JPH06100671B2 - Reactor coolant purification system - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a reactor coolant purification system provided in a boiling water reactor auxiliary facility.

[Technical background of the invention and its problems] In order to remove impurities generated in the reactor and maintain the coolant at a predetermined water quality, that is, high purity, a boiling water reactor has a reactor coolant purification system. There is. That is, as shown in FIG. 1, in the boiling water reactor, the heat of the core 2 in the reactor pressure vessel 1 heats the coolant water flowing from the water supply pipe 3 to vaporize it to separate it from water and water. Vessel 4 and steam dryer 5
Through a main steam pipe 6 to a turbine system (not shown). Further, a recirculation system pipe 7 is provided in order to effectively extract heat from the core 2 and easily generate steam, and a jet pump 9 in the pressure vessel 1 is provided by the recirculation pump 8.
Drive water is supplied to the core 2 to forcibly circulate the coolant in the core 2.

This recirculation system is formed by two circuits, and the flow rate of the core coolant is controlled by adjusting the speed of the recirculation pump 8.

The reactor coolant cleaning system passes through the cleaning system inlet pipes 10 and 11 branched from the blow-in side of each reactor recirculation pump 8 and the lower head of the pressure vessel 1, and from the cleaning system pump 12 to the regenerative heat exchanger 1.
3, a non-regeneration heat exchanger 14 and a filtration desalination device 15, and a purification system outlet pipe 16 connected from the regeneration heat exchanger 13 to the water supply pipe 3.

By the way, at the time of periodical inspection of the nuclear reactor, maintenance and inspection of each device of the nuclear power plant are performed. In this case, maintenance and inspection of the reactor cooling water purification system is also performed, but the work at this time is about 5 to 10% of the total radiation exposure dose of the nuclear power plant. Most of these are maintenance work for pumps. Currently, the recycle system has the largest contribution to the radiation dose.

However, when an internal pump that replaces the recirculation pump 8 is installed, the recirculation system is deleted, and it is considered that the contribution rate to the exposure dose of the reactor coolant purification system is further increased. Therefore, from the viewpoint of reducing radiation exposure, it is an important problem to reduce the radiation dose of the reactor cleaning system pump section.

[Object of the Invention] The present invention has been made in order to solve the problems of the background art described above, and in a reactor coolant purification system in a boiling water nuclear power plant, for example, during periodic inspection and maintenance inspection of the reactor. An object of the present invention is to provide a reactor coolant purification system capable of reducing the radiation exposure of workers.

SUMMARY OF THE INVENTION The present invention is connected to a purification system inlet pipe branched from a drain system or a reactor recirculation system of a boiling water reactor pressure vessel or other coolant distribution system, and to this purification system inlet pipe. The regenerative heat exchanger, the non-regenerative heat exchanger installed in the downstream pipe of the regenerative heat exchanger, the filter desalting device installed in the downstream pipe of the non-regenerative heat exchanger, and the filter desalination A purification system outlet pipe connected to the downstream side of the device and connected to the coolant flow system of the boiling water reactor pressure vessel via the regenerative heat exchanger, and a downstream side pipe of the regenerative heat exchanger or the non- Reactor coolant purification, comprising: a purification system pump installed in the downstream pipe of the regenerative heat exchanger and arranged in the upstream pipe of the filter desalination apparatus, which is operated during plant operation and plant shutdown. It is a system.

[Embodiment of the Invention] A second embodiment of the reactor coolant purification system according to the present invention will be described below.
Description will be given with reference to the drawings.

In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description of the overlapping parts will be omitted. The difference between the embodiment of the present invention shown in FIG. 2 and the conventional example shown in FIG.
The drive purification pump 12 connected to the upstream side of 0, 11 is connected to the outlet pipe 13a of the regenerative heat exchanger 13, and the purification system pump 1
The discharge side of 2 is connected to the non-regenerative heat exchanger 14.

Then, the reactor water in the reactor pressure vessel 1 is forcibly flown around the core 2 by the circulation pump 8 of the recirculation system pipe 7 to be heated. In addition, in order to remove impurities in the reactor water, the reactor water is fed from the purification system inlet pipes 10 and 11 to the regenerative heat exchanger 1.
The temperature is lowered at 3 and further lowered to about 80 ° C. or lower at which the ion exchange resin can work in the non-regenerated heat exchanger 14, and then highly purified through a filter desalting apparatus 15 filled with the ion exchange resin.

