JPS6070393A - Improved method for manufacturing nuclear fuel and binder and product obtained by said method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the Reramik technology a5 and to the production of sintered bodies from particulate oxide materials. More specifically, the present invention provides solidification units 1 to 1 of the granular ceramic material, which comprises compression molding a granular ceramic material to form a compacted compact that can be handled, and then sintering it to integrate it. Related to manufacturing method. In particular, the present invention aims at producing nuclear fuel pellets from granular particles containing uranium dioxide.

Description of Related Uses This light generally refers to George L. Garihan Lee and Barry M. L., Qaines, Jr.
, PaLr1cia A, Piacente ,
William J, Ward [1, J) etc.
C, 3m1th, l-imothy J, Ga1
livan & l-1arry M, La5ka)
No. 331,492, filed December 17, 1981, and George L. Guins Jr. and William G. Ward (Ge.
oroe L, Ga1nes & William
No. 273,900 filed June 15, 1981 in the name of J. Wardull. All of the above patent applications are assigned to the same assignee as the present application, and the contents of their specifications are incorporated herein by reference.

BACKGROUND OF THE INVENTION Fissile nuclear fuel contains fissile material of various compositions and forms, including ceramic compounds of uranium, plutonium, and thorium.

Nuclear fuel materials commonly used in commercial power reactors include oxides of uranium, plutonium, and thorium, and mixtures thereof. Among these, the most commonly used nuclear fuel material of choice in commercial nuclear reactors is uranium dioxide. Such commercial nuclear fuel materials may also be blended with small amounts of other ingredients, including neutron flux modifiers such as cadrinium.

Commercially produced uranium dioxide is a fine, porous powder, which is in a form unsuitable for use as is in nuclear fuels in commercial nuclear reactors. Various means have been developed and used to convert uranium dioxide into a form suitable as nuclear fuel in power reactors. One technique commonly used is to convert uranium dioxide into a suitable By sintering the mass of the powder at high temperatures, strong diffusion bonding was created between the individual powder particles.

However, the sintering technology of 41 has been developed by compression molding the bulk powder, which increases the strength and bonding properties of the handling and sintering operations. It is necessary to obtain a particle molded body in advance.

Therefore, C, by molding the slightly 1 particles into 11 shrinkage),
Obtaining compacted compacts with sufficient strength and homogeneity to withstand subsequent handling and sintering at a sufficiently low defect rate is an important research topic in the nuclear fuel industry. Ta.

Conventional organic binders or PlusDeck binders commonly used in powder processing are considered unsuitable for use in nuclear fuel processing operations. This is because the introduction of binder residues such as carbon into the nuclear fuel product after sintering is unacceptable for nuclear reactor applications. Moreover, the presence of organic binders between the particles prevents the formation of strong diffusion bonds between the particles during sintering, and thus the density of the sintered product is adversely affected. Complete removal of the binder or its decomposition products prior to sintering is particularly difficult and typically requires costly additional operations during nuclear fuel production.

Therefore, it has been conventional practice to compression mold uranium dioxide powder in a mold to form a compact green compact of approximately 100 ml without the aid of any binder. However, with this h method, 1. i. The low strength of green compacts of binder-free powders results in a high rate of rejects and waste A recycling operations, which are costly.

Yonee 1, Qalli Van, December 6, 1977, assigned to the same assignee as in the case of the present application.
Special Edition No. 40 [11700] describes a group of unique fugitive binders that improve the production of sintered pellets of granular nuclear fuel material for nuclear reactors. The fugitive binder of this patent acts without contaminating the resulting nuclear fuel product and provides effective interparticle bonding during sintering without adversely affecting the desired porosity of the sintered belene. Enables bonding to be formed and covered.

Further, U.S. Pat.
No. 27154 also concerns important issues in the field of manufacturing nuclear fuel pellets from fissile granular ceramic material (15). [All contents disclosed in the specification of No. 4061700 are incorporated herein by reference (
11. Take those that match.

However, two prior art techniques (although disclosed in U.S. Pat. No. 4,061,700)
It turned out that there were some dissatisfaction with the situation.

For example, when using the fugitive binder of the above patent, it is possible to obtain consistent results in terms of pellet strength and bonding properties, regardless of the blending conditions or particle properties of the uranium dioxide powder. There is. Specifically, the agitation intensity during compounding, the relative humidity and temperature, the storage period, and the properties of the carbon dioxide powder (e.g., particle size, surface area, and water content) all affect the physical properties of the -C imparted by such fugitive binders. This can be a factor that clearly impairs the uniformity of physical characteristics. These drawbacks become more noticeable when the speed of compression molding by the mold is avoided.

