The dry method of processing scrap nuclear fuel from mixed oxide (u, pu) o2

 

The invention relates to the field of production and processing of nuclear fuel. The inventive method of dry recycling scrap nuclear fuel from mixed oxide (U, Pu)O2formed during the cooking fuel or for referral to waste fuel due to the absence or cessation of its use, includes dosage, and the first mixing powdered scrap and, in some cases, powders PuO2and/or UO2. Then perform fine grinding - micronization and forced sieving received the first mix of the new dosing and a second mixture of the first sifted mixture of powders Rio2and, in some cases, powder waste. The second mixture is subjected to pelletizing, and the resulting tablets sintering. Process pre-treatment of waste is that exercise tableting and sintering powdered scrap for receiving tablets from waste and fine grinding of pellets from waste for introduction as powdered waste in the first mixture and/or the second mixture. Advantages of the invention lie in the fact that the processing of scrap nuclear fuel from mixed oxide (U, Ri)O2it is possible to carry out on the camping to the dry method of processing scrap nuclear fuel from mixed oxide (U, Pu)O2.

Cooking fuel for light-water reactors on the basis of the oxides of uranium and plutonium, usually called MOX fuel, is an object of various developments, due to the desire to re-use the plutonium generated during the reprocessing of spent fuels.

Preparation and irradiation of MOX fuel in LWRs is now seen as one solution that provides reasonable protection from plutonium, regardless of whether the plutonium civilian or military origin.

In the last two decades, there have been developed several methods of cooking fuel MOSS, some of which to get thin mixture include grinding of the total number of powders UO2and Rio2while others are limited to grinding only part of these powders. The MIMAS process (reduction for Micronisation and MASter blend) fine grinding masterbatches (original mix) MIMAS, which was developed by the author of the present invention (Fig.1), is carried out by fine grinding (micronisation) only part of the final mixture and includes two sequential mixing, which provide isotopic homogenization and allow the use of fluid out is to participate in the process (for example, by eliminating operations pre-compaction-granulation or spheroidizing mixture of oxide and considerably easier to implement in industry testing of MOX fuel users and permits administration Nuclear Supervision (due to the similar characteristics of MOX fuel and fuel UO2).

In the production of fuel mixed oxide for light-water reactors at startup formed of a significant amount of scrap and continue to be formed during subsequent production. This waste is caused by the process, the technical requirements of the user of fuel in the production of batches of products) and monitor quality by sampling.

There are ways to recycle scrap mixed oxide wet method. These processes have a number of different serious drawbacks: on the one hand, they provide significant amounts of liquid waste, which creates additional risk, on the other hand, they require the fulfillment of additional conditions and means of transportation in those cases (and this happens often), when installing a wet processing method is not there, where is the setting that produces scrap.

Task nastoyashte its production in the manufacture of fuel.

In addition, from experience, it follows that the processing of scrap without special precautions may lead to defects in the manufacture of tablets: excessive variability of the physical characteristics of the product, damages resulting from differential shrinkage, for example due to the direct utilization of powders after grinding, the defects such as bubbles, due to the volatile impurities, etc. In General, when the production of the product with adjustable characteristics should ensure that the control characteristics of the source material.

To eliminate the above disadvantages of the dry method of processing scrap nuclear fuel from mixed oxide (U, Ri)O2formed during the cooking fuel or sent to the waste due to the absence or cessation of its use, according to the invention lies in the fact that carry out the dosing and the first mixing powdered scrap and, in some cases, powders Rio2and/or UO2, pulverisation (micronization) and compulsory screening of the first mixture, a new dosing and a second mixture of the first sifted mixture of powders Rio2and, in some cases, powder waste, tableting second mixture and the volume, what does tableting and sintering powdered scrap for receiving tablets from waste, fine grinding pellets from waste for introduction as powdered waste in the first and/or second mixture.

It is advisable that the method further contained crushing tablets waste production before fine grinding.

It is useful to have as powdered scrap for tabletting and sintering in the pre-treatment used green powders sent to the waste and/or generated during the grinding of fuel pellets.

It is advantageous for the processing of irradiated nuclear fuel tablets from (U, Ri)O produced in various industrial processes and sent to the waste, these tablets are to be subjected to the specified pre-treatment process.

It is expedient in the specified process for production of fuel pellets to enter up to 40% of waste in the calculation of net mass produced tablets.

Useful in the first mixture to enter up to 100% waste.

