JP2024027548A - Radiation detection device and inspection method for radiation detection device - Google Patents

Abstract

An object of the present invention is to adjust the amount of inspection light irradiated from a light source to a detector so that it does not become excessive, and to prevent problems occurring in the detector. [Solution] A scintillator 11 that converts radiation into scintillation light 15, a detector 12 that detects the radiation dose by inputting the scintillation light 15, and an inspection device for inspecting the detector 12 instead of the scintillation light 15. The light emitting element 13 that irradiates the light 16 onto the detector 12 and the light emitting element current 18 flowing to the light emitting element 13 are controlled based on the magnitude of the detector output signal B output from the detector 12 upon incidence of the inspection light 16. The feedback circuit section 14 is configured to include a feedback circuit section 14 for adjustment. [Selection diagram] Figure 1

Description

Embodiments of the present invention relate to a radiation detection device equipped with a detector inspection function, and a radiation detection device inspection method.

At nuclear power research facilities, reprocessing plants, etc. that handle nuclear fuel, criticality warning devices are installed for the purpose of prompt evacuation of workers in the event of a criticality accident. This criticality alarm system is required to reliably detect high dose rates even in extremely high dose rate fields as a means of reliably detecting increases in radiation levels associated with critical events, so it uses current mode. Uses working radiation detection equipment (including ionization chambers and scintillation detectors).

The radiation detection equipment used in the criticality alarm system must undergo periodic trip operation tests to confirm that the criticality detection function is operating properly. Equipped with a light-emitting element for Normally, a scintillator converts incident radiation into light (scintillation light) and provides scintillation light to the detector, but during inspections, a light emitting element is turned on to detect light that simulates scintillation light (inspection light). Give it to the vessel.

Japanese Patent Application Publication No. 2000-249796

A conventional radiation detection apparatus 100 shown in FIG. 5 includes a scintillator 101, a detector 102, and a light emitting element 103 for inspection. In normal times, the scintillator 101 converts radiation into light (scintillation light 104), the detector 102 receives the scintillation light 104, and detects the amount of radiation that has entered the scintillator 101. During the trip operation test of the detector 102, the light emitting element 103 receives the inspection signal _A0 and emits light, and the detector 102 receives the inspection light 105 from the light emitting element 103 instead of the scintillation light 104. This allows inspection of internal measurement circuits, etc.

By the way, at the time of inspection such as a trip operation test, the inspection light 105 from the light emitting element 103 needs to be adjusted to an appropriate amount of light. However, due to the efficiency of the detector 102, individual differences in the light emitting elements 103, changes over time, etc., it is difficult to adjust the inspection light 105, which simulates the scintillation light 104 corresponding to trip operation level radiation, to an appropriate light intensity. There are cases.

For example, if the light emitting element 103 emits an excessive amount of inspection light 105 when tripping the detector 102, the charge accumulated in each measurement circuit in the detector 102 may be discharged after the inspection is completed. Progress is slow, and it takes a considerable amount of time for the current signal in the measurement circuit to return to the actual radiation level. For this reason, there is a problem in the restoration operation of the criticality warning device after the inspection is completed.

Note that FIG. 3B shows that the amount of inspection light 105 irradiated from the light emitting element 103 is excessive, and that the detector output signal B ₀ is output from the detector 102 into which this inspection light 105 is incident. indicates a situation where the trip threshold is significantly exceeded.

The embodiments of the present invention have been made in consideration of the above-mentioned circumstances, and are able to adjust the amount of inspection light irradiated from the light source to the detector so that it does not become excessive, thereby preventing malfunctions occurring in the detector. The purpose of the present invention is to provide a radiation detection device and a radiation detection device inspection method that can avoid such problems.

A radiation detection device according to an embodiment of the present invention includes a scintillator that converts radiation into scintillation light, a detector that detects a radiation dose by receiving the scintillation light, and a detector that inspects the detector instead of the scintillation light. a light source that irradiates the detector with inspection light for inspection; and a feedback that adjusts a light source current that flows to the light source based on the magnitude of a detector output signal output from the detector upon incidence of the inspection light. The device is characterized in that it is configured to include a circuit section.

A method for inspecting a radiation detection device according to an embodiment of the present invention is a method for inspecting a radiation detection device having a scintillator that converts radiation into scintillation light and a detector that detects a radiation dose by receiving the scintillation light. When the inspection light for inspecting the detector is irradiated from the light source to the detector instead of the scintillation light, a detector output signal output from the detector due to the incidence of the inspection light. The light source current flowing to the light source is adjusted based on the magnitude of the light source.

According to the embodiment of the present invention, it is possible to adjust the amount of inspection light irradiated from the light source to the detector so that it does not become excessive, and it is possible to avoid problems occurring in the detector.