By imparting greater plasticity to such granular ceramic materials, the industry has developed a method of producing compact compacts with minimal rejects over a wide range of IC production rates, including high-speed compression molding using continuous rotary presses. A more effective and practical fugitive binder system has already been provided that allows for this.

Examples of such improved fugitive binder systems include the aforementioned U.S. Pat.
No. (r) 7-mine type binders are mentioned.

However, it has been found that the improved plasticity imparted by such binder systems is not always sufficiently sustained as they tend to reduce -C over long periods of time after blending with nuclear fuel materials. It is therefore not possible to store or preserve molding compositions consisting of mixtures of particulate ceramic 1,1r3t and such amine-type binders for long periods of time. These drawbacks create obstacles to production schedules and long-term transportation.

Experience with fugitive binders of the amine carbamate type mixed with uranium dioxide-containing nuclear fuel materials indicates that one of the factors that reduces the effective initial plasticity imparted by such binders is
One of the factors is thought to be exposure to moisture1, and high temperatures have also been found to reduce the plasticity of such mixtures. In short, molding compositions consisting of granular ceramics containing uranium dioxide and such amine-type binders lose C stability due to increased brittleness over time and undergo high compression rates. This is in response to the trend of products that cannot withstand molding and have a high defect rate.

SUMMARY OF THE INVENTION According to the present invention, when producing a coagulable compressed body from granular ceramic nuclear fuel material, compression molding can be carried out for a long period of time by imparting and retaining plasticity to the granular ceramic nuclear fuel material. A method is provided for characterizing what is possible. More specifically, the present invention is directed to a process that features the combination of certain ingredients, including the essential ingredients, to produce a fugitive binder for a compression molding process.

OBJECTS OF THE INVENTION The main object of the present invention is to provide a method, a fugitive binder, and a product obtained thereby to enable compression molding of granular nuclear fuel material over a long period of time.

Granules also provide a means to overcome the brittleness problem of lamic nuclear fuel materials, while imparting sustained plasticity to such nuclear fuel materials, allowing them to withstand almost all compression conditions and high speeds over long periods of time. It is also one of the objects of the present invention to enable compression molding of the same while reducing the rejection rate.

Furthermore, the period of compression molding the granular Hiramic nuclear fuel material containing uranium dioxide powder J) and a fugitive binder of a uranyl sikolate carbonate compound to form a coagulable compact is extended. It is also an object of the present invention to maintain the plasticity and moldability of such granular ceramic nuclear combustion materials.

Furthermore, in a method for producing a uranium dioxide-containing nuclear fuel material from a granular ceramic nuclear fuel material, the granular ceramic nuclear fuel material contains uranium dioxide and a fugitive binder, and the properties of the material remain long after the components are blended. An object of the present invention is to provide a method capable of forming a cohesive compact by compression molding at high speed while minimizing the defect rate due to crushing, which is stable over a period of time. No. 1
It is one.

Furthermore, J: due to its persistent plasticity, it has a length of 1 l.
Between the IJ and IJ, a compression moldable granular mixture containing carbon dioxide and cran, which can be molded into cotton, is prepared.
It is one of the objects of the present invention to provide the following.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing pelletized fissile nuclear fuel products from granular helical nuclear fuel material using a fugitive binder system that is removed during a subsequent sintering operation. Such methods involve compression molding a blend of granular hiramic nuclear fuel material containing uranium dioxide powder and the unique fugitive binder composition of the present invention to form a suitable compacted compact, and then It consists of sintering a compacted body to produce a sintered body of fissile nuclear fuel material suitable for use in a nuclear reactor.

The granular fissile nuclear fuel material that can be used in the present invention C refers to various materials used as nuclear fuel for nuclear reactors, including ceramic compounds such as oxides of uranium, plutonium, and thorium. can be mentioned. Among the preferred nuclear fuel materials are uranium oxide, plutonium oxide, thorium oxide and mixtures thereof.

The particulate ceramic nuclear fuel material used in the practice of the present invention may also contain various additives, such as neutron absorbers containing gadolinium, to adjust neutron flux density.

