JPS59107294A - Reactor monitoring 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 provides a reactor monitoring device that monitors the in-core neutron flux and in-reactor thermal behavior of a boiling water nuclear reactor and maintains the integrity of fuel cladding. Regarding.

[Technical background of the invention and its problems]

The fuel cladding plays the most important role in preventing the leakage of radioactive products produced by nuclear fission reactions to the outside. Therefore, the reactor must be operated under conditions that allow the integrity of the cladding to be maintained with sufficient margin, that is, to prevent the cladding from reaching its thermal limits.

The health of the fuel cladding is evaluated by determining the critical power (cp) at the fuel assembly surface and dividing this by the actual fuel assembly power. The critical power ratio (CPR) is determined based on the smallest value of the critical power ratio (CPR) for each fuel assembly in the core, that is, the minimum critical power ratio (MCPR).Here, the critical power (cp) is Air bubbles form all over the surface of the fuel cladding tube, which is at the highest temperature in the furnace.
It is set as the output at which a phenomenon in which a film of steam is generated between the surface of the cladding tube and the coolant and the cladding tube is heated (film boiling phenomenon) begins to occur. Therefore, if the actual output exceeds the limit output (MCPR falls below 1.0), a film boiling phenomenon will occur, so in order to prevent the actual output from exceeding the limit output, MCPR must be set to 1, It is necessary to keep it above 0. However, in consideration of safety in actual driving, the allowable limit value of MCPH is set to 1.06 to 1.07. These allowable limit values are set assuming the occurrence of a failure of a nuclear reactor component or an operator's erroneous operation, but they are is not taken into account.

Generally, when a reactor component malfunctions, an emergency device is activated, but if there are multiple failures in which the emergency device does not function, it is expected that the MCPR will be lower than in the case of a single failure. Therefore, even if the vehicle is operated under conditions in which the MCPR does not fall below the allowable value in the event of a single failure, the MCPR may fall below the allowable value in the event of multiple failures.

By the way, even if film boiling occurs and the fuel cladding tube (made of Zircaloy) begins to heat up, the cladding will fail under a certain heating temperature and heating time (including after-effects such as weakening of the strength). It has been shown that the tubes are not affected.

Therefore, from the relationship between the heating temperature and heating time of the 5-covered tube, a health limit curve S of the cladding tube can be drawn as shown in FIG. In other words, the area above the soundness limit curve S is regarded as a dangerous area. Therefore, based on this curve, the allowable heating temperature T1 and allowable heating time, tl, are set in consideration of appropriate safety, so that the heating temperature T is below T1 and the heating time is 1. If it is below, it can be considered that the integrity of the fuel cladding is sufficiently maintained.

On the other hand, regarding the behavior of the cladding material after film boiling, experimental results (experiments ① to ①) as shown in Fig. 2 have been obtained. That is, the surface temperature of the fuel assembly does not rise rapidly within the allowable heating time t1, and the peak temperature at this time is much lower than the allowable heating temperature T1. If the MCPR falls below the allowable value due to abnormalities not considered in the current design, such as multiple failures, the time during which it falls below the allowable heating time is 1. It is thought that the integrity of the fuel cladding can be maintained sufficiently even if operation continues until the

[Purpose of the invention]

The present invention was made based on the results of such considerations, and its purpose is to provide an atomic system that can sufficiently maintain the integrity of the fuel cladding even when the MCPR falls below the allowable limit value due to multiple failures, etc. An object of the present invention is to provide a furnace monitoring device.

[Summary of the invention]

