JP2000088988A - Reactor containment with flammable gas treatment equipment - Google Patents

Abstract

(57) [Summary] An object of the present invention is to remove combustible gas generated in a containment vessel efficiently and for a long period of time without taking it out of the containment vessel. A catalytic recombiner (8) provided in a reactor containment vessel (1) and using a catalyst that promotes the recombination of hydrogen gas and oxygen gas is used. The temperature of the recombination reaction surface attached to the plate surface is raised to about 184 ° C. or higher, which is a temperature at which iodine can be released, by a heating element capable of raising the temperature by converting electric energy from the power supply 11 into heat, and It is possible to prevent iodine from deteriorating by removing iodine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a containment vessel provided with a combustible gas processing facility utilizing a catalytic reaction.

[0002]

2. Description of the Related Art In a nuclear power plant, if the primary piping of a nuclear reactor is damaged, a coolant for cooling the reactor is released as steam into a reactor containment vessel from a location where the piping is broken. Coolant in the pressure vessel is reduced.
As a result, the pressure and temperature in the containment vessel rise.

[0003] The above-described coolant loss accident (hereinafter referred to as LO
Called CA. At times, the reactor is cooled down and fuel is not damaged by the automatic start of the emergency core cooling system (hereinafter, referred to as ECCS) even if a single failure of the ECCS is assumed, but the reactor pressure does not increase. In the vessel and the containment vessel, hydrogen gas and oxygen gas generated by radiolysis of water by the high radiation field are generated. These gases are released into the containment from the pipe break.

[0004] This state continues and the hydrogen gas concentration becomes 4
If the vol% and the oxygen gas concentration exceed 5 vol%, the flammability limit is reached and the possibility of combustion increases.

In order to cope with such an event, a boiling water reactor (hereinafter, referred to as a BWR) which employs a pressure-suppressed type containment vessel among light water reactor type nuclear power plants is usually provided as a countermeasure. In the event of an accident, the atmosphere inside the reactor containment vessel was replaced with nitrogen gas, and in the unlikely event of an accident, the atmosphere inside the containment vessel was taken out with a blower, the temperature was raised with an electric heater, hydrogen and oxygen were recombined into water, and the remaining gas was removed. At the same time, a combustible gas concentration control system (hereinafter, referred to as FCS) using a heating type recombiner that is cooled by a cooler and then returned to the containment vessel is installed.

[0006] The FCS is mainly adapted to recombining hydrogen gas and oxygen gas generated by water decomposition of radiation for a long time after LOCA to form water. With regard to the generation of a large amount of hydrogen gas due to the water-metal reaction expected at the time of a severe accident exceeding the design standard, the flammable area can be maintained because the atmosphere in the reactor containment vessel can be maintained in a low oxygen gas concentration atmosphere by replacing the atmosphere with nitrogen gas. Do not lead to.

[0007] In a nuclear power plant having a large containment vessel, the hydrogen gas concentration after the accident rises slowly since it is diluted to the atmosphere of the large-capacity containment vessel in the design standard accident. It is not necessary to respond to equipment. Water assumed in case of severe accident exceeding design standard accident-
To generate a large amount of hydrogen gas due to a metal reaction, there is a plan to adopt a forced ignition type FCS called an igniter.

In the above-described conventional type, a forced driving force such as a blower or a heater and a power supply necessary for driving the same are used. Couplers have been developed. This device combines a catalyst-type hydrogen-reactive material in the form of a pellet in a steel box into a cartridge, and uses a gas flow path between the cartridges to recombine hydrogen and oxygen, or a catalytic-type hydrogen-reactive material Is attached to the surface of the plate, and hydrogen and oxygen are recombined using a gas flow path between the plates. Proceedings of 2nd ASME / JSME Nuclear Engineer
ing JointConference (ICONE2) Vol.1 (1993) p435−43
8th (Proceeding of 2nd ASME / JSME Nuclear Engineering Conference (ICONE
2) As described in Vol. 1 (1993) p435-438), there is an example in which a catalytic combustible gas treatment facility for recombining combustible gas with a catalyst such as palladium is installed in a reactor containment vessel. Japanese Patent Application Laid-Open No. 58-139591 discloses an example of disposing a hydrogen oxidation catalyst in a storage container. Japanese Patent Application Laid-Open No. 6-130170 discloses a hydrogen concentration reducing material comprising a catalytic hydrogen reactant in a storage container. Is disclosed.

