KR101013166B1 - On-line monitoring of sub-critical multiplication calculation in nuclear reactor - Google Patents

Abstract

The present invention relates to the measurement of neutron pulse signals and calculation of the reverse count ratio of an out-of-measuring instrument for monitoring the subcritical state of a nuclear reactor in nuclear power plants. In particular, the neutron count rate and the inverse measured manually in the main control room during fuel loading in a nuclear power plant. The present invention relates to a device for automatically measuring the counting ratio ratio and determining in real time whether fuel loading is continued. The present invention, unlike the conventional method of informing the fuel loading personnel of the containment building through direct communication (direct line) of the result of calculating the reverse coefficient ratio performed in the main control room and the next fuel loading, the reverse coefficient ratio measured in the main control room Is displayed on the electronic signboard installed in the containment building using communication and continuously delivered to the entire fuel loading workers, and based on this, it is possible to directly determine whether to load the next fuel on site, thereby reducing the fuel loading time and improving the utilization rate of the power plant. It can increase.

Out-of-measure instrument, neutron counting ratio, inverse counting ratio, neutron multiplication factor

Description

On-line monitoring of sub-critical multiplication calculation in nuclear reactor}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to supercritical monitoring of nuclear reactors in the field of nuclear power generation. In particular, neutrons measured by an out-of-source area off-site instrument to prevent the reactor from approaching a critical state unexpectedly during fuel loading of a PWR reactor. Real-time reactor subcritical multiplication monitoring method for monitoring subcritical multiplication using count and reverse count rates.

Every pressurized and light nuclear power plant replaces one-third of the fuel assembly in the core with a new fuel assembly every 18 months for economic power generation. This is called the fuel loading of the reactor, and the fuel loading position is determined by the nuclear designer through core design and safety analysis. The fuel assemblies are loaded into the reactor one by one with the inserted components in the order established and approved. This sequence is determined to provide the lowest possible core damage to the core and to provide reliable core monitoring.

1 is a view showing a direct communication connection state during fuel loading. As shown in FIG. 1, the containment building (main control room) and fuel building (sub-control room) are arranged with a license holder for nuclear material handling supervisors and a person who has been trained on handling fuel materials, and under the direction and supervision of a nuclear reactor control supervisor in charge of core change. Perform loading tasks. During the fuel transfer period, the main control room, fuel transfer equipment (reactor building, fuel building), used fuel handling crane, reloader crane, supervisor, etc. are provided so that direct contact is always possible between the main control room, the reactor building, and the maintenance personnel in the fuel building. Install communication equipment, such as telephones or headphones, and install the fuel assembly flow chart.

In the main control room, all power plants should be able to measure neutron counting and reverse counting rates from two excore detector source channel channels prior to fuel loading to prevent critical access that may occur during fuel loading. In the case of nuclear fuel handling equipment and tool failures during nuclear fuel loading operations, measures should be taken to ensure rapid recovery under the supervision and direction of the relevant maintenance department, depending on the nature of the failure (electrical, mechanical, measurement, etc.). Additional regulatory guidelines are in place to ensure safety during fuel loading. In addition, detailed procedures and work instructions for nuclear fuel withdrawal and reloading are established to ensure safe and systematic reloading.

At present, subcritical multiplication monitoring is carried out using two methods to prevent the core from reaching a critical state each time a bundle of fuel is loaded into the core and a positive reactivity is inserted.

 1) Short-term critical state access monitoring

When the loader lifts the fuel assembly down to the core floor, it counts. The criterion for safe loading of fuel is to require the refueling of fuel to be stopped immediately if:

A) the neutron count rate due to this stage of fuel loading unexpectedly doubles in the two interim nuclear instrument channels compared to the neutron count rate measured after the previous fuel charge,

B) the neutron count rate due to the current fuel load increases more than five times in any nuclear instrument channel compared to the neutron count rate measured after the previous fuel load.

The fuel assembly is not separated from the reloader until a stable counting rate is obtained.

2) Long-term critical state access monitoring

A) When the fuel is initially loaded in the core, the initial reference coefficient (Co) is measured six times at 100-second intervals and set as the reference coefficient (Co).

B) Each time the loading crane lowers the fuel assembly to the core floor for fuel loading, the neutron counting ratio (Ci) is measured three times at 100 second intervals to calculate the reverse counting ratio (1 / M = Co / Ci). It is written in "reverse ratio ratio graph."

C) If the 1 / M calculation result is not approaching the critical state even after the next fuel is inserted, the next fuel is moved with the approval of the reactor pilot.

D) If the 1 / M calculation result does not appear as expected, or if the subcritical condition is not confirmed when the next fuel is loaded, stop the fuel loading immediately, determine the cause and solve the problem. Resume loading.

