JP2022184277A - radiation monitor - Google Patents

Abstract

To solve the problem in which, when an alarm occurs based on a count value of detected radiation, an investigation of an occurrence cause of the alarm is required as necessary that includes a checkup such as soundness verification of devices and the like as to whether irregularity of detectors and the like exist.SOLUTION: A radiation monitor comprises: a first detection unit 11 that detects radiation from a measurement object instrument; and a second detection unit 12 that is to measure whether the radiation flies from a direction of the object instrument. When an alarm according to the radiation detected by the first detection unit is issued, the radiation monitor is configured to check presence or absence of a radiation incidence from the object instrument radiation detection by the second detection unit, and perform a diagnosis of an alarm cause.SELECTED DRAWING: Figure 1

Description

The present application relates to radiation monitors.

High-sensitivity radiation monitor that confirms the soundness of the steam generator by monitoring the leakage from the primary system cooling water to the secondary system cooling water of the steam generator of the nuclear power plant. There is a radiation monitor that goes by the name of a main steam line monitor. This high-sensitivity main steam pipe monitor consists of a radiation detector that is placed close to the main steam pipe and that detects radiation and outputs an analog voltage pulse. discriminating analog voltage pulses falling within a high energy window set to encompass the N-16 gamma 6.13 MeV photopeak, single escape peak, and double escape peak of the included radionuclide and outputting a digital pulse; a counting rate measuring unit for measuring the counting rate of the digital pulse, and monitors changes in the counting rate.

In this way, conventional radiation monitors input analog voltage pulses from radiation detectors to the counting rate unit, discriminate and count peak values that fall within a set window, and have a constant standard deviation based on the count values. The time constant is processed by software so that only the count rate is output with priority given to responsiveness, and the alarm setting is close to the background count rate. Therefore, systematic fluctuations in the counting rate, so-called fluctuations, can cause erroneous alarms to be issued. Even after the counting rate returns to normal, it is necessary to conduct an off-line inspection of the device to confirm its soundness just in case. Met.

On the other hand, there is a known method of obtaining count rates with different standard deviations from the same input and comparing their transitions. , and the diagnostic count rate with slow response only follows it, and because the input is the same pulse train, there is a problem that it is difficult to identify the cause.

There is also a proposal to determine whether the event is due to a signal or noise based on whether the indicated values rise synchronously at two detection positions upstream and downstream of the main steam pipe. In this method, since the background count rate is as small as several cpm, the probability that the rising tendency will be the same cannot be ignored, and there is a problem that it cannot be a fundamental solution.

On the other hand, the steam in the main steam pipe is a secondary system and normally does not contain artificial radionuclides. In addition, since cosmic rays are dominant and the background count rate during normal times is as low as a few cpm, and the background count rate and the alarm set point are close to each other, false alarms can be suppressed and alarms issued with high accuracy. If you try to do so, the standard deviation will be reduced, resulting in a delayed response to alarm transmission. Therefore, in some cases, the warning is divided into two stages, a warning warning and a high warning level above it, and a caution warning is issued at the stage of security leakage, and detailed investigations are conducted, including the possibility of false alarms.

In response to such a problem, the applicant has also proposed a radiation device that automatically determines whether the cause of the alarm is fluctuation or other factors and displays the result (see, for example, Patent Document 1).

Japanese Patent No. 6072977

In the radiological apparatus disclosed in the above-mentioned Patent Document 1, which automatically determines whether the cause of the alarm is fluctuation or other factors and displays it, it is possible to prevent erroneous alarm transmission due to fluctuation. However, in recent years, there has been a demand for advanced detection of radiation monitors, that is, details of alarm contents. Therefore, in order to eliminate the need for investigation work at the site where the radiation equipment is installed every time an alarm is issued to notify that the indicated value has risen, it is necessary to check that the cause of the alarm is other than fluctuation when the indicated value rise alarm is issued. There is a demand for automatic determination of whether there is a problem, for example, whether it is due to an abnormality in the surrounding environment.

