JPH03273192A - Movement monitoring device for reactor irradiated fuel assemblies - 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] [Objective of the Invention] (Industrial Application Field) The present invention is directed to the movement and passage of fuel assemblies in a passageway through which the fuel assemblies move in a storage facility for nuclear irradiated fuel assemblies. This invention relates to a movement monitoring device for nuclear reactor irradiated fuel assemblies for reliable detection.

(Prior Art) Nuclear fuel material handled in a storage facility for nuclear reactor irradiated fuel assemblies usually has the shape of a fuel assembly. In such facilities, in order to manage nuclear materials, it is necessary to accurately monitor the movement of stored fuel assemblies and to check the balance of the number of materials transferred. for that purpose,
It is important to accurately count the number of fuel assemblies passing through entrances and exits of limited areas such as storage boules to one.

Conventionally, ITV has been used as a device for monitoring the movement of fuel assemblies in storage facilities for nuclear reactor irradiated fuel assemblies.
Visual devices such as cameras, methods for operating and transporting fuel assemblies, cranes for transporting fuel assemblies, methods for checking the driving records of vehicles in front, methods for measuring radiation emitted from fuel assemblies, and methods for measuring radiation emitted from fuel assemblies, or methods for determining radiation induced by that radiation. Visible light (Cherenkov light)
Methods of detecting this are being considered.

As a method for measuring radiation emitted by a nuclear reactor irradiated fuel assembly, there may be a method of measuring gamma rays, a method of measuring II ions, and a method of combining these methods.

Conventionally, radiation detectors used in these
A method is used to monitor the movement of reactor irradiated fuel assemblies using one class of detectors.

(Problem to be solved by the invention) The conventional method of determining the radiation emitted by a nuclear reactor irradiated fuel assembly using JFI and monitoring its movement uses only IFIi type radiation detectors. If the objects passing through a location are limited to only fuel assemblies 4, when the measurement signal of a certain t4-1 radiation detector rises, it must be detected as a fuel assembly having passed there. However, if a high gamma ray emitter that emits gamma rays as strong as that emitted by the fuel assembly moves in the same manner as the fuel assembly, it cannot be detected separately. There is a problem.

That is, when high gamma ray detectors and fuel assemblies coexist, it is not possible to distinguish between the fuel t'1 assemblies and other high gamma ray emitters by gamma fjI measurement alone.

Furthermore, this is difficult even when determining jl using one type of neutron detector.

There are several types of neutron detectors, including fission counters, boron 10 line counters, BF3 counters, and He3 counters. It is required to maintain high detection sensitivity. It is difficult to realize a single type of neutron detector that meets these purposes.

In other words, fission = 1 tube, which has excellent gamma ray resistance, has poor neutron sensitivity, and conversely, He 3 = 1 tube, which has high neutron sensitivity.
Several tubes are sensitive to gamma ray background. Even with regard to boron 10 lined = 1 number tubes and BF3 counter tubes, which have neutral properties, it is a national problem to achieve sufficient performance in terms of both 111J gamma ray property and neutron sensitivity.

For example, consider here the use of a boron 10-line counter to monitor the movement of four sets of fuel cylinders.

At this time, when a high gamma ray emitter passes through other than the fuel assembly, the intensity of the gamma rays emitted is strong, and boron 1
If the signal from the 11 0-line pipes is affected, it is difficult to distinguish between this and the signal from the fuel assembly.

This inconvenience arises from the sensitivity and gamma ray resistance of the boron 10 lined 21 tube. This is B
The same is true for the F 3 ;:l number position, and the BF3:l number position is generally more susceptible to the gamma ray background than the boron 10 line = 1 number tube.

On the other hand, in the case of a fission counter, which is not easily affected by gamma rays, the neutron detection sensitivity is generally much lower than that of a boron 10-line counter. Therefore, when the amount of neutrons extracted from the fuel assembly is small, precise measurements are impossible.

The present invention was made in consideration of these points, and is capable of clearly distinguishing and detecting fuel assemblies moving inside a nuclear reactor fuel storage facility and other high gamma ray emitters. An object of the present invention is to provide a moving monitoring device for a nuclear reactor heat IAJ fuel assembly.