[0009]

In a BWR having a pressure suppression type reactor containment vessel, when a catalytic combustible gas treatment facility is used, hydrogen generated under conditions inside the BWR reactor containment vessel at the time of the accident is considered. The gas and oxygen gas must recombine at the surface of the catalyst contained in the flammable gas treatment facility.

[0010] However, some of the conditions inside the BWR containment vessel at the time of the accident include a condition in which both the hydrogen gas concentration and the oxygen gas concentration are low at the initial stage after the accident and after the combustible gas treatment equipment is operated. There are some conditions. During the transition from the low hydrogen gas concentration and low oxygen gas concentration state to the combustible region, it is required that the catalytic combustible gas processing equipment be started reliably. In addition to the above conditions, assuming LOCA, fission products present in the reactor coolant and fission products released from the fuel rods are released from the fracture into the reactor containment vessel. Among the fission products released into the gas phase in the reactor containment vessel, iodine is thought to adhere to the catalyst due to the flow in the containment vessel formed by the reaction heat of hydrogen and oxygen on the catalyst. Therefore, the reaction of the combustible gas on the catalyst may be alienated. The temperature at which iodine is desorbed from the catalyst due to the heat of reaction of the combustible gas on the catalyst is above the boiling point of 184 ° C. If the catalyst is kept at that temperature, iodine may ignite the reaction of the combustible gas. Is thought to be lower. However, when the hydrogen gas concentration and the oxygen gas concentration are both low, the temperature of the catalyst may not be maintained at 184 ° C. or higher in some cases, and iodine may adhere to the catalyst, preventing the start of the reaction of the combustible gas on the catalyst. There is a possibility.

At the time of LOCA in BWR, control of combustible gas is required for FCS for a long time. Therefore, the concentration of flammable gas in the containment vessel rises again even after hydrogen and oxygen gases are recombined, the concentration decreases, the recombination reaction by the catalyst stops, and iodine adheres to the catalyst. If so, the FCS must be activated.

An object of the present invention is to prevent a reaction of a catalyst from being alienated due to adhesion of iodine released into a containment vessel in an accident in a reactor containment vessel equipped with a combustible gas treatment facility using a catalyst. Even when the hydrogen concentration and oxygen concentration are low and the iodine adheres, the catalytic reaction is reliably started,
By recombining the hydrogen gas and oxygen gas contained in the atmosphere gas inside the containment vessel after the accident, it is possible to prevent the flammable area from being re-combined, and even if equipped with a function to prevent iodine adhesion, maintenance of flammable gas treatment equipment Without deteriorating
An object of the present invention is to provide a highly reliable reactor containment vessel equipped with a combustible gas treatment facility.

[0013]

The above object can be attained by providing the following apparatus.

According to a first aspect of the present invention, there is provided a combustible gas treatment facility using a catalyst for promoting the recombination of hydrogen gas and oxygen gas provided in a reactor containment vessel containing a reactor pressure vessel, A catalyst-type recombiner that combines the pelletized catalyst into a cartridge and recombines oxygen gas and hydrogen gas with a gas flow path between the cartridges, or a catalyst attached to the plate surface and the gap between the plates In a catalytic recombiner of the type in which hydrogen gas and oxygen gas are recombined in a gas flow path, the boiling point of iodine is used to release iodine to cartridges and plates in order to prevent iodine from adhering, which reduces the performance of the catalyst. 184 ° C. or more.

