JPH04178598A - Measuring device for neutron in center of reactor - Google Patents

Abstract

PURPOSE:To simplify the calibration work for a sensor in a movable neutron bundle monitoring system by determining the calibration factor of this monitor system sensor on the basis of sensing values given by a plurality of local region neutron bundle sensors. CONSTITUTION:All TIP sensors 5 are simultaneously inserted in a guide tube 6 of LPRM common string 3X, and the neutron bundle level is sensed in positions of LPRM sensor 4a-4d. A TIP calculation processor part 9c receives LPRM conversion signals La-Ld from a photoelectric conversion part 7c, and determines the calibration factor of TIP sensor 5, i.e. the gain value GTIP, from formula GTIP=(1/4)SIGMAl-a-dLl. This calibration factor of TIP sensor 5 and the axial direction position are given when necessary on a display 9f by turning a switch 9e on. Thus the calibration work for TIP sensor 5 can be simplified.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a core neutron measurement device suitable for boiling water nuclear power plants, and particularly relates to a movable neutron flux monitor system (hereinafter referred to as TI).
This invention relates to a core neutron measurement device with improved detector calibration method.

(Prior art) Generally, a nuclear coupler is equipped with a core neutron flux measurement device, but since the reactor output is proportional to the neutron flux, this measures the neutron flux to display the reactor output. and evaluating the burn-up of the fuel.
This is because it responds quickly to fluctuations in reactor power, so it is used as a detection means to protect the reactor in the event of excessive power.

Conventional core neutron measurement equipment is installed in the core of a nuclear reactor, for example, with four
Three LPR~1 (Local Area Neutron Flux Monitor System) strings are arranged almost equally, and each LPRM string has the following:
In the axial direction, four LPRM detectors are built-in and fixed at each position that roughly divides the effective length of the fuel into four equal parts, and a guide that guides the TIP (mobile neutron flux monitor system) detector so that it can move up and down. The LPRM detector is used for constant monitoring, and the TIP detector is used for calibrating the LPRIVi detector.

This is because when using a fission ionization chamber as a neutron detector, the LPRM detector is always placed inside the reactor core, resulting in a decrease in initial sensitivity, which requires periodic calibration. be.

That is, the LPRM calculates the core performance based on the detected value from the LPRM detector, and calculates the core average power, local maximum power, etc. from the calculation results.

On the other hand, when calibrating the LPRM detector, the TIP detector is inserted into the guide tube of a predetermined LPRM string so as to be able to move up and down, and
At each location where the detector is installed, the neutron flux level is detected to obtain data for LPRM detector calibration.

On the other hand, since LPRM calculates the absolute value of the in-reactor neutron flux level, by adjusting the gain of the TIP detector so that the absolute value matches the absolute value of the TIP detector, the The pressure value is being calibrated.

(Problem to be Solved by the Invention) However, in such a conventional core neutron measuring device, the TIP pressure detector is manually calculated based on each detected value from the four PRM detectors of each LPRM string. The gain, that is, the calibration coefficient, is calculated and the gain is manually entered into a computer. These manual calculations and manual inputs require the number of TIP detectors, for example, five, and this calibration work is complicated. There is a problem.

Further, the axial (scanning) position of the TIP detector is obtained from the output results of a plotter, which is an output device of the TIP signal processing device.

In other words, the TIP detector detects the minimum value due to the decrease in the neutron flux level at the same insertion position as the fuel spacer of the fuel assembly, so first, this fuel spacer position is determined, and then based on the fuel spacer position, The axial position of the TIP detector is determined by hand calculation.

Furthermore, if the position of the TIP detector in the hanger direction is deviated from the fixed position of the LPRM detector, an adjustment value for adjusting the position of the TIP detector is manually input into the computer.

Moreover, these manual calculations and input operations are required for all 43 LPRs.
Since it is necessary to perform this for the M string, at least 43
The problem is that it requires multiple operations and is complicated.

Therefore, the present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a core neutron measurement device that can automatically determine the calibration coefficient and axial insertion position of a TIP detector.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention is configured as follows.

In other words, the present invention provides a plurality of fuel rods arranged in the axial direction of a reactor core loaded with a plurality of fuel assemblies formed by bundling a plurality of fuel rods with a plurality of fuel spacers, and each detecting the neutron flux level in the core. A reactor core neutron measurement device having a local region neutron flux monitoring system detector and a movable neutron flux monitoring system detector that reciprocates in the axial direction of the core to detect the neutron flux level in the reactor core, wherein the plurality of local Calibration coefficient calculation means for calculating a calibration coefficient of the movable neutron flux monitor system detector based on the detection values respectively detected by the area neutron flux detector and displaying it on a display means;
Detecting the axial position of the movable neutron flux monitor system detector by comparing the minimum position of the neutron flux level due to the fuel spacer detected by the movable neutron flux monitor system detector with a previously input position of the fuel spacer. and position calculation means for displaying the information on the display means.

