WO2015176553A1

WO2015176553A1 - Method for monitoring 16n leaked by nuclear power reactor steam generator

Info

Publication number: WO2015176553A1
Application number: PCT/CN2015/071668
Authority: WO
Inventors: 田志恒
Original assignee: 田志恒; 田立; 田陆
Priority date: 2014-05-21
Filing date: 2015-01-27
Publication date: 2015-11-26
Also published as: CN103985423A; CN103985423B

Abstract

A method for monitoring ¹⁶N leaked by a nuclear power reactor steam generator, the method comprising the following steps: S01, enabling a scintillator detection device comprising γ sources to maintain the scale peak of a stable γ energy spectrum to monitor the ¹⁶N leaked by a nuclear power reactor steam generator and generate a monitoring signal; S02, utilizing a signal processor to process the monitoring signal, and outputting a monitoring result. Utilizing the scintillator comprising γ sources avoids an uncertainty factor of the scintillator caused by a packaging process operation such as an embedded source, and solves the technical problem of false alarms affecting a monitoring result due to the low sensitivity of a monitoring system.

Description

16N monitoring method for leakage from nuclear power reactor steam generator

Technical field

The invention relates to the field of nuclear power reactor radiation monitoring, in particular to a ¹⁶ N monitoring method for leakage from a nuclear power reactor steam generator.

Background technique

Embedded into nuclear power reactors ^{241 Amα} source NaI (Tl) scintillator for decades history monitoring probe member leaking steam generator ¹⁶ N technology, currently still widely used, wherein the source for stabilizing α ¹⁶ The gamma spectrum of N, but the 3.5 MeV equivalent gamma energy peak region generated by ionization of ²⁴¹ Amα particles in the scintillator is wider (about 3.0-3.7 MeV, which is related to the in-line process), and is monitored in the ¹⁶ N technique. The -4.5MeV energy zone produces a high background count rate, and the monitoring system has low sensitivity and is prone to false alarms. The scintillator embedded with the alpha source also has technical problems such as causing uncertainty to the scintillator during the manufacturing process and affecting the monitoring result. In addition, the existing NaI(Tl) scintillator also has a problem that the detection efficiency and energy resolution of the ¹⁶ N monitoring are relatively low.

Summary of the invention

The object of the present invention is to provide a ¹⁶ N monitoring method for leaking out of a nuclear power reactor steam generator, so as to solve the technical problem that the monitoring system has low sensitivity and is prone to false alarms.

In order to achieve the above object, the present invention provides a ¹⁶ N monitoring method for a nuclear power reactor steam generator, comprising the following steps: S01, the scintillator detecting device containing the gamma source is retained after the background peeling The scaled peak of the stable gamma energy spectrum is used to monitor the ¹⁶ N leaked by the nuclear power reactor steam generator and generate a monitoring signal; S02, the signal processor is used to process the monitoring signal, and the monitoring result is output.

Further, in step S01, the background peeling means that the scintillator detecting device containing the gamma source is placed in the low background chamber for a sufficiently long period of time to reduce the statistical error of the obtained count to a negligible degree, and the result is obtained. The count is divided by the measurement time to give the count rate of each energy zone and the energy spectrum meter and stored; when the nuclear power reactor is measured in the field, the count rate of the graduated peak region is reserved for stabilizing the gamma energy spectrum, and the scale peak region is deducted. The count rate stored outside.

Further, in step S02, the monitoring result includes a count rate of three energy zones of 0.2-2.2 MeV, 2.2-4.5 MeV, 4.5-7.0 MeV, a peak height count rate of the ¹⁶ N characteristic peak, and an integral of the count rate integral. Count, and the count rate of the three energy zones, the peak height count rate of the ¹⁶ N characteristic peak, and the integral count of the integral count of the count rate over time, the count rate of each spectrum spectrometer, and the energy spectrum meter The energy score obtained by the count rate integration.

Further, the ¹⁶ N monitoring method leaked by the nuclear power reactor steam generator further comprises dividing the level of the nuclear power reactor steam generator leakage into a leakage warning level, a leakage level, and a leakage according to a counting rate of the 0.2-2.2 MeV energy region. The second step.

Further, when the nuclear power reactor steam generator leakage alarm is detected, the count rate of the three energy zones, the peak height count rate of the ¹⁶ N characteristic peak, and the integral count of the count rate integral over time are plotted, and The count rate of each channel of the spectrometer is integrated over the set time T to obtain the energy spectrum.

Further, the set time T is shortened as the leak level is increased.

Further, the monitoring results are displayed in real time and stored by the memory.

