Method of compacting radioactive long-length members of zirconium and zirconium alloy structures

FIELD: nuclear power engineering.

SUBSTANCE: compaction involves cutting members into fragments using electroerosive destruction of member wall by pulse spark-arch discharges emerging between member and electrode. In addition, high-temperature treatment in oxidizing medium, in particular vapor formed, is carried out. Cutting and heat treatment are accomplished in water.

EFFECT: simplified procedure and increased safety.

3 cl

 

The invention relates to the field of nuclear technology and can be used for compacting radioactive contaminated lengthy construction elements made of zirconium or its alloys, which are formed during regeneration of nuclear fuel from the fuel assemblies of nuclear reactors and equipment dismantling nuclear power plants.

Closest to the claimed invention, the set of essential characteristics is a method of compacting radioactive long structural elements made of zirconium or its alloys, as described in UK patent No. 1359104, CL G 21 19/04, publ. 10.07.1974. The method involves cutting EDM by destruction of the walls of the elements on the part of the pulse iscrobble discharge created between the element and the electrode, as well as high-temperature treatment in an oxidizing environment.

The disadvantages of this method, selected as a prototype, are low radiation and environmental safety and high energy costs.

The present invention is to create a simple and radiation-safe method of compacting radioactive long structural elements made of zirconium or its alloys, which will allow you to receive radioactive waste from small volume that will provide them with reliable and safe the second burial.

The technical result of the invention is to reduce the energy released during oxidation of zirconium or its alloys, to values at which the possibility of occurrence of uncontrollable exothermic reaction, and almost simultaneous processes of cutting and processing of long radioactive elements due to the exclusion of the delivery process of the cut parts of the items to the place of processing.

This technical result is achieved in that in the method of compacting radioactive long structural elements made of zirconium or its alloys are cutting elements on the part of the EDM destruction of the wall element pulse iscrobble discharge created between the element and the electrode. Produce high-temperature treatment in an oxidizing environment, which use steam. The cutting and processing is carried out in water. When this treatment is carried out by an electro-erosive destruction of parts of the element pulse iscrobble discharge created between these parts.

In addition, the cutting can be carried out with alternating voltage from 20 to 40 V and a current of from 200 to 1000 A.

In addition, the cutting is performed at alternating voltage of from 25 to 40 V and a current of from 200 to 1200 A.

The method is as follows.

Long elem the HT design, for example, the channel of a nuclear reactor of zirconium alloy (tube length of 8-10 m, diameter 90 mm, wall thickness 4-5 mm), placed in a tank filled with water, fix not less than two points and produce cutting. For this element and the electrode-tool connected to a pulse generator (AC voltage from 20 to 40 V and a current of 200 to 1000 A). Then the element rotates at a speed ranging from 0.1 to 10 cm/sec, and the electrode is moved until it touches the element. Occurs a series of powerful isroughly discharges between the element and the electrode. When the wall element is subjected to electrical discharge destruction at the height exceeding the thickness of the electrode, and on the whole circumference of the element, which leads to the cutting element into two parts. The local part of the element constituting the length of several mm, is melted. Drops of molten zirconium or its alloy, the super-heated above the melting temperature, react with oxidizing environment - steam formed in the cavity around each droplet, and turn into particles of Zirconia. After cutting element electrode returns to its original state, while sections of the element connected to the pulse generator (AC voltage from 25 to 40 V, 200 to 1200). The upper section is moved with simultaneous rotation until it touches the bottom of the cut (the rate of convergence of the 0.1 to 2.0 mm/sec) and the emergence of sustainable isroughly discharges between their end surfaces. This cuts locally melted, and droplets of molten zirconium or its alloy, the super-heated above the melting temperature, react with oxidizing medium is steam. Mutual EDM destruction of the segments is carried out before the moment when the length of the bottom segment reaches the specified value. Then turn off the pulse generator, free the remaining part of the lower segment and drop it into the chamber of the deposition of solid radioactive waste. Next, the remaining part of the upper segment is cut into two segments and repeat the operation for their mutual destruction. In the end from the source element 1 remains n+1 cylindrical segments, where n is the number of cuts, and a large mass of decay products of zirconium alloy in the form of spherical microcapsules Zirconia with a diameter of 0.1 to 3 mm, and particles much smaller oxides, which are practically insoluble in water. The process parameters are chosen so that eye-catching in each period of the destruction of energy sufficient to initiate self-sustaining and samorasprostranyayushchiisya exothermic reaction. This is achieved by selecting the speed of convergence, area of occurrence iscrobble discharge, i.e. the restriction weight of zirconium, which may react. Since the processes of cutting and processing occurs in water, practically no ha is obraznye and liquid radioactive waste. The whole mass of the radioactive metal is converted into the solid radioactive waste is not soluble in water. While the resulting product is significantly less than the structural elements prior to processing. According thermotechnical calculations the performance of the method of compacting can reach up to 100 kg/hour.

1. Method of compacting radioactive long structural elements made of zirconium or its alloys, including the cutting elements on the part of the EDM destruction of the wall element pulse iscrobble discharge created between the element and the electrode, and high-temperature treatment in an oxidizing environment, characterized in that the cutting and processing is carried out in water, and the treatment is carried out by an electro-erosive destruction of parts of the element pulse iscrobble discharge created between the said parts, as well as oxidizing environment using the generated pairs.

2. The method according to claim 1, characterized in that the cutting is carried out at an alternating voltage of 20 to 40 V and a current of 200-1000 A.

3. The method according to claim 1 or 2, characterized in that the treatment is carried out under AC voltage 25-40 and In the current 200-1200 A.



 

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FIELD: nuclear power engineering.

SUBSTANCE: compaction involves cutting members into fragments using electroerosive destruction of member wall by pulse spark-arch discharges emerging between member and electrode. In addition, high-temperature treatment in oxidizing medium, in particular vapor formed, is carried out. Cutting and heat treatment are accomplished in water.

EFFECT: simplified procedure and increased safety.

3 cl

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