JPS6069599A - Hydrogen treater for light-water 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 invention] The present invention relates to a novel hydrogen treatment device for a light water reactor.

[Technical background of the invention and its problems]

Nuclear couplants generate various types of radioactive waste in the form of gas, liquid, and solid as they continue to operate.

Therefore, radioactive materials in waste can be attenuated or diluted to lower their concentration, or they can be separated from non-radioactive materials.
JIL#) A waste treatment system is provided to perform treatments such as shrinkage and volume reduction, and to fix the waste in a safe state.

Among the wastes, gaseous wastes are discharged into the atmosphere after being treated in an exhaust gas treatment system to reduce the radioactivity level sufficiently below the permissible limit.

For example, the main gaseous waste in a boiling water reactor (BWR) is the exhaust gas from the air extractor of the turbine condenser; 13N, 16N, and 13N, 16N, which are generated when the hydrogen and oxygen that are generated as a result of being decomposed by neutron irradiation, as well as the coolant and the dissolved gas contained therein, undergo a neutron absorption reaction.
+90.41A, etc.

Hydrogen and oxygen in the exhaust gas from the air extractor are converted back into water by a recombiner and sent back to the reactor water supply system for reuse within the plant. The remaining exhaust gas is stored for a certain period of time, adsorbed onto activated carbon, etc., and is discharged into the atmosphere after its radioactivity level is sufficiently attenuated.

In a pressurized water reactor (P%VB), the gaseous waste tj mainly consists of nitrogen, hydrogen, and various radioactive gases, and this exhaust gas is stored in an attenuation tank to attenuate the radioactivity level and then released into the atmosphere. or reused as cover gas for secondary coolant storage tanks.

Although hydrogen and oxygen in these exhaust gases are not necessarily radioactive substances, they behave in the same way as radioactive substances in the overall flow, so they are substances that must be taken into consideration in exhaust gas treatment technology in waste treatment systems. be handled.

On the other hand, in some light water reactors such as BWR and PWR, hydrogen is added to the reactor water for the following reasons.

First, in PWR, water supply is made to facilitate the recombination of oxygen and hydrogen in the reactor core, suppress neutron irradiation decomposition of water, reduce the oxygen concentration in reactor water, and suppress corrosion of the core materials that make up the reactor. Hydrogen is added inside. In addition, in BWR, hydrogen addition to reactor water has been proposed with the aim of reducing the dissolved oxygen concentration in reactor water, which is one of the causes of stress corrosion cracking (5CC) of pipework. It has been implemented.

Such addition of hydrogen to reactor water results in an increase in the amount of hydrogen to be treated in the exhaust gas treatment system and an increase in the total amount of exhaust gas, and accordingly exhaust gas treatment equipment corresponding to this is required.

For example, as the concentration of hydrogen in the exhaust gas increases, the risk of explosion due to the mixture of hydrogen and oxygen also increases, and measures must be taken to prevent this. Conventionally, to prevent this explosion, water vapor is added to the exhaust gas (in the case of BWR) and nitrogen gas is sealed (in the case of PIvR).
An increase in the amount of hydrogen in exhaust gas requires a correspondingly large amount of water vapor and nitrogen gas, which leads to an increase in the total amount of exhaust gas, that is, the amount of exhaust gas treated, which is disadvantageous in terms of waste treatment technology. .

On the other hand, in recent years, there has been a strong social demand to prevent the gaseous waste generated in nuclear couplants from being released outside the plant as much as possible from the viewpoint of preserving the environment. In other words, even if the gas contains a very small amount of radioactive gas far below the allowable amount, it is required to store it within the plant as much as possible. Considering these demands and considering that there is a limit to the storage capacity within the plant, an increase in the total amount of exhaust gas due to hydrogen addition is an undesirable situation.

As described above, the treatment of hydrogen in the waste treatment system of a light water reactor has become an important issue from the viewpoint of measures to prevent explosions, reduce the total amount of exhaust gas, and suppress the release of exhaust gas to the outside.

Further, the above-mentioned hydrogen added to the reactor water is conventionally supplied from a hydrogen gas cylinder or a hydrogen tank, and a new cylinder or the like is replenished from outside at ff:lim depending on the consumption of hydrogen gas. However, this supply method is not necessarily a highly safe method for handling cylinders, etc., and cannot be said to be economically advantageous since the cylinders, etc. must occupy a large space.

[Purpose of the invention]

The present invention solves the above-mentioned problems related to hydrogen treatment in the gaseous waste treatment system of a light water reactor, that is, removes hydrogen from exhaust gas, adjusts the hydrogen concentration in exhaust gas, and recovers residual hydrogen, thereby preventing explosions and reducing the total amount of exhaust gas. The purpose of the present invention is to provide a hydrogen treatment device for a light water reactor that has a full nJ capacity, which enables reduction of hydrogen and suppression of release outside the plant, and at the same time, supplies recovered hydrogen to reactor water and reuses it.

[Summary of the invention]

The hydrogen treatment device for a light water reactor of the present invention is characterized in that a hydrogen absorption/supply mechanism containing a hydrogen storage alloy is disposed in the waste treatment system path and/or the reactor water system path.

The hydrogen treatment apparatus of the present invention has a hydrogen absorption/supply machine (1) containing a hydrogen storage alloy as a central structural element.