It is also useful to re-use in a dry form of 99.5% (expressed as weight of Rio2waste process described above for the production of fuel pellets.

It is desirable for the fine grinding of the first seem add lubricating agent, which is used as zinc stearate.

It is useful to have carried out the sintering of the pellets containing waste, or tablets of waste in the atmosphere of argon or hydrogen at a temperature mainly from 1670-1760oC.

Preferably, the sintering process was adjusting the partial pressure of oxygen PuO2using to improve mutual diffusion of oxides Rio2and UO2moisturizing.

Useful for carrying out operations of way or for transportation of dust from waste and oxides from Rio2and UO2was recuperable with cleanable filters for re-use on stage, as pellets and sintering in tablets of waste.

The invention is further explained in the description of the preferred variants of the embodiment with reference to the accompanying drawings, in which: Fig. 1 depicts the stages of fuel production from mixed oxide method MIMAS;
Fig. 2 depicts the stage of fuel production from mixed oxide and the stage of dry reuse according to the invention.

To eliminate these defects, the method according to the invention the dry processing of scrap mixed oxide (U, Pu)O2has its foundations is m, exercising
dosing and the first mixing stage (stage 1) scrap and, in some cases, powders PuO2- 32 and/or UO2- 31,
pulverisation (micronization) (stage 2) first mixture, in particular by grinding and compulsory screening (stage 3) this product 1, for example, through the cell size 250m,
new dosing and the second mixing stage (stage 4) first sifted mixture 3, powders UO223 and, in some cases, scrap,
homogenization (stage 5) the second mixture 4 and the addition agent or agents, lubricating and/or regulation of porosity,
pressing (stage 6) of the second mixture in tablet presses (tableting) and
sintering (stage 7) thus obtained fuel pellets 6 mainly in the humidified atmosphere of argon and hydrogen.

This process of manufacturing fuel pellets from mixed oxide usually contains also the following stages
dry grinding (stage 8),
sort by appearance (stage 9),
stacking (aktirovanie) (stage 10),
the location of the tablets in the shell and brewing membranes in the form of fuel rods,
the pressing rods
non-destructive control rods (stage 12) and
the Assembly rods (the SS pre-treatment of waste 6, 8, 9 including, in particular,
tableting (stage 20) and sintering (stage 21) scrap generated in the specified process of manufacturing fuel pellets from mixed oxide, to obtain pellets from waste and
pulverisation (micronization)(stage 23) pellets from waste to obtain a powder of waste intended for inclusion as powdered scrap in the first and/or second mixture (stages 1 and/or 4).

It should be noted that the above-described dry method of processing does not include the stage(s) pre-compaction-granulation (or spheroidizing), usually intended to improve the fluidity of the final mixture, and facilitating the filling of the mold during pressing. Such stages to the present invention are excessive due to the presence of used stages of the method of the invention and sequences.

Below is the example illustrates several non-limiting of the invention the parameters of the manufacturing process of tablets:
work with the parties preferable to continuous operation,
the plutonium content of the first mixture is from 20 to 40%,
grinding parties 60 kg for the shortest effective time 5 hours,
the use of powder is parohinog agent AZB, well-known experts,
pressing under a pressure of from 400 to 600 MPa,
sintering for at least 4 hours at a temperature of 1650-1760oWith in argon with 5% hydrogen and the ratio of N2/N2O from 20 to 30,
dry grinding without centering.

During these operations the manufacture of tablets scrap can be made in the amount of from 10 to 20% of the net weight, and these limits depend on several significant variables, such as specific technical requirements of the user of the method or its client (for example, technical requirements for visible defects), the sizes of manufactured parties and so on,

To reduce the time spent on pulverisation 23 tablets of waste, the method can include them prior to fragmentation (stage 22).

As scrap for tabletting and sintering (stage 20 and 21) in the method of pre-processing, you can use green, bred in waste powders and/or powder from grinding (stage 8) fuel pellets.

To limit the necessary materials and space for stages dry waste treatment (stage 20-23) for their processing can be applied normal to the manufacture of fuel pellets equipment, such as crushers, briketi the change from default settings, used mainly manufacture fuel pellets. Manufacturing of parties makes it possible to perform operations of processing between the actual manufacture of tablets.

As for the dust from waste and oxides from Rio2and UO2formed during the process or during transportation, this dust can be recovered by using filters, which are cleared for processing at stages, as pellets and sintering (stage 20 and 21) with the formation of pellets from waste.

