Radiation monitor and method of analyzing radiation monitor

Patent metadata

Field	Value
Publication number	US-10877167-B2
Application number	US-201716325735-A
Country	US
Kind code	B2
Filing date	Aug 8, 2017
Priority date	Sep 1, 2016
Publication date	Dec 29, 2020
Grant date	Dec 29, 2020

Abstract

Provided is a radiation monitor, including: a radiation detection unit which includes a radiation detection element, the radiation detection element emitting light of a predetermined light emission wavelength; a light emission unit which emits light of a wavelength different from the light emission wavelength; a wavelength selection unit which passes the light of the light emission wavelength, and is set to a first mode to block the light from the light emission unit; an optical transmission line which transmits the light; a light detection unit which converts the light passing through the wavelength selection unit into an electric pulse; and a control unit which measures a count rate of the electric pulse, and determines whether at least the light emission unit is degraded on the basis of the count rate and a light intensity of the light emission unit.

First claim

The invention claimed is:

1. A radiation monitor, comprising:
a radiation detection unit which includes a radiation detection element, the radiation detection element sensing radiation and light, and emitting light of a predetermined light emission wavelength when receiving the radiation or the light;
a light emission unit which emits light of a wavelength different from the light emission wavelength;
a wavelength selection unit which passes the light of the light emission wavelength, and is set to a first mode to block the light from the light emission unit;
an optical transmission line which transmits the light from the light emission unit to the radiation detection unit, and transmits the light from the radiation detection unit to the wavelength selection unit;
a light detection unit which converts the light passing through the wavelength selection unit into an electric pulse; and
a control unit which measures a count rate of the electric pulse, and determines whether at least the light emission unit is degraded on the basis of the count rate and a light intensity of the light emission unit,
wherein the control unit is configured to
include a memory unit which stores first light intensity-count rate information indicating a relation between the light intensity of the light emission unit when it is already known that the radiation monitor functions normally and the count rate in a state where the wavelength selection unit is set to the first mode, and
set the wavelength selection unit to the first mode in maintenance of the radiation monitor which is performed in a state where a dose rate of radiation incident on the radiation detection element is at a level of natural radiation and determine, on the basis of a setting value of a predetermined light intensity, that the light emission unit is degraded when an actual light intensity of the light emission unit is smaller than the setting value in a case where the count rate caused by light emitted from the light emission unit is lowered below the first light intensity-count rate information.

2. The radiation monitor according to claim 1 ,
wherein the wavelength selection unit further includes a second mode in which the light from the light emission unit passes, and the light of the light emission wavelength is blocked,
wherein the memory unit stores second light intensity-count rate information indicating the relation between the light intensity of the light emission unit and the count rate when it is already known that the radiation monitor functions normally in a state where the wavelength selection unit is set to the second mode, and
wherein the control unit sets the wavelength selection unit to the second mode when the actual light intensity of the light emission unit is not smaller than the setting value in a case where the count rate in the first mode is lowered below the first light intensity-count rate information, and determines that the optical transmission line is degraded in a case where the count rate caused by the light emitted from the light emission unit is lowered below the second light intensity-count rate information.

3. The radiation monitor according to claim 2 ,
wherein the memory unit is configured to
store wavelength-transmittance information in which a relation between a wavelength and a transmittance of the light in the optical transmission line is associated with a numerical value indicating a degree of degradation of the optical transmission line, and
store count rate-dose rate information indicating a relation between the count rate and the dose rate of radiation incident on the radiation detection element, and
wherein, in a case where it is determined that the optical transmission line is degraded, the control unit calibrates the count rate-dose rate information on the basis of a wavelength of the light of the light emission unit which is transmitted through the optical transmission line, the transmittance of the light in the optical transmission line, and the wavelength-transmittance information.

4. The radiation monitor according to claim 2 ,
wherein, in a case where the count rate in the first mode is lowered below the first light intensity-count rate information, the control unit determines that the radiation detection element is degraded when the actual light intensity of the light emission unit is not smaller than the setting value, and the count rate in the second mode is not lowered below the second light intensity-count rate information.

5. The radiation monitor according to claim 1 ,
wherein the control unit is configured to set the wavelength selection unit to the first mode in an operation confirmation of the radiation monitor which is performed in a state where a dose rate of radiation incident on the radiation detection element is higher than a level of natural radiation, and to determine, on the basis of a setting value of a predetermined light intensity, that the light emission unit is degraded when an actual light intensity of the light emission unit is smaller than the setting value in a case where the count rate caused by the light emitted from the light emission unit is lowered in a state where the setting value is kept.

6. The radiation monitor according to claim 5 ,
wherein the wavelength selection unit further includes a second mode in which the light from the light emission unit passes, and the light of the light emission wavelength is blocked,
wherein the control unit is configured to
include a memory unit which stores second light intensity-count rate information indicating a relation between the light intensity of the light emission unit when it is already known that the radiation monitor functions normally in a state where the wavelength selection unit is set to the second mode and the count rate, and
set the wavelength selection unit to the second mode when the actual light intensity of the light emission unit is not smaller than the setting value in a case where the count rate is lowered in a state where the setting value is kept, and determine that the optical transmission line is degraded in a case where the count rate caused by the light emitted from the light emission unit is lowered below the second light intensity-count rate information.

7. The radiation monitor according to claim 6 ,
wherein the memory unit is configured to
store wavelength-transmittance information in which a relation between a wavelength and a transmittance of the light in the optical transmission line is associated with a numerical value indicating a degree of degradation of the optical transmission line, and
store count rate-dose rate information indicating a relation between the count rate and the dose rate of radiation incident on the radiation detection element, and
wherein, in a case where it is determined that the optical transmission line is degraded, the control unit calibrates the count rate-dose rate information on the basis of a wavelength of the light of the light emission unit which is transmitted through the optical transmission line, the transmittance of the light in the optical transmission line, and the wavelength-transmittance information.

8. The radiation monitor according to claim 6 ,
wherein the control unit is configured to set the wavelength selection unit to the first mode when the actual light intensity of the light emission unit is not smaller than the setting value and the count rate in the second mode is not lowered below the second light intensity-count rate information in a case where the count rate is lowered in a state where the setting value is kept, and determine that the radiation detection element is degraded in a case where the count rate caused by the light emitted from the light emission unit is lowered below

Assignees

• Hitachi Ltd

Inventors

• Tadokoro Takahiro
• Ueno Katsunori
• Ueno Yuichiro
• Okada Kouichi
• Hatakeyama Shuichi
• Nagumo Yasushi
• Sakakibara Yoshinobu
• Shibutani Toru
• Itou Takahiro

Classifications

• G01T1/40 Primary

  Stabilisation of spectrometers · CPC title

• G01T1/20

  with scintillation detectors · CPC title

• G01T1/2002

  Optical details, e.g. reflecting or diffusing layers · CPC title

• G01T1/208 Primary

  Circuits specially adapted for scintillation detectors, e.g. for the photo-multiplier section · CPC title