Therefore, according to the first or second aspect of the present invention, iodine can be reliably released and the performance of the catalyst can be prevented from being deteriorated, and maintenance can be prevented, as compared with a catalytic combustible gas processing facility without a temperature raising function. It does not degrade sex.

According to a third or fourth aspect of the present invention, there is provided a combustible gas treatment facility using a catalyst for promoting the recombination of hydrogen gas and oxygen gas provided in a reactor containment vessel containing a reactor pressure vessel, Combine the pelletized catalyst into a cartridge, and use a catalytic combustible gas treatment facility of the type that recombines oxygen gas and hydrogen gas with a gas flow path between the cartridges, or paste the catalyst on the plate surface, In a catalytic combustible gas treatment facility of the type in which hydrogen gas and oxygen gas are recombined with a gas flow path between plates, between cartridges and between plates,
A heating element for raising the temperature of the catalyst to about 184 ° C. or higher, which is a temperature at which iodine attached to the catalyst can be released, is arranged.

Therefore, according to the third or fourth aspect of the present invention, there is no need to change the design and processing of the cartridges and plates of the catalytic combustible gas processing equipment having no temperature raising function, and the iodine can be reliably removed. It is possible to prevent the catalyst from deteriorating and to prevent the deterioration of the maintenance performance.

Further, as set forth in claim 5, in claim 1 or 2, the power source for the cartridge or plate having the function of increasing the temperature by electric energy is placed outside the containment vessel.

Therefore, according to the invention corresponding to claim 5, in addition to the effect of claim 1 or 2, maintenance of the power supply of the combustible gas processing equipment can be easily performed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to FIGS. 1, 2, 3, 4 and 5. FIG.

FIG. 1 shows an example of an embodiment in which flammable gas processing equipment using a catalyst for promoting hydrogen gas and oxygen gas is installed inside a reactor containment vessel having a pressure suppression pool.
As the catalyst, a white metal is used, and specifically, platinum or palladium is employed. At the time of LOCA or the like, the reactor coolant flows out of the reactor pressure vessel 5 through the break port 6 into the reactor containment vessel 1. At this time, together with the reactor coolant, hydrogen gas and oxygen gas generated by radiolysis of water inside the reactor pressure vessel 5 are also dry wells (hereinafter, referred to as D / W) inside the reactor containment vessel 1.
2 and a suppression chamber (hereinafter, referred to as S / C) 3. Hydrogen gas and oxygen gas are D / W
2 and S / C3, but the catalytic recombiner 8
The hydrogen gas and the oxygen gas are recombined by the catalyst 7 that promotes the recombination of the hydrogen gas and the oxygen gas installed inside.

Further, the fission products present in the reactor coolant and the fission products released from the fuel rods are released from the fracture 6 into the reactor containment vessel 1. Of the fission products released into the gas phase in the reactor containment vessel 1, iodine flows into the containment vessel formed by the heat of reaction between hydrogen and oxygen on the catalyst 7, and iodine is removed. A function for heating and raising the temperature of the surface of the catalyst 7 so as to be separated from the catalyst is provided in the catalytic combustible gas processing equipment. Catalytic recombiner 8
Power is supplied from a power supply (for example, a battery) 11 installed outside the reactor containment vessel 1. A thermometer 10 is installed in the combustible gas processing equipment, and the temperature of the catalyst 7 rises to a temperature of about 184 ° C. or more at which iodine can be desorbed from the catalyst by a recombination reaction of hydrogen gas and oxygen gas, The thermometer 10 detects that the recombination reaction on the catalyst is being performed stably, and drives the switch 13 based on the detection signal to cut off the power supply from the power supply 11 to the catalyst by the switch 13. Can be.