The reactor monitoring device of the present invention includes an in-core neutron flux detector that detects neutron flux at various locations in the reactor core loaded with fuel assemblies and outputs a neutron flux signal, and a reactor neutron flux detector that detects neutron flux at various locations in the reactor core loaded with fuel assemblies and outputs a neutron flux signal. A process computer that calculates the heat output of each reactor, a transient phenomenon recorder that records the main reactor parameters based on the neutron flux signal when a reactor abnormality occurs, and a reactor that is recorded in this transient phenomenon recorder. an MCPR value calculator that calculates a minimum output ratio of a fuel assembly surface when a reactor abnormality occurs from the parameters and the thermal output of each fuel assembly before the reactor abnormality occurs, which is calculated by the process computer; An MCPR value comparator that compares the minimum limit output ratio calculated by this MCPR value calculator with a preset allowable limit output ratio, and a minimum limit output ratio as a result of the comparison in this MCPR value comparator. Based on the output from the MCPR value comparator and the alarm device that operates when a fuel assembly exceeding the allowable limit output ratio appears, the fuel assembly whose minimum minimum output ratio exceeds the allowable limit output ratio is identified and the identification result is output as a monitor signal. and a transient discrimination device that measures the duration of the warning limit output ratio that exceeds the allowable limit output ratio and outputs the duration as a transient discrimination signal; a warning fuel assembly display device that displays fuel assemblies with a composite limit output ratio that exceeds the allowable limit output ratio; and a duration that compares the transient discrimination signal from the transient discrimination device with a preset allowable duration. A time comparator, and a warning duration identification device that identifies fuel assemblies whose duration of the warning limit output ratio exceeds one permissible duration based on the comparison result of the duration comparator and outputs the identification result as a monitor signal. and, based on the monitor signal from this warning duration identification device, the most visible warning fuel that displays the fuel assembly whose minimum limit output ratio exceeds the allowable limit output ratio and the duration of the warning limit output ratio exceeds the allowable duration. and an aggregate display device.

Therefore, when a fuel assembly whose MCPR exceeds the allowable limit output ratio appears, the warning device is activated and the corresponding fuel assembly is displayed on the warning fuel assembly display device. When a fuel assembly whose duration exceeds the allowable duration appears, the corresponding fuel assembly will be displayed on the most recommended fuel assembly display device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

There are multiple fuel assemblies (not shown) in the reactor pressure vessel 1.
A reactor core 2 is constructed by loading the reactor core 2.
In-core neutron flux detectors 3 for detecting neutron flux at various locations are provided at several locations (only one location is shown). This in-core neutron flux detector 3 outputs a neutron flux signal S1, and this signal sl is transmitted to a process computer 4 and a transient phenomenon recording device 5 provided outside the pressure vessel 1. Therefore, in process calculation a4, the thermal output of each fuel assembly is calculated based on this neutron flux signal S.

In addition, the transient phenomenon recording device 5 recognizes the burrow as a reactor abnormality when the thermal output fluctuates greatly, records the main reactor parameters based on the neutron flux signal s1 at the time of this reactor abnormality, and records the MCPR. Send the heat output signal s2 to the value calculator 6. The MCPR value calculator 6 inputs the thermal output signal S: from the transient phenomenon recording device 5, and inputs the thermal output of each fuel assembly before the occurrence of reactor abnormality from the process computer 4 as a thermal output signal s3. . These two signals S, , S, and the minimum critical power ratio (MCPR) of the fuel assembly surface in the event of a nuclear reactor abnormality are
) and outputs the result of the calculation as the MCPR information signal S4.

On the other hand, the setting device 7 uses the allowable heating temperature T1 (MCP
A permissible limit value (permissible limit output ratio) of R is set in advance, and this is sent to the MCPR value comparator 8 as a reference MCPR signal s6. Therefore, in the MCPR value comparator 8, the M
The CPR information signal S4 and the reference MCPR signal S5 are compared, and if the MCPR information signal S4 is larger than the reference MCPR signal S5, the MCPR value comparator 8 sends an activation signal S6 to the AND circuit 9, and An alarm activation signal s7 is sent to the alarm device 10 to activate the alarm device 10. Further, the melon circuit 9 inputs the heat output signal S3 from the process computer 4, and when the MCPR value comparator 8 generates the operation signal S6, it opens the dart and sends the heat output signal S3 to the transient state discrimination device 11. Send. Therefore, the transient discrimination device 1
At No., fuel assemblies whose MCPR exceeds the allowable limit output ratio are identified based on the thermal output signal S3. In this way, the MCPR exceeding the allowable limit output ratio is a warning limit output ratio that requires caution, and the identification result of the transient discrimination device 1 is output as a monitor signal S8. In addition, the transient determination device 11 measures the duration of the warning limit output ratio exceeding the allowable limit output ratio on each fuel assembly surface, and transmits the measurement result to the duration comparator 13 as a transient determination signal S9. Therefore, the duration comparator 13 inputs the transient determination signal S9 and also inputs the allowable heating time t! Based on this, a preset allowable duration is input into the setter 14 as a reference time signal 810, and both signals so and sto are compared. When the transient discrimination signal S9 exceeds the reference time signal SIO, the discrimination signal 811 is sent to the alert duration discrimination device 15.
Send to. Therefore, the warning duration identification bag w15 identifies fuel assemblies whose warning limit output ratio duration exceeds the permissible duration based on the discrimination signal 811, and displays the identification result as a monitor signal 812 for the fuel assembly that is most likely to be moved. Output to device 16. Therefore, if a fuel assembly appears whose minimum limit output ratio exceeds the allowable limit output ratio and the duration of the warning limit output ratio exceeds the allowable duration, the corresponding fuel assembly becomes the maximum warning fuel assembly. It will be displayed on the display device 16.