Further, the ¹⁶ N characteristic peak refers to an energy peak having gamma ray energies of 5.11 MeV, 5.62 MeV, and 6.13 MeV, respectively.

Further, the ¹⁶ N monitoring method leaked by the nuclear power reactor steam generator also includes the steps of the nuclear power reactor steam generator leakage simulation.

Further, the step of simulating the leakage of the nuclear power reactor steam generator means that the scintillation detecting device Ts containing the γ source is irradiated with the ¹⁶ N scale source for N times, and the energy spectrum obtained by averaging the N measurements is obtained. The video is shown in K*Ts time, where K is the ¹⁶ N scale source and the gamma source-containing scintillator detection device is in the 0.2-2.2 MeV energy zone and the nuclear power reactor steam generator leakage level is in the energy. The ratio of the count rate of the zone.

Further, if K<1, the video of the energy spectrum obtained by averaging the N measurements is fast-released in K*Ts time; if K>1, the energy spectrum obtained by N measurements is averaged. The video of the obtained energy spectrum was slowed down in K*Ts time.

Further, the scintillator of the scintillator detecting device containing the γ source is a LaBr ₃ :Ce scintillator.

Further, the 1.436 MeV γ-ray energy peak of the natural radionuclide ¹³⁸ La radiation contained in the LaBr ₃ :Ce scintillation body and the 0.037 MeV X-ray energy peak of the K electron capture radiation are coincident with the energy peak added to 1.473 MeV.

Further, the scale peak region refers to an energy interval in which the gamma ray energy is 1.434 to 1.497 MeV.

Further, the ¹⁶ N scale source is a ²³⁸ Pu- ¹³ C source.

The invention has the following beneficial effects:

The use of the scintillator containing the gamma source avoids the uncertainty of the packaging process operation such as the embedded source, and solves the technical problem that the monitoring system has low sensitivity and is prone to false alarms and affects the monitoring result.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The invention will now be described in further detail with reference to the drawings.

DRAWINGS

The accompanying drawings, which are incorporated in the claims In the drawing:

1 is a schematic diagram showing the steps of a ¹⁶ N monitoring method for a nuclear power reactor steam generator leaking according to the present invention;

FIG 2 is a monitoring method using LaBr ₃ ¹⁶ N leaking steam generator for nuclear reactor according to the present invention: Ce schematic front peeling detection means measuring the background;

FIG 3 is a monitoring method ¹⁶ N ₃ of the steam generator leaks out by LaBr nuclear reactor according to the present invention: Ce view after peeling detection means measuring the background;

FIG 4 is a stack with monitoring method LaBr ₃ ¹⁶ N leaking out of the steam generator according to the present invention, nuclear: Ce detecting means ¹⁶ N measured calibration source 50s schematic spectrum;

FIG 5 is (Tl) detection means ¹⁶ N measured calibration source 50s schematic stack with NaI spectrum monitoring method ¹⁶ N leaking out of the steam generator according to the present invention, nuclear power;

₃ LaBr FIG 6 is a leak monitoring method according to the present invention nuclear reactor steam generator ¹⁶ N: Ce-detecting means ¹⁶ N measured calibration source spectrum schematic 1800s; and

FIG 7 is (Tl) detection means ¹⁶ N measured calibration source schematic 1800s spectrum stack monitoring method using NaI ¹⁶ N leaking out of the steam generator according to the present invention is nuclear.

detailed description

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

Referring to FIG. 1 to FIG. 3, a ¹⁶ N monitoring method for leaking out of a nuclear power reactor steam generator according to the present invention includes the following steps: S01, the scintillator detecting device containing the γ source is left after the background peeling The scaled peak of the stable gamma energy spectrum is used to monitor the ¹⁶ N leaked by the nuclear power reactor steam generator and generate a monitoring signal; S02, the monitoring signal is processed by a signal processor, and the monitoring result is output. The use of the scintillator containing the gamma source avoids the uncertainty of the packaging process operation such as the embedded source, and solves the technical problem that the monitoring system has low sensitivity and is prone to false alarms and affects the monitoring result.