Another object of the present invention is to provide a movement monitoring device for a 1.1 fuel assembly that is capable of detecting the type of fuel being moved.

[Structure of the invention]

(F stage for M-determining the problem) The first invention of the present invention is the above! As a means of achieving this goal, the neutron detection sensitivity of the reactor irradiated fuel assemblies that are installed in the waterways through which they move and pass through for storage, and when the background of gamma rays is high, is compared. a first neutron detector with a high accuracy, a number rate measuring river channel connected to the first neutron detector and capable of measuring a plurality of output signals with a plurality of wave height discrimination levels (1'), and a number rate measurement river channel installed in the waterway. and the neutron detection sensitivity is a (but is equipped with a second neutron detector that is not easily affected by the background of gamma rays, and each j1 count from the above-mentioned counting rate A?+constant circuit and second neutron detector) It is characterized by being able to distinguish and detect fuel assemblies and other gamma ray emitters at the 1-level level based on the time change of the heavy signal.

In addition, the second aspect of the present invention is, as a means for achieving the above-mentioned objective 1-1, that the fuel assemblies of the facility for storing the reactor irradiated fuel assemblies are installed in a waterway through which they move and pass, and the background of gamma rays is reduced. A first neutron detector is connected to the first neutron detector and has a relatively high neutron detection sensitivity even though it is affected when the neutron is high, and it is possible to measure multiple output signals by passing through multiple pulse height discrimination levels. N = 1 car side I-1
A fixed circuit, a second neutron detector installed in the waterway and having low neutron detection sensitivity but not easily affected by gamma ray background, and a gamma ray collimator and a gamma 1i1 detector installed in the waterway. , from the time change of each count rate signal from the Nido number J constant circuit and the second neutron detector, it is possible to distinguish and detect fuel east 0 bodies and other high level gamma ray emitters. , the gamma ray detector is characterized in that the rough outline of the passing fuel assembly can be detected by the signal from the gamma ray detector.

(Function) In the movement monitoring device for a nuclear reactor irradiated fuel assembly according to the first aspect of the present invention, a 2Flj class neutron detector is used, which has excellent characteristics of neutron detection sensitivity and gamma ray resistance.

This means that when reactor fuel is burned in the reactor and extracted, the burnup is a (when the burnup is a, there are fewer neutrons and gamma rays released, and conversely, when the burnup is high, there are many neutrons and gamma rays. This is to take advantage of its characteristics.

In addition, the wave height discrimination level of the number of plates is set in the =1 number wheel side foot circuit of the first neutral detection detector, and the output signal of the number of stages is measured.
It has become J Noh. The ratio of these output signals does not change much when only neutrons are involved, but when there is a background influence of gamma rays, it changes gradually depending on the degree of influence. By combining this with the signal from the second neutron detection detector, which can reliably detect only neutrons if there are a certain amount of neutrons, fuel! ! UJ functionality is achieved by accurately distinguishing and detecting the signal due to the merger and the signal due to other high gamma ray emitters.

Further, in the movement monitoring device for a nuclear reactor irradiated fuel assembly according to the second aspect of the present invention, in addition to the configuration of the first aspect, 75FJ determination of collimated gamma rays is performed. For this reason,? IP+ constant signal rising II
! From the axis between f, we can know the approximate width of the passing object,
For example, BWR'! It becomes possible to distinguish and detect F fuel and PWR type fuel.

(Example) Hereinafter, a first length example of the present invention will be described with reference to FIGS. 1 to 5.

In Figure 1, No. 1 is Harryo Reactor Terwari fuel! J! This is a waterway for the combined storage facility, and a fuel assembly 2 moves and passes through this waterway 1 in the direction of the white arrow.

On the side wall of this water 781, as shown in FIG.
In the two front guides 4 on both sides, first neutron detectors 5, which are affected by high gamma ray background but have relatively high neutron detection sensitivity, are arranged as catchers, and the central one is arranged as a catcher. Inside the book guide tube 4, a second neutral detector 6, which has low neutron detection sensitivity but is not easily affected by gamma ray background, is arranged.