〔Effect of the invention〕

As detailed above, according to the present invention, when a fuel assembly whose minimum critical output ratio exceeds the allowable critical output ratio appears, the warning device is activated and the fuel assembly corresponding to the warning fuel assembly display device is activated. is displayed, and when a warning limit output ratio duration exceeds the allowable duration, the corresponding fuel assembly is displayed on the most warning fuel assembly display device, so multiple warnings can be displayed. Due to malfunction etc.
Even if the minimum output ratio falls below the allowable limit output ratio, the integrity of the fuel cladding can be maintained sufficiently.

[Brief explanation of drawings]

Figure 1 is a diagram showing the health limit curve of the cladding in relation to the fuel cladding heating temperature T and heating time, and Figure 2 is a diagram showing the actual results regarding the behavior of the cladding material after film boiling. , FIG. 3 is a system diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reactor pressure vessel, 2... Reactor core, 3 Inner reactor neutron flux detector, 4... Process computer, 5... Transient phenomenon recording device, 6... MCPR value calculator, 8...・・MC
PR value comparator, 10... Alarm device, 1... Transient time discrimination device, 12... Fuel warning fuel assembly display device, 13.
... Duration comparator, 15... Alert duration identification device, 16... Most alert fuel assembly display device. Applicant's agent Takehiko E, patent attorney

Claims (1)

[Claims] an in-core neutron flux detector that outputs neutron flux signals at various locations in a reactor core loaded with a plurality of fuel assemblies; a process calculator that calculates heat output for each fuel assembly based on the neutron flux signals from the detector; A transient phenomenon recording device that records main reactor/main meters based on the neutron flux signal when a reactor abnormality occurs, and reactor parameters recorded in the transient phenomenon recording device and calculations performed by the process computer. An MCPR value calculator that calculates the minimum limit power ratio of the fuel assembly surface at the time of reactor abnormality from the thermal output of each fuel assembly before the reactor abnormality occurs, and the minimum limit power calculated by this MCPR value calculator. an MCPR value comparator that compares the ratio with a preset allowable limit output ratio;
An alarm device is activated when a fuel assembly whose minimum output ratio exceeds the allowable limit output ratio as a result of the comparison in the MCPR value comparator appears, and the minimum limit output ratio is the allowable limit based on the output from the MCPrt value comparator. During a transient period, the fuel assembly that exceeds the output ratio is identified and the identification result is output as a monitor signal, and the duration of the warning limit output ratio that exceeds the allowable limit output ratio is measured and the duration is output as a transient determination signal. a discrimination device; a warning fuel assembly display device for displaying fuel assemblies whose limit output ratios exceed a permissible limit output ratio based on a monitor signal from the transient discrimination device; and the transient discrimination device. a duration comparator that compares the transient discrimination signal from the 1000 with a preset allowable duration, and a fuel set whose duration of the warning limit output ratio exceeds the allowable duration based on the comparison result of the duration comparator. an alert duration identification device that identifies the body and outputs the identification result as a monitor signal;
Based on the monitor signal from this warning duration identification device, the most visible fuel assembly displays fuel assemblies whose minimum limit output ratio exceeds the allowable limit output ratio and the duration of the warning limit output ratio exceeds the allowable duration. A nuclear reactor monitoring device comprising: a display device; and a display device.