(Operation) The detection value of the core neutron flux level detected by the LPRM (Local Area Neutron Flux Monitor System) detector is given to the calibration coefficient calculation means, where the calibration coefficient of the TIP (Mobile Neutron Flux Monitor System) detector is calculated. is automatically determined and displayed on the display means as appropriate.

On the other hand, when calibrating the LPRM detector, the TIP pressure detector is inserted into the reactor core so as to be movable in the axial direction, and detects the neutron flux level at a fixed position of each LPRM.

Since this TIP detector detects the minimum value of the neutron flux level at a certain position of the fuel spacer of the fuel assembly,
The position calculation means determines the fuel spacer position and the axial position of the TIP detector based on this minimum value.

The axial position of this TIP detector is displayed on the display means.

Therefore, according to the present invention, the calibration coefficient and insertion position of the TIP detector can be automatically determined, which simplifies the calibration work. Furthermore, since these can be confirmed by the display means, the suitability of the TIP detector can be checked. This can be confirmed by operators, etc., increasing operational safety and reliability.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 4.

FIG. 2 is a core plan view of, for example, a 1.1 million kW class boiling water reactor. The fuel assembly 2 has a plurality of fuel rods (not shown) bound together into a bundle by a plurality of fuel spacers arranged in a plurality of stages in the axial direction.

In this reactor core 1, for example, 43 LPRM (local area neutron flux monitor system) strings 3, 3, . . . are arranged almost evenly.

As shown in FIGS. 3(A) and 3(B), each LPRM string 3 includes four LPRM detectors 4a that detect the neutron flux level at each position that divides the effective fuel length of the fuel assembly into approximately four equal parts, for example. , 4b, 4c.

4d is built into and fixed in the storage tube 3a, and a guide tube 6 for guiding the TIP (mobile neutron flux monitor system) detector 5 shown in FIG.
It is built inside.

An LPRM common string 3X is arranged at the center of the plane of the reactor core 1, and this string has a built-in guide tube 6 into which a plurality of, for example, five TI'P detectors 5, 5, . . . are inserted simultaneously. are doing.

Each LPRM detector 4a-4d of each LPRM string 3
As shown in FIG. 1, is electrically connected to the signal reading section 7a of the LPRM signal processing device 7, and each LPRM signal read here is further transmitted to the LPRM arithmetic processor section 7.
b, each neutron flux level is calculated here, converted into an optical signal by the electrical/optical converter 7C, and then provided to the optical/electrical converter 9a of the TIP signal processing device 9 via the optical cable 8. It has become.

On the other hand, there are a plurality of TIP detectors 5, for example, five (5ch), depending on the number of groups of the LPRM strings 3, which are divided into a predetermined number of groups, and these are shown in FIGS. 1 and 4. As shown, the tip end is electrically connected to the branch end of a single TIP cable 10 branched into five branches,
By winding or unwinding this TIP cable 10 by the winding cylinder 11a with the motor M of the TIP drive device 11, etc., each TIP detector 5 is connected to the guide tube 6 for each group of LPRM strings 3, 3... Insert it inside and move it up and down.

By vertically moving the TIP detector 5, the neutron flux level within the core 1 is scanned in its axial direction, and each LPRM detector 4a
The neutron flux level is detected at the same axial position as ~4d.

Furthermore, the TIP cable 10 is
The TI from each TIP detector 5 is electrically connected to the signal reading section 9b of the IP signal processing device 9 and read here.
The P signal is further given to the TIP calculation processor section 9C.

The TIP calculation processor section 9c has the function of calculating the calibration coefficient, that is, the TIP gain, of the TIP detector 5, as well as calculating its axial position. Core 1 shown
All, for example, five channels of TTP detectors 5 are inserted simultaneously in the LPRM common string 3x at the center of the plane, and the neutron flux level is adjusted at the same position as each axial position of each LPRM detector 4a to 4d. Let it be detected.

The TIP calculation processor section 9c is the LPRM signal processing device 9
Each LPR, M detector 4a from the electrical/optical converter 7c
-4d LPRM signals La to Ld are received, and the TIP gain GTIP is determined by the following equation (1).

The maximum lJ value at which the neutron flux level detected by the detector 5 decreases is determined by a peak convex downward (on the negative value side) using a conventionally known peak search method, while also being confirmed before reactor startup. The positional information of the fuel spacer of the fuel assembly stored in the memory 9d is read out from the memory 9d, and compared with the peak position 1, the information is determined in the axial direction (scanning) of the TIP detector 5.
At the same time as determining the position, the deviation of the position is determined, and the minimum position is given as the fuel spacer position to the memory 9d together with the axial position of the TIP detector 5, and the memory contents are updated.