The present application discloses a technique for solving the above-described problems, and automatically determines the cause of not only the fluctuation of the cause of an alarm that notifies an increase in the indicated value, but also the cause of the alarm. It is an object of the present invention to provide a highly reliable radiation monitor that obtains results by

The radiation monitor disclosed in the present application includes: a first radiation detection unit that detects gamma rays emitted from a radionuclide to be measured among radiation emitted from a device to be measured and outputs an analog voltage pulse; A radiation counting calculation unit that calculates the radiation count using the output of the radiation detection unit, and a second radiation detection unit that two-dimensionally detects the gamma rays emitted from the radionuclides to be measured and outputs an analog voltage pulse. a radiation position distribution calculation unit that calculates a two-dimensional position distribution of radiation using the output of the second radiation detection unit; and a radiation generation alarm based on the results of the radiation counting calculation unit and the radiation position distribution calculation unit. and an alarm diagnosis unit that determines and outputs the cause of the radiation monitor, wherein the radiation counting calculation unit sets the analog voltage pulse output from the first radiation detection unit to the voltage level The pulse entering the high energy window and the pulse entering the low energy window are discriminated, the pulse entering the high energy window is subjected to time constant processing so that the standard deviation is constant, and the high energy counting rate is calculated. A high energy counting rate calculation unit that outputs an alarm when the high energy counting rate deviates from an allowable set value and outputs an alarm; a low energy count rate calculation unit that calculates and outputs an energy count rate, wherein the radiation position distribution calculation unit converts the analog voltage pulse output from the second radiation detection unit to a voltage level A pulse height analysis unit that outputs a two-dimensional energy spectrum corresponding to a pulse exceeding a preset value, and calculates the yield of the energy spectrum at each position obtained from the pulse height analysis unit and outputs a two-dimensional position distribution of radiation. and a distribution analysis unit, wherein the alarm diagnosis unit presets the low energy count rate output from the low energy count rate calculation unit when an alarm is output from the high energy count rate calculation unit. If it is within the allowable range, the cause of the alarm is determined to be the fluctuation of the first radiation detection unit,
When an alarm is output from the high energy count rate calculation unit and the low energy count rate output from the low energy count rate calculation unit is outside a preset allowable range, two-dimensional radiation output from the distribution analysis unit By comparing the position of the peak of the position distribution and the position of the equipment to be measured, it is determined whether the cause of the alarm is an abnormality in the surrounding environment or the leakage of the target nuclide, and the determination result is output along with the alarm.

According to the radiation monitor disclosed in the present application, it is possible to automatically determine the cause of the alarm issuance and obtain the result together with the alarm in response to the issuance of an alarm indicating an increase in the indicated value. becomes unnecessary, and a highly reliable radiation monitor can be provided.

1 is a schematic diagram showing the configuration of a radiation monitor according to Embodiment 1; FIG. FIG. 4A is a side view of the configuration of the second detection unit of the radiation monitor according to Embodiment 1, and FIG. 1 is a functional block diagram showing the configuration of a radiation monitor according to Embodiment 1; FIG. FIG. 4 is a diagram showing the positional relationship between the main steam pipes and spectral peaks of radiation according to Embodiment 1; FIG. 4 is a diagram showing the positional relationship between the main steam pipes and spectral peaks of radiation according to Embodiment 1; FIG. 7 is a diagram showing the procedure of alarm diagnosis processing in the radiation monitor according to Embodiment 1; FIG. 10 is a diagram showing the procedure of alarm diagnosis processing in the radiation monitor according to Embodiment 2; FIG. 10 is a diagram showing the configuration of a radiation monitor according to Embodiment 3; FIG. 10 is a diagram showing the procedure of alarm diagnosis processing in the radiation monitor according to Embodiment 3; FIG. 12 is a diagram showing the procedure of alarm diagnosis processing in the radiation monitor according to Embodiment 4; FIG. 10 is a diagram showing a background calculation method according to Embodiment 4; 4 is a hardware configuration diagram of an arithmetic processing unit according to Embodiments 1 to 4; FIG.

Embodiments of a radiation monitor disclosed in the present application will be described below with reference to the drawings. In addition, in each figure, the same code|symbol shall show the same or a corresponding part.

Embodiment 1.
A radiation monitor according to Embodiment 1 will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing the configuration of a radiation monitor according to Embodiment 1. FIG. In FIG. 1, a first radiation detection unit 11 (hereinafter referred to as the detection unit 11) that detects gamma rays to be measured using, for example, a scintillator detector for the purpose of detecting leakage of the main steam pipe 1 is composed of, for example, lead A second radiation detection unit 12 (hereinafter referred to as detection unit 12) is externally attached for the purpose of detecting the position distribution of γ-rays to be measured. Signals detected by the detection units 11 and 12 are transmitted to the arithmetic processing unit 10, and the arithmetic processing unit 10 performs counting rate calculation, alarm signal processing, and the like.