As the first neutron detection detector 5, for example, a boron 10-line counter is used, and as the second neutron detection '1A6, for example, a nuclear crack counter is used, and the first neutron detection As shown in FIG. 2, the counting rate 71p1 constant circuit 7 is connected to the counting rate 71p1 constant circuit 7.

As shown in FIG. 2, this count rate measuring circuit 7 includes a preamplifier to which a high voltage power supply 8 is connected, and a linear amplifier 0 to which a signal from the preamplifier 9 is input. The signals are input to the first pulse height discriminator 2g11 and the second pulse height discriminator 12 which respectively set the pulse height discrimination levels DI and B2. The counting rate meter 13 and the second counting rate meter 14 output counting rate output signals S] and B2 which are light on the counter.

Figure 3 (a) and (b) show the general output wave direction spectrum and wave height discrimination level D of a boron 10 line counter.
I + D 2 and count rate output signal '3 S 1 .

It is a conceptual diagram showing the relationship with B2. In addition, Fig. 3(a)
, In (b), the area where the count is high in the a() part of the wave ρi value is caused by noise in the measurement system and pile-up of background gamma rays, etc. When the amount of background gamma rays increases, , the pile-up rate increases by 341j, and the region with a large number of 51° gradually shifts to the higher wave height side.

Next, the operation of this embodiment will be explained.

When detecting the movement of the fuel assembly 2, each of the =1 number rate ApI foot circuit 7 and the second neutron detector 6 connected to the first neutron detector 5 =1 number rate ApI output signal value. n! j H
Measure f4 change.

For example, if the change between the output No. 15 and +7 is as shown in Figure 4, it is assumed that the fuel assembly 2 has passed through the water channel 1 when the signal value increases! -11 can be terminated.

By the way, if the objects passing through the waterway 1 are limited to the fuel assembly 2, as long as the detector for obtaining the signal shown in Figure 4 has sufficient sensitivity for gamma rays and neutrons, However, in addition to the fuel 11 aggregate 2, objects that emit strong gamma rays (high gamma ray emitters) cannot be distinguished and detected by the HA passing through the waterway 1.

Therefore, in this embodiment, these can be distinguished and detected using the following method.

That is, first, objects passing through the waterway 1 are classified and considered as follows.

A1: PWR fuel assembly with low burnup A2
: PWR fuel assembly with high burnup B1:B
Burnup a of the WR fuel assembly (B2: BWR
C) Other objects with high burnup C): Other objects that emit gamma rays (C2; Other objects with strong gamma rays D: Empty Here, A1 and B] are gamma rays that emit On the other hand, A2 and B2 both emit a large amount of gamma rays and a large amount of neutrons.In addition, in the case of A2, B2 and C2, which emit strong gamma rays, boron as the first neutron detector 5 is used. 10 lines: The output signals of several tubes are affected by the background of gamma rays.

Therefore, if only one Oshima discrimination level is set and measured in the measurement circuit 7 of the boron 10-line counter, the No. 11 response relationship will be as shown in Table 1 (not shown), and A2 or It is not possible to distinguish between a B2 assembly and a C2 assembly, and it is not possible to detect whether it is a fuel assembly.

Table 1 Relationship between the passing object and the signal 6 valley when the wave height discrimination level of the boron 10 lined counter is one The distinction becomes clear. Also, A2 and B2
Since a signal from the French splitting counter as the second neutron detector 6 is also output at field 0, it can also be clearly distinguished by this.

On the other hand, as shown in FIGS. 5(a) to 5(e), boron 10 lines = 1 number revision S 1 number early 8-1 constant circuit 7,
Two different wave height discrimination levels DI.

When B2 is set and the respective output signals Sl and B2 are measured, the ratio HIX of the signal 31, Nakamoto output signal Sl, and B2 as shown in Table 2 below, and the signal of nuclear fission = one several tubes. This relationship tends to compensate for the burnup of the fuel f1 aggregate 2 and the objects of C2 because they tend to compensate for each other's judgments, so when measurements are carried out with this configuration, Can be clearly distinguished and detected.