(In the formula, M is metal, MJ (XFi metal hydrogenation 1, ΔH
(represents the enthalpy change of the reaction), it easily forms a metal hydride with hydrogen, and conversely, when heated to a certain temperature or placed in an environment where the hydrogen pressure is lower than the equilibrium pressure above, it can be occluded. A metal or alloy that has the property of releasing hydrogen.

For example, TiFe-based alloy, Mgi Ni-based alloy, La
NIB alloys are known.

When hydrogen is stored in such a hydrogen storage alloy, the hydrogen stored in the alloy has a hydrogen density approximately 1000 times higher than that when stored in a hydrogen gas state in a cylinder, etc. Even small-capacity alloys can store large amounts of hydrogen. Further, hydrogen can be recovered by recovering all alloys whose hydrogen storage capacity is saturated. In this way, by converting hydrogen, which is highly dangerous in gaseous form, into a hydride, it becomes possible to store it in a safe and easily handled state.

The main body of the hydrogen absorption/supply mechanism used in the present invention has the following structure.

The main body is a container that stores the above-mentioned powder or porous molded body of the hydrogen storage alloy, and this container has a plumber for introducing the exhaust gas and a pipe for the residual gas after hydrogen storage or a mechanism for mixing the residual gas and hydrogen. A pipe 2 is attached to lead out the gas.

If this main body is placed in series in the route of the waste treatment system,
The exhaust gas flowing through this waste treatment system was introduced into the main body through pipe 1, where hydrogen gas was occluded, and hydrogen was removed from pipe 2, or the hydrogen concentration was adjusted by the method described below. Residual gas will be led out. That is, all or part of the hydrogen in the exhaust gas is removed, and the total amount of exhaust gas is reduced. At this time, if a temperature control system (=J is installed around the main body and the temperature of the alloy is controlled to the desired temperature to control the balance between the hydrogen absorption reaction and the hydrogen release reaction), the exhaust gas drawn out from the pipe 2 It becomes possible to maintain the hydrogen concentration inside at a certain value.Therefore,
By linking this temperature control system with a hydrogen concentration monitor, it is possible to control the hydrogen concentration of the discharged exhaust gas to be constant.

Thus, the addition of water vapor (B
In the case of WR) or nitrogen gas injection (in the case of PWRT) to reduce the hydrogen concentration in the exhaust gas becomes unnecessary.

For example, in the case of BWft, the above-mentioned hydrogen absorber Nlt may be installed in the intermediate path between the air extractor and the preheater.

With this arrangement, the gases generated in the reactor core are led together with steam directly through the turbine to the condenser, and then introduced into the mechanism according to the present invention via the air extractor, where they undergo recombination processing in the recombiner. The exhaust gas can be made to have a hydrogen concentration that is convenient for this purpose.

Furthermore, in the case of a PWH, the hydrogen absorption mechanism can be disposed in the upper gas phase of a tank with an open water surface for accommodating a secondary coolant, such as a volume control tank or a hold-up tank. By absorbing hydrogen in the gas phase into the hydrogen storage alloy and removing it, the amount of exhaust gas discharged from these tanks can be reduced. Moreover, the total amount of exhaust gas is reduced because the conventional filling of nitrogen gas to prevent explosions is no longer necessary. In this way, a very small amount of exhaust gas can be fed into the gas collapse tank and then stored in a small-volume storage tank.

Next, if the main body mechanism that has already stored hydrogen in the exhaust gas is placed in the reactor water system, which is the path for the coolant circulating in the reactor core, it can function as a hydrogen supply mechanism to the reactor water.

At this time, if a temperature control system is attached to the main body mechanism and the alloy temperature is controlled to a predetermined temperature, hydrogen at an equilibrium pressure corresponding to that temperature will be released from the alloy and supplied to the reactor water. That is, the flow time for hydrogen supply to reactor water can be controlled by controlling the alloy temperature. Since the temperature dependence V of hydrogen release characteristics of an alloy varies depending on the type of alloy, the heating temperature cannot be determined unambiguously.

For example, when using a TiFe-based alloy, it is sufficient to heat it to 100° C. or higher, and in the case of Mg5Ni dilated pupil, heating to 300° C. or higher is required.

〔Effect of the invention〕

As is clear from the above explanation, if the device of the present invention is applied, hydrogen in the exhaust gas can be removed or controlled to a predetermined temperature in a gaseous waste treatment system, thereby eliminating the risk of explosion due to mixing with oxygen. In addition, since water vapor addition and nitrogen gas injection become unnecessary, the total amount of exhaust gas can be reduced, and at the same time, the amount of exhaust gas released into the atmosphere can be suppressed. In addition, in the reactor water system, the hydrogen recovered in the waste treatment system can be directly reused as added hydrogen to the reactor water. In other words, hydrogen, which has conventionally been a waste, can be effectively reused within the plant without being released to the outside, which is useful from the standpoint of resource and environmental conservation. Since this device is inherently compact, there is no need to occupy a huge amount of space as in conventional devices, and the device can be installed simply by inserting the device in series in each path, so its benefits from an industrial perspective are significant.

Claims (1)

[Claims] 1. A hydrogen treatment system for a light water reactor, characterized in that a hydrogen absorption/supply mechanism containing a hydrogen storage alloy is disposed in the waste treatment system path and/or the reactor water system path. . 2. The hydrogen absorption/supply mechanism includes a main body container containing a hydrogen storage alloy, a gas introduction pipe and a gas outlet pipe attached to the container, and a temperature control system and/or a hydrogen pressure control system. A hydrogen treatment device for a light water reactor according to claim 1.