JP6433764B2 - Radiation measurement apparatus and radiation measurement method - Google Patents

Description

  Embodiments of the invention relate to an apparatus and method for measuring radiation dose.

  The radiation monitor detector is installed, for example, in a nuclear power plant or a nuclear fuel handling facility, and measures the radiation level at each location. Here, for example, a radiation detector using an ion chamber does not operate normally under high humidity. For this reason, a structure is known in which a protective can is attached so as to cover the connector portion connecting the radiation detector and the cable, and the radiation detector and the protective can are covered with a heat shrinkable tube to prevent moisture from entering. ing.

  However, assuming a severe accident (severe accident) more severe than a loss of coolant accident (LOCA) as a design standard accident that had been considered in the past as an accident at a nuclear power plant, a detector for radiation monitoring was installed. The environment becomes more severe, and it may be difficult to ensure the soundness of the detector by the conventional method.

  In addition, as a technique for enhancing the sealing performance of the cable penetration portion during severe accidents, for example, a method in which the penetration portion is solidified with a member that is not carbonized even at high temperature and high pressure, and the cable and the penetration portion are integrated (Patent Document 1) is known.

Japanese Patent Laid-Open No. 5-45488

  Conventional protective cans installed for the purpose of protecting the detector are designed to maintain their functions under conventional LOCA conditions, for example, temperature 171 ° C., relative humidity 100%, pressure 1.7 kPa [gage]. It is difficult to respond to the environmental conditions at the time of severe accidents as they are.

  As the installation environment of the radiation monitor detector, it is assumed that the environment temperature is 200 ° C. or higher, the relative humidity is 100%, and the pressure is 4 kPa [gage] during a severe accident for 10 days. Under these conditions, a leak path is generated in the cable penetration part of the protective can and the gap between the protective can and the detector, so moisture is leaked in and condensation is generated at the connector, and the detector signal is expected to be disturbed. . Therefore, it is necessary to further improve the moisture resistance of the detector.

  It is possible to improve the sealing performance of the detector by completely closing the connector penetration portion using the conventional penetration portion sealing technique as described above. However, in that case, the cable and the protective can become an integral structure, which makes it difficult to remove. Since it is necessary to calibrate the detector periodically, it is desirable that the protective can and the connector can be easily attached and detached. Improving the airtightness by molding the cable penetration part and the connector becomes a factor of reducing maintainability.

  Therefore, an object of the embodiment of the present invention is to improve moisture resistance while maintaining maintainability required for a radiation measuring apparatus.

In order to solve the above problems, a radiation measuring apparatus according to an embodiment of the present invention includes a detector container that can be opened and closed, a radiation detector accommodated in the detector container, and a penetrating through the detector container. A cable that extends and is connected to the radiation detector to supply power to the radiation detector and transmit a signal, and is accommodated in the detector container, and pressurizes the detector container to pressurize the detector container A pressure device capable of maintaining a pressure inside the detector container higher than the pressure outside the detector container for a predetermined period of time , and the environment inside the detector container is in an abnormal state affecting the operation of the radiation detector. have a, and environmental abnormality detector for detecting the pressure device, the detector vessel is configured to pressurize when the environmental abnormality detector detects an environmental abnormality of the detector vessel It is characterized by that.

The radiation measuring method according to the embodiment of the present invention includes a detector container that can be opened and closed, a radiation detector accommodated in the detector container, and the radiation detector that extends through the detector container. And a cable for supplying power to the radiation detector and transmitting signals to the radiation detector, and an environmental abnormality detection for detecting that the environment in the detector container is in an abnormal state affecting the operation of the radiation detector. And a radiation measuring device using a radiation measuring device, and measuring the radiation dose at a location where humidity increases at the time of an accident, wherein the environment in the detector container affects the operation of the radiation detector at the time of the accident detecting by the environment anomaly detector that becomes abnormal state giving, steps to increase than the pressure outside the detector chamber pressure of said detector container when said abnormal state is detected , Characterized by comprising the steps of: measuring a radiation dosage using the radiation measuring device in a state of higher than the pressure of the detector container outside the pressure of the detector vessel.

  According to the embodiment of the present invention, it is possible to improve the moisture resistance while maintaining the maintainability required for the radiation measuring apparatus.

