CN115236717A - A Critical Accident Detection Method - Google Patents

Abstract

The invention relates to a critical accident detection method, which belongs to the field of critical accident detection. The critical accident identification and alarm are carried out through multi-signal and multi-dimension, which reduces the omission rate of critical identification and improves the critical accident identification capability of a critical accident alarm system. The health and safety protection of workers provides favorable guarantees. In order to improve the detection accuracy and sensitivity of critical accidents, the location of the detector is determined according to the dose rate distribution of the three-dimensional dose field, and the background cumulative dose of the detector under normal operation is deducted when calculating the cumulative dose, so that the critical accident judgment result is more accurate. Accurate and credible, laying the foundation for the health and safety protection of workers. The critical accident detection method disclosed by the invention has the advantages of low false alarm rate, strong critical accident identification ability, high determination accuracy and sensitive response.

Description

A Critical Accident Detection Method

technical field

The invention belongs to the field of critical accident detection, in particular to a critical accident detection method.

Background technique

According to GB15146.9 and other regulations and standards, in an independent area, any operation involving fissile isotopes of more than 700g ²³⁵ U, 520g ²³³ U, 450g plutonium or any combination of these isotopes must be evaluated. The need for an alarm system. In areas requiring critical accident alarm coverage, means must be provided to detect excess radiation doses or dose rates and to signal evacuation of personnel.

Therefore, an important issue is how to trigger the critical accident alarm system to generate an alarm. The design of the critical alarm system should be able to ensure that the alarm can also be triggered when the minimum critical accident concerned occurs. The minimum critical accident concerned is defined in GB15146.9 The total absorbed dose of neutron and gamma radiation induced in free air at a distance of 2 m from the reacting object within 60 s is 0.2 Gy under unshielded conditions. From this definition, it can be seen that the definition of the minimum criticality accident of interest is based on the dose rate.

However, according to the simulation experiments, this critical accident judgment standard for dose rate can only identify the critical accident with rapid power growth and issue an alarm signal. When some critical accidents with slow power growth occur, the dose rate may be lower than the defined value. In this case, if it is not recognized as a critical accident, the critical accident alarm system is not alarmed, and the staff is exposed to this accident. It will also lead to a high cumulative dose for a long time, which will cause harm to the human body.

In these low-power critical accidents with a dose rate below the standard 0.2Gy/min, there is no instrument other than a neutron counter to indicate an accident, and no sound or light can indicate an accident, but It will cause harm to the staff, and even bring fatal injury to the staff. Therefore, the critical accident identification and alarm only based on the dose rate has certain limitations, there is the possibility of missing reports, and it is easy to bring huge security risks.

SUMMARY OF THE INVENTION

Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a critical accident detection method, which can identify and alarm critical accidents based on dose rate and cumulative dose, improve the critical accident identification capability of the critical accident alarm system, and improve work efficiency. The health and safety protection of personnel provides favorable guarantees.

In order to achieve the above purpose, the technical scheme adopted in the present invention is:

A criticality accident detection method, the method comprises the steps of:

S1. Set up critical accident source items that meet the requirements of the standard according to the standard regulations and the actual equipment location of the plant;

S2, performing a three-dimensional dose field analysis of a critical accident according to the critical accident source item information;

S3. Determine the arrangement position of the detector and the detection limit of the detector according to the dose rate distribution of the three-dimensional dose field of the critical accident, where the detection limit includes a dose rate limit and a cumulative dose limit;

S4. Compare the dose rate of the detection data of the detector with the dose rate limit, and when the dose rate of the detector detection data exceeds the dose rate limit, it is determined as a critical accident;

If the dose rate limit is not exceeded, the cumulative dose of the detector detection data is further compared with the cumulative dose limit, and when the cumulative dose detected by the detector exceeds the cumulative dose limit, It is judged as a critical accident.

In this way, the detection can also be performed better when a small critical accident occurs, so as to protect the health of the operator.

Further, the standard described in step S1 is the GB15146.9 standard, and the dose rate specified in the GB15146.9 standard is 0.2 Gy/min when the dose rate is generated at a distance of 2 m from the equipment.

Further, the critical accident source item information in step S2 includes the particle number and energy spectrum of the equipment corresponding to the critical accident source item.

Further, in step S3, the arrangement position of the detector is determined according to the three-dimensional dose field dose rate distribution, and the dose rate limit value of the detector is the three-dimensional dose field dose rate value corresponding to the arrangement position of the detector, The cumulative dose limit of the detector is the product of the standard specified time t and the dose rate limit.

Further, in step S3, the arrangement position of the detector is the central position of the maximum dose rate of the three-dimensional dose field, the dose rate limit of the detector is the maximum dose rate of the three-dimensional dose field, and the detector The cumulative dose limit of is the product of the standard specified time t and the maximum dose rate of the three-dimensional dose field.

Further, the detector includes a neutron detector and a photon detector, and the detection data of the detector includes the detection data of the neutron detector and the photon detector.

