said reaction region at a temperature sufficient to convert said actinide fuels to a solubilized state;
maintaining said reflux region at a temperature sufficient to reflux said tin solvent, said reflux temperature being lower than said reaction region temperature;
introducing spent nuclear fuels into said tin solvent;
forming CO within said molten tin solvent from actinide fuels which are oxides;
allowing CO and volatile fission products within said molten tin solvent, along with some molten tin, to evaporate and flow into said reflux region;
removing CO and volatile fission products which are not condensable at said reflux temperature from said reflux region through said vessel aperture, leaving evaporated tin and less volatile fission products in said reflux region; and allowing evaporated tin and less volatile fission products disposed within said reflux region which are condensable at said reflux temperature to cool sufficiently and return to said molten tin solvent in said reaction region.
providing a separation vessel formed of a carbon-containing material, said separation vessel defining a reaction region housing said molten tin solvent and a reflux region positioned adjacent to and above said reaction region, said separation vessel including an aperture disposed within a vessel wall member in a position adjacent said reflux region;
adding a first catalyst to said tin solvent which increases the solubility of carbon in said solvent;
maintaining said reaction region at a temperature sufficient to convert said actinide fuels to a solubilized state;
maintaining said reflux region at a temperature sufficient to reflux said tin solvent, said reflux temperature being lower than said reaction region temperature;
introducing spent nuclear fuels into said tin solvent;
forming CO within said molten tin solvent from actinide fuels which are oxides;
allowing CO and volatile fission products within said molten tin solvent, along with some molten tin, to evaporate and flow into said reflux region;
removing CO and volatile fission products which are not condensable at said reflux temperature from said reflux region through said vessel aperture, leaving evaporated tin and less volatile fission products in said reflux region; and allowing evaporated tin and less volatile fission products disposed within said reflux region which are condensable at said reflux temperature to cool sufficiently and return to said molten tin solvent in said reaction region.
11. The method according to Claim 7, wherein the temperature of the reaction vessel is varied;
the said separation vessel is evacuated and various atmospheres are introduced into said separation vessel and said separation vessel contents are filtered through a porous filter disposed within a separation vessel wall member.
the said separation vessel is evacuated and various atmospheres are introduced into said separation vessel and said separation vessel contents are filtered through a porous filter disposed within a separation vessel wall member.
12. The method according to Claim 11, wherein said filter has a pore size of about 10 to 100 microns.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US34062682A | 1982-01-19 | 1982-01-19 | |
| US34062282A | 1982-01-19 | 1982-01-19 | |
| US06/340,591 US4399108A (en) | 1982-01-19 | 1982-01-19 | Method for reprocessing and separating spent nuclear fuels |
| US340,626 | 1982-01-19 | ||
| US340,591 | 1982-01-19 | ||
| US340,622 | 1982-01-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1202787A true CA1202787A (en) | 1986-04-08 |
Family
ID=27407408
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000418317A Expired CA1202787A (en) | 1982-01-19 | 1982-12-22 | Apparatus and method for reprocessing and separating spent nuclear fuels |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1202787A (en) |
| DE (1) | DE3301641A1 (en) |
| FR (1) | FR2520151B1 (en) |
| GB (1) | GB2113901B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP4235693A3 (en) | 2016-03-08 | 2023-10-11 | TerraPower LLC | Fission product getter |
| CN207038182U (en) * | 2017-03-29 | 2018-02-23 | 泰拉能源有限责任公司 | Caesium collector |
| US11626213B2 (en) | 2019-08-23 | 2023-04-11 | Terrapower, Llc | Sodium vaporizer and methods |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2064983C3 (en) * | 1969-05-19 | 1979-03-08 | Robert N. Palo Alto Anderson | Process for removing metallic fission products from spent actinide fuel assemblies |
| BE758901A (en) * | 1969-05-19 | 1971-04-16 | Anderson Robert Neil | NUCLEAR FUEL REACTOR INCLUDING A CRITICAL MASS OF ACTINIDE NITRIDE AND PROCEDURE FOR CONDUCTING THIS |
| US3843766A (en) * | 1969-12-09 | 1974-10-22 | Us Navy | Method of reprocessing nuclear fuels |
| NL7001798A (en) * | 1970-02-09 | 1971-08-11 | ||
| US3794482A (en) * | 1971-02-05 | 1974-02-26 | Parlee Anderson Corp | Carbothermic reduction method for converting metal oxides to metal form |
| US3867510A (en) * | 1973-04-23 | 1975-02-18 | Atomic Energy Commission | Process for recovering uranium and plutonium from irradiated nuclear fuel oxides |
-
1982
- 1982-12-22 CA CA000418317A patent/CA1202787A/en not_active Expired
- 1982-12-22 GB GB8236505A patent/GB2113901B/en not_active Expired
-
1983
- 1983-01-18 FR FR8300691A patent/FR2520151B1/en not_active Expired
- 1983-01-19 DE DE19833301641 patent/DE3301641A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| GB2113901B (en) | 1986-06-11 |
| FR2520151B1 (en) | 1987-08-28 |
| FR2520151A1 (en) | 1983-07-22 |
| DE3301641A1 (en) | 1983-08-18 |
| GB2113901A (en) | 1983-08-10 |
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