2A and 2B are diagrams showing the configuration of the second detection unit 12 of the radiation monitor according to Embodiment 1, in which FIG. 2A is a side view and FIG. 2B is a top view showing the detection surface. As shown in FIG. 2(a), a plurality of prismatic scintillators 12a to which multi-anode photomultiplier tubes 12b are attached is used as the second detector 12, and the prismatic scintillators 12a are arranged as shown in FIG. They are arranged in a two-dimensional array.

3 is a functional block diagram showing the configuration of the radiation monitor according to Embodiment 1. FIG. In FIG. 3, the calculation processing unit 10 includes a radiation counting calculation unit 100 that calculates the radiation count from the signal of the detection unit 11, a radiation position distribution calculation unit 200 that calculates the two-dimensional distribution of radiation from the signal of the detection unit 12, and an alarm A diagnostic unit 300 is provided. The radiation count calculator 100 has an amplifier 110 , a pulse height analyzer 120 , a high energy count rate calculator 131 and a low energy count rate calculator 132 . The radiation position distribution calculator 200 also has an amplifier 210 , a wave height analyzer 220 and a distribution analyzer 230 . The results calculated by the radiation counting calculation unit 100 and the radiation position distribution calculation unit 200 are transmitted to the alarm diagnosis unit 300, and diagnosis is made as to whether or not to output an alarm signal. In the display unit 15, each output from the arithmetic processing unit 10 is displayed on the screen, and an input device is used to operate and set each unit (for example, threshold value adjustment for alarm diagnosis).

A detection unit 11 intended to detect leakage of cooling water in the main steam pipe 1 detects gamma rays emitted from N-16, which is the nuclide to be measured, and outputs an analog voltage pulse. The analog voltage pulse output from the detection unit 11 is input to the amplification unit 110 and amplified. The analog voltage pulse input from the amplification unit 110 to the pulse height analysis unit 120 is discriminated into a pulse that enters the high energy window set for the voltage level and a pulse that does not enter the high energy window but enters the low energy window, and then is digitalized. Output as a pulse.

The high energy count rate calculator 131 counts the digital pulses discriminated as the pulses entering the high energy window by the pulse height analyzer 120 at regular intervals to obtain count values. A high energy count rate is calculated and output by processing. Furthermore, if the calculated high energy counting rate deviates from the permissible set value and rises, an alarm is output to inform the rise of the indicated value.

The low energy count rate calculator 132 periodically counts the digital pulses discriminated as pulses entering the low energy window by the pulse height analyzer 120 to obtain a count value, and performs a moving average on the count value for a constant measurement time to lower the count value. Calculate and output the energy counting rate.

On the other hand, the detection unit 12, which aims to detect the position distribution of gamma rays to be measured, detects gamma rays emitted from N-16, which is the nuclide to be measured, with each prismatic scintillator 12a, and through the multi-anode photomultiplier tube 12b. The detection signal from each prismatic scintillator 12a is output to the amplifier 210 as an independent analog voltage pulse. Each analog voltage pulse output from the detection unit 12 is input to the amplification unit 210 and amplified, and output to the pulse height analysis unit 220 after removing superimposed high-frequency noise.

The wave-height analysis section 220 performs wave-height analysis of the analog voltage pulse input from the amplifier section 210 to the wave-height analysis section 220 as follows.
Of the pulse signals amplified by the amplifying unit 210, the peak value of the pulse signal exceeding a preset value is subjected to AD conversion (Analog to Digital conversion). Then, one count is added to the channel corresponding to the AD-converted peak value. By subjecting the pulse signal from each prismatic scintillator 12a to this processing, the energy spectrum of the pulse signal obtained by each prismatic scintillator 12a is obtained.

The distribution analysis unit 230 integrates the yield of each channel of the energy spectrum obtained by each prism scintillator 12a input from the wave height analysis unit 220 for a certain period of time, and calculates the radiation intensity measured by each prism scintillator 12a. A channel for recording the calculated total yield is set according to the position of each prismatic scintillator 12a, and the radiation intensity measured by each prismatic scintillator 12a calculated above is recorded in the channel of the corresponding prismatic scintillator. . Through the above operations, the distribution analysis unit 230 can obtain the two-dimensional position distribution of the gamma rays measured by the detection unit 12 . The two-dimensional position distribution obtained by distribution analysis section 230 is output to alarm diagnosis section 300 .