Then, the highly purified coolant is passed through the regenerative heat exchanger 13 to raise the temperature, connected from the purification system outlet pipe 16 to the feed water pipe 3, and returned to the reactor pressure vessel 1.

In this case, the purification system pump 12 has conventionally been provided in the purification system inlet pipes 10 and 11 having a high temperature as shown in FIG. 1, but this is designed with a head with a margin of the pump 12. Because it was. However, in the present invention, as described above, the purification system pump 12 is connected to the outlet pipe 13 of the regenerative heat exchanger 13.
Since it is provided between a and, the radiation exposure dose due to the maintenance and inspection of the purification system pump can be reduced to 1/10 of the conventional level.

FIG. 3 shows the relationship between the system temperature and the system surface dose rate in the system configuration of the conventional reactor cleaning system.

The system surface dose rate is a value that is directly related to the individual radiation dose. In the figure, the vertical axis represents the surface dose rate logarithmically, and the horizontal axis represents the temperature of the filtered water. As you can see from the figure, near 230 ℃ and 280 ℃
There is a difference of one digit or more in the nearby measured values, and it is low at 230 ° C or lower. This is because when the temperature becomes 230 ° C or lower compared to the temperature near 280 ° C, the rate of oxide film formation inside the pipe decreases, and therefore it is taken into this oxide film.
This is because the ratio of radioisotopes such as Co-60 decreases.

On the other hand, since the purification system pump 12 is operated near 280 ° C., the surface dose rate is high, which is a factor of increasing the exposure dose rate.

Therefore, according to the present invention, the purification system pump 12 is replaced by the regenerative heat exchanger 13.
Since it is provided on the downstream side of the pump and can be operated at a temperature of 230 ° C. or less, the radiation exposure dose due to the maintenance and inspection of the purification system pump 12 can be reduced by almost one digit.

The present invention can be applied not only to the embodiment shown in FIG. 2 but also to the following examples.

(1) The purification system pump 12 should be provided in the downstream pipe of the non-regenerative heat exchanger 14.

(2) In a nuclear power plant where a reactor circulation system does not exist, when the system is constructed by directly extracting it from the reactor pressure vessel or branching from another system to construct the system.

[Advantages of the Invention] According to the present invention, the radiation exposure dose at the time of maintenance and inspection of the conventional purification system pump can be reduced to 1/10, and the radiation exposure can be reduced by 4 to 9% of the entire nuclear power plant. . Further, in a plant without a reactor recirculation system, the total radiation dose is considered to be about 70% of the conventional level, and the contribution rate of the present invention can reduce the radiation dose by 5 to 12% of the entire plant.

[Brief description of drawings]

FIG. 1 is a system diagram for explaining a conventional reactor coolant purification system, FIG. 2 is a system diagram for explaining one embodiment of a reactor coolant purification system according to the present invention, and FIG. 3 is It is a graph figure for demonstrating the operation effect of a prior art example and this invention. 1 ... Reactor pressure vessel, 2 ... Reactor core, 3 ... Water supply pipe, 4 ... Steam separator, 5 ... Steam dryer, 6 ... Main steam pipe, 7 ... Recirculation system pipe, 8 ... Re Circulation pump 9 …… Jet pump 10,11 …… Purification system inlet piping 12 …… Purification system pump, 13 …… Regeneration heat exchanger 14 …… Non-regeneration heat exchanger, 15 …… Filtration desalination device 16 …… Purification System outlet piping

Claims (1)

[Claims] 1. A purification system inlet pipe branched from a drain system or a reactor recirculation system of a boiling water reactor pressure vessel or another coolant distribution system, and regenerative heat exchange communicated with this purification system inlet pipe. Unit, a non-regenerative heat exchanger installed in the downstream pipe of the regenerative heat exchanger, a filtration desalination device installed in the downstream pipe of the non-regeneration heat exchanger, and a downstream of the filtration desalination device. Side outlet pipe connected to the coolant circulation system of the boiling water reactor pressure vessel through the regenerative heat exchanger, and a downstream side pipe of the regenerative heat exchanger or the non-regenerative heat exchange And a purification system pump which is installed in a downstream side pipe of the reactor and is arranged in an upstream side pipe of the filter desalination apparatus and which is operated during plant operation and plant stoppage.