Dose rate measuring device

Patent metadata

Field	Value
Publication number	US-9841508-B2
Application number	US-201415501411-A
Country	US
Kind code	B2
Filing date	Aug 26, 2014
Priority date	Aug 26, 2014
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Three semiconductor detectors are installed at positions where incidence of radiation on a scintillation detector is not blocked, at equal intervals centered on a central axis of the scintillation detector and at equal angles with respect to a plane which is at a right angle to the central axis. An energy compensation factor is determined on the basis of an average pulse height value obtained from a second pulse height spectrum obtained by analog voltage pulses which are output from these semiconductor detectors, and energy characteristics of a high-range dose rate obtained by a direct-current voltage which is output from the scintillation detector are compensated for.

First claim

The invention claimed is:

1. A dose rate measuring device comprising:
a detection unit including first radiation detector for detecting radiation and outputting an analog voltage pulse and a direct-current voltage, and second radiation detector for detecting radiation in three or more sensor units and outputting analog voltage pulses; and
a measurement unit including a calculator to convert a first pulse height spectrum, obtained by the analog voltage pulse which is output from the first radiation detector, into a low-range dose rate, and to convert the direct-current voltage, which is output from the first radiation detector, into a high-range dose rate, and to determine an energy compensation factor for the high-range dose rate on the basis of an average pulse height value obtained from a second pulse height spectrum obtained by the analog voltage pulses which are output from the second radiation detector, and to multiply the high-range dose rate by the energy compensation factor, and to compensate for energy characteristics of the high-range dose rate,
wherein the respective sensor units of the second radiation detector are installed at positions where incidence of radiation on the first radiation detector is not blocked, at equal intervals centered on a central axis of the first radiation detector and at equal angles with respect to a plane which is at a right angle to the central axis, and are disposed so that a sum of areas seen through sensitive surfaces of the respective sensor units from a direction parallel to the central axis, and areas seen through the sensitive surfaces of the respective sensor units from a direction at a right anqle to the central axis become equal to each other.

2. The dose rate measuring device according to claim 1 , wherein the calculator obtains a ratio of the high-range dose rate obtained by compensating for the energy characteristics to the low-range dose rate, and switch and output the low-range dose rate and the high-range dose rate obtained by compensating for the energy characteristics, on the basis of the ratio and the high-range dose rate obtained by compensating for the energy characteristics.

3. The dose rate measuring device according to claim 1 , wherein a semiconductor detector in which the sensor unit is a semiconductor sensor is used as the second radiation detector.

4. The dose rate measuring device according to claim 1 , wherein a scintillation fiber detector in which the sensor unit is a scintillation fiber is used as the second radiation detector.

5. The dose rate measuring device according to claim 1 , wherein the calculator inputs the first pulse height spectrum in a fixed period to convert a pulse height into a dose rate, and obtains the low-range dose rate from an average dose rate obtained by a moving average.

6. The dose rate measuring device according to claim 1 , wherein the calculator inputs a count value obtained by counting a digital pulse of a repetitive frequency directly proportional to the direct-current voltage which is output from the first radiation detector to convert the count value into a dose rate, and obtains the high-range dose rate from the average dose rate obtained by a moving average.

7. The dose rate measuring device according to claim 1 , wherein the calculator obtains a dark current of the first radiation detector on the basis of a high voltage setting value of high voltage power supply for supplying a high voltage to the first radiation detector, and calculates a dark current dose rate equivalent to the dark current, and
multiplies the high-range dose rate by the energy compensation factor, and then subtracts the dark current dose rate to compensate for the energy characteristics of the high-range dose rate and the dark current.

8. The dose rate measuring device according to claim 7 , wherein the detection unit includes a temperature sensor that detects a temperature of a space having the first radiation detector installed therein and outputs a temperature signal, the measurement unit includes a temperature measurement unit that outputs the temperature measured on the basis of the temperature signal which is output from the temperature sensor, and the calculator obtains the dark current of the first radiation detector on the basis of the temperature which is output from the temperature measurement unit and the high voltage setting value of the high voltage power supply, and calculates the dark current dose rate equivalent to the dark current.

9. The dose rate measuring device according to claim 1 , wherein the detection unit includes the temperature sensor that detects a temperature of a space having the first radiation detector installed therein and outputs a temperature signal, and the measurement unit includes the temperature measurement unit that outputs the temperature measured on the basis of the temperature signal which is output from the temperature sensor, the calculator detects a spectrum peak of a natural radionuclide K-40included in a configuration material of the first radiation detector on the basis of the first pulse height spectrum, and determines a gain for compensating for a shift of the spectrum peak of K-40 from a reference position, on the basis of the temperature acquired from the temperature measurement unit and a detection result of the spectrum peak of K-40.

Assignees

• Mitsubishi Electric Corp

Inventors

• Moteki Kenichi
• Aiba Toshihide

Classifications

• G01T1/02 Primary

  Dosimeters (G01T1/15 takes precedence) · CPC title

• G01T1/026 Primary

  Semiconductor dose-rate meters · CPC title

• G01T1/023

  Scintillation dose-rate meters · CPC title

• G01T1/15

  Instruments in which pulses generated by a radiation detector are integrated, e.g. by a diode pump circuit · CPC title

• G01T1/1603

  with a combination of at least two different types of detectors · CPC title