JPS59180486A - Reactor protecting device - 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 nuclear reactor protection device for maintaining the thermal integrity of nuclear reactor fuel.

[Technical background of the invention]

FIG. 1 shows a schematic configuration of a boiling water reactor (hereinafter referred to as BWR) plant. Steam generated in a reactor pressure vessel 1 is passed through a main steam pipe 3 equipped with a main steam control valve 2 into a steam cube bin 4. and drives this turbine 4.

The steam turbine 4 then drives the generator 5 to obtain electrical energy. Further, the steam after driving the steam turbine 4 is condensed and liquefied in a condenser 7 equipped with a cooling pipe 6 to become condensed water. This condensate is then passed through a condensate pipe 8 to a low pressure condensate pump 9
The water is sent to the condensate desalination device 10, where it is desalinated, and then sent to the feed water heater 12 to be heated by the high pressure condensate pump I, and then passed through the water feed pipe I3 to the feed water pump 1.
4 so as to circulate back into the reactor pressure vessel 1. In the drawing, reference numeral 15 denotes a bypass pipe that connects the main steam pipe 3 with the steam control valve 2 and the condenser 7, and a bypass valve 16 is inserted into the bypass pipe I5.

On the other hand, 17 in the figure is a reactor pressure control device.

This reactor pressure control device 17 inputs an output request signal 18 generated due to load fluctuation, and operates an output control device 19. Further, the neutron flux of the reactor core within the reactor pressure vessel 1 is detected by a neutron flux detection device 20 .

The signal from output controller 19 is then input to recirculation flow controller 21 which controls recirculation pump drive motor 22 . Therefore, the recirculation pump 23 functions to control the recirculation flow rate and keep the reactor output constant.

By the way, in such a WR plant, for example, if a positive reactivity is applied due to an increase in reactor pressure, a control rod is withdrawn, or some other cause, and an abnormal power substation occurs that causes an increase in neutron flux, the neutron flux will increase. This decreases due to the inhibition of fuel rod lifting and heat removal from the fuel rods. The safe limit value of MCPR is 1.06 to 1.07, but in consideration of the transient decrease when an abnormal event occurs (the decrease in MCPR is expressed as ΔMCPR), the value should be larger during normal operation. (for example, 1.26 or higher). Causes of such abnormal events include turbine trips, recirculation pump trips, loss of feed water flow, and the like. Therefore, BWRs are generally equipped with various protection functions to prevent ΔMCPR from increasing transiently even when such an abnormal event occurs. It has a function that generates a reactor scram signal when it reaches (for example, 120% of the rated value), emergency inserts all control rods, and shuts down the reactor.

[Problems with background technology]

However, in conventional BWR plants, even if the neutron flux level increases, no protective action is taken until it reaches the level at which a reactor scram signal is generated. As a result, there have been problems such as an increase in neutron flux, which impairs the integrity of the fuel rods, and a reduction in the operating rate of the plant due to reactor shutdown.

[Purpose of the invention]

The present invention was made based on these circumstances, and
The purpose is to maintain the thermal integrity of the fuel rods without causing reactor shutdown in the event of an abnormal event such as a sudden rise in neutron flux levels, thereby improving plant availability. The purpose is to provide nuclear reactor protection equipment.

[Summary of the invention]

The reactor protection device of the present invention uses a neutron flux safety level setting device to set a neutron flux safety level that is lower than the generation level of a reactor scram signal due to an increase in neutron flux and higher than the level during normal operation, and When the detection level reaches the neutron flux safety level, the command signal generator outputs a neutron flux reduction command signal to the recirculation flow rate control device to activate this control device, thereby reducing the recirculation flow rate and shutting down the reactor. The purpose is to maintain the thermal integrity of the fuel rods by lowering the neutron flux without causing damage, and to improve reactor operating efficiency.

[Embodiment of the Invention] FIG. 2 shows an embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In the figure, 24 is a command signal generator that manually generates a neutron flux detection level signal from the neutron flux detection device 2o, and 25 is a neutron flux safety level setting device. Neutron flux safety level setting device 25
is to set a neutron flux safety level that is lower than the level at which a reactor scram signal is generated due to an increase in neutron flux and higher than the level during normal operation.

The command signal generator 24 receives the neutron flux detection level signal, inputs the neutron flux safety level signal from the neutron flux safety level setter 25, and compares both signals.

When the neutron flux detection level reaches the neutron flux safety level, a neutron flux reduction command signal is sent to the recirculation flow rate control device 26.
This is what is output to.

