A method of making a tubular membrane fuel rods and tubular membrane obtained by the above method

 

(57) Abstract:

The method allows to produce tubes that are designed to seal the nuclear fuel rod. Made the bar of an alloy based on zirconium content of 50 to 250 weight.h. iron, 0.8 to 1.3 wt.% niobium, less than 1600 weight. including oxygen, less than 200 weight.h. carbon and less than 120 weight.h. of silicon. Dip the strips into the water after heating at 1000 - 1200oWith, squeeze the workpiece after heating at 600 - 800oWith, carry out cold rolling the workpiece in at least four stages for receiving the tube, with intermediate stages of heat treatment at 560 - 620oWith and carry out a final heat treatment at 560 - 620oWith, and all stages of the heat treatment is carried out in an inert atmosphere or in vacuum. The technical result - high corrosion strength tubular membranes in an aqueous environment at high temperatures and adequate resistance to fluidity. 2 S. and 6 C.p. f-crystals, 1 Il.

The present invention relates to a pipe made of an alloy based on zirconium, intended to form the complete shell of a nuclear fuel rod or external parts or guide tube. It is important, though not the only, application in the field of technology the Department.

Up to the present time has been used mainly shell from an alloy based on zirconium, the so-called "Zircaloy-4", with content in wt.%: 1,20-1,70% - tin, 0.18 to 0.24 per cent iron, 0.07 to 0.13% of chromium, and the total content of iron and chromium is from 0.28 to 0.37 wt.%. In the classic version of the ratio of the content of iron and chromium, approximately, from 1,38 $ 3.42.

The oxygen content in Zircaloy-4 is typically less than 0.16 per cent and, as a rule, much lower.

The mechanical strength of the membranes of "Zircaloy-4" is quite high, however their susceptibility to corrosion as a result of the pressure of water at high temperatures limits their lifetime in the reactor.

Has already been proposed shell of alloy Zr-Nb approximately 2.5% niobium (US-A-4717534), which showed high corrosion strength in the aquatic environment at high temperature. However, this alloy has a low resistance to creep at high temperatures. It can be improved by increasing the oxygen content in the alloy up to 0.10 to 0.16 wt.% and through implementation of the final heat treatment of the membrane by recrystallization. However, the creep resistance of this alloy at high temperatures remains below that of other materials about the, allowing to obtain a pipe having high corrosion strength in the aquatic environment at high temperatures and adequate resistance to creep at high temperatures, and at the same time does not create difficulties in its implementation, leading to a high degree of waste.

This serves, in particular, a method of manufacturing a pipe from an alloy based on zirconium content of 50 to 250 weight. including iron, 0.8 to 1.3 wt.% niobium, less than 1600 weight. including oxygen, less than 200 weight. including carbon and less than 120 weight. including silicon, this process includes:

- hot pressure treatment ingots (for example, forging or rolling) to get the bar;

- dip the strips into the water after heating in an electric furnace or after induction heating at a temperature of from 1000 to 1200oC;

- the hood of a hollow workpiece after heating at a temperature of from 600 to 800oC;

- if necessary, heat treatment of the workpiece at a temperature of from 560 to 620oC;

at least four stages of cold rolling on the shape of a tube with decreasing thickness, with intermediate stages of heat treatment and final heat treatment at a temperature of from 560 to 620oC, and the first stages of the heat treatment osushestvlyaetsya, changing its metallurgical structure, until its use as a pipe for sealing or guide tube. However, to produce a single surface treatment and subsequent testing. The surface treatment may, in particular, to include sandblasting and chemical dekatirovke with subsequent washing. The surface treatment may be supplemented by grinding with a rotating belt or wheel. The control is carried out in a classical way.

It is important that the iron content did not exceed 250 weight. C. was obtained an unexpected result, namely, that the creep resistance at high temperature is sharply reduced, if the iron content exceeds 250 weight. 'clock In practice, the iron content of from 100 to 200 weight. hours gives good results from the standpoint of resistance to fluidity. The drawing shows the results of tests showing the magnitude of the deformations in diameter at different percentage content of iron in conditions typical of the shell, at 1% the content of niobium.

It is also important not to subject the alloy to heat treatment at a temperature above 620oC after extraction. Heat treatment at higher temperature leads to znachitelnaya on corrosion of zirconium alloys with a content of 1% niobium, carried out in an autoclave in an environment of steam at 500oC.