FIG. 2 shows a cartridge 23 in which a pellet type 20 catalyst is used. The catalyst processed into the pellet type 20 is supported by the wire net 21. Cartridge 23 with heating function
Is provided with a socket 22 for receiving electricity. When electricity is supplied to the cartridge 23 having a temperature raising function, the wire net 21 generates heat, and the surface of the pellet type catalyst 20 rises to a temperature of about 184 ° C. or more at which iodine can be desorbed from the surface of the catalyst, and the temperature is raised. You. The method of receiving electricity is a socket method for facilitating attachment / detachment of the cartridge and preventing leakage. The electricity received by the socket 22 is distributed from the socket 22 to the wire net 21,
The wire net 21 generates heat. In this way, a cartridge 23 with a temperature raising function is obtained.

FIG. 3 shows a catalyst plate 30 in which a catalyst 32 is attached to the surface of a plate 33. The catalyst plate 30 having the temperature raising function is provided with a socket 31 for receiving electricity. Catalyst plate 30 with temperature rise
When electricity is supplied to the plate, the plate 33 generates heat, and the temperature of the catalyst is raised to about 184 ° C. or more at which iodine can be desorbed from the catalyst. There is also a type in which the unevenness of the surface of the catalyst 32 of the catalyst plate 30 having the temperature raising function is reduced (specifically, plated with platinum or palladium) so that iodine can be easily separated. . The plate 33 itself is a heating wire such as a nichrome wire.
The catalyst plate 30 has a configuration in which the plate 33 is buried in the inside 3 and receives electricity received by the socket 31 to generate heat by giving it to the nichrome wire, thereby generating heat.

As shown in FIG. 4, in the catalytic recombiner, FIG.
The cartridge 23 having the temperature raising function or the catalyst plate 30 having the temperature raising function shown in FIG.

The cartridge 4 having the temperature raising function or the holder 4 of the catalyst plate 30 having the temperature raising function
2, the socket 2 shown in FIGS.
Outlets 43 for mounting and 31 and supplying electricity
Is provided.

The outlet 43 to which the sockets 22 and 31 are connected is waterproofed to prevent leakage. The plurality of cartridges 23 or the catalyst plates 30 are grouped by a plurality of holding bodies 42 and are installed in parallel with the flow of the atmosphere.

Between the cartridge 23 having the heating function or the catalyst plate 30 having the heating function,
A plurality of cartridges 41 and 42 without a temperature raising function or catalyst plates 41 and 42 without a temperature raising function are provided at regular, equal intervals.

The cartridge 23 without the heating function or the catalyst plate 41 without the heating function which is close to the cartridge 23 with the heating function or the catalyst plate 30 with the heating function The catalyst is supplied to the cartridge 40 or the plate 4 having the temperature raising function.
The temperature is raised to about 184 ° C. or more at which iodine can be desorbed from the catalyst by receiving radiant heat from 0.

The cartridge 23 without the temperature raising function which is not close to the cartridge 23 with the temperature raising function or the catalyst plate 30 with the temperature raising function, or the catalyst plate 42 without the temperature raising function. The catalyst is
Cartridge 41 or catalyst plate 4 with heating function
Since the temperature rises by receiving the radiant heat from 1, the temperature at which iodine can be desorbed from the catalyst by the radiant heat is about 1
The temperature is raised to 84 ° C. or higher.

FIG. 5 shows that a cartridge provided with a catalyst or a catalyst plate itself does not have a heating function, and a cartridge without a heating function or a catalyst plate 52 without a heating function is arranged in parallel at equal intervals. A plurality of heating elements 50, such as nichrome wires, which are held in a holding body 51 and generate heat by electricity from the power supply 11, are provided between the cartridges without the temperature raising function or the catalyst plates 52 without the temperature raising function. An example in the case of installation in places will be described.

The temperature of the cartridge without the temperature raising function or the catalyst on the catalyst plate 52 without the temperature raising function is about 184 ° C. or higher at which iodine can be desorbed from the catalyst by receiving heat from the heating element 50. The temperature rises to
It is possible to suppress a decrease in the function of the catalyst due to iodine.

According to this embodiment, there is no need to perform a process of adding a temperature increasing function to the cartridge or the catalyst plate, and the cartridge or the plate can be easily attached and detached.

