JPS6285897A - Method of controlling impurity concentration of boiling water type reactor feed water system - 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 the Invention] The present invention relates to a method for controlling impurity concentration in a boiling water reactor feed water system, and in particular, by optimally controlling the crud concentration in the feed water system, ) 5 Relates to control methods for keeping radioactivity low.

[Technical backbone of the invention and its problems]

In the boiling water reactor (BWR) Brun 1-, steam from the reactor 1 is supplied to the turbine 2, as shown in Figure 4, and the steam that has been squeezed by the turbine 2 is stored in the condenser 3. 47 with condensate. This condensate is purified by a condensate filter 4, roughly purified by a condensate demineralizer 5, heated by a feed water heater 6, and introduced into the reactor.

As described above, in the conventional reactor water supply system, in order to reduce crud in the feed water 4, the condensate filter 4 and the condensate demineralizer 5 remove crud from the feed water. Conventionally, as shown in Figure 3, a method has been adopted to reduce the amount of crud in the water supply as much as possible, from the perspective that the less crud in the water supply, the less radioactivity will be generated from the iron-based crud. was.

However, in Plan 1~, which uses a lot of nickel alloy piping in recent years, if the amount of crud in the water supply is extremely reduced, the amount of adsorption and removal of ionic radioactivity by the crud and the eutectoid removal drop are reduced, and the reactor is restarted. It was found that as a result of the increase in ionic radioactivity in the circulation system, ionic radioactivity was accumulated on the inner surfaces of recirculation system structures such as recirculation system piping. As a result, when inspecting the reactor recirculation system, a problem arises in that maintenance costs increase in order to avoid exposure of workers performing the inspection work.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and is aimed at reducing ionic radioactivity in the recirculation system of a nuclear reactor.
The purpose of the present invention is to provide a method for controlling impurity concentration in a boiling water reactor water supply system by reducing radiation exposure by +5 L during inspection.

[Summary of the Invention] In order to achieve the above-mentioned objective 1, the impurity concentration control method of the boiling water reactor feed water system according to the present invention is used to reduce the iron concentration in the boiling water reactor feed water system. and the ratio of Nickelbuchi 19 (F
e/Ni) is controlled to be 2 or more.

[Embodiments of the invention]

Hereinafter, an example of a droplet of the present invention will be explained based on the drawings.

FIG. 1 shows the flow [1-] of a water supply system for carrying out the control method according to the present invention. Incidentally, since the basic system is the same as the conventional configuration shown in FIG. 4, the same reference numerals are given to the corresponding parts in the figure and the explanation thereof will be omitted.

In the system of this embodiment, the feed water is introduced into the reactor 1.
A turbidity meter 7 was installed in the middle of the thread path of the water supply system in step 4, and Fe1l was analyzed from the crud 11111 detected by this.
The concentration is calculated.

From this calculated value, the ratio (Fe/Ni) of the Fe degree and the Ni + 1J degree separately measured by the ion cross meter 8
The calculated value is set as the set value (Fe
/N1=2> or less, a command signal to open the bypass valve 9 provided in the middle of the bypass line 10 is output, and the set value (1:e/N1=2) and Fe/Ni glue] The opening degree of the bypass valve 11 is adjusted according to the deviation m from the output value. As a result, crud in the feed water is not captured by the condensate filter 4 and is removed by the feed water superheater 6.
is supplied to the raw material reactor 1, and the bypass valve 11
By adjusting the opening of the reactor 1, water having a predetermined crud concentration or less is supplied to the reactor 1. Similarly, by adjusting the opening degree of the bypass valve 13, a predetermined crud concentration can be achieved without trapping crud in the condensate demineralizer 5.

Moreover, such a bypass valve 11 or bypass valve 12
The impurity concentration in the water supply is controlled by the following method, together with the method of controlling the impurity concentration by the opening degree of the pump, or by the following method alone. First, the Fe1 degree is analyzed from the crud concentration measured by the turbidity meter 7, and the concentration is determined.