Then, as shown in FIG. 4, a drive request signal is given to the TIP drive device 11 to make the axial position of the TIP detector 5 coincide with the axial position of each of the LPRM detectors 4a to 4d, and the TI
Adjust the axial position of the P detector 5.

The calibration coefficient and axial position of the TIP detector 5 are appropriately displayed on the display section 9f by operating the switch 9e, and the suitability of the calibration coefficients and the axial position can be confirmed by an operator or the like.

In addition, in FIGS. 1 and 3, the reference numeral 12 is a reactor pressure vessel, and the reference numeral 13 is a reactor containment vessel that stores this reactor pressure vessel.

Next, the operation of this embodiment will be explained.

Each LPRM detector 4a-4d of each LPRM string 3
Each of the LPRM signals La to Ld detected by
The signal is read by the signal reading section 7a of the signal processing device 7, and the LP
The neutron flux level within the reactor core 1 is detected by the calculation of the RM calculation processor section 7b.

This electrical signal at the neutron flux level is converted into an electrical/'optical converter 7C.
is converted into an optical signal by TIP via optical cable 8.
The signal is applied to the optical/'electrical converter 9a of the signal processing device 9.

On the other hand, all TIP detectors 5 are LPRM detectors 4a to
During the calibration of 4d, by driving the TIP drive device 11,
They are simultaneously inserted into the guide tube 6 of the LPRM common string 3X, and the neutron flux level is detected at the position of each LPRM detector 4a to 4d.

Each TIP signal from each TIP detector 5 is read by a signal reading section 9d of the TIP signal processing device 9, and is provided to a TfP arithmetic processor section 9c.

The TIP calculation processor section 9c receives each LPRM conversion signal La-Ld from the optical/electrical conversion section 7c and calculates the calibration coefficient of the TIP detector 5, that is, the gain value G, according to the above equation (1).
Ask for TIP.

Further, the TIP calculation processor section 9C determines the minimum value of the neutron flux level that decreases at the fuel spacer position as a downwardly convex peak using a peak search method, and uses this as the fuel spacer position to determine the axial position of the TIP detector 5. At the same time, this fuel spacer position, the axial position of the TrP detector, and the calibration coefficient are stored in the memory section 9d, and the memory contents are updated.

The calibration coefficient and axial position of this TIP detector 5 are appropriately displayed on the display device 9f by turning on the switch 9e, and an operator or the like confirms whether the calibration coefficient and axial position of this TIP detector 5 are appropriate. giving an opportunity.

Therefore, according to this embodiment, the calibration coefficients of all TIP detectors 5 and their axial positions are calculated by the TIP calculation processor section 9.
Since it is calculated automatically by C, the TIP detector 5
In addition to simplifying the calibration work of the TIP detector 5, the calibration coefficient and axial position of the TIP detector 5 can be checked on the display device 9f, making it possible to improve the safety and reliability of reactor operation. can.

〔Effect of the invention〕

As explained above, the present invention automatically calculates and determines the calibration coefficient and axial position of the movable neutron flux monitor system detector, thereby simplifying the calibration work of the movable neutron flux monitor system detector. I can do it.

In addition, since the calibration coefficient and axial position of the movable neutron flux monitor system detector are displayed on the display means, operators can confirm the suitability of the calibration coefficient and the reliability of the calibration work can be improved. .

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the core neutron measurement device according to the present invention, FIG. 2 is a plan view of the core shown in FIG. 1, and FIG. 3(A) is a configuration diagram of an LPRM string. (B) is a partially enlarged view of the same figure (A), and Figure 4 is the T and I shown in Figure 1.
It is a block diagram of P. 1... Core, 2... Fuel assembly, 3... LPRM
String, 3X...LPRM common string, 4a
~4d...LPRM detector, 5...TIP detector,
6... Guide tube, 7... LPRM signal processing device, 7b
...Arithmetic processor section (calibration coefficient calculation means), 9...
- LPRM signal processing device, 9C... Arithmetic processor section (position calculation means). Applicant's agent Hisashi Hatano 2m (A)

Claims (1)

[Claims] A plurality of local area neutron flux monitors each arranged in the axial direction of a reactor core loaded with a plurality of fuel assemblies formed by bundling a plurality of fuel rods with a plurality of fuel spacers, and each detecting the neutron flux level within the reactor core. In the core neutron measurement device having a system detector and a movable neutron flux monitor system detector that reciprocates in the axial direction of the reactor core to respectively detect a neutron flux level in the reactor core, the plurality of local area neutron flux detectors calibration coefficient calculating means for calculating a calibration coefficient of the movable neutron flux monitor system detector based on the detection values respectively detected by and displaying the calibration coefficient on a display means; and the fuel spacer detected by the movable neutron flux monitor system detector. position calculation means for calculating the axial position of the movable neutron flux monitoring system detector by comparing the minimum position of the neutron flux level according to the position with the previously input position of the fuel spacer and displaying the axial position on the display means. Characteristic core neutron measurement device.