JP2008039579A - Supercritical light water reactor, treatment method thereof and oxidation treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control corrosion of metallic materials in a super-critical pressure light water reactor using a direct cycle, reduce transfer of radioactive corrosion products to a turbine system and reduce the dose of the turbine system. <P>SOLUTION: Oxidation treatment using high-temperature water or high-temperature steam is applied on at least part of the surface of a solid metallic material in contact with a coolant in the super-critical pressure light water reactor. The surface of the solid metallic material as an object of oxidation treatment may be mechanically polished or electrolytically polished before the oxidation treatment. Preferably, high-temperature water containing at least one of Ni, Zn, Fe, Cr, Mn, Cu, Pd, Pt, Al, Mo, V and W is used for the oxidation treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a supercritical light water reactor using a direct cycle, a treatment method for suppressing material corrosion of the supercritical light water reactor, and an oxidation apparatus for the treatment method.

  The boiling water light water reactor (BWR) is a direct cycle, in which the reactor cooling water is heated to about 288 ° C in the core, and the generated steam is sent directly to the steam turbine without going through the heat exchanger (steam generator). It is done. The cooling water contains radioactive substances such as cobalt 60, but most of them are present in the liquid phase, and the ratio of transition to steam turbine is considered to be 1/1000 or less.

On the other hand, in the supercritical light water reactor that is currently being researched, the temperature of the cooling water is set to a supercritical state of 374 ° C. and the pressure is 22.1 MPa or more, and the entire amount is sent to the turbine, so that the thermal efficiency is higher than that of the conventional BWR. It is thought that can be obtained (patent document 1). In addition, in BWR, a steam separator and a steam dryer are necessary to remove moisture in the steam. However, these devices are unnecessary in a supercritical light water reactor, and the reactor can be simplified. is there.
JP-A-8-313664 K. Sue et al. “Solubility of lead (II) oxide and copper (II) oxide in subcritical and supercritical water” J. Chem. Eng. Data, No. 44, p1422 (1999)

  By the way, in the above supercritical pressure light water reactor, the entire amount of cooling water flowing through the core becomes supercritical and shifts to the turbine. As a result, there is a problem that all radioactive substances contained in the cooling water are transferred to the turbine together with the cooling water. The source of radioactive material in the cooling water is that cobalt contained in the nuclear reactor structural material and fuel cladding material is activated and released. The form of the activated metal when released is in the form of a metal oxide or ion. Therefore, the migration of radioactive materials to the turbine can be suppressed by suppressing the separation and dissolution due to the corrosion of the metal material. From the results of recent studies, it is known that the solubility of metal oxides increases around 350 ° C. (Non-patent Document 1).

  The present invention has been made to solve the above-mentioned problems of the background art, suppresses the metal material corrosion of the supercritical pressure light water reactor using the direct cycle, reduces the transition of radioactive corrosion products to the turbine system, The purpose is to reduce the dose of the turbine system.

  The present invention achieves the above object, and the supercritical pressure light water reactor treatment method according to the present invention is a treatment method of a supercritical pressure light water reactor using a direct cycle, and a coolant in the supercritical pressure light water reactor An oxidation treatment is performed on at least a part of the surface of the solid metal material in a portion in contact with the surface.

  Further, the supercritical pressure light water reactor according to the present invention is characterized in that in the supercritical pressure light water reactor using a direct cycle, at least a part of the surface of the solid metal material in contact with the coolant is subjected to oxidation treatment. And

  Moreover, the oxidation treatment apparatus according to the present invention is an oxidation treatment apparatus for performing oxidation treatment on at least a part of the surface of the solid metal material in contact with the coolant of the supercritical light water reactor using a direct cycle, A reservoir tank for storing water; an oxidation processing container that is a pressure-resistant container containing a solid metal material to be processed and having a heater; a pump for sending water in the reservoir tank to the oxidation processing container; A heat exchanger for exchanging heat between the water flowing into the oxidation treatment vessel and the water from the oxidation treatment vessel toward the reservoir tank; and a pressure gauge for measuring the pressure in the oxidation treatment vessel; And a thermometer for measuring the temperature in the oxidation treatment container.

  According to the present invention, material corrosion of a supercritical pressure light water reactor using a direct cycle can be suppressed, thereby reducing the migration of radioactive corrosion products to the turbine system and reducing the dose of the turbine system.

  Embodiments of the present invention will be described below with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
A supercritical light water reactor, a treatment method thereof, and an oxidation treatment apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a schematic system diagram showing a supercritical light water reactor according to a first embodiment of the present invention. This supercritical light water reactor uses a direct cycle, and the steam in the reactor is sent directly to the steam turbine without going through the heat exchanger (steam generator), and again into the reactor after condensing. It has a back structure.