In the alarm diagnosis unit 300, when the indicated value from the high energy count rate calculation unit 131 rises, the low energy count rate output from the low energy count rate calculation unit 132 is input, and the low energy Determine whether the count rate is within a preset allowable range.
If the low energy count rate is within the set allowable range, the cause of the rise in the indicated value is due to fluctuations in the detector 11, and if it is outside the allowable range, an alarm notifying that the indicated value has risen due to reasons other than fluctuations. is transmitted, and the incoming direction of the γ-rays is determined based on the positional distribution of the γ-rays to be measured output from the distribution analysis unit 230 .

4 and 5 are diagrams showing an example of the spectral distribution obtained by the radiation monitor according to Embodiment 1, showing the two-dimensional positional distribution of γ-rays obtained from the distribution analysis unit 230 with respect to the main steam pipe 1. is a diagram showing the relationship of
FIG. 4 is a diagram schematically showing a case where the position b of the peak a of the two-dimensional position distribution output from the distribution analysis unit 230 is located within the main steam pipe position range c. The peak position b corresponds to the position of the prismatic scintillator 12a of the detection unit 12 where the maximum radiation intensity was measured in the two-dimensional position distribution obtained by the distribution analysis unit 230. FIG. As shown in FIG. 4, when the peak position b is located within the main steam pipe position range, the alarm diagnosis unit 300 determines that the increase in the indicated value output from the high energy counting rate calculation unit 131 It is determined that the γ-rays to be measured come from the direction, and an alarm signal of "leakage of the target nuclide" is output.

FIG. 5 is a diagram schematically showing a case where the position b of the peak a of the two-dimensional position distribution output from the distribution analysis unit 230 is not located within the main steam pipe position range c. When the peak position b of the two-dimensional position distribution is not located within the main steam pipe position range as shown in FIG. It is determined that the γ-rays to be measured coming from one direction of the main steam pipe are not the cause, and an alarm signal of "surrounding environment abnormality" is output.

If there is no increase in the indicated value in the high energy counting rate calculation unit 131, even if the detection unit 11 and the detection unit 12 perform the counting rate calculation and the position distribution calculation of the gamma rays to be measured, the above-described alarm diagnosis processing is not performed. Not done.
The display unit 15 displays each output such as the diagnosis result of the alarm diagnosis unit 300, the calculation result of the radiation counting calculation unit 100 and the radiation position distribution calculation unit 200, and performs operation and setting of each unit.

FIG. 6 is a flow chart showing the procedure of alarm diagnosis processing in the radiation monitor according to the first embodiment.
In step S1, if there is an increase in the indicated value from the high energy counting rate calculation unit 131 based on the signal output from the detection unit 11 (YES in step S1), output from the low energy counting rate calculation unit 132 in step S2 Enter the low energy count rate determined, and determine whether the low energy count rate is within the set allowable range by synchronizing with the issuance of an alarm.

If the low energy count rate is within the allowable range (YES in step S2), it is determined that the instruction rise signal is due to fluctuations in the detector 11 (step S3).
If the low energy count rate is out of the allowable range (NO in step S2), the incoming direction of γ-rays is determined based on the positional distribution of γ-rays to be measured output from the distribution analysis unit 230 in step S4.

As described above, the determination in step S4 is performed when the position b of the peak a of the two-dimensional position distribution output from the distribution analysis unit 230 is located in the main steam pipe position range c (YES in step S4), "the target nuclide leak" (step S6).
If the position b of the peak a of the two-dimensional position distribution output from the distribution analysis unit 230 is not located within the main steam pipe position range c (NO in step S4), it is determined that there is an "abnormality in the surrounding environment" (step S5).
The determination results of steps S3, S5, and S6 are output to the display unit 15 (step S7), and an alarm signal is output as appropriate.

