JPH1020080A - Nuclear power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the concentration of an organic matter in reactor water, and suppression of corrosion by the adhesion of the organic matter onto the incore structure surface by providing an organic matter decomposing device within a hot well vessel to which the condensate of a reactor and the make-up water from a condensate storage tank are carried. SOLUTION: The steam generated in a reactor 1 is cooled by sea water in a condenser 2 after it rotates a turbine to generate a power, returned to water, and stored in a hot well 3 in the lower part of the condenser 2. An organic matter decomposing device 10 such as ultraviolet ray emitting lamp is set in the hot well 3, and an ultraviolet ray is emitted into the condensedwater by this device 10. Then, the organic matter is decomposed by the ultraviolet ray and changed to an inorganic ion of sulfuric acid, nitric acid or the like. The resulting inorganic ion is removed by a condensate demineralizer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear power plant, and more particularly, to a nuclear power plant having high reliability by maintaining good water quality of reactor water so as to prevent corrosion or the like of a reactor internal structure from occurring.

[0002]

2. Description of the Related Art When organic matter is mixed in reactor water of a nuclear power plant, the organic matter is thermally and radiolytically decomposed in a reactor pressure vessel to generate inorganic ion impurities. Ionic impurities adhere to the surface of structural materials inside the furnace and promote corrosion, so nuclear power plants continuously monitor the conductivity of reactor water,
Furthermore, the quality of the water is monitored by periodically analyzing the ion concentration and the like.

[0003] The main factors of organic matter generation include elution from the ion exchange resin loaded in the condensate filtration and desalination unit of the condensate purification system, and treatment water having a high organic matter concentration from the waste treatment system. It is conceivable that the water is collected in the storage tank and is mixed into the hot well as primary make-up water, and is eluted from the ion exchange resin of the purification equipment of the reactor purification system.

[0004] In particular, when the reactor is started, water is supplied to the reactor after purifying system water by a feed-back water recirculation operation.
The amount of organic substances eluted from the condensate filtration and desalination equipment increases due to an increase in the flow rate, etc., and is decomposed into inorganic ion impurities in the furnace, and the reactor water conductivity exceeds the plant-specified limit value. Postponement also occurs.

[0005] Further, the existing purification equipment aims at removing inorganic ion components, and cannot remove organic substances as they are. Instead, the present generation source is isolated, and organic substance components are washed out by recirculation operation, and the like. I have.

[0006]

In the above-mentioned prior art, there is a possibility that organic matter is mixed into the reactor water and decomposed into inorganic ion components, thereby deteriorating the reactor water quality and affecting plant operation.

[0007] It is an object of the present invention to provide a nuclear power plant having means for effectively removing organic matter in reactor water.

[0008]

According to a first aspect of the present invention, there is provided a hot well vessel in which condensate of a nuclear reactor and make-up water from a condensate storage tank flow. A nuclear power plant provided with an organic matter decomposition device is provided.

With the above structure, since the organic matter is decomposed into inorganic ions, it can be recovered as impurities in the condensate filtration and desalination apparatus, and the concentration of organic matter in the reactor water can be reduced.
Thereby, it is possible to suppress the occurrence of corrosion due to the adhesion of the organic matter to the surface of the furnace internal structure.

According to a second aspect of the present invention, there is provided a nuclear power plant in which the organic matter decomposer in the first aspect is an ultraviolet ray generator. Irradiation with ultraviolet rays can efficiently decompose organic substances into inorganic ions.

According to a third aspect of the present invention, in the nuclear power plant according to the first aspect of the present invention, a plurality of the hot wells are provided. A nuclear power plant is provided that is provided with a valve at each outlet of the hotwell to flow.

According to the above configuration, the residence time of the hot water in the reactor water can be increased, so that the decomposition of organic substances can be promoted.

That is, an organic matter decomposer is installed in a hot well having a long residence time of primary system water, and a replenishment water from a condensate storage tank and a condensate desalination device outlet during a recirculation operation of a feed condensate water at start-up. It decomposes organic matter in the return water.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, an organic substance decomposing apparatus is installed in a hot well, whereby organic substances can be decomposed into ionic impurities, and can be removed by a condensate desalination apparatus. Is characterized in that it can be reduced.

An embodiment of the present invention will be described below.