  A reactor core 32 is accommodated in the reactor pressure vessel 31. Supercritical high-temperature water (steam) generated in the core 32 is guided to the steam turbine 33, where the steam turbine 33 is driven, and the generator 40 is driven by the steam turbine 33. The steam that has finished work in the steam turbine 33 is cooled in the condenser 34 to become condensed water. This condensate is returned to the reactor pressure vessel 31 as feed water through the coolant purification device 35, the condensate pump 36, and the feed water heater 37. A large number of fuel rods covered with a fuel cladding tube are loaded in the core 32.

  In this embodiment, at least a part of the surface of the solid metal material in the portion in contact with the coolant, such as the structural material in the reactor pressure vessel 31 or the fuel cladding tube, is subjected to a pre-oxidation treatment. The oxide film is formed on the treated portion. Thereby, corrosion of a to-be-processed material is suppressed and the quantity of the radioactive substance discharge | released in water is suppressed. As a result, the radioactive concentration in the reactor water decreases, and the migration of radioactive corrosion products to the turbine system including the steam turbine 33 and the condenser 34 can be suppressed.

  FIG. 2 is a schematic system diagram showing the surface oxidation apparatus according to the first embodiment of the present invention. Here, the case of a fuel cladding tube will be described as an example of the material to be processed. The fuel cladding tube 1 used in the supercritical light water reactor is installed in the oxidation treatment container 2 before loading into the nuclear reactor. Water is stored in the reservoir tank 3, and the water quality is adjusted by the oxygen injection device 20, the hydrogen injection device 21, and the nitrogen injection device 22. The water in the reservoir tank 3 is pressurized by the high-pressure pump 4, heated through the heat exchanger 5, and then sent to the oxidation treatment container 2. A heater 6 is installed in the oxidation treatment container 2 and heated to a predetermined temperature. The pressure and temperature in the oxidation treatment container 2 are measured by a pressure gauge 7 and a thermometer 8, respectively.

  The water in the oxidation treatment container 2 is cooled through the heat exchanger 5 and returns to the reservoir tank 3 through the dissolved hydrogen meter 23, dissolved oxygen meter 24, conductivity meter 25, and ion exchange resin 26 in order. In order to measure the quality of the water accumulated in the reservoir tank 3, a dissolved hydrogen meter 26, a dissolved oxygen meter 27, and a conductivity meter 28 are arranged.

  By using this apparatus, a target oxide film can be formed on the surface of the fuel cladding tube 1.

  FIG. 3 is a graph of test results showing the effect of reducing the corrosion elution amount by pre-oxidation treatment for austenitic stainless steel (SUS316L). A corrosion test for 500 hours in 350 ° C. water was performed on the standard material (as received from the manufacturer) and a test material subjected to a pre-oxidation treatment for 200 hours in pure water at 350 ° C. The relative value of the film elution amount in this corrosion test is shown in the graph. As is apparent from FIG. 3, the amount of elution of stainless steel decreases due to the pre-oxidation treatment.

  As described above, in the solid metal material subjected to the pre-oxidation treatment, the amount of elution is reduced, and the amount of radioactive substance released into water is reduced. As a result, a reduction in radioactivity concentration in the reactor water can be achieved.

  The conditions for the pre-oxidation treatment can be controlled by changing the temperature and pressure. When treated for 20 to 200 hours with subcritical high temperature water at 350 ° C. or higher, there was a significant corrosion inhibition effect. Moreover, the same effect can be obtained by using high-temperature water vapor in addition to high-temperature water. For example, when treated for 20 to 200 hours using high-temperature steam at 500 ° C. or higher, there was a significant corrosion inhibition effect.

  Further, the oxygen concentration in water can be adjusted to a predetermined oxygen concentration by controlling the gas in the reservoir tank 3. Oxidation treatment using high temperature water having a dissolved oxygen concentration of 8 ppm or more had a good corrosion inhibitory effect.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. In this embodiment, prior to the above-described preliminary oxidation treatment, a mechanical polishing treatment is performed on the surface of the solid metal material to be oxidized. In the example shown in FIG. 4, it is assumed that the solid metal material to be processed is the fuel cladding tube 1. While the fuel cladding 1 is fixed and rotated, the surface is mechanically polished by the polishing device 9. In the material subjected to the mechanical polishing treatment, the surface becomes smooth and the liquid contact area becomes small. After this mechanical polishing process, for example, an oxidation process similar to that of the first embodiment is performed.

  By performing the polishing treatment prior to the pre-oxidation treatment, the wetted area of the metal material becomes relatively small, the amount of elution is reduced, and the amount of radioactive substance released into water is reduced. As a result, a reduction in radioactivity concentration in the reactor water can be achieved.

  As a modification of this embodiment, the same effect can be obtained by using chemical polishing such as acid, electrolytic polishing using an electrolytic solution, or the like in addition to mechanical polishing as a polishing method.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic system diagram showing a surface oxidation apparatus according to the third embodiment of the present invention. This embodiment is a modification of the first embodiment, and a pipe for injecting a chemical from the chemical tank 10 by the chemical pump 11 is connected to the middle of the pipe from the heat exchanger 5 toward the oxidation treatment container 2. Yes. The chemical tank 10 contains a solution containing metal ions to be injected. Here, the metal ions to be implanted are, for example, one or more of Ni, Zn, Fe, Cr, Mn, Cu, Pd, Pt, Al, Mo, V, and W.