As described above, according to the radiation monitor according to the first embodiment, in addition to the first detection unit 11 for detecting the radiation for the purpose of leakage of the main steam pipe 1, the radiation comes flying from the direction of the main steam pipe 1. Since the second detection unit 12 is provided for measuring whether the main steam pipe 1 is Confirm the presence or absence of radiation incident from the part, and make an alarm diagnosis. That is, the radiation detected by the first detection unit 11 is detected, the analog voltage pulse is amplified, the pulse that enters the high energy window and the pulse that enters the low energy window are discriminated and output as a digital pulse, Digital pulses discriminated as pulses entering the high energy window are periodically counted to obtain a count value, and if a rise deviates from the allowable set value, an indication rise signal is output as an alarm. Also, it is determined whether the low energy count rate counted from pulses entering the low energy window at the same time as the command rise signal is within a preset allowable range. Furthermore, by obtaining the two-dimensional position distribution of the gamma rays to be measured detected by the second detection unit 12, it is possible to determine whether the detected radiation alarm is "fluctuation" or "surrounding environment abnormality". , or "leakage of target nuclide". In addition, by displaying the judgment result together with the warning, the visibility is improved, and it becomes possible to provide a radiation monitor with high reliability.

Embodiment 2.
A radiation monitor according to Embodiment 2 will be described below with reference to the drawings.
In Embodiment 1, when there is an increase in the indicated value from the high-energy counting rate calculator 131, only the incoming direction of γ-rays is determined based on the positional distribution of the γ-rays to be measured output from the distribution analyzer 230. rice field. In the second embodiment, the alarm diagnostic unit 300 of the first embodiment calculates the total yield of the gamma rays to be measured detected by the detection unit 12, obtains the counting rate, and determines the increase in the indication of the gamma rays to be measured by the detection unit 12. A function to determine the presence or absence has been added. The radiation monitor of Embodiment 2 has the same configuration as the radiation monitor shown in FIG. 3 of Embodiment 1, and the description thereof is omitted.

FIG. 7 is a flow chart showing the procedure of alarm diagnosis processing in the radiation monitor according to the second embodiment. Between steps S1 and S2 in the flow chart of FIG. 6 of the first embodiment, step S21 is inserted to determine whether or not the detection unit 12 indicates an increase in γ-rays to be measured.
In step S1, when there is an increase in the indicated value from the high energy counting rate calculation unit 131 as an alarm related to the detection unit 11, the process proceeds to step S21. In step S21, the total yield of the two-dimensional position distribution obtained from the distribution analysis unit 230 is calculated by accumulating the yield of each position and performing time constant processing so that the standard deviation becomes constant. The calculated total yield of the position distribution is compared with a permissible set value to determine whether or not the detection unit 12 is raised.

If the calculated value of the total yield of γ-rays detected by the detection unit 12 is less than the permissible set value (YES in step S21), it is determined that the indication increase related to the detection unit 12 has not been confirmed, and the detection unit 12 is equal to or greater than the set value, it is determined that an increase in the indication has been confirmed for the detection unit 12 (NO in step S21).

When the indicated rise of the gamma ray to be measured by the detection unit 12 is not confirmed (YES in step S21), the low energy count rate output from the low energy count rate calculation unit 132 is input and synchronized with the issuance of the alarm. Step S2 is performed to determine whether the low energy count rate is within the set allowable range.

If the low energy count rate is within the allowable range (YES in step S2), it is determined that the instruction rise signal is due to fluctuations in the detector 11 (step S3).
If the low energy count rate is out of the allowable range (NO in step S2), it is determined that an abnormality has occurred in the detection section 11, and an alarm signal "detection section 11 abnormality" is output (step S22).

If the total yield of the detection unit 12 calculated in step S21 is equal to or greater than the permissible set value (NO in step S21), the position distribution of the gamma rays to be measured output from the distribution analysis unit 230 in step S4 γ-ray incoming direction is determined based on the The determination in step S4 is the same as that described in the first embodiment. YES), it is determined that "leakage of target nuclide" (step S6).
If the position b of the peak a of the two-dimensional position distribution output from the distribution analysis unit 230 is not located within the main steam pipe position range c (NO in step S4), it is determined that there is an "abnormality in the surrounding environment" (step S5).

The determination results of steps S3, S5, S6, and S22 are output to the display unit 15 (step S7), and an alarm signal is output as appropriate.

As described above, the radiation monitor according to the second embodiment has the same effect as the first embodiment. Furthermore, in the alarm diagnosis unit 300 of Embodiment 2, since the abnormality of the detection unit 11 is determined, the cause of the alarm is determined not only by the fluctuation of the detection unit 11 but also by the failure of the detection unit 11. Therefore, it is possible to omit confirmation of the soundness of the device due to an increase in the indicated value, and labor can be saved.