It is a typical lineblock diagram of a radiation measuring device concerning a 1st embodiment of the present invention. It is a typical block diagram of the opening-closing mechanism of the radiation measuring device which concerns on the 1st Embodiment of this invention, and its periphery. It is a typical block diagram of the radiation measuring device which concerns on the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of a radiation measuring apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic configuration diagram of an opening / closing mechanism of the radiation measuring apparatus according to the first embodiment of the present invention and its periphery.

  The radiation measuring device 11 includes a radiation detector 12, a connector 13, a cable 14, a pressurizing device 15, an environmental abnormality detector 16, and a detector container 17.

  The radiation detector 12 is a radiation detector using an ion chamber, for example. The connector 13 removably connects the radiation detector 12 and the cable 14.

  The detector container 17 accommodates the radiation detector 12, the connector 13, the pressurization device 15, and the environmental abnormality detector 16, and can be opened and closed.

  The cable 14 penetrates the detector container 17 at the penetration 18. The cable 14 supplies power to the radiation detector 12 from the outside, and transmits signals to and from the outside.

  With the detector container 17 closed, the penetrating part 18 is sealed with, for example, an adhesive, and with the penetrating part 18 sealed, the detector container 17 can be kept almost sealed. In order to open and close the detector container 17, for example, a plurality of flanges (not shown) are provided, and sealing is performed by tightening these flanges with screws.

  The pressurizing device 15 includes a high-pressure tank (cylinder) 20 and an opening / closing mechanism 21. In the high-pressure tank 20, an inert gas (for example, nitrogen gas) having a pressure higher than the maximum pressure outside the detector container 17 expected at the time of a severe accident is sealed in advance.

  The opening / closing mechanism 21 includes an electric valve 22 connected to the high-pressure tank 20 and a valve drive mechanism 23 that drives the electric valve 22. The valve drive mechanism 23 includes an electric motor 24 that directly drives the electric valve 22, a battery 25 that supplies electric power to the electric motor 24, and a switch 26 that turns on / off electric power supplied to the electric motor 24. The switch 26 is normally open, and is configured to close when the environmental abnormality detector 16 detects an environmental abnormality in the detector container 17.

  The motor-operated valve 22 is normally closed. When the environmental abnormality detector 16 detects an environmental abnormality in the detector container 17 and the switch 26 is closed, the electric motor 24 is activated and the electric valve 22 is opened.

  The environmental abnormality detector 16 is for detecting a situation in which the environment inside the detector container 17 changes due to a severe accident or the like and the radiation detector 12 does not operate normally. In the first embodiment, A temperature detector. The temperature detector (environmental abnormality detector) 16 may be a bimetal, for example.

  In the configuration described above, at the normal time, as described above, the switch 26 is off and the motor-operated valve 22 is closed. During a severe accident, the temperature around the detector container 17 rises abnormally, and the temperature in the detector container 17 also rises accordingly. This temperature rise is detected by a temperature detector (environmental abnormality detector) 16, whereby the switch 26 is automatically turned on, and the electric valve 22 is opened by the operation of the electric motor 24. As a result, the inert gas in the high-pressure tank 20 flows out into the detector container 17 through the motor-operated valve 22, and the pressure in the detector container 17 increases. Thereby, moisture outside the detector container 17 can be prevented from flowing into the detector container 17, and malfunction and failure of the radiation detector 12 due to moisture can be prevented.

  When the radiation detector 12 is calibrated, the detector container 17 is opened, the radiation detector 12 and the connector 13 are disconnected, and the radiation detector 12 is taken out from the detector container 17. After the calibration of the radiation detector 12 is completed, the radiation detector 12 is accommodated in the detector container 17 and the radiation detector 12 and the connector 13 are connected. Thereafter, the detector container 17 is closed and sealed.

  In the conventional connector penetrating portion, there is a decrease in airtightness, but according to this embodiment, it is possible to suppress a decrease in airtightness. In addition, the seal of the detector container 17 depends only on the tightening torque of the screw for tightening the flange, and no special technique is required for installation compared to the conventional method in which the seal is performed with the heat-shrinkable tube.