Suitable fugitive binder systems for use in the practice of the present invention include the aforementioned U.S. Pat.
No. 3900, In 8. Such amine-containing compounds are selected from the group consisting of amine carbonates and amine carbamates, illustrative of which are ethylenediamine, monomethylamine, 3,3-dianodi1L1pyramine,
1,3-diaminopropane, 1,6-diamithexane, n-butylamine, diethylene 1-liamine and 1
, 7-diaminohezotane carbonate or carbamic acid salt.

In the present invention, C includes the above-mentioned amine-containing compounds and
Ammonium chloride is added. The added binder components and their reaction products are then substantially homogeneously blended with the particulate seminic nuclear fuel material.

In accordance with the present invention, an improved granular ceramic nuclear fuel product V containing uranium dioxide is provided which serves to impart a lasting plasticity to it, thereby making it capable of withstanding adverse conditions for extended periods of time. The fugitive binder system is prepared as follows.

Ammonium oxalate, which has a low solubility in water, is added to the uranium dioxide powder along with an aqueous solution of the amine. As a result of the pH of the aqueous solution rising due to the hydrolysis of the amine, ammonium oxalate dissolves while rapidly generating ammonia gas at high temperatures. That is, at temperatures of at least about 65° C., the reaction between the binder components occurs within a short period of time (e.g., about 10 to 30 minutes or more) after mixing the ammonium oxalate and the amine in aqueous solution. A fugitive binder is produced as a product. The components of the reactant, including the resulting binder composition, are then dried to remove excess by any suitable means, such as by passing a nitrogen gas heated to a moderate temperature of up to about 150°C. Moisture is removed.

This unique binder system with a high degree of plasticity (= J M, -9) was found to be stable and at the same time extremely resistant to reaction with water and thus to degradation. It also
It was also found that it is stable for a long period of time at relatively high temperatures up to 1cm. Furthermore, it decomposes sufficiently at high temperatures of about 200 DEG C. that it can be effectively eliminated in the subsequent sintering process.

Therefore, the unique binder system of the present invention does not deteriorate even when its combination with particulate ceramic nuclear fuel material is stored or stored for long periods of time under adverse conditions of high temperature and humidity.

Regarding the proportions of the binder components used to obtain the binder compositions of the present invention, the above amines are about 0.5 to about 1 (amount) based on the volume of particulate relamic nuclear fuel material. It is preferable to use a proportion of %. Further, ammonium oxalate is used in a proportion of about 0.25 to about 4 (tfn)% based on the width of the granular ceramic nuclear fuel material. If the proportion of such binder components exceeds the upper limits of the above ranges, not only will generally no increase in benefits be obtained in terms of binding properties, but the benefits will be diminished due to undesirable effects and costs will increase due to increased amounts of components. will occur.

As mentioned above, in order to facilitate the reaction between ammonium oxalate, which has low solubility, and the amine, the amine is dissolved in water in advance. Any concentration of aqueous amine solution useful for accomplishing the reaction and addition to the particulate relamic nuclear fuel material can be used. For example, it is not advisable C to remove excess water in subsequent operations. 8 (X), it is generally appropriate to use an aqueous amine solution with a solids content of about 40 to about 50%. In this case,
Excess water is removed after the reaction period. Suitable water removal means include nitrogen gas at a temperature of up to about 150° C., typically for about 20 to about 60 minutes, or longer if necessary, into the overlying granular mixture containing the binder components and their reaction products. Niwata ℃ through Ubayoi.

After a binder system prepared from an amine and ammonium oxalate in aqueous solution in accordance with the present invention is blended with granular ceramic nuclear fuel material containing uranium dioxide, the resulting blend is well known in the art. By compression molding according to the operating procedure described in the following, a suitably cohesive compact can be formed. The method of the present invention imparts a high degree of plasticity to the blend of fugitive binder and granular nuclear fuel 1F+ material, so that such blends can be used immediately or have long-term use. It is also difficult to use the product after long delays due to storage and transportation. The persistent plasticity imparted by the present invention extends over a long period of time from the preparation of the formulation to the unsintered condensed t1 heavy bodies from such formulations in high speed continuous production operations using rotary presses. There is not enough to form it efficiently.

The unsintered compacted compact thus formed is then sintered according to operating procedures well known in the art, thereby removing the binder and at the same time creating a homogeneous material that avoids unifying the Leramiku particles. A continuum is produced. The sintered product, usually in the form of pellets, is then milled to specified dimensions depending on the intended use.

The added binder component can be blended using any suitable dry mixing device.
Examples include low shear mixers such as fluidized bed mixers, slab blenders and ribbon blenders, and high shear mixers such as vibratory mills, ball mills and centrifugal mills.