Embodiment 3.
A radiation monitor according to Embodiment 3 will be described below with reference to the drawings.
FIG. 8 is a functional block diagram showing the configuration of a radiation monitor according to Embodiment 3. FIG. 3 of Embodiment 1 is that in Embodiment 3, the energy spectrum output from wave height analysis section 220 is directly output to alarm diagnosis section 300 as shown in FIG.

FIG. 9 is a flow chart showing the procedure of alarm diagnosis processing in the radiation monitor according to the third embodiment. After step S4 in the flow chart of FIG. 7 of the second embodiment, step S31 of determining whether or not the γ-ray is to be measured is entered.
Since the procedure from step S1 to step S4 is the same as that of the second embodiment, the explanation is omitted.
In step S4, the γ-ray incoming direction is determined based on the position distribution of the γ-rays to be measured output from the distribution analysis unit 230, and the position b of the peak a of the two-dimensional position distribution output from the distribution analysis unit 230 is the main position. If it is located in the steam pipe position range c (YES in step S4), the process proceeds to step S31.

In step S31, the following determination processing is performed. The energy spectrum of the prismatic scintillator 12a of the detection unit 12 that measured the maximum γ-ray yield of the measurement object in the two-dimensional position distribution output by the distribution analysis unit 230 is read from the pulse height analysis unit 220, and the measured value of the peak energy of the energy spectrum. and Since the gamma rays to be measured have an intrinsic energy of 6.13 MeV, when radiation other than the measured nuclide is incident on the detection unit 12, the peak position of the read energy spectrum will be a different position from 6.13 MeV. . Therefore, in step S31, an allowable peak energy range is set in consideration of the energy width due to the resolution of the detection unit 12, and if the peak energy of the read energy spectrum is outside the allowable range (NO in step S31), , it is determined that the cause of the alarm is "generation of radiation sources other than the target nuclide" (step S32). In addition, "generation of radiation sources other than target nuclides" means that radiation sources other than those to be measured exist nearby. If the peak energy of the read energy spectrum is within the allowable range (YES in step S31), it is determined that the gamma ray to be measured has been detected, and the cause of the alarm is determined to be "leakage of the target nuclide" ( step S6).

The determination results of steps S3, S5, S6, S22, and S32 are output to the display unit 15 (step S7), and an alarm signal is output as appropriate.

As described above, the radiation monitor according to the third embodiment has the same effects as the first and second embodiments. Furthermore, in Embodiment 3, radiation other than the target nuclide within the detection range can be discriminated, so that determination of alarm transmission with higher reliability becomes possible.

Embodiment 4.
A radiation monitor according to Embodiment 4 will be described below with reference to the drawings.
In the fourth embodiment, the alarm diagnostic unit 300 is additionally provided with a function of judging an abnormality in the surrounding environment due to an increase in the background. A radiation monitor according to Embodiment 4 has the same configuration as the radiation monitor shown in FIG. 8 of Embodiment 2, and description thereof is omitted.

FIG. 10 is a flow chart showing the procedure of alarm diagnosis processing in the radiation monitor according to the fourth embodiment. In step S31 of the flowchart of FIG. 9 of Embodiment 3, if the peak energy of the γ-ray detected by the detection unit 12 is outside the allowable range (NO in step S31), it is determined whether the γ-ray is the measurement object or not. A step S41 is provided for determining whether or not this is the cause.

In FIG. 10, the procedure from step S1 to step S31 is the same as that of the third embodiment, so the explanation is omitted.
In step S31, considering the energy width due to the resolution of the detection unit 12, the peak energy allowable range is set, and if the peak energy of the read energy spectrum is outside the allowable range (NO in step S31), step Proceed to S41.

In step S41, the following determination processing is performed.
Among the prismatic scintillators 12a of the detection unit 12, the background yield _QB in the peak region P of the energy spectrum of the prismatic scintillator 12a that detected the peak energy used for the determination in step S31 is calculated.
FIG. 11 is a diagram for explaining a method for calculating the background yield _QB , where P is the peak region in the energy spectrum, p is the channel width of the peak, and the number of channels on the high energy side of the peak channel region P is Let B1 be the number of channels on the low energy side, and B2 be the number of channels. When the count number of each channel is n _ch , the peak yield Q _N and the background yield Q _B in the peak region P are obtained by the following equations (1) and (2), respectively, by subtracting the background represented by a straight line. Desired.