FIG. 1 shows a schematic configuration of a primary system of a boiling water nuclear power plant. After the steam generated in the reactor 1 rotates the turbine to generate power, the steam is cooled by seawater in the condenser 2, returned to water, and accumulated in the hot well 3 below the condenser. The hot well 3 has a maze-like flow path for attenuating short-lived nuclides that have been transported as steam from the nuclear reactor, and has a structure that stays long. Condensation is performed by sufficiently attenuating the short-lived nuclides in the hot well 3 and then using the low-pressure condensing pump 4.
Is transferred from the hot well 3 to the condensate piping on the downstream side, purified by the condensate filtration and desalination device 5 and the condensate demineralization device 6, heated by the feed water heater 7, and returned to the nuclear reactor 1.
In addition, a condensate storage tank 8 for storing recovered water from waste treatment equipment is provided. The condensate storage tank water is supplied to the condenser 2 as make-up water during operation. Water is supplied to the reactor as a water source 9.

In such a configuration, an organic matter decomposer 10 such as an ultraviolet irradiation lamp is installed in a hot well in which system water stays for 2 minutes or more during normal operation. FIG. 2 shows an example of installation of an ultraviolet irradiation lamp on a hot well. FIG. 3 shows the flow of water as viewed from above the hot well.

The organic matter present in the condensed water is decomposed by ultraviolet irradiation by the organic matter decomposing device and changed into inorganic ions such as sulfuric acid and nitric acid. For example, in the case of elution of an organic substance from a cationic resin, it is known that sulfuric acid is generated by the following formula.

[0019] _{^{R-SO 3H + → R-}} OH + H 2 SO 3 3H 2 SO 3 → 2H 2 SO 4 + S + H 2 O decomposed inorganic ions chlorine ions during seawater leakage from the condenser, such as sodium ions The condensate is removed by a condensate desalination device 6 installed for the purpose of removing inorganic ions.

At the start-up, the condenser 2, the condensate desalination device 6,
A water supply / recirculation system recirculation operation that returns to the condenser 2 via the water supply / recirculation pipe 11 or the like is performed to purify water accumulated in the pipe.

At this time, a valve is additionally provided at each hot well outlet, and the supply / recovery water recirculation pipe is closed. The valve at the hot well outlet where the water returns is closed, and the system water is connected to the communication pipe for adjusting the water level between the hot wells. By cascade-connecting to flow through another hot well via the hot well, the residence time of the hot well is increased, and the decomposition of organic substances eluted from the ion exchange resin of the condensate desalination apparatus into inorganic ions can be further promoted. FIG. 4 shows the configuration of the hot well and the flow of water.

According to the above embodiment, organic substances brought into the furnace can be decomposed into inorganic ions in the hot well in advance and can be removed by the condensate desalination apparatus, so that the water quality of the furnace water can be kept good.

[0023]

According to the first aspect of the present invention, since organic substances are decomposed into inorganic ions, they can be recovered as impurities in the condensate filtration and desalination apparatus, and the concentration of organic substances in the reactor water can be reduced. . Thereby, it is possible to suppress the occurrence of corrosion due to the adhesion of the organic matter to the surface of the furnace internal structure.

According to the second aspect of the present invention, an organic substance can be efficiently decomposed into inorganic ions by irradiation with ultraviolet rays.

According to the third invention of the present invention, the residence time of the hot water in the reactor water can be increased, so that the decomposition of organic substances can be promoted.

That is, according to the present invention, by decomposing organic matter into inorganic ions before flowing into the furnace, it becomes possible to remove decomposition-generated ions in existing purification equipment, and the effect of maintaining good reactor water quality is obtained. is there.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of primary system water of a boiling water reactor.

FIG. 2 is an installation example of an organic matter decomposition apparatus.

FIG. 3 is a diagram showing a flow of water in a hot well.

FIG. 4 is an example of a hot well operation at the time of startup.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Condenser, 3 ... Hot well, 4 ... Low pressure condensate pump, 5 ... Condensate filtration device, 6 ... Condensate desalination device, 7
... feed water heater, 8 ... condensate storage tank, 9 ... control rod drive water system, 10 ... organic matter decomposer, 11 ... feed water recirculation pipe.

Claims (3)

[Claims] 1. A nuclear power plant, wherein an organic matter decomposing device is provided in a hot well vessel into which condensate water from a condensate storage tank and condensate of a nuclear reactor flows. 2. A nuclear power plant, wherein the organic matter decomposer according to claim 1 is an ultraviolet ray generator. 3. The nuclear power plant according to claim 1, wherein
A nuclear power plant, wherein a plurality of the hot wells are provided, and valves are provided at respective outlets of the hot wells so that feed water recirculation water flows through all the hot wells and then flows to a condensate pump.