  As described above, in the event of a nuclear power plant accident such as a severe accident, the pressure in the detector container 17 is maintained higher than the pressure outside the detector container 17, and in-leak from the outside of the detector container 17 is prevented. By pre-filling the detector container 17 with an inert gas that lasts for 10 days in this state, the radiation detector 12 can be protected until the environmental conditions settle down while continuing the outleak.

  The volume of the detector container 17 is V1, the volume of the high-pressure tank 20 is V2, the pressure of the gas in the high-pressure tank 20 is P1, the pressure outside the high-pressure tank 20 in the detector container 17 is P2, and the area around the detector container 17 is If the external pressure is P3, the leak rate at the motor-operated valve 22 of the detector container 17 is K, and the period required for airtightness is T, the internal pressure P1 is maintained higher than the external pressure P2 if the following equation is satisfied. Can do.

When V1 = 9L, V2 = 1L, P1 = 1000 kPa, P2 = 101.3 kPa, and P3 = 105.3 kPa, the leak rate at which the internal pressure becomes equal to the external pressure in 10 days is about 1 Pa · L / sec. Since the leak rate of a general O-ring is about 1 × 10 ⁻¹ to 1 × 10 ⁻⁴ Pa · L / sec, set the parameters to satisfy the above formula to prevent in-leak for 10 days after the accident. Is possible.

[Second Embodiment]
The second embodiment is a modification of the first embodiment, and a pressure detector is used as the environmental abnormality detector 16. For example, a diaphragm type pressure gauge can be used as the pressure detector. Other configurations are the same as those of the first embodiment.

  During a severe accident at a nuclear power plant, it is conceivable that not only the temperature but also the pressure rises abnormally at the position where the radiation measuring apparatus 11 is installed. In that case, the gas outside the detector container 17 flows into the detector container 17 due to the pressure increase outside the detector container 17, and the pressure inside the detector container 17 abnormally increases. An abnormal rise in pressure in the detector container 17 is detected by a pressure detector (environmental abnormality detector) 16. Thereby, similarly to the first embodiment, the switch 26 of the valve drive mechanism 23 is turned on, the motor-operated valve 22 is opened, and the inert gas in the high-pressure tank 20 flows into the detector container 17. Thereby, after that, the inflow of moisture from the outside of the detector container 17 into the detector container 17 can be prevented.

[Third Embodiment]
The third embodiment is a modification of the first embodiment. As the environmental abnormality detector 16, a radiation dose abnormality rise detector that detects an abnormal rise in the radiation dose in the detector container 17 is used. Other configurations are the same as those of the first embodiment.

  During a severe accident at a nuclear power plant, it is conceivable that not only the temperature but also the radiation dose will rise abnormally at the installation position of the radiation measuring device 11. Therefore, the radiation dose abnormality rise detector (environmental abnormality detector) 16 detects the radiation dose abnormality rise. Thereby, similarly to the first embodiment, the switch 26 of the valve drive mechanism 23 is turned on, the motor-operated valve 22 is opened, and the inert gas in the high-pressure tank 20 flows into the detector container 17. Thereby, after that, the inflow of moisture from the outside of the detector container 17 into the detector container 17 can be prevented.

  As a modified example in this case, the radiation detector 12 can also be used as the radiation dose abnormality rise detector (environmental abnormality detector) 16.

[Fourth Embodiment]
FIG. 3 is a schematic configuration diagram of a radiation measuring apparatus according to the fourth embodiment of the present invention.

  In this embodiment, a thermoplastic valve 30 is used instead of the motor-operated valve 22 (FIGS. 1 and 2) of the first to third embodiments. And in this embodiment, the valve drive mechanism 23 and the environmental abnormality detector 16 (FIG. 1, FIG. 2) are unnecessary. Other configurations are the same as those in the first to third embodiments.

  Normally, the thermoplastic valve 30 is closed. During a severe accident, the temperature around the detector container 17 rises abnormally, and the thermoplastic valve 30 is deformed and opened. As a result, as in the first to third embodiments, the inert gas in the high-pressure tank 20 flows out into the detector container 17 through the thermoplastic valve 30, and the pressure in the detector container 17 increases. . Thereby, moisture outside the detector container 17 can be prevented from flowing into the detector container 17, and malfunction and failure of the radiation detector 12 due to moisture can be prevented.

