JPS60181689A - Nuclear reactor - 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 [Technical Field of the Invention] The present invention relates to a nuclear reactor that is capable of capturing and retaining radionuclides in a coolant at a specific location.

[Technical background of the invention]

In fast breeder reactors, alkaline liquid metal, typically liquid sodium, is generally used as a coolant. After being heated in the reactor core installed inside the reactor vessel, such liquid metal coolant is guided to an intermediate heat exchanger installed outside the vessel, and then returned to the reactor vessel. , circulate.

By the way, in fast breeder reactors, the cladding tubes and core structures of nuclear fuel rods are usually made of stainless steel, which has high corrosion resistance. However, stainless steel can still be corroded by liquid sodium. Since the toughened materials of the cladding and the core structure are radioactive, as mentioned above, when corroded, radioactive corrosion products will be mixed into the coolant. The radioactive corrosion products mixed into the coolant are carried by the coolant to the main circulation system and deposited on the pipe walls of the main circulation system. In this way, the radioactivity of radionuclides deposited on the walls of the main circulation system, etc., can interfere with maintenance and repair work of equipment such as pumps, heat exchangers, pulp, flow meters, etc., and the piping connected to these equipment. give. Radioactive nuclides such as Nimanganese-54, Copal)-6Q, and Barto-58 are produced in large amounts and have long half-lives, so their effects are large.

In order to solve this problem, it has recently been considered to install a radioactive corrosion product capture device using a radionuclide capture material such as nickel inside the reactor vessel. This radioactive corrosion product capture device has a plurality of elements containing the capture material arranged opposite to the coolant outlet of the reactor core, that is, above the core, and brings the capture material into direct contact with the coolant flowing out from the core. This allows radionuclides to be captured. With this kind of configuration,
As the coolant repeatedly circulates through the main circulation system, radionuclides are gradually captured by the capture material.

[Problems with the background technology] However, in such nuclear reactors, the capture device is installed in the upper part of the core where the coolant temperature is high, so the capture material, such as nickel, is likely to corrode. . For this reason, when the corroded nickel detaches from the capture device, the radionuclides also detach and sometimes deposit on the primary cooling system piping or the surface of the primary cooling system equipment.゛In addition, if nickel, which is a capture material that has migrated into the coolant due to corrosion, adheres to the piping or equipment surfaces of the primary cooling system, this nickel will capture radionuclides, reducing the capture efficiency of the capture device. There was a problem in that the amount of deposition on the piping and equipment surfaces was increased.

Furthermore, when a capture device is installed above the core, non-radioactive nuclides that migrate into the coolant due to corrosion of the core material also adhere to the surface of the capture device, which also reduces capture efficiency. There was a problem in that it caused a decrease in

[Purpose of the invention]

The present invention was made in view of such problems, and its purpose is to prevent the corrosion of the radionuclide capture material stage and the adhesion of non-radioactive nuclides to the same.
It is an object of the present invention to provide a nuclear reactor that can maintain high capture efficiency in radionuclide capture means over a long period of time and facilitate maintenance.

[Summary of the invention]

The gist of the present invention is to arrange radionuclide capture means (hereinafter referred to as "capture means") on the low temperature side of the main circulation path of the coolant.

That is, the present invention is characterized in that a capture means is provided in the upstream portion of the reactor core in the main circulation path of the coolant circulating between the reactor core and the intermediate heat exchanger.

〔Effect of the invention〕

As mentioned above, radionuclides transferred to the coolant are gradually captured by the capture means by repeatedly circulating the coolant through the main circulation system. In this case, the amount of radionuclides captured by the capture means is far greater than the amount attached to the piping and equipment of the primary cooling system. Therefore, it can be said that the trapping efficiency essentially remains the same no matter where the trapping means is placed in the ball circulation system.

Therefore, in the present invention, the capture means is arranged in the upstream part of the core in the main circulation path of the coolant, on the low temperature side of the core, so that the material constituting the capture means does not corrode. Therefore, the above-mentioned substances will not adhere to the pipes or the like and will not increase the amount of radionuclides deposited on the pipes or the like.

Furthermore, non-radioactive nuclides released into the coolant due to corrosion of the core material, which are different from the manganese-54'4j- radioactive nuclides, are deposited on the cold legs of piping before reaching the capture means. Therefore, the non-radioactive nuclide does not adhere to the capture means, and the capture efficiency does not decrease due to this.

Therefore, according to the present invention, it is possible to maintain high trapping efficiency in the trapping means over a long period of time, which ultimately contributes to easier maintenance.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained based on an illustrated embodiment.