The background yield _QB in the peak region P obtained by Equation (1) is calculated at regular intervals, and time constant processing is performed so that the standard deviation becomes constant. In step S41, the calculated background yield _QB in the peak region P is compared with the preset background value around the main steam pipe during reactor operation other than the target nuclide to be measured. If the calculated background yield _QB is large, it is determined that the background increase has been confirmed, and if the calculated background yield _QB is small, it is determined that the background increase has not been confirmed.

If an increase in the background is confirmed (YES in step S41), it is determined that the ambient environment is abnormal (step S5). If an increase in the background is not confirmed (NO in step S41), it is determined that "radiation sources other than the target nuclide are generated" (step S32).

The determination results of steps S3, S5, S6, S22, and S32 are output to the display unit 15 (step S7), and an alarm signal is output as appropriate.

As described above, the radiation monitor according to the fourth embodiment has the same effect as the third embodiment. Furthermore, among the radiation from outside the main steam pipe, radiation with a high background value can be discriminated, so it is possible to determine alarm transmission with even higher reliability.

[Hardware configuration diagram of arithmetic processing unit 10]
FIG. 12 is a hardware configuration diagram of the arithmetic processing unit 10. As shown in FIG. As shown in FIG. 12, the arithmetic processing unit 10 shown in Embodiments 1 to 4 is composed of a processor 1001 and a storage device 1002 . Although not shown, the storage device includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. Also, an auxiliary storage device such as a hard disk may be provided instead of the flash memory. Processor 1001 executes a program input from storage device 1002 . In this case, the program is input from the auxiliary storage device to the processor 1001 via the volatile storage device. In addition, the processor 1001 may output data such as calculation results to the volatile storage device of the storage device 1002, or may store data in an auxiliary storage device via the volatile storage device.

The radiation monitors according to Embodiments 1 to 4 above are particularly suitable for monitoring leaks of cooling water from steam generators in pressurized water reactor plants and for checking the soundness of steam generators. The description has been made on the premise that it is arranged close to the steam generator. However, application of the radiation monitor of the present application is not limited to this. Needless to say, the above effects can be obtained by arranging the sensor in close proximity to an object whose leakage of radiation is to be detected.

While this application describes various exemplary embodiments and examples, various features, aspects, and functions described in one or more embodiments may not apply to particular embodiments. can be applied to the embodiments singly or in various combinations.
Accordingly, numerous variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, modification, addition or omission of at least one component, extraction of at least one component, and combination with components of other embodiments shall be included.

1: Main steam pipe 10: Arithmetic processing unit 11: Detecting unit 12: Detecting unit 12a: Prismatic scintillator 12b: Multi-anode photomultiplier tube 13: Shield 300: Alarm diagnosis unit 15: Display Section 100: Radiation Count Calculator 110: Amplifier 120: Pulse Height Analyzer 131: High Energy Count Rate Calculator 132: Low Energy Count Rate Calculator 200: Radiation Position Distribution Calculator 210: Amplifier , 220: wave height analysis unit, 230: distribution analysis unit

Claims (6)