When the number of neutrons measured by an out-of-measuring instrument is absolutely small compared to the neutrons leaking from the reactor, the neutron count rate shows extreme probabilistic perturbation. Therefore, in order to understand the subcritical state characteristics of the reactor, the neutron counts of the two channels are measured three times in 100 seconds, and the arithmetic average thereof is measured. Therefore, for each measurement, the task of manually recording the measured values by selecting the start / stop button of the counter / timer must be repeated 177 x 3 times during the entire fuel loading process.

In addition, the current subcritical multiplication monitoring is carried out in the main control room, and only the next fuel loading is informed according to the 1 / M calculation result, and the core change dedicated to supervising the core change during the fuel withdrawal and loading period Nuclear reactor supervisors or principal control room personnel performing fuel withdrawal and loading operations will not be intuitively aware of changes in subcritical multiplication.

The present invention automates the process of measuring the out-of-measuring instrument neutron pulse signal in the main control room during nuclear fuel loading and calculating the reverse coefficient ratio and neutron multiplication factor, and (1) monitoring the subcritical state of the reactor in real time. To ensure safety, (2) to immediately determine whether the fuel has continued to be loaded, to shorten the fuel loading time, thereby increasing the utilization of the power plant, and (3) the reverse coefficient ratio measured in the main control room and the neutron multiplication factor such as ADSL It aims to provide a method for real-time subcritical multiplication monitoring of nuclear reactors by using communication to display on nuclear power station containment boards so that fuel loading workers can quickly prevent the reactor from approaching critical states.

A real-time subcritical multiplication monitoring method for a nuclear reactor for achieving the object of the present invention, in the real-time monitoring of the subcritical multiplication of the reactor using an off-road instrument disposed near the reactor and a controller, by the controller, Digitizing a neutron pulse signal from the out-of-furnace instrument before one fuel is loaded into the reactor to obtain neutron count values before fuel loading; The controller calculates the neutron count rate before fuel loading by using a weighted moving average using a filtering window of several hundred seconds, and multiplies the derived neutron count rate before fuel loading by an integer multiple to set the limit value. step; Digitizing a neutron pulse signal from the out-of-laboratory instrument after one fuel is loaded into the reactor by the controller to obtain a neutron coefficient value after fuel loading by the controller, for the neutron coefficient value after the fuel loading Deriving a neutron count after fuel loading by a weighted moving average using a filtering window of several tens of seconds; And determining, by the controller, whether the neutron count rate after the fuel loading is equal to or less than the limit value.

According to a preferred embodiment of the invention, in the setting of the limit value, the neutron count value before the fuel loading can be filtered for 300 seconds, and the derived neutron count rate before the fuel loading can be multiplied by 2 or 5 times. ,
In the deriving of the neutron count rate after the fuel loading, the neutron count value after the fuel loading may be filtered for 10 seconds.

According to a preferred embodiment of the invention, in the step of determining whether the neutron counting rate after the fuel loading is equal to or less than the limit value, when it is determined that the neutron counting rate after the fuel loading is equal to or less than the limiting value, real-time using communication to the effect The method may further include displaying on the subcritical multiplication monitoring display means of the main control room.

According to the present invention, the reverse coefficient ratio and the neutron multiplication factor measured in the nuclear power plant main room can be displayed on the nuclear power plant containment panel using ADSL communication.

The present invention automates the process of measuring the outside neutron pulse signal and calculating the reverse coefficient ratio in the main control room during nuclear fuel loading, (1) ensuring the safety of the nuclear power plant by monitoring the subcritical state of the reactor in real time, (2) It is possible to immediately determine whether the fuel loading condition is satisfied by shortening the fuel loading time and increase the utilization rate of the power plant. (3) The reverse factor ratio and the neutron multiplication factor measured in the main control room by using ADSL communication. The display on the containment signboard can be used to enable the refueling workers to quickly prevent the reactor from approaching critical states.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings in order to describe in detail enough to enable those skilled in the art to easily carry out the present invention. . Other objects, features, and operational advantages, including the object, operation, and effect of the present invention will become more apparent from the description of the preferred embodiment.

2 is an elevational view of the reactor external instrument. In order to achieve the object of the present invention, in the present invention, the neutron pulse signal generated from the out-of-measuring instrument 22 disposed near the reactor 20 is digitized at an interval of every second using a high-speed digitizer (not shown) to obtain a neutron counting rate. In order to calculate the reverse coefficient ratio by filtering the signal using the controller as described in detail below, for example, the neutron count ratio and the reverse coefficient ratio measured in the main control room using ADSL communication are installed in the containment building. It is configured to display.