FIG. 1 is a diagram schematically showing a fast breeder reactor according to this embodiment, and numeral 1 in the figure is a reactor main vessel. A reactor core 2 is housed inside the reactor main vessel 1 . A radionuclide capture device 3 is arranged below the bottom of the reactor core 2, that is, on the bottom side of the reactor main 8 vessel 1. The capture device 3 is made of, for example, a mesh made of nickel.

The reactor core 2 is cooled by liquid sodium P contained in a first part of the main vessel of the rjA reactor. One end sides of primary cooling system backs 4 and 5 are connected to the side and bottom surfaces of the reactor main vessel 1, respectively.

The other end 1j of the primary cooling system piping 4.5 is connected via an intermediate heat exchanger 6. In addition, 7 in the figure is a pump for circulating the liquid (IJumP).

In the fast breeder reactor according to this embodiment configured as described above, when the pongua is operated, the liquid sodium P flows from the inside of the reactor main vessel 1 to the piping 4 to the intermediate heat exchanger 6 to It circulates through the main circulation path consisting of the pipe 5 (pump 7) and the inside of the reactor main vessel 1. Through this circulation, the capture device 3 captures a considerable amount of radionuclides transferred from the reactor core 2 into the liquid sodium.

In this case, since the capture device 3 is disposed downstream of the intermediate heat exchanger 6 where the liquid sodium temperature is low, that is, below the core 2, the degree of corrosion is low. Furthermore, since the capture device 3 is placed farthest in the movement path of the non-radioactive nuclides that have left the upper part of the reactor core 2, the probability that the non-radioactive nuclides will adhere to the capture device 3 is very low.

Note that the present invention is not limited to the above embodiments.

For example, the capture device 3 may be constructed of a nickel plating layer 12 formed on the surface of the nuclear fuel rods constituting the reactor core 2, as shown in FIGS. 2 and 3. That is, the nuclear fuel rod 11 includes a cladding tube 13 made of thin stainless steel, a lower end plug 14 that closes the lower opening of the cladding tube 13, an upper end plug (not shown) that opens the upper opening, and the cladding tube 13. Fuel pellets 15 housed in the virtue pipe 13
and a spring 18 inserted between the fuel pellet 15 and the lower end plug 14 via a plate 16 to form a gas solenum 17 between the lower end plug 14 and the fuel pellet 15. There is.

A nickel plating layer 12 is formed on the lower outer peripheral surface of the cladding tube 13 in the figure.

Even with such a configuration, radionuclides penetrate into the highly active nickel plating layer 12 by diffusion.
Demonstrates high capture ability.

In this case, since the number of nuclear fuel rods loaded into the reactor core is large, ranging from tens to hundreds per assembly, the capture area is extremely large, and the capture/capture performance is is very good.The external dimensions of the fuel rods themselves, the flow paths for the coolant, etc. can be maintained in the same way as in the past, and the reactor as a whole does not become larger or more expensive.

In the above embodiments, the υ capture means was constructed using nickel and nickel plating, but metals such as nickel alloys, nickel-plated stainless steel, and nickel-plated nickel alloys may also be used. Good too. Moreover, what is plated may not be the nuclear fuel rod but also the reactor core structure. In addition, the capture means does not have to be specifically placed inside the reactor main vessel 1, but may be placed outside the reactor main vessel 1 if it is on the route from the downstream side of the intermediate heat exchanger 6 to the reactor core 2. You can also do this.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a nuclear reactor according to one embodiment of the present invention, FIG. 2 is a sectional view showing the -tf15 configuration of nuclear fuel rods in a nuclear reactor according to another embodiment of the present invention, In the diagram, the part A in Figure 2 is entered with 1 + 1 broom + new M - 1...Reactor main vessel, 2...Reactor core, 3...Capture device, 4, 5...・Primary cooling system piping, 6...Intermediate heat exchanger, 7...Pump, U...Nuclear fuel rod, 12...Nickel plating layer, 13...Willed pipe, 14...Lower part End plug, 15...Fuel pellet, 16...Plate body, 17.
...Gas Blenheim, 18...Spring, P...Liquid Sodium. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (3)

[Claims] (1) A nuclear reactor characterized in that a radionuclide capturing means is provided at an upstream portion of the reactor core in a main circulation path of coolant circulating between the reactor core and an intermediate heat exchanger. (2) The patented blue water range item characterized in that the radionuclide capture means is made of at least one of nickel, nickel alloy, nickel-plated stainless steel, and nickel-plated nickel alloy. The nuclear reactor described in item 1. (3) The radionuclide capture means is comprised of a nickel plating layer formed on the upstream portion of the main circulation path of the nuclear fuel rods constituting the reactor core. nuclear reactor.