FIG. 1 is a block diagram showing the configuration of a radiation detection device according to the present embodiment. FIG. 2 is a block diagram showing the configuration of a feedback circuit section in FIG. 1. FIG. (A) is a graph showing the time course of the inspection signal, (B) is a graph showing the time course of the detector output signal in the conventional technique, and (C) is a graph showing the time course of the detector output signal in the present embodiment. 2 is a flowchart showing a procedure for adjusting a light emitting element current, etc., executed by the feedback circuit section in FIG. 1; FIG. 1 is a block diagram showing a conventional radiation detection device.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing.
FIG. 1 is a block diagram showing the configuration of a radiation detection apparatus according to this embodiment. The radiation detection device 10 shown in FIG. 1 has a scintillator 11 and a detector 12 to detect radiation dose, and also includes a light emitting element 13 as a light source and a feedback circuit section 14 in order to check the detector 12. It is composed of:

The scintillator 11 converts incident radiation into light (scintillation light 15). The detector 12 receives the scintillation light 15 from the scintillator 11 and detects the amount of radiation incident on the scintillator 11 . This detector 12 needs to be checked periodically to ensure that the tripping operation is working properly, for example.

The light emitting element 13 emits inspection light 16 in order to check whether the operation (for example, tripping operation) of the detector 12 is normal or not. For example, the light emitting element 13 is a light emitting diode (LED). configured. That is, when the inspection signal A is input from the inspection switch 17 by the ON operation of the inspection switch 17, the light emitting element 13 transmits the inspection light 16 for inspecting the detector 12 to the detector 12, and sends the scintillation light 15 to the detector 12. irradiate instead. Using this inspection light 16, the detector 12 is inspected to see if its operation is normal.

The feedback circuit section 14 outputs a detector output signal B that the detector 12 outputs upon the incidence of the inspection light 16 so that the amount of inspection light 16 incident on the detector 12 from the light emitting element 13 becomes an appropriate value. The light emitting element current 18 as a light source current flowing to the light emitting element 13 is adjusted based on the magnitude of . As shown in FIG. 2, the feedback circuit section 14 is configured to include a comparator circuit 20, a peak hold circuit 21, a voltage/current conversion circuit 22, and a charge discharge circuit 23.

The comparator circuit 20 compares the detector output signal B output from the detector 12 when the inspection light 16 is incident on the detector 12 from the light emitting element 13 shown in FIG. 1 with a trip threshold (see FIG. 3). By this, the magnitude of the detector output signal B is determined. As shown in FIG. 2, this comparator circuit 20 includes a comparator 24 and an AND circuit 25 that are electrically connected to each other.

The comparator 24 compares the detector output signal B and the trip threshold, and turns on the comparator output signal C (H level) when the detector output signal B is below the trip threshold (detector output signal B≦trip threshold). Output as . Further, when the detector output signal B exceeds the trip threshold (detector output signal B>trip threshold), the comparator 24 turns the comparator output signal C OFF (L level) and does not output it.

The AND circuit 25 performs an AND operation and outputs an AND circuit output signal D (ON) when the comparator output signal C is output from the comparator 24 and the inspection signal A is output from the inspection switch 17. The AND circuit 25 outputs the comparator output signal C when either the comparator output signal C from the comparator 24 or the inspection signal A from the inspection switch 17 is no longer output, for example, when the detector output signal B exceeds the trip threshold. When the output signal D is no longer output, the output of the AND circuit output signal D is stopped (turned OFF).

The peak hold circuit 21 includes a diode 26 electrically connected to the AND circuit 25 of the comparator circuit 20, and a capacitor 27 electrically connected to the diode 26 to store charge. The diode 26 and the capacitor 27 are also electrically connected to the first transistor 31 of the voltage/current conversion circuit 22 and the discharge switch 36 of the charge discharge circuit 23 .

In this peak hold circuit 21, when the detector output signal B from the detector 12 shown in FIG. When the AND circuit output signal D is output from the AND circuit 25, the diode 26 transmits the AND circuit output signal D to the capacitor 27, the first transistor 31, and the discharge switch 36. The capacitor 27 accumulates the transmitted AND circuit output signal D (current) as a charge and gradually changes (increases) the voltage between the terminals.

When the comparator 24 determines that the detector output signal B output from the detector 12 exceeds the trip threshold (detector output signal B>trip threshold), the comparator 24 no longer outputs the comparator output signal C. Therefore, the AND circuit output signal D is no longer output from the AND circuit 25 to the diode 26, and the diode 26 no longer transmits the AND circuit output signal D to the capacitor 27, the first transistor 31, and the discharge switch 36. At this time, the charge accumulated in the capacitor 27 is not discharged by the diode 26 and is held at the peak value, so that the voltage between the terminals of the capacitor 27 is also held at the peak value.