  When performing a pre-oxidation process substantially the same as that of the first embodiment using the surface oxidation apparatus having the above-described configuration, the chemical solution in the chemical solution tank 10 is injected into the oxidation treatment container 2. As a result, a highly protective composite oxide film layer containing the metal in the chemical tank 10 is formed on the surface of the fuel cladding tube 1. Since the composite oxide film formed in this way is dense and highly protective, the amount of elution of the film decreases and the amount of radioactive material released into water decreases. As a result, a reduction in radioactivity concentration in the reactor water can be achieved.

1 is a schematic system diagram showing a supercritical light water reactor according to a first embodiment of the present invention. 1 is a schematic system diagram showing a surface oxidation apparatus according to a first embodiment of the present invention. It is a graph which shows the effect of the 1st Embodiment of this invention, Comprising: The graph which shows the corrosion elution amount of the pre-oxidation material oxidized by this embodiment and this embodiment by a relative value. The typical perspective view which shows the appearance of the mechanical polishing process which concerns on the 2nd Embodiment of this invention. The typical systematic diagram which shows the surface oxidation apparatus which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cladding tube, 2 ... Oxidation processing container, 3 ... Reservoir tank, 4 ... High pressure pump, 5 ... Heat exchanger, 6 ... Heater, 7 ... Pressure gauge, 8 ... Thermometer, 9 ... Polishing apparatus, 10 ... Chemical solution tank, 11 ... Chemical solution pump, 31 ... Reactor pressure vessel, 32 ... Reactor core, 33 ... Steam turbine, 34 ... Condenser, 35 ... Coolant purification device, 36 ... Condensate pump, 37 ... Feed water heater, 40 …Generator

Claims (13)

  A supercritical pressure light water reactor treatment method using a direct cycle, characterized in that at least part of the surface of the solid metal material in contact with the coolant in the supercritical pressure light water reactor is subjected to oxidation treatment Pressure light water reactor treatment method.   The supercritical pressure light water reactor treatment method according to claim 1, wherein the oxidation treatment uses high-temperature water or high-temperature steam.   The supercritical pressure light water reactor treatment method according to claim 2, wherein the oxidation treatment is performed for 20 hours to 200 hours using high-temperature water under subcritical conditions at a temperature of 350 ° C or higher.   The supercritical pressure light water reactor treatment method according to claim 2, wherein the oxidation treatment is performed using high temperature steam having a temperature of 500 ° C or higher for 20 hours to 200 hours.   The supercritical pressure light water reactor treatment method according to claim 2 or 3, wherein the oxidation treatment uses high-temperature water having a dissolved oxygen concentration of 8 ppm or more.   The oxidation treatment is performed using high-temperature water containing at least one of Ni, Zn, Fe, Cr, Mn, Cu, Pd, Pt, Al, Mo, V, and W. A supercritical light water reactor treatment method according to any one of claims 1 to 5.   The supercritical pressure light water reactor treatment method according to any one of claims 1 to 6, wherein a polishing process is performed on a surface of the solid metal material to be oxidized prior to the oxidation process.   The supercritical pressure light water reactor treatment method according to claim 7, wherein the polishing treatment is mechanical polishing or electrolytic polishing.   The supercritical light water reactor treatment method according to any one of claims 1 to 8, wherein the solid metal material to be subjected to the oxidation treatment includes a fuel cladding tube.   A supercritical light water reactor using a direct cycle, wherein at least part of the surface of the solid metal material in contact with the coolant is oxidized. An oxidation treatment apparatus for subjecting at least part of the surface of a solid metal material in contact with a coolant of a supercritical pressure light water reactor using a direct cycle to oxidation treatment,
A reservoir tank for storing water,
A container for oxidation treatment which is a pressure vessel containing a solid metal material to be treated and having a heater;
A pump for sending water in the reservoir tank to the oxidation treatment container;
A heat exchanger that exchanges heat between water flowing from the reservoir tank into the oxidation treatment container and water from the oxidation treatment container toward the reservoir tank;
A pressure gauge for measuring the pressure in the oxidation treatment container;
A thermometer for measuring the temperature in the oxidation treatment container;
An oxidation processing apparatus comprising: A dissolved hydrogen meter for measuring dissolved hydrogen in the water;
A dissolved oxygen meter for measuring the dissolved oxygen of the water;
A conductivity meter for measuring the conductivity of the water;
The oxidation processing apparatus according to claim 11, further comprising: A chemical tank for storing a chemical containing metal ions;
A chemical pump for injecting the chemical in the chemical tank into the oxidation container;
The oxidation treatment apparatus according to claim 11, further comprising:

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