In step S01, the background peeling refers to placing the scintillator detecting device containing the gamma source in a low background chamber (such as a lead chamber) for a sufficiently long time to reduce the statistical error of the obtained count to a negligible degree. Dividing the obtained count by the measurement time gives the energy rate of each energy zone and the energy meter (the count rate of the present invention is the net count rate) and stores it; retains the scale peak when the nuclear power reactor is measured in the field. The count rate of the zone is used to stabilize the gamma spectrum while deducting the count rate stored outside of the graduated peak region. In the present embodiment, the LaBr ₃ :Ce scintillator detecting device is preferably a scintillator detecting device containing a γ source, and in other embodiments, other scintillator detecting devices containing a γ source suitable for high-energy gamma ray detection may be selected. Further, the scale peak refers to the 1.473 MeV energy peak of the sum of the 1.436 MeV γ-ray energy peak of the natural radionuclide ¹³⁸ La radiation and the 0.037 MeV X-ray energy peak of the K electron trapping radiation contained in the LaBr ₃ :Ce scintillation body, and the scale peak region is Refers to the energy range of gamma ray energy from 1.434 to 1.497 MeV.

Γ is to LaBr ₃ containing source: Ce scintillator detecting means described in detail as an example background release: the contents of the source γ LaBr _3: Ce scintillator detection means disposed lead measuring chamber for 48 hours, the resulting count by 48*3600 seconds gives the count rate N _b1 , N _b2 (unit: cps) of each energy region and each spectrum spectrometer (4096 channels in total) and stores it; the gamma ray energy is 1.434-1.497 MeV when measured in the field. The energy interval is the count rate of each channel of the 886-925 channel on the energy spectrum meter for stabilizing the gamma energy spectrum, and subtracting the energy interval, that is, the count rate stored outside the channel interval (that is, each obtained in the field measurement) The count rate of the energy spectrum and the energy spectrum of each channel except the energy range of 1.434-1.497MeV and the energy spectrum of each channel except 886-925 ). Figures 2 and 3 show the energy spectra of the substrate before and after stripping (under normal conditions) using a LaBr ₃ :Ce detector. After the background peeling, the background count rate of the 0.2-2.2 MeV energy region was measured by the LaBr ₃ :Ce scintillator detection device to be only 10 cps. However, the background count of the 0.2-2.2 MeV energy region was measured by the NaI(Tl) scintillator detection device to be 186 cps.

In step S02, the monitoring result includes a count rate of three energy zones of 0.2-2.2 MeV, 2.2-4.5 MeV, 4.5-7.0 MeV, a peak height count rate of ¹⁶ N characteristic peaks, and an integral count of the integrals of these count rates, and The count rate of the three energy zones, the peak height count rate of the ¹⁶ N characteristic peaks, and the integral count of the integration counts of these count rates over time, the count rate of each spectrum spectrometer, and the count of each channel of the spectrometer The energy spectrum obtained by the rate integral. Wherein, when the nuclear power reactor steam generator leakage alarm is detected, the count rate of the above three energy zones, the peak height count rate of the ¹⁶ N characteristic peak, and the integral count of the integrated count of these count rate integrals are outputted, And the count rate of each of the spectrometers is integrated over the set time T, and further, the set time T is shortened as the leak level is increased. For easy viewing and analysis, the above monitoring results are displayed in real time and stored in memory. Further, the ¹⁶ N characteristic peak refers to an energy peak having gamma ray energies of 5.11 MeV, 5.62 MeV, and 6.13 MeV, respectively.

Optionally, in addition to the steps of S01 and S02, the method of the present invention further comprises dividing the level of leakage of the nuclear power reactor steam generator into a leakage warning level, a leakage level, and a leakage level according to a counting rate of a 0.2-2.2 MeV energy region. The steps, as well as the steps of the simulation of the nuclear power reactor steam generator leak.

Two-stage leak levels are currently used when dividing the nuclear power reactor steam generator leakage levels. The threshold level of the leakage of these two stages is based on the count rate of the 0.2-2.2 MeV energy zone measured by the NaI(Tl) scintillator detection device embedded with the alpha source: Ne=500 cps (leakage level), Nc=8500 cps (leakage) Level 2). In view of LaBr _3: Ce scintillator ¹⁶ N measured for a high detection efficiency and energy resolution and low background count rate after the release of this bottom, the leakage can be provided early warning threshold level Np = 100cps, to achieve early warning. Experiments have shown that the count rate of the ¹⁶ N scale source in the energy range of 0.2-2.2 MeV is 1.21 times that of NaI(Tl) using the LaBr ₃ :Ce scintillator detection device (as shown in Table 1).

Table 1 is a comparison chart of the counting rate of the 1800s of the ¹⁶ N scale source measured by LaBr ₃ :Ce and NaI(Tl) using the ¹⁶ N monitoring method leaked by the nuclear power reactor steam generator according to the present invention.