Further, the cumulative dose of the data detected by the detector is a corrected cumulative dose obtained by subtracting the cumulative background dose during normal operation from the original cumulative dose data detected by the detector.

Further, the cumulative background dose in normal operation is equal to the local dose rate of the detector in normal operation times the cumulative operating time.

Further, step S4 further includes: when it is determined as a critical accident, triggering a critical accident alarm.

Further, the standard stipulates that the time t is 60s.

The effects of the present invention are: the critical accident detection method disclosed in the present invention can perform critical accident identification and alarm through multi-signal and multi-dimension, which reduces the missed alarm rate of critical identification and improves the critical accident identification of the critical accident alarm system. It provides a favorable guarantee for the health and safety protection of the staff.

In order to further improve the detection accuracy and sensitivity of critical accidents, the detector is set at the position with the maximum detection signal strength, and the background cumulative dose of the detector under normal operation is deducted when calculating the cumulative dose, so that the critical accident judgment result is more accurate. Credible, laying the foundation for the health and safety protection of workers.

Description of drawings

1 is a method flowchart of a critical accident detection method shown in an embodiment of the present invention;

Figure 2 is the distribution diagram of the dose rate distribution of the wall of the building during the critical accident, which is obtained by the three-dimensional dose field analysis using the critical accident source term that meets the requirements of the standard.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

Example 1

As shown in FIG. 1, an embodiment of the present invention discloses a critical accident detection method, and the method includes the steps:

S1. According to the standard requirements and the actual equipment location of the plant, set up critical accident source items that meet the requirements.

When designing a critical accident alarm system, each channel should include a neutron probe and a photon probe. In the actual design, redundancy should be considered, and two or multiple channels can be used to respond together. In this embodiment, only one channel is described.

In this embodiment, according to the definition in the standard GB15146.9, when the dose rate generated at a distance of 2 m from the equipment is 0.2 Gy/min, the equipment can be set as the corresponding critical accident source item. Assuming that for a spherical device, it is calculated that when the frequency of fission is 9.06*E ¹³ fission/second, a dose rate of 0.2Gy/min can be generated at a distance of 2m from the device, which is regarded as the critical accident source term.

In fact, the selected standard is not limited to the GB15146.9 standard, and can be adjusted according to the actual situation.

S2. Perform critical accident three-dimensional dose field analysis according to the critical accident source item information determined in step S1.

According to the critical accident source item information determined in step S1, the three-dimensional dose field of the workshop is determined when a critical accident occurs.

The critical accident source item information includes the particle number and energy spectrum of the source item equipment.

Assuming that the spherical equipment is located in the middle of the factory building, and there is only one device in the factory building, the critical accident alarm system is to be arranged on the wall of the factory building. As shown in Fig. 2, using the source term in step S1, the dose rate of the building wall is obtained by performing three-dimensional volume field analysis and calculation.

S3. According to the three-dimensional dose field of the critical accident, combined with the three-dimensional dose field during normal operation, determine the arrangement position of the detector.

Generally speaking, in a factory where personnel can operate, the dose in the air is relatively small. Setting the detector at the maximum dose rate position can improve the response speed of the detector and the signal-to-noise ratio of the detection signal, which is not limited in fact. , as long as the detector is arranged at a position where the dose rate is relatively high, at the position where the detector is arranged, a detector whose detection signal strength is within the sensitive range of the detector is used.

It can be seen from the figure that the maximum dose rate of the wall of the factory building is 10mGy/h, and the signal intensity detected by the detector set here is the largest, which is beneficial to improve the response speed of the detector and the signal-to-noise ratio of the detection signal, improve the detection accuracy and sensitivity.

Therefore, in this embodiment, the detector is placed at the center position of 10 mGy/h in the figure. After analysis, under normal operating conditions, the dose rate at this point is 0.0001 mGy/h. Since it is many orders of magnitude smaller than the accident state, it can be ignored in the analysis.

S4. According to step S3, the detection limit of the detector is determined according to the maximum dose rate value at the detector position, and the detection signal of the detector is processed. First, the sum of the dose rates detected by the neutron and photon detectors is compared with the detection limit. , when the sum of the dose rates detected by the neutron and photon detectors exceeds the detection limit, it is judged as a critical accident and a critical accident alarm is triggered.

If the detection limit is not exceeded, the sum of the cumulative dose detected by the neutron and photon detectors is further compared with the cumulative dose limit corresponding to the standard specified dose rate, and the sum of the cumulative dose detected by the neutron and photon detectors exceeds the standard specified dose. When the cumulative dose limit corresponding to the rate is exceeded, it is judged as a critical accident, and a critical accident alarm is also triggered.

Following the above example, according to step S2, the dose rate limit is determined to be 10mGy/h. When the total detected dose rate of the detector photon and neutron probe exceeds 10mGy/h, it is determined as a critical accident and a critical accident alarm is triggered.