[0034]

According to the present invention, in a reactor containment vessel equipped with a combustible gas treatment facility using a catalyst, the reaction of the catalyst is prevented from being alienated by the adhesion of iodine released into the containment vessel in the event of an accident, and a low hydrogen concentration is achieved. In addition, even if the oxygen concentration is low and the iodine is attached, the catalytic reaction is surely started, and the hydrogen gas and oxygen gas contained in the atmosphere gas in the containment vessel after the accident are recombined to prevent the gas from coming to the flammable region. It is possible, even if it has a function of preventing iodine adhesion, it does not deteriorate the maintainability of flammable gas treatment equipment,
It is possible to provide a containment vessel provided with a combustible gas processing facility.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a reactor containment vessel equipped with a combustible gas processing facility according to an embodiment of the present invention.

FIG. 2 is a perspective view of a cartridge type catalyst with a catalyst temperature increasing function according to an embodiment of the present invention.

FIG. 3 is a perspective view of a plate-type catalyst with a catalyst temperature increasing function according to an embodiment of the present invention.

FIG. 4 is a partially cutaway perspective view illustrating a structure in which a cartridge type and a plate type catalyst are held in a catalytic recombiner according to an embodiment of the present invention.

FIG. 5 is a perspective view of a catalyst-type recombiner according to an embodiment of the present invention, in which a cartridge type and a plate type catalyst and a holding body provided with a heating element therebetween are partially cut away. It is.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor containment vessel, 8 ... Catalytic recombiner, 11 ... Power supply, 20 ... Catalyst pellet, 21 ... Wire mesh, 22, 31 ... Socket, 23 ... Cartridge, 30 ... Catalyst plate, 3
2 ... catalyst, 33 ... base, 43 ... outlet, 44, 51
... a holder, 50 ... a heating element.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shozo Yamanari 3-1-1 Sakaicho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Hidetoshi Karasawa Omika, Hitachi City, Ibaraki Prefecture 7-2-1, Machi-cho, Hitachi, Ltd. Electric Power & Electric Development Division (72) Inventor Noriaki Uesuma 3-2-1, Sachimachi, Hitachi-shi, Ibaraki F-term in Hitachi Engineering Co., Ltd. (Reference) 2G002 AA01 BA01 CA10 DA10 EA10

Claims (5)

[Claims] 1. A catalyst which promotes recombination of hydrogen gas and oxygen gas in the form of pellets is assembled into a cartridge, and the cartridge is heated to a temperature at which iodine attached to the catalyst can be desorbed. Reactor containment with flammable gas treatment equipment with body. 2. A catalyst for promoting recombination of hydrogen gas and oxygen gas is attached to the surface of each of a plurality of plates, and a space between the plates is formed as a flow path for the hydrogen gas and the oxygen gas. A reactor containment vessel equipped with a combustible gas treatment facility equipped with a heating element capable of raising the temperature to a temperature at which iodine attached to a catalyst can be desorbed. 3. A method in which a catalyst for promoting the recombination of hydrogen gas and oxygen gas in the form of a pellet is collected into a plurality of cartridges, and a passage for the hydrogen gas and oxygen gas is provided between the cartridges. A containment vessel having a flammable gas treatment facility between which a heating element capable of heating the catalyst to a temperature at which iodine attached to the catalyst can be desorbed is arranged. 4. A catalyst for promoting recombination of hydrogen gas and oxygen gas is attached to the surface of each of a plurality of plates, and a space between the plates is formed as a flow path for the hydrogen gas and the oxygen gas. And a reactor containment unit provided with a combustible gas treatment facility in which a heating element capable of raising the temperature of the catalyst to a temperature at which iodine attached to the catalyst can be desorbed. 5. The heating element according to claim 1, wherein the heating element converts electric energy supplied from a power supply into heat, and the power supply is placed outside the containment vessel. Reactor containment vessel with flammable gas processing equipment.