Among the preferred mixing devices are Peri and Chilton (Pe
rry & chilton) m r'y mikal-
Engineering Handbook (Chemical
En(1inceringl-1andbook)
This is a vibratory mill of the type described in 8-29 to 8-30@ of J No. 51 & (McGraw-Hill Book Company).

An example of a suitable operating procedure for carrying out the present invention and an example of a fugitive binder composition of the present invention is set forth below. The uranium powder is processed using a vibrating mill.
V 1bro-Energ manufactured by c,)
y) It was put into Mill 1 and blended with the binder component. To be more specific, it is approximately 0.8 based on the Φ distance of uranium dioxide.
A solid powder of ammonium oxalate in a proportion of 〈mm〉% was added to the uranium dioxide.

Also, by adding about 48 (mffi)% aqueous solution of ethylenediamine carbame 1 to uranium dioxide,
Approximately 1.63 (ili) based on the weight of uranium dioxide
U't )% water and about 1. ! Provide i% (by weight) of solid ethylenediamine carbamate. The weight ratio of amine carbamate to ammonium oxalate is approximately 1
．． The ratio was 9:1. Combining and reacting these components in a video mill at a temperature of at least 65° C. for about 25 minutes produced an effective fugitive binder consisting of uranyl oxalate carbonate.

The reacted components were then dried by covering with a scum heated to a temperature below about 150 DEG C., while at the same time removing the brenny scum formed during the reaction from the formulation.

The product obtained by reacting these components as described above was confirmed to be uranyl carbonate having the formula % (20).

The results of chemical analysis of two binder samples prepared from the above components according to the procedure 1 above were as follows.

The molar ratio of U:C2042-:CO3'-:H2O was as follows.

The above composition was also confirmed by infrared spectrum measurements.

Patent Applicant General Electric 1 ~ Rick Company Agent <7
630> Ushinuma i Awa 2 Continued from page 1 0 Inventors John Donald Coan/Lee, Junior, 0 Inventors Timothy Jose Af Gallivan
14:00, Wilmingt-Parliament Trino 21, North Carolina, United States Wilmingt Corn Road, North Carolina, United States

Claims (1)