That is, when the combustion dust in the fuel assembly 2 is low, C2
The value of Sl/S2 is obviously different compared to the case of , and the two can be clearly distinguished and detected. On the other hand, the burnup of the fuel assembly 2 increases and Sl/S
As the value of 2 approaches C2, the output of the fission counter increases! Therefore, the two can be clearly distinguished and detected.

FIG. 6 shows a second embodiment of the present invention.
In addition to the configuration of the embodiment, a gamma ray collimator 15 and a gamma ray detector 16 are provided, respectively.

That is, a gamma ray collimator 15 in which a thin through hole 15a is provided in lead is installed in a boule wall 17 that is continuous with the water channel 1, and inside the end of this gamma ray collimator 15 there is a NAL watertight container 18 that is housed. A Na1 (TfI) scintillation detector with extremely high gamma ray detection sensitivity is arranged as the gamma ray detector 16, and its signal cable 19 is led out through the guide tube 201.

Note that the other points have the same configuration as the first embodiment.

In this way, the gamma ray collimator 15 and the gamma ray detector 16 transmit collimated gamma rays at the same l:i
By measuring this, it is possible to detect the approximate width of a passing object. Thereby, it is possible to distinguish and detect whether the passing fuel assembly 2 is a PWR type (a prismatic shape with a negative side of about 20e111) or a BWR type (a prismatic shape with a negative side of about 13 cm).

Note that the output signals are distinguished by utilizing the fact that, as shown in FIG. 4, the width of +1 corresponds to the width of the passing object while the signal level is rising.

FIGS. 7 and 8 show a third embodiment of the present invention, in which both neutron detectors 5 and 6 in the second embodiment,
Gamma ray collimator] 5 and gamma ray detector 16':
rj are arranged on both sides of the waterway 1.

In addition, regarding other points, it has the same configuration as the above-mentioned double length line side.

By installing the fuel assemblies 2 on both sides of the waterway 1 in this way, even if the fuel assembly 2 and the like passes through the waterway 1 in a biased direction, stable measurement can be performed and reliable detection can be performed.

In this case, the knob method that takes the ilt pure 1 filter average of the output signals of each detector installed on both sides is the most l'l', but in order to perform more stable measurements, it is necessary to It is effective to take the average of the number 3 values of the device.

That is, in storage facilities for fA=1 fuel-containing bodies in front of the reactor, the place where fuel assemblies are handled is usually underwater. It has been found that in water, the intensity of neutrons or gamma rays at a certain distance from the fuel assembly decreases exponentially with decreasing distance from the fuel assembly.

Now, there is a fuel assembly at a certain point in the water of the waterway through which the fuel assembly W passes, and the signal values of the detectors on both sides at this time are assumed to be 'Nl' and 'N2, respectively. Then, considering the case where the fuel assembly moves by ΔX or IJ in the direction of any of the detectors, the signals Nl and N2 of each detector change as shown in the following equation.

Nl −' Nl ・exp (−λ・Δx) ・−(
1) N2-" N2- exp (λ・Δx) --
-(2) Here, the equations II + 1 of equations (1) and (2) are (Nl・N2) ” 1 [' Nl ・exp(−λ・Δx) ・' N2
・cxp(λ・Δx)]l/2− (”Nl・'N
2) 1/2...(3), and the signals from the detectors on both sides are It turns out that the geometric mean of the values remains unchanged.

FIG. 9 shows an example of a device for obtaining such an effect, in which the detector 21 on one side and the detector 22 on the other side are connected to a geometric mean calculation circuit via 11FIk circuits 23 and 24, respectively. 25, and from the outputs Nl and N2 of each detector 21.22, the geometric mean value (Nl ・N2)
'/2 is now available.

Figures 10 and 11 show a fourth failed embodiment of the present invention, in which the device shown in the third failed embodiment is installed at the population and outlet of water 1181, respectively. be.

In addition, regarding other points, it has the same configuration as the previous 2nd and 3rd length example.

In this manner, by providing the devices at the person (2) and the exit (2) of the waterway 1, it is possible to detect the direction of passage of the object from the time series of changes in the output signals of each detector.