Further, the degree of NillJ is analyzed by the ion cross l-ff+8, and its concentration is reported. From this quotation value, “e”
The ratio Fe/Ni between the concentration and Ni fuchika is calculated, and Fe/N
When the calculated value of i becomes less than the set value (Fe/N i = 2), iron oxide or iron hydroxide is suspended in water, and the pipe connected from the tank 13 to the water supply pipe is An opening command signal is output to the ferrous intake valve 14 provided at the
The opening degree of the ferrous valve 14 is adjusted based on the deviation value from the calculated value of i.

In this way, by increasing the Pc/Ni in the water supply to 2 or more, the ratio in the reactor water is +3 and 1. 2+ II +Fe 203 + To-120-+N
i Fe 2 0 4 -1-2 To1
・・・ ・・・ (1)
60CO21+Fe2O3+1-120→60COFe
O+21-1+ 24 ...The reaction shown in (2) proceeds, and the ion radioactivity of 60Co2'' is reduced.

This point also applies to 58CO. In this case, the relationship between F'e/Ni in the feed water and the ion radioactivity concentration in the reactor water is as shown in Figure 2. In the region where Fe/Ni is lower than 2, the ion radioactivity concentration in the reactor water is Although the concentration was high, it was found that the ion radioactivity concentration in the reactor water was low in the cases where the Fe/Ni ratio in the feed water was 2 or more. Therefore, Fe/
By controlling Ni to 2 or more, the ionic radioactivity concentration in the reactor water is lowered, so the accumulation of ionic radioactivity in the reactor recirculation system is greatly reduced.

In addition, in the embodiment shown in FIG. 1, a bypass line 10 and a bypass valve 11 are provided, and since feed water often flows through this bypass line 10 or bypass valve 11, the condensate filter 4 and the condensate The life of the demineralizer 5 can be extended.

(Effects of the Invention) As described above, according to the present invention, the ion radioactivity concentration in reactor water is reduced by optimally controlling the crud concentration in the water supply system, and therefore, the concentration of ion radioactivity in the reactor water is reduced. The accumulation of ionic radioactivity is reduced, and the exposure of workers to radiation during inspection of the recirculation system can be greatly reduced.

[Brief explanation of drawings]

Figure 1 shows the state of feng shui for carrying out the present invention! A flow diagram of the reactor water supply system, Figure 2 is the Fc of the water supply system! /Graph 3 regarding the relationship between Ni and ion radioactive concentration in reactor water.
The figure is a graph showing the relationship between the cladding of the water supply system and the radioactivity concentration in reactor water, and Figure 4 is a flow diagram of the water supply system of a boiling water reactor. 1... Nuclear reactor, 2... Turbine, 3... Condenser,
4... Condensate filter, 5... Condensate demineralizer, 6... Feed water heater, 7... Turbidity meter, 8... Ion clost meter, 9... S1 machine , 10... bypass system path, 11.
...Bypass valve, 13...tank, 14...iron valve. Applicant's agent Hisashi Hatano Fth HO, 0/ 0.1 /2 □ Is the FC/A/ inside the tree in Figure 2? 1 □ Flood in lead water Part 3

Claims (1)

[Claims] 1. A boiling water nuclear reactor characterized by controlling the ratio of iron concentration to nickel concentration (Fe/Ni) in the water supply system of a boiling water reactor to a predetermined value or more. Method for controlling impurity concentration in reactor feed water system. 2. Claim 1 of injecting an iron oxide suspension or an iron hydroxide suspension into the water supply system when Fe/Ni in the water supply system falls below a predetermined value. A method for controlling impurity concentration in a boiling water reactor feed water system as described in . 3. A bypass system is provided for the condensate filter and condensate demineralizer installed in the water supply system, and when Fe/Ni in the water supply system falls below a predetermined value, the supply water is distributed into the bypass system. A method for controlling impurity concentration in a boiling water reactor feed water system according to claim 1.