Example 1

intermediate processing stages: 2 hours at 580oC,

final treatment: 2 hours at 580oC.

Example 2

intermediate processing stages: 2 hours at 700oC,

final treatment: 2 hours at 580oC.

Example 3

intermediate processing stages: 2 hours at 700oC,

final treatment: 2 hours at 700oC.

When tested in the autoclave obtained shell weight:

- example 1 - 48 mg/DM2;

- example 2 - 57 mg/DM2;

- example 3 - 63 mg/DM2.

The samples in the three examples had an iron content of 150 weight. h

It was found that the alloy had the phenomenon of memory, i.e., the consequences of even one treatment after the first pass rolling at a temperature above 620oC is not completely eliminated.

Typically, the intermediate heat treatment was carried out at the recommended temperature of from 565 to 605oC, and temperatures above 580oC for intermediate stages of heat treatment and about 580oC for final processing was sufficient for most compounds.

The oxygen content of the order of 1200 weight. hours is sufficient to exert a positive effect on the creep resistance recrystallized alloy.

In the invention it is also proposed sealing or guiding pipe for connecting the fuel of a nuclear reactor, cooled and slow water under pressure, made of an alloy of zirconium with a fully recrystallized condition, with an iron content of 50-250 weight. 'clock, 0.8 to 1.3 wt.% niobium, 1000/1600 weight. including oxygen, less than 200 weight. including carbon, less than 120 weight. including silicon, and zirconium, except for inevitable impurities.

The analysis of the alloy revealed the absence of the equation Zr precipitation, harmful from the point of view of corrosion.

Conducted comparative testing of alloys containing niobium from 0.86% to 1.3%, and iron from 100 to 150 weight. h

Below are the typical steps used in the manufacture of products made of wrought iron rod with a diameter of 177 mm:

- immersion in water after heating for 1 hour at 1050oC;

- machining of the workpiece with an outer diameter of 168 mm and an inner diameter of 48 mm;

- hood after the Indus the rink pipes in five cycles, including intermediate stages of heat treatment for 2 hours at 580oC;

- final heat treatment for two hours at 580oC.

Tests showed resistance to General corrosion in an aqueous environment at a high temperature, typical conditions water reactor high pressure, comparable to the corrosion resistance of the known alloys of Zr-Nb with a high content of niobium; testing also showed resistance to creep at high temperatures, much higher than in the known alloys, and comparable with the best alloys Zircaloy-4": thus, after 240 hours at 400oC and 130 MPa can be measured following deformation yield by diameter:

- Zr, 1%, 150 weight. including Fe, precrystallization: 0,5%;

- recrystallized "Zircaloy-4" optimal composition from the viewpoint of fluidity: 1,0%.

1. A method of making a tubular membrane fuel rods, which is full shell or outer part of the shell specified rod or tubular guide rod nuclear fuel, characterized in that made the bar of an alloy based on zirconium content of 50 to 250 weight. including iron, 0.8 to 1.3 wt.% niobium, less than 1600 weight. including oxygen, less than 200 ve is cooking after heating at 600 - 800oC, carry out cold rolling the workpiece in at least four stages for receiving the tube, with intermediate stages of heat treatment at 560 - 620oC, carry out a final heat treatment at 560 - 620oC, and all stages of the heat treatment is carried out in an inert atmosphere or vacuum.

2. The method according to p. 1, characterized in that the tubular sheath receive as a result of four or five passages cold rolling of the workpiece subjected to the hood.

3. The method according to p. 1 and 2, characterized in that the extrusion billet is followed by heat treatment at 560 - 620oC.

4. The method according to PP.1, 2 and 3, characterized in that the intermediate stages of the heat treatment is carried out at the recommended temperature from 560 to 605oC.

5. The method according to one of paragraphs.1 to 4, characterized in that the final heat treatment is carried out preferably at a temperature of about 580oC.

6. The method according to one of paragraphs.1 to 5, characterized in that the iron content is approximately 150 weight. h

7. The method according to one of paragraphs.1 - 6, characterized in that the oxygen content is 1000 - 1600 weight. h

8. Tubular sealed blockages, made of an alloy based on zirconium in the fully recrystallized condition, with an iron content of 50 to 250 weight. hours 0.8 to 1.3 wt.% niobium, 1000 - 1600 weight. including oxygen, less than 200 weight. including carbon, less than 120 weight. including silicon, and zirconium, except for inevitable impurities.

 

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