In each of the above embodiments, a case has been described in which boron 10 line II number blue is used as the first neutron detector 5, but a BF3 21 number tube device may also be used. Further, the wave height discrimination level of the 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 7, 7 wave height discrimination levels may be limited to two, but may be three or more.

〔Effect of the invention〕

As explained above, the first aspect of the present invention uses two types of neutron detectors having different characteristics of neutron detection sensitivity and gamma ray resistance, and the first neutron detector has JI number 1
A stage number wave discrimination level is installed in the 11 constant four-way so that the stage number output signal can be A111 constant. It is possible to clearly distinguish and detect the coracoid gamma ray absorber.

In addition to the configuration of the first invention, a second invention of the present invention provides a gamma ray collimator and a gamma ray detector that detect collimated gamma rays. Since the width of the moving fuel assembly is set at +, the approximate width of the moving fuel assembly can be detected, and PWR type fuel and BWR type fuel can be distinguished and detected.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a movement monitoring device for a nuclear reactor irradiated fuel assembly according to a first failed embodiment of the present invention, and FIG. 2 is a block diagram showing a counting rate side stop circuit of the first neutron detector. Figure 3 (
a) and (b) are conceptual diagrams showing the general output wave sieve spectrum of a boron 10 lined = 1 number tube, and the relationship between the wave height discrimination level and the 31 number rate output signal, respectively. 5(a) to 5(e) are graphs showing the relationship between the type of passing object and the detector output, and FIG. Fig. 1 is a view corresponding to Fig. 1 showing the second embodiment, Fig. 7 is a partially broken flat curved view showing the third embodiment of the present invention, Fig. 8 is a similar partially broken front view, and Fig. 9 is a view of the third embodiment. In the example, the number of detector outputs on both sides (111'l') is a block diagram showing an example of a device for calculating the average value. The figure is a similar diagram corresponding to Figure 8. 1... Waterway, 2... Fuel assembly, 5... First neutron detector, 6... Second ψ tron detector, 7... 51 Number speed measurement circuit,]]...First wave height discriminator, 12...Second wave height F discriminator, 13...First counting A; 1゛, ]4.
... 2nd = 1 number of condolences; 1゜15... Gamma ray collimator, 16... Gamma ray detector, 21.22... Detector, 23.24... AFI constant four-way, 25... Ikui 1
1 average calculation tri-path, DI, D2... wave height discrimination level,
51. , S2...=11 number rate output signal. Vendor Agent Figure Output Wave Height (a) Figure Output Wave Height (b) Poron 10 Line Counter Post Division Counter Figure Figure Figure 9 Figure 0 Figure

Claims (1)

[Scope of Claims] 1. Comparison of neutron detection sensitivity of a facility installed in a waterway through which fuel assemblies of a facility storing reactor irradiated fuel assemblies move and pass and are affected by high background gamma rays. a first neutron detector with high accuracy; a count rate measurement circuit connected to the first neutron detector and capable of measuring a plurality of output signals having a plurality of wave height discrimination levels; a second neutron detector that has low sensitivity but is not easily affected by the background of gamma rays; and a fuel assembly and its A movement monitoring device for a nuclear reactor irradiated fuel assembly, characterized in that it is capable of distinguishing and detecting high-level gamma ray emitters from other sources. 2. The first neutron detection method is installed in a waterway through which fuel assemblies of a facility that stores reactor irradiated fuel assemblies move and pass through, and is affected by high gamma ray background, but has relatively high neutron detection sensitivity. a count rate measurement circuit connected to the first neutron detector and capable of measuring a plurality of output signals with a plurality of wave height discrimination levels; a second neutron detector that is less susceptible to background effects; a gamma ray collimator and a gamma ray detector installed in the waterway; and the time of each count rate signal from the count rate measurement circuit and the second neutron detector. Based on the changes, it is possible to distinguish between fuel assemblies and other high-level gamma ray emitters, and it is also possible to detect the approximate width of the passing fuel assemblies based on the signal from the gamma ray detector. Features: A moving monitoring device for nuclear reactor irradiated fuel assemblies.