[Other Embodiments]
The features of the embodiments described above may be combined. For example, as the environmental abnormality detector 16 of the first to third embodiments, two or three of a temperature detector, a pressure detector, and a radiation dose abnormality rise detector are arranged in the detector container 17, When these environmental abnormality detectors 16 output abnormal outputs indicating the occurrence of severe accidents, the logic circuit is configured to turn on the switch 26 of the valve drive mechanism 23 according to the AND condition or the OR condition of those outputs. Can be considered. Thereby, the function of the radiation measuring apparatus 11 can be maintained while considering the reliability of various environmental abnormality detectors 16 and avoiding malfunctions.

  In the above description, the radiation measuring apparatus used in the nuclear power plant has been described. However, the radiation measuring apparatus is not limited to the nuclear power plant but can be applied to other nuclear material handling facilities.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 Radiation measuring device 12 Radiation detector 13 Connector 14 Cable 15 Pressurization device 16 Environmental abnormality detector (a temperature detector, a pressure detector, a radiation dose abnormality rise detector)
17 detector container 18 penetrating part 20 high pressure tank (cylinder)
21 Opening / closing mechanism 22 Electric valve 23 Valve drive mechanism 24 Electric motor 25 Battery 26 Switch 30 Thermoplastic valve

Claims (9)

A detector container that can be opened and closed;
A radiation detector housed in the detector container;
A cable extending through the detector container and connected to the radiation detector to supply power and transmit signals to the radiation detector;
A pressurizing device that is housed in the detector container and pressurizes the detector container to maintain a pressure in the detector container higher than the pressure outside the detector container for a predetermined period;
An environmental anomaly detector for detecting that the environment in the detector container is in an anomalous state affecting the operation of the radiation detector;
I have a,
The pressurizing device is configured to pressurize the inside of the detector container when the environmental anomaly detector detects an environmental anomaly in the detector container;
A radiation measuring apparatus characterized by the above. The pressure device is
A high-pressure tank capable of containing high-pressure gas higher than atmospheric pressure,
An opening / closing mechanism capable of releasing the high-pressure gas sealed in the high-pressure tank into the detector container outside the high-pressure tank;
The radiation measuring apparatus according to claim 1, further comprising:   The radiation measuring apparatus according to claim 2, wherein the opening / closing mechanism includes an electric valve and a valve driving mechanism that drives the electric valve. The environmental abnormality detector is a temperature detector,
The pressurizing device is configured to pressurize the inside of the detector container when the temperature detector detects an abnormal temperature rise in the detector container. 4. The radiation measuring apparatus according to any one of 3. The environmental abnormality detector is a pressure detector,
The pressurizing device is configured to further pressurize the inside of the detector container when the pressure detector detects an abnormal increase in pressure in the detector container. Item 5. The radiation measurement apparatus according to any one of Items 4 to 4 . The environmental anomaly detector is a radiation anomaly rise detector for detecting an anomalous dose rise in the detector container,
The pressurizing device is configured to pressurize the inside of the detector container when the detector for detecting an abnormal radiation dose rise detects an abnormal increase in the radiation dose in the detector container. The radiation measuring apparatus according to any one of claims 1 to 5 . The radiation measurement apparatus according to claim 6 , wherein the radiation dose abnormality rise detector is also used as the radiation detector . The radiation measuring apparatus according to claim 2 , wherein the opening / closing mechanism includes a thermoplastic valve that opens due to an abnormal temperature rise in the detector container . A detector container that can be opened and closed;
A radiation detector housed in the detector container;
A cable extending through the detector container and connected to the radiation detector to supply power and transmit signals to the radiation detector;
An environmental anomaly detector for detecting that the environment in the detector container is in an anomalous state affecting the operation of the radiation detector;
A method for measuring the radiation dose at a location where the humidity increases at the time of an accident using a radiation measuring device having
Detecting by the environmental abnormality detector that the environment in the detector container is in an abnormal state affecting the operation of the radiation detector at the time of the accident;
Increasing the pressure in the detector container above the pressure outside the detector container when the abnormal condition is detected;
Measuring the radiation dose using the radiation measuring device in a state where the pressure in the detector container is higher than the pressure outside the detector container;
A radiation measurement method comprising:

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