[Scope of Claims] 1. (a) A fugitive binder consisting of a mixture of amine and ammonium oxalate is added and blended into a granular ceramic nuclear fuel material containing uranium dioxide, and then (b)
) Compression molding of the resulting blend of granular ceramic nuclear fuel material and binder to form a cohesive compact results in the granular reflexive nuclear fuel material having a persistent plasticity. (Condensability of granular ceramic nuclear fuel material characterized by being able to be processed over a long period of time 1) [Method for producing a condensate. 2. Features in which the amine is in an aqueous solution state (claim 1 3. The method according to claim 1, wherein the amine is an amine carbamic acid salt [[Jl No.] 1rJ. 4. The method according to claim 1, wherein the amine is 1-ethylene diamine carbamate. Method. 5. (a) Adding to a granular ceramic nuclear fuel material containing uranium dioxide a fugitive compound comprising a mixture of at least one amine selected from the group consisting of amine carbonates and amine carbamates and ammonium oxalate. As a result of including both steps of adding a binder and blending M, and then (il) compression molding the thus obtained blend with the binder and the granular ceramic nuclear fuel material to form a coagulable compact, the granular A method for producing a coagulable compressed body of granular ceramic nuclear fuel material, characterized in that the Refmic nuclear fuel material has persistent plasticity and can be processed over a long period of time. 6. The amine is in the state of an aqueous solution. 7. The method of claim 5, wherein the amine is 1-dylenediamine carbamate. 8. The method of claim 5, wherein the fugitive binder is a 6. The method of claim 5 comprising a mixture of about 0.5% to about 7% (by weight) amine and about 0.25% to about 4% (by weight) ammonium oxalate. 9. The method according to claim 5, wherein the amine and ammonium oxalate components of the fugitive binder are mixed prior to addition to the particulate ceramic nuclear fuel material. 10. A fugitive binder consisting of a mixture of ethylenediamine carbamate and ammonium oxalate is added to the granular Reramic nuclear fuel material contained in the mixture, and (b) the mixture of the granular Reramic nuclear fuel material and the binder thus obtained is blended. As a result of including both steps of compression molding to form a compacted compacted body, sustained plasticity is imparted to the granular ceramic nuclear fuel material and long-term rolling is possible. A method for producing a coagulable compressed body of granular heramic nuclear combustion material T1, characterized by The method according to claim 10. 12. The method of claim 10, wherein the ethylene diamine carbamate is in an aqueous solution and the ammonium oxalate is dispersed into the aqueous solution of the ethylene diamine carbamate prior to addition to the particulate ceramic nuclear fuel material. 13. The fugitive binder comprises about 0.5% to about 1% (by weight) ethylenediamine carbonate and about 0.25% to about 4% (by weight) C based on the weight of the particulate ceramic nuclear fuel material.
11. A method according to claim 10, comprising a mixture with % ammonium oxalate. 14. The fugitive binder comprises a mixture of about 1.5% (by weight) ethylenediamine carbamate and about 0.8% (by M) ammonium oxalate, based on the weight of the particulate ceramic nuclear fuel material. Claim 10
The method described in section. 15. (a) Preparing a fugitive binder for granular ceramic nuclear fuel material by adding to the granular ceramic nuclear fuel material about 1.9 parts by weight of an aqueous solution of ethylenediamine carbonate and about 1 part of ammonium oxalate; and then add r(b) to about 65
The granular ceramic nuclear fuel material is blended with the granular ceramic nuclear fuel material at temperatures higher than 10°F (°C) to cause the components to react to form a binder for the granular ceramic nuclear fuel material so that the granular ceramic nuclear fuel material remains 1. A method for producing a coagulable compressed body of a granular helical core material, which is characterized by imparting a high level of plasticity and making it possible to form a solid material between C lengths 1 and 11. 16. Granular Hiramic nuclear combustion containing uranium dioxide 1
4 by compression molding a blend of material and binder.
16. The method of claim 15, wherein a compacted compact is formed. 17, (a) granular pyramic nuclear fuel material v'1 containing uranium dioxide; and (1)) the granular pyramic nuclear fuel material containing uranium dioxide and amine and silica acid in an aqueous solution state. A compression moldable granular mixture containing granular nuclear fuel material mixed with a fugitive binder consisting of a reaction product. 18. The compression moldable granular mixture according to claim 17, which is compression molded into a coagulable compact. 19. The compression moldable granular mixture according to claim 17, wherein the amine comprises at least one amine selected from the group consisting of amine carbonates and amine carbamates. 20, a mixture of (a) a granular relamic nuclear fuel material containing uranium dioxide and (b) a fugitive binder consisting of a reaction product of ethylenediamine carbonate and ammonium oxalate with said uranium dioxide in an aqueous solution state. Compression moldable granular mixture containing granular nuclear fuel material. 21. The fugitive binder is about 0.5 to about 7 (wt.%) ethylenediamine carbonate to about 4 (wt.%) based on the weight of the particulate Leramitsu nuclear fuel material.
21. Compression moldable granular mixture according to claim 20, comprising the reaction product of ammonium oxalate with % ammonium oxalate. 22, Formula [UO2(CO8)(C204) ・21120] ・
A uranyl oxalate carbonate composition represented by No. 2820 and which imparts improved bonding properties to particulate ceramic nuclear fuel material. 23, characterized in that it is formed by reacting at least one amine selected from the group consisting of amine carbonates and amine carbamates and ammonium oxalate with uranium dioxide, and is represented by the formula % formula %) and A uranyl oxalate carbonate composition that imparts improved continuous bonding properties to particulate ceramic nuclear fuel material containing uranium dioxide. 24. Improved granular ceramic nuclear fuel material expressed by the formula % and containing uranium dioxide, obtained by reacting an aqueous solution of ethylenediaminecarbame-1-1 and ammonium oxalate with uranium dioxide. A uranyl oxalate carbonate composition that exhibits sustained binding properties. 25. (a) Adding to the granular ceramic nuclear fuel material an aqueous solution of ethylenediamine carbamate and ammonium oxalate in a ratio of about 1 part by weight of ammonium oxalate to about 1.9 mff of ethylenediamine carbamate. preparing a fugitive binder for nuclear fuel material; (b) blending the added components with the particulate ceramic nuclear fuel material at a temperature above about 65° C. to react the components; producing a binder for granular ceramic nuclear fuel material, and then (c) drying the reacted components using heated gas at a temperature below 150°C and extracting water and ammonia from the prepared mixture. As a result of including gas removal steps, the granular ceramic nuclear fuel material has a persistent plasticity (
1. A method for producing a coagulable compact of granular ceramic nuclear fuel material, which is characterized in that it can be processed over a long period of time.