The voltage/current conversion circuit 22 causes a current corresponding to the charge accumulated in the capacitor 27 of the peak hold circuit 21 to flow through the light emitting element 13 as a light emitting element current 18, and includes a first transistor 31, a second transistor 32, and The third transistor 33 is configured. The first transistor 31 is electrically connected to a second transistor 32 and a third transistor 33, which are electrically connected to each other.

In this voltage/current conversion circuit 22, the voltage between the terminals of the capacitor 27 of the peak hold circuit 21 is directly reflected in the first transistor 31, and a current flows from the first transistor 31 to the second transistor 32. The second transistor 32 and the third transistor 33 have a structure in which currents are synchronized, and a current having the same current value as the current flowing through the second transistor 32 also flows through the third transistor 33. The current flowing through the third transistor 33 directly flows to the light emitting element 13 as the light emitting element current 18.

Therefore, when the detector output signal B output from the detector 12 is below the trip threshold (detector output signal B≦trip threshold), the voltage/current conversion circuit 22 gradually increases the voltage between the terminals of the capacitor 27. A light emitting element current 18 that gradually increases in accordance with the current is caused to flow through the light emitting element 13. Further, when the detector output signal B exceeds the trip threshold (detector output signal B>trip threshold), the voltage/current conversion circuit 22 emits light according to the voltage between the terminals of the capacitor 27 that is maintained at the peak value. The light emitting element current 18 flowing through the element 13 is maintained at its peak value.

The charge discharging circuit 23 is capable of discharging the charges accumulated in the capacitor 27 of the peak hold circuit 21, and includes a NOT circuit 34, a relay 35, and a discharge switch 36. A NOT circuit 34 is electrically connected to the inspection switch 17, and this NOT circuit 34, relay 35, and discharge switch 36 are electrically connected in sequence.

In this charge discharge circuit 23, when the inspection switch 17 is turned on and the light emitting element 13 (FIG. 1) emits the inspection light 16, the inspection signal A from the inspection switch 17 is output as shown in FIG. , is input to the NOT circuit 34 and becomes L level (OFF state), and the relay 35 does not operate. Therefore, the discharge switch 36 is in the OFF operating state and does not discharge the accumulated charge from the capacitor 27 of the peak hold circuit 21.

On the other hand, when the inspection switch 17 is turned OFF and the light emitting element 13 no longer emits the inspection light 16, the inspection signal A from the inspection switch 17 is set to H level (ON state) by the NOT circuit 34, and the relay 35 is turned on. Operate. Therefore, the discharge switch 36 is turned on, and the excess charge accumulated in the capacitor 27 of the peak hold circuit 21 is discharged to, for example, a ground circuit. As a result, the light emitting element current 18 no longer flows through the light emitting element 13.

Next, the operation of the feedback circuit section 14 configured as described above will be explained mainly with reference to FIG. 4.
When the inspection switch 17 shown in FIG. 1 is turned on and the inspection signal A is output from the inspection switch 17 to the light emitting element 13, the light emitting element 13 irradiates the detector 12 with inspection light 16 (S11). . When the inspection light 16 enters the detector 12, a detector output signal B is output, and the comparator 24 of the comparator circuit 20 in the feedback circuit section 14 inputs the detector output signal B, and outputs the detector output signal B. It is determined whether or not exceeds the trip threshold (S12).

When the detector output signal B is below the trip threshold (detector output signal B≦trip threshold), the comparator 24 outputs (ON) the comparator output signal C (S13). Next, the AND circuit 25 of the comparator circuit 20 outputs (ON) an AND circuit output signal D when both the comparator output signal C from the comparator 24 and the inspection signal A from the inspection switch 17 are input (S14 ).

By inputting the AND circuit output signal D from the AND circuit 25 via the diode 26, the capacitor 27 of the peak hold circuit 21 gradually accumulates charge and gradually increases the voltage between terminals (S15).

The voltage/current conversion circuit 22 causes a current that increases in accordance with the voltage between the terminals of the capacitor 27 (that is, the accumulated charge) to flow through the light emitting element 13 as the light emitting element current 18 (S16). As a result, the detector output signal B output from the detector 12 into which the inspection light 16 from the light emitting element 13 is incident corresponds to the current value of the light emitting element current 18, as shown in FIG. 3(C). Gradually increases until the trip threshold is reached.

In step S12 in FIG. 4, when the detector output signal B exceeds the trip threshold (detector output signal B>trip threshold), the comparator 24 of the comparator circuit 20 stops (OFF) the comparator output signal C ( S17). Next, the AND circuit 25 of the comparator circuit 20 stops (OFF) the AND circuit output signal D by stopping the comparator output signal C from the comparator 24 (S18).