A first radiation detection unit that detects gamma rays emitted from the nuclide to be measured among the radiation emitted from the measurement target equipment and outputs an analog voltage pulse, and using the output of the first radiation detection unit, a radiation counting calculation unit that calculates the radiation count; a second radiation detection unit that two-dimensionally detects gamma rays emitted from the radionuclide to be measured and outputs an analog voltage pulse; and the second radiation detection unit. and a radiation position distribution calculation unit for calculating a two-dimensional position distribution of radiation using the output of, and an alarm diagnosis for determining and outputting the cause of a radiation generation alarm from the results of the radiation counting calculation unit and the radiation position distribution calculation unit. A radiation monitor comprising:
The radiation counting calculation unit is
discriminating an analog voltage pulse output from the first radiation detection unit into a pulse entering a high energy window and a pulse entering a low energy window set with respect to the voltage level;
The pulse entering the high energy window is subjected to time constant processing so that the standard deviation becomes constant, and the high energy count rate is calculated and output. a high energy counting rate calculator that outputs an alarm;
a low energy count rate calculation unit that calculates and outputs a low energy count rate by moving averaging the pulses that have entered the low energy window at a constant measurement time,
The radiation position distribution calculator,
a pulse-height analysis unit that outputs a two-dimensional energy spectrum corresponding to an analog voltage pulse output from the second radiation detection unit that exceeds a preset value with respect to the voltage level;
a distribution analysis unit that calculates the yield of the energy spectrum at each position obtained from the wave height analysis unit and outputs a two-dimensional position distribution of radiation;
The alarm diagnosis unit
When an alarm is output from the high energy counting rate calculation unit, if the low energy counting rate output from the low energy counting rate calculation unit is within a preset allowable range, the cause of the alarm is the first radiation Judged as the fluctuation of the detection part,
When an alarm is output from the high energy count rate calculation unit and the low energy count rate output from the low energy count rate calculation unit is outside a preset allowable range, two-dimensional radiation output from the distribution analysis unit Comparing the peak position of the position distribution with the position of the device to be measured to determine whether the cause of the alarm is an abnormality in the surrounding environment or the leakage of the target nuclide,
A radiation monitor that outputs judgment results along with an alarm. The distribution analysis unit of the radiation position distribution calculation unit calculates the total yield of the energy spectrum at each position obtained from the wave height analysis unit, outputs the two-dimensional position distribution of radiation, and outputs the energy spectrum at each position. Calculate and output the total yield by accumulating the yield,
The alarm diagnosis unit
When the warning is output from the high energy count rate calculation unit, when the total yield output from the distribution analysis unit is less than a preset value, the low energy count output from the low energy count rate calculation unit It is determined whether or not the rate is within a preset allowable range, and if the low energy counting rate output from the low energy counting rate calculation unit is within the preset allowable range, the cause of the alarm is the first If the low energy count rate output from the low energy count rate calculation unit is outside the preset allowable range, the cause of the alarm is the abnormality of the first radiation detection unit. judge,
When an alarm is output from the high energy counting rate calculation unit and the total yield output from the distribution analysis unit is equal to or greater than a preset value, the peak position of the radiation two-dimensional position distribution output from the distribution analysis unit and the position of the device to be measured to determine whether the cause of the alarm is an abnormality in the surrounding environment or the leakage of the target nuclide,
2. The radiation monitor according to claim 1, which outputs a judgment result together with an alarm. The wave height analysis unit of the radiation position distribution calculation unit,
outputting a two-dimensional energy spectrum corresponding to the analog voltage pulse output from the second radiation detection unit exceeding a preset value with respect to the voltage level, and outputting the peak energy in the energy spectrum; death,
The alarm diagnosis unit
By comparing the peak position of the two-dimensional radiation position distribution output from the distribution analysis unit and the position of the device to be measured, the peak position corresponds to the position of the device to be measured, and the cause of the alarm is determined. When it is determined that the surrounding environment is not abnormal, it is determined whether or not the detected radiation is a gamma ray emitted from the radionuclide to be measured from the energy width of the peak energy in the energy spectrum output from the wave height analysis unit. However, if the detected radiation is gamma rays emitted from the nuclide to be measured, it is determined that the cause of the alarm is leakage of the nuclide to be measured, and the detected radiation is not gamma rays emitted from the nuclide to be measured. , determine that the cause of the alarm is the generation of a radiation source other than the target nuclide,
3. The radiation monitor according to claim 2, which outputs a determination result together with an alarm. The alarm diagnosis unit
From the energy width of the peak energy in the energy spectrum output from the wave height analysis unit, it is determined whether or not the detected radiation is gamma rays emitted from the nuclide to be measured, and the detected radiation is determined by the measurement target. If it is not a gamma ray emitted from a nuclide, it is determined whether the background yield for the region containing the peak energy in the energy spectrum output from the wave height analysis unit has increased, and if the background yield has increased, the cause of the alarm determines that there is an abnormality in the surrounding environment, and if the background yield does not increase, determine that the cause of the alarm is the generation of a radiation source other than the target nuclide,
4. The radiation monitor according to claim 3, which outputs a determination result together with an alarm. 5. Any one of claims 1 to 4, wherein the second radiation detection unit comprises a plurality of prismatic scintillators and a multi-anode photomultiplier tube, and the prismatic scintillators are aligned in a two-dimensional array. a radiation monitor as described in . 6. The radiation monitor according to any one of claims 1 to 5, wherein said equipment to be measured is a main steam pipe of a nuclear power plant.

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