3 is a hardware module configuration of the real-time reactor subcritical multiplication monitoring equipment. The real-time reactor subcritical multiplication monitoring apparatus of this invention is comprised by the controller 1, the digitizer (not shown), the alarm lamp 2, and the communication module 3, as shown in FIG. The PXI Type Chassis 33 includes a count module 4 that receives signals from an outside instrument through sensors 31 and 32, a controller 1, and a scope that performs a signal analysis function. 5) and a power supply 6 for supplying power. The alarm lamp 2 serves as an alarm informing the user when the output of the core rises.

The count module 4 can be embodied as a digitizer, which is a device for measuring and digitizing neutron coefficients in real time by receiving signals from the reactor channel out-of-band instrument.

Even if the neutron count rate is properly removed, even if the gamma signal and power supply noise are removed, the neutron count rate exhibits extremely probabilistic perturbation because the number of neutrons measured by the out-of-measuring instrument is absolutely smaller than that of the neutron leaked from the reactor. Therefore, in the conventional method, the neutron count rate should be measured and arithmetic averaged for 3-5 minutes in order to understand the subcritical state of the reactor. In the present invention, a weighted moving average method is used as a method of weighting and neutron counting rate recently measured for neutron counting rate.

As described above, the object of the present invention is that when the fuel-loading crane lowers the fuel assembly to the bottom of the core, it compares the neutron counting rate measured after the previous fuel-loading to the two nuclear instrument channels due to the current fuel-loading. The goal is to determine in real time whether the average neutron count rate doubles unexpectedly or if the neutron count rate in a single nuclear instrument channel increases more than five times. Therefore, the present invention sets a limit value by multiplying the neutron count rate obtained by obtaining a weighted moving average with a filtering window of 300 seconds before one fuel is loaded, and a weighting window with a filtering window of 10 seconds after one fuel is loaded. As shown in FIG. 4, it is possible to immediately determine whether the fuel is loaded continuously by checking whether the neutron count rate obtained by obtaining the moving average is equal to or less than the limit value. That is, Figure 4 shows the output screen of the real-time neutron count rate margin, a represents a limit line, b represents a real-time measurement neutron count rate, in this case, for example as below the limit value.

According to the present invention, when the measured reverse coefficient ratio and the neutral multiplier exceed a preset value, an alarm lamp may be activated to allow a fuel-load worker to take sufficient time to deal with an unwanted threshold state approach occurring during fuel loading. To make it work.

The present invention preferably transmits the reverse coefficient ratio and the neutron multiplication factor measured in the main control room using ADSL communication in the main control room of the containment building, for example, on an electronic board as shown in FIG. In addition, the fuel loading time can be shortened by determining whether to load the next fuel directly at the fuel loading site.

1 is a direct communication connection diagram during fuel loading.

2 is an elevational view of the reactor external instrument.

3 is a hardware module configuration of the real-time reactor subcritical multiplication monitoring equipment.

4 is an output screen of the real time neutron count rate margin.

Figure 5 shows a subcritical multiplication monitoring electronic signboard installed in the containment building.

-Explanation of the symbols for the main parts of the drawings-

One; controller

2; Alarm light

3; Communication module

4; Count module

5; scope

6; Power supply

33; PXI type chassis

31, 32; sensor

Claims (3)

In the method for monitoring in real time the subcritical multiplication of the reactor using an off-road instrument and a controller disposed near the reactor, Digitizing, by the controller, neutron pulse signals from the out-of-laboratory instrument before one fuel is loaded into the reactor to obtain neutron count values before fuel loading; The controller calculates the neutron count rate before fuel loading by using a weighted moving average using a filtering window of several hundred seconds, and multiplies the derived neutron count rate before fuel loading by an integer multiple to set the limit value. step; By the controller, digitizing a neutron pulse signal from the out-of-furnace instrument after one fuel is loaded into the reactor to obtain neutron count values after fuel loading; Deriving, by the controller, a neutron count rate after fuel loading by a weighted moving average using a filtering window of several tens of seconds for the neutron count value after fuel loading; And And determining, by the controller, whether the neutron count rate after the fuel loading is equal to or less than the limit value. The method of claim 1, wherein in the setting of the limit value, the neutron count value before the fuel loading is filtered for 300 seconds, and the derived neutron counting rate before the fuel loading is multiplied by 2 times or 5 times. And in the step of deriving the neutron counting rate after the fuel loading, the neutron counting value after the fuel loading is filtered for 10 seconds. 2. The method according to claim 1, wherein in the step of determining whether the neutron count rate after the fuel loading is equal to or less than the limit value, when it is determined that the neutron count rate after the fuel loading is equal to or less than the limit value, the effect is notified in real time using communication. And displaying on the subcritical multiplication monitoring display means of the control room.

Images