On the other hand, the recirculation flow rate control device 26 controls the recirculation pump 23 via the recirculation pump drive motor 22 in response to the signal from the output control device 19, thereby maintaining the reactor output constant during normal operation. However, as soon as the neutron flux reduction command signal is generated from the command signal generator 24, the recirculation pump 23 is activated via the recirculation pump drive motor 22.
This acts to reduce the rotational speed of the pump and reduce the recirculation flow rate.

According to the reactor protection device configured as described above, when the neutron flux in the reactor core increases, the neutron flux safety level is reached before the reactor scram signal generation level is reached, and the recirculation flow rate is reduced. This suppresses the increase in the neutron flux level. Therefore, the thermal integrity of the fuel rods is preserved. Furthermore, the generation of a reactor scram signal can be avoided and the reactor will not shut down due to an increase in neutron flux, so the reactor operating rate will be improved.

Note that by making the neutron flux safety level set by the neutron flux safety level setting device 25 variable, the operation start point of the recirculation flow rate control device 26 can be adjusted as desired.

Furthermore, the configuration of the recirculation flow rate control device 26 is not limited to one that reduces the rotation speed of the recirculation pump 23, but also reduces the recirculation flow rate by reducing the opening degree of a recirculation flow rate adjustment valve (not shown). It may also be something that allows you to do so. Further, the recirculation flow rate may be reduced by tripping at least some of the plurality of recirculation pumps.

〔Effect of the invention〕

As described in detail above, according to the nuclear reactor protection device of the present invention, the neutron flux safety level setting device detects that the neutron flux is lower than the t level of the reactor scram signal due to an increase in neutron flux and higher than the level during normal operation. The safety level is set, and when the neutron flux detection level of the reactor core reaches the neutron flux safety level, the command signal generator outputs a neutron flux reduction command signal to the recirculation flow rate control device to activate this control device. By reducing the recirculation flow rate, even in the event of an abnormal event that increases the neutron flux level, the recirculation flow rate can be reduced before the reactor scram signal is generated to lower the neutron flux level. , the thermal integrity of the fuel rods can be maintained. Further, the reactor operating rate can be improved without causing the reactor to shut down.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional example, and FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention. 20... Neutron flux detection device, 2310. Recirculation pump, 24... Command signal generator, 25... Neutron flux safety level setting device, 26... Recirculation flow rate control device. Applicant's agent Patent attorney Takehiko Suzue Procedural amendment (
The sword was completed in 1982; Japanese 'h' + Mr. Wakasugi Kazuo, Director-General of the Correction Agency],,
:Indication of IT Patent Application No. 58-56174 2, Title of Invention Relationship with the Itr Haruko Stir-Fry Oven Protective Device Amendment Case Patent Applicant (307) Tokyo Shiba Yudenki Co., Ltd. (etc.) 4 , Agent (,1:i9i Toranomon 1-26-5υ, Tokyo)
No. 17 Mori Building 5, date of amendment order June 28, 1980 6, document clarifying the power of attorney for the amendment, full text of the specification, 7'
−〜−゛＼ 7. Contents of amendment (1) One document certifying authority of representation shall be amended as shown in the attached sheet. (2) Engraving of the specification (no changes to the contents).

Claims (5)

[Claims] (1) A neutron flux safety level setting device that sets a neutron flux safety level that is lower than the generation level of the reactor scram signal due to an increase in neutron flux and higher than the level during normal operation, and the neutron flux safety level signal from this setting device and the reactor core. A command signal generator that outputs a neutron flux reduction command signal when the neutron flux detection level reaches a neutron flux safety level by comparing it with a neutron flux detection level signal, and a neutron flux reduction command signal output from the command signal generator. A nuclear reactor protection device comprising: a recirculation flow rate control device that is activated by a command signal to reduce a recirculation flow rate. (2) The nuclear reactor safety system according to claim (1), wherein the neutron flux safety level set by the neutron flux safety level setting device is variable. (3) The reactor protection device according to claim 1, wherein the recirculation flow rate control device reduces the recirculation flow rate by lowering the rotational speed of the recirculation pump. (4) The reactor protection device according to claim 1, wherein the recirculation flow rate control device reduces the recirculation flow rate by reducing the opening degree of a recirculation flow rate regulating valve. (5) The reactor protection device according to claim 1, wherein the recirculation flow rate control device trips at least a portion of the recirculation pump to reduce the recirculation flow rate.