From this, it is estimated that when the count rate of the 0.2-2.2 MeV energy region is measured by the LaBr ₃ :Ce scintillator detecting device containing the γ source, the three leakage level thresholds of Np, Ne, and Nc are 121 cps, 605 cps, and 10285 cps, respectively. Table 2).

Table 2 is a leakage simulation data table of the ¹⁶ N monitoring method leaked by the nuclear power reactor steam generator according to the present invention.

Therefore, the leak warning level threshold of the LaBr ₃ :Ce scintillator detection device is 12 times (121/10) of its background count rate, which has higher reliability; and the leakage of the NaI (Tl) scintillator detection device is adopted. The warning level threshold is 0.54 times (100/186) of its background count rate, and the leak warning level cannot be set.

Figure 4 and Figure 5 show the energy spectrum after averaging the ¹⁶ N scale source for 5 seconds using the LaBr ₃ :Ce and NaI(Tl) scintillation detectors (the high-energy end of the energy spectrum of the linear coordinate system is shown) As a general method, this embodiment is magnified 100 times display), according to the energy spectrum of 4096 channels, it is shown that due to the low detection efficiency and poor energy resolution of the NaI(Tl) scintillator, it is also an integral count of 50 seconds, which is not only low in amplitude ( The 6.13 MeV energy peak is 4.2 times lower, the 5.62 MeV energy peak is 2.3 times lower, and the fluctuation is larger. Only some divergent spikes can be seen, and the well-defined ¹⁶ N characteristic peak image is not seen. Preferably, the ¹⁶ N scale source is a ²³⁸ Pu- ¹³ C source.

Due to the low probability of leakage of the nuclear power reactor steam generator, for example, some nuclear power plants have not experienced a steam generator leakage accident since the start of operation. In order to obtain the true situation of the nuclear power reactor steam generator leakage, the leakage law is known in advance. To provide a basis for a real leak in the future, it is necessary to perform a leak simulation. Leakage simulation refers to the use of a ¹⁶ N scale source to illuminate the scintillator detection device Ts containing the γ source for N times, and the video of the energy spectrum obtained by averaging the N measurements is displayed in K*Ts time. The K is a ¹⁶ N scale source illuminating the ratio of the count rate of the scintillator detection device containing the gamma source in the energy range of 0.2-2.2 MeV to the count rate of each leak level of the nuclear power reactor steam generator in the energy region. Further, if K<1, the video of the energy spectrum obtained by averaging the N measurements is fast-released in K*Ts time; if K>1, the energy spectrum obtained by N measurements is averaged. The video of the obtained energy spectrum was slowed down in K*Ts time.

It can be seen from the data in Table 1 that the count rates in the energy range of 0.2-2.2 MeV are 21.3, 4.26, and 0.25 times of the three leak level count rates of Np, Ne, and Nc, respectively (this value and the activity of the ¹⁶ N scale source used). related). Therefore, the screen recording of all 50s spectrum of Figure 4 and Figure 5 is extended to 1066s and 213s slow release, which can simulate the rise of the steam generator leakage warning level and the leakage level of the integral count over time; also for Figure 4 and Figure 5 The screen recording of all 50s energy spectrum is shortened to 12.5s fast release, which can simulate the rise of the integral count of the nuclear power reactor steam generator leakage level over time. Similarly, the leakage simulation of the nuclear power reactor steam generator can be performed according to the counting rate of 2.2-4.5MeV, 4.5-7MeV, 0-7MeV energy region or the peak height counting rate of 5.11MeV, 5.62MeV and 6.13MeV energy peaks. ,As shown in table 2.

As shown in Fig. 6 and Fig. 7, the energy spectrum (logarithmic coordinates) of the 1800s of the ¹⁶ N scale source is measured by the LaBr ₃ :Ce and NaI(Tl) scintillator detection device. The former has excellent energy spectrum for the ¹⁶ N characteristic peak. In the latter.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

The method of the present invention provides LaBr _3: Ce scintillator ¹⁶ N for measuring the ratio of NaI (Tl) scintillator with a higher detection efficiency and energy resolution, leaving only 1.473MeV energy peak after a background process scale peak release The background count rate in the energy range of 0.2-2.2 MeV and 2.2-4.5 MeV is only 5% and 0.7% of the embedded α-source NaI(Tl) scintillator, which can balance 0.2-2.2 MeV, 2.2-4.5 MeV, 4.5. The count rate of the three energy regions of -7.0 MeV and the peak height count rate of the ¹⁶ N characteristic peak. Especially when the leak alarm occurs, the detection system immediately starts the integral counting function for integrating these counting rates, and measures the integral count of each of the three energy zones and the characteristic peak of ¹⁶ N as time rises in time, only one or two minutes. The real image of the leak can be displayed, and the true and false alarms are easy to distinguish and there will be no false alarms. In view of the fact that the selected scintillator has the advantages of high detection efficiency and low background count rate after background stripping, the leakage warning level which increases the leakage alarm sensitivity of the nuclear power reactor steam generator by 5 times is increased. The use of the LaBr ₃ :Ce scintillator containing the γ source avoids the technical problems such as the inconsistency of the encapsulation process by the embedded source and the like, which affects the monitoring result.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