The capacitor 27 of the peak hold circuit 21 stops accumulating charges because the AND circuit output signal D from the AND circuit 25 is not input, and holds the inter-terminal voltage at the peak value without changing it (S19).

The voltage/current conversion circuit 22 maintains the light emitting element current 18 flowing through the light emitting element 13 at the peak value in accordance with the peak value of the voltage across the terminals of the capacitor 27 (S20). As a result, the detector output signal B output by the detector 12 that receives the inspection light 16 from the light emitting element 13 becomes as shown in FIG. As shown, it is held near the trip threshold.

After step S16 or S20 shown in FIG. 27 is discharged to, for example, a ground circuit (S21). As a result, the light emitting element current 18 no longer flows from the voltage/current conversion circuit 22 to the light emitting element 13, and as shown in FIG. It disappears quickly afterwards.

As configured as above, the present embodiment provides the following effect (1).
(1) As shown in FIGS. 1 and 2, the feedback circuit section 14 receives a detector output signal B output from the detector 12 when the inspection light 16 from the light emitting element 13 is incident on the detector 12. The light emitting element current 18 flowing to the light emitting element 13 is adjusted based on the magnitude of . For example, in the feedback circuit unit 14, when the comparator 24 of the comparator circuit 20 determines that the detector output signal B has exceeded the trip threshold, the capacitor 27 of the peak hold circuit 21 is activated to peak the voltage between the terminals without changing the voltage between the terminals. hold value. Then, in response to the peak value of the voltage across the capacitor 27, the voltage/current conversion circuit 22 maintains the light emitting element current 18 flowing to the light emitting element 13 at the peak value, and causes the light emitting element 13 to emit light with an excessive current. Adjustment is made so that the element current 18 does not flow.

As a result, the amount of inspection light 16 irradiated from the light emitting element 13 to the detector 12 can be adjusted so that it does not become excessive. It is possible to avoid the problem that it takes a considerable amount of time for the current signal of the internal measurement circuit to return to the actual radiation level.

Although the embodiment of the present invention has been described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be implemented in various other forms, and various omissions, substitutions, changes, and combinations can be made without departing from the gist of the invention. Changes and combinations are not only included within the scope and gist of the invention, but also within the scope of the invention described in the claims and its equivalents.
For example, although the light source is a light emitting element such as a light emitting diode, other light sources such as an incandescent bulb, a halogen bulb, or a fluorescent lamp may be used.

10...Radiation detection device, 11...Scintillator, 12...Detector, 13...Light emitting element (light source), 14...Feedback circuit section, 15...Scintillation light, 16...Inspection light, 18...Light emitting element current (current for light source) , 20... Comparator circuit, 21... Peak hold circuit, 22... Voltage/current conversion circuit, 23... Charge discharge circuit, 24... Comparator, 27... Capacitor, A... Inspection signal, B... Detector output signal

Claims (5)

A scintillator that converts radiation into scintillation light,
a detector that detects a radiation dose by inputting the scintillation light;
a light source that irradiates the detector with inspection light for inspecting the detector instead of the scintillation light;
A feedback circuit unit that adjusts a light source current flowing to the light source based on the magnitude of a detector output signal output from the detector upon incidence of the inspection light. radiation detection device. The radiation source according to claim 1, wherein the feedback circuit unit includes a comparator circuit that determines the magnitude of the detector output signal by comparing the detector output signal with a threshold value. Detection device. The feedback circuit unit includes a peak hold circuit including a capacitor that accumulates charge, and a voltage/current conversion circuit that causes a current corresponding to the charge accumulated in the capacitor to flow to the light source as a light source current,
When the comparator circuit determines that the detector output signal exceeds the threshold, the peak hold circuit holds the charge accumulated in the capacitor at its peak value, and the voltage/current conversion circuit causes the charge to flow to the light source. The radiation detection device according to claim 2, wherein the radiation detection device is configured such that the light source current is maintained at a peak value. 4. The radiation detection apparatus according to claim 3, wherein the feedback circuit section includes a charge discharge circuit that can discharge charges accumulated in a capacitor of a peak hold circuit. A method for inspecting a radiation detection device including a scintillator that converts radiation into scintillation light, and a detector that detects a radiation dose by receiving the scintillation light, the method comprising:
When the inspection light for inspecting the detector is irradiated from the light source to the detector instead of the scintillation light, the magnitude of the detector output signal output from the detector due to the incidence of the inspection light A method for inspecting a radiation detection device, comprising adjusting a light source current flowing to the light source based on the current.

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