It is advisable to enter up to 40% of pre-treated (at the stages 20-23) waste in the calculation of net weight of fuel pellets produced in the above-described manufacturing process.

Experience has shown that it is possible to recycle the scrap produced in the manufacture of tablets in the mode of production, amounting to from 20 to 25% of the net weight of the produced tablets.

In particular re-used in a dry form of 99.5%, expressed in weight PuO2waste production of the above-described process of manufacturing fuel pellets.

The possibilities of the method of the invention to reuse significant amounts of waste can be used to re-use the unscheduled theodicy in the above first mixture to 100% pre-treated in accordance with the invention, waste, regardless of, if they are in the process of manufacturing tablets MOSS (MIMAS process) or in any other process.

For fine grinding of the first mixture (stage 2) the above-mentioned pellets from waste (stage 23), mainly used ball mill.

In the sintering process (stage 7, 21) it is possible to adjust the partial pressure of oxygen RHO2mainly using to improve mutual diffusion of oxides Rio2and UO2moisturizing.

The main types of waste occurring given in the table as example.

Crushing stage (stage 22, optional) and fine grinding (stage 23) tablets can also be used for reuse of the waste of tablets, for example, when sorting (stage 9) and to increase the size of the batches of powder scrap, homogenised and characterized reuse.

The present invention is not limited to the above-described forms of exercise and it can be made many changes, without leaving the scope of the claims.

Laboratory nitrate solutions can be subjected to deposition and annealing before re-using the dry method described but to resort to a preliminary chemical treatment in the aqueous phase.

A way to reuse waste according to the invention can also be applied for re-use as source material unirradiated nuclear fuel tablets from mixed oxide (U, Pu)O2, which may be formed in different processes (for example, when the direction of deviation of unirradiated fuel mixed oxide intended for new and research reactors).


Claims

1. The dry method of processing scrap nuclear fuel from mixed oxide (U, Pu)O2formed during the cooking fuel or for referral to waste fuel due to the absence or cessation of its use, including dosage and the first mixture (1) powdered scrap and, in some cases, powders PuO2and/or UO2, pulverisation - micronization (2) and forced sieving (3) received the first mix of the new dosing and the second mixture (4) the first sifted mixture of powders Rio2and, in some cases, powder waste, tableting (6) the resulting second mixture and sintering (7) thus obtained tablets and process pre-treatment of waste, which consists in the fact that assests Lonnie (23) tablets of departure for introduction as powdered waste in the first mixture (1) and/or the second mixture (4).

2. The method according to p. 1, characterized in that it further comprises splitting (22) tablets waste production before fine grinding.

3. The method according to p. 1 or 2, characterized in that as powdered scrap for tabletting (20) and sintering (21) in the pre-treatment use of green powders sent to the waste and/or generated during grinding (8) fuel pellets.

4. The method according to any of paragraphs.1-3, characterized in that it is subjected to pre-treatment process unirradiated tablets nuclear fuel (U, Ri)O2produced in various industrial processes and sent to waste.

5. The method according to any of paragraphs.1-3, characterized in that the above process of manufacturing fuel pellets enter up to 40% of waste in the calculation of net mass produced tablets.

6. The method according to any of paragraphs.1-3, characterized in that when you first mix (1) in the first mixture is injected up to 100% waste.

7. The method according to any of paragraphs.1-3, characterized in that the re-use dry 99.5% of waste from the production of fuel pellets, expressed in weight Rio2contained in the total amount of waste recycled.

8. The method according to any of paragraphs.1-7, characterized in that the manual according to any one of paragraphs.1-8, characterized in that, prior to pelletizing (6 and 20) add lubricating agent, which is used as zinc stearate.

10. The method according to any of paragraphs.1-9, characterized in that exercise sintering (7, 21) fuel pellets containing waste, or tablets of waste in the atmosphere of argon or hydrogen at a temperature mainly from 1670 to 1760C.

11. The method according to any of paragraphs.1-10, characterized in that the sintering process (7, 21) adjust the partial pressure of oxygen RHO2using to improve mutual diffusion of oxides Rio2and UO2moisturizing.

12. The method according to any of paragraphs.1-11, characterized in that during operations the way the dust from waste and/or oxides from PuO2and UO2Recuperat with cleanable filters for re-use on stage tabletting (20) and sintering (21) in tablets of waste.

 

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