A 16 N monitoring method for leakage from a nuclear power reactor steam generator, comprising the steps of:

S01, the scintillator detecting device containing the gamma source retains a stable peak of the stable gamma spectrum after the background is stripped, and is used for monitoring the 16 N leaked by the nuclear power reactor steam generator and generating a monitoring signal;

S02: The monitoring signal is processed by a signal processor, and the monitoring result is output.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 1, wherein in the step S01, the background peeling refers to the scintillating body containing the γ source. The detection device is placed in the low background chamber for a sufficient period of time to reduce the statistical error of the obtained count to a negligible degree, and the obtained count is divided by the measurement time to give the count rate of each energy region and the energy spectrum meter and store The count rate of the scale peak region is retained during the on-site measurement of the nuclear power reactor for stabilizing the gamma energy spectrum, and the count rate stored outside the scale peak region is subtracted.
A 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 1, wherein

In step S02, the monitoring result includes a count rate of three energy regions of 0.2-2.2 MeV, 2.2-4.5 MeV, 4.5-7.0 MeV, a peak height count rate of a 16 N characteristic peak, and an integral of the count rate. The integral count, and the count rate of the three energy zones, the peak height count rate of the 16 N characteristic peak, and the curve of the integral count obtained by integrating the count rate with time, the count rate of each channel of the spectrometer, and the pair The energy spectrum obtained by integrating the count rate of each spectrum spectrometer.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to any one of claims 1 to 3, characterized in that it further comprises generating nuclear power reactor steam according to a counting rate of a 0.2-2.2 MeV energy region. The level of leakage is divided into the steps of leakage warning level, leakage level, and leakage level.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 3, wherein the three energy zones are outputted when the nuclear power reactor steam generator leakage alarm is detected The count rate, the peak height count rate of the 16 N characteristic peak, and the curve of the integral count obtained by integrating the count rate over time, and the count rate of each track of the spectrometer are integrated every set time T Energy spectrum.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 5, wherein the set time T is shortened as the leakage level is increased.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to any one of claims 1 to 3, characterized in that the monitoring result is displayed in real time and stored by a memory.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 3 or 5, wherein the 16 N characteristic peak means that the gamma ray energy is 5.11 MeV, 5.62 MeV and 6.13, respectively. The energy peak of MeV.
The 16 N monitoring method for a nuclear power reactor steam generator leak according to claim 8, further comprising the step of simulating the nuclear power reactor steam generator leakage simulation.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 9, wherein the step of simulating the nuclear power reactor steam generator leakage means that the 16 N scale source is irradiated with the content The gamma source scintillator detecting device Ts takes N times, and the video of the energy spectrum obtained by averaging the N measurements is displayed in K*Ts time, wherein the K is a 16 N scale source illuminating γ The ratio of the count rate of the source scintillator detection device in the 0.2-2.2 MeV energy region to the count rate of each leakage level of the nuclear power reactor steam generator in the energy region.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 10, wherein if K < 1, the average energy spectrum obtained by averaging the N measurements is recorded. The K*Ts time is fast-release; if K>1, the spectrum of the energy spectrum obtained by averaging the N measurements is slowed down in K*Ts time.
The 16 N monitoring method for leakage from a nuclear power reactor steam generator according to any one of claims 1, 2 or 10, wherein the scintillator of the gamma source-containing scintillator detecting device is LaBr 3 : Ce scintillator.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 12, wherein the LaBr 3 :Ce scintillation body contains 1.436 MeV γ ray energy of the natural radionuclide 138 La radiation. The 0.037 MeV X-ray energy peak of the peak and K electron trapping radiation is equal to the energy peak added to 1.473 MeV as the scale peak.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 2, wherein the scale peak region refers to an energy interval in which the gamma ray energy is 1.434 - 1.497 MeV.
The 16 N monitoring method for leaking out of a nuclear power reactor steam generator according to claim 10, wherein the 16 N scale source is a 238 Pu- 13 C source.