The dose rate limit determined in step S2 is 10mGy/h, and the cumulative dose limit is determined according to the dose level of 1min, which is 0.167mGy (10mGy/h÷60min/h=0.167mGy/min). The dose rate is 0.0001mGy/h. Therefore, in order to eliminate environmental interference and improve the measurement accuracy, the corrected cumulative dose obtained after subtracting the cumulative background dose detected by the detector from the cumulative background dose during normal operation should be compared with the cumulative dose limit. In comparison, when the cumulative dose of the detector minus the normal operating dose reaches 0.167mGy, it is judged as a critical accident and an alarm will also be triggered.

For example, when the detector records a dose rate of 12mGy/h at a certain moment, exceeding the dose rate limit of 10mGy/h, it is judged as a critical accident and the alarm system will be triggered. When the dose rate level recorded by the detector has been fluctuating around 0.5mGy/h, it did not exceed 10mGy/h, but at 20 minutes, its cumulative dose reached 0.17mGy, minus the cumulative background dose generated by normal operation for 20 minutes 0.0001* 20=0.002mGy, which is 0.168mGy, more than 0.167mGy, therefore, the alarm will also be triggered.

The accumulated dose of the detection data of the detector is the integral of the detection dose at each moment.

It can be seen from the above embodiments that the critical accident detection method disclosed in the present invention uses multi-signal and multi-dimensional identification and alarming of critical accidents, which reduces the missed alarm rate of critical identification and improves the critical accident identification of the critical accident alarm system. It provides a favorable guarantee for the health and safety protection of the staff. In order to improve the detection accuracy and sensitivity of critical accidents, the detector is set at the position with the maximum detection signal strength, and the background cumulative dose of the detector under normal operation is deducted when calculating the cumulative dose, so that the critical accident judgment result is more accurate and reliable. The letter laid the foundation for the health and safety protection of the staff. It has the advantages of low false negative rate, strong critical accident identification ability, high judgment accuracy and sensitive response.

The method described in the present invention is not limited to the examples described in the specific implementation manner. Those skilled in the art can obtain other implementation manners according to the technical solutions of the present invention, which also belong to the technical innovation scope of the present invention.

Claims (10)

1. A method of critical event detection, the method comprising the steps of:

s1, setting a critical accident source item meeting the standard requirement according to standard regulations and actual plant equipment positions;

s2, performing critical accident three-dimensional dose field analysis according to the critical accident source item information;

s3, determining the arrangement position of a detector and the detection limit value of the detector according to the dose rate distribution of the critical accident three-dimensional dose field, wherein the detection limit comprises dose rate limit and accumulated dose limit;

s4, comparing the dose rate of the data detected by the detector with the dose rate limit value, and judging as a critical accident when the dose rate of the data detected by the detector exceeds the dose rate limit value;

if the dosage rate limit value is not exceeded, the accumulated dosage of the detector detection data is further compared with the accumulated dosage limit value, and when the accumulated dosage detected by the detector exceeds the accumulated dosage limit value, a critical accident is determined.

2. A critical accident detection method according to claim 1, wherein: the standard in step S1 is the GB15146.9 standard, which stipulates a dose rate of 0.2Gy/min for a dose rate generated at a distance of 2m from the apparatus.

3. A critical accident detection method according to claim 2, wherein: and the critical accident source item information in the step S2 comprises the particle number and the energy spectrum of the equipment corresponding to the critical accident source item.

4. A critical accident detection method according to claim 3, wherein: and S3, determining the arrangement position of the detector according to the three-dimensional dose field dose rate distribution, wherein the dose rate limit value of the detector is the dose rate numerical value of the three-dimensional dose field corresponding to the arrangement position of the detector, and the accumulated dose limit value of the detector is the product of the standard specified time t and the dose rate limit value.

5. A critical accident detection method according to claim 4, wherein: in step S3, the arrangement position of the detector is the central position of the maximum dose rate of the three-dimensional dose field, the dose rate limit value of the detector is the maximum dose rate of the three-dimensional dose field, and the accumulated dose limit value of the detector is the product of the standard specified time t and the maximum dose rate of the three-dimensional dose field.

6. A critical accident detection method according to claim 1, wherein: the detector comprises a neutron detector and a photon detector, and the detector detection data comprises the neutron detector and the photon detector detection data.

7. A critical accident detection method according to claim 1, wherein: the accumulated dose of the data detected by the detector is a corrected accumulated dose obtained by subtracting the accumulated background dose in normal operation from the original accumulated dose data detected by the detector.

8. A critical accident detection method according to claim 7, wherein: the accumulated background dose during normal operation is equal to the local dose rate of the detector multiplied by the accumulated operation time during normal operation.

9. A critical accident detection method according to claim 1, wherein step S4 further comprises: and triggering a critical accident alarm when the critical accident is judged.

10. A critical accident detection method according to any one of claims 4 or 5, wherein: the standard specifies a time t of 60s.

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