Method for nuclear power plant primary coolant sampling and gamma spectrum analysis

Abstract

The present application relates to nuclear power plant nuclear chemistry sampling analysis technical field, specifically to a kind of nuclear power plant one loop coolant sampling analysis gamma spectrum method.The method comprises: step one: obtaining one loop coolant sample;And calculate the time interval t of sample from leaving one loop coolant system ideal water to entering sample bottle;Step two: one loop coolant sample decay treatment, in high-purity germanium gamma spectrometer analysis input system setting, measure sample nuclide specific activity.Step three: calculate FRI value by the nuclide I-134 and nuclide I-131 specific activity data obtained.The method is by the technical means that the sampling time of input high-purity germanium gamma spectrometer becomes T0-t time, realizes the technical effect that the RCP high radioactivity sample is stored in nuclear island laboratory, improves overall analysis speed, reduces the chemical collective irradiation dose of each unit.

Description

Technical Field

[0001] This invention relates to the field of nuclear chemical sampling and analysis technology in nuclear power plants, specifically to a method for analyzing gamma spectra of primary coolant samples from nuclear power plants. Background Technology

[0002] Nuclear power plants periodically monitor the gamma spectrum of the coolant in the reactor primary coolant system (RCP) to obtain the specific activity of nuclides including I-131 and I-134. This activity is then used to calculate the World Nuclear Organization Fuel Reliability Index (FRI value) to determine whether nuclear fuel is currently damaged.

[0003] Current methods for analyzing gamma spectroscopy in primary coolant samples at nuclear power plants start timing from the end of sampling, place the sample in a laboratory for decay, and begin measuring the gamma spectrum using a high-purity germanium gamma spectrometer (HPGe). However, this method ignores the time interval between the ideal RCP coolant entering the sampling line and the coolant sample flowing into the sample vial. During this time, coolant samples I-131 and I-134 continuously decay, leading to lower specific activities of I-131 and I-134 measured by existing methods, thus reducing the accuracy of calculated FRI values. Based on experience with physical fuels in nuclear power plants, when the FRI value calculated from the primary coolant iodine radioactivity data exceeds 0.037, resampling and analysis are necessary to verify the authenticity of the gamma spectroscopy data. This will result in increased primary coolant leakage, increased personnel radiation dose, and increased chemical analysis and control time. Summary of the Invention

[0004] The purpose of this invention is to provide a method for sampling and analyzing gamma spectra of primary coolant in nuclear power plants, which solves the technical problems of large deviations between the measured specific activity of radionuclides and the true specific activity in current methods for sampling and analyzing gamma spectra of primary coolant, resulting in inaccurate FRI values, increased leakage of primary coolant, increased radiation dose to personnel, and increased chemical analysis control time.

[0005] The technical solution of the present invention:

[0006] This invention provides a method for sampling and analyzing the gamma spectrum of the primary coolant in a nuclear power plant, the method comprising:

[0007] Step 1: Obtain a sample of the primary coolant and record the sampling start time T0; and calculate the time interval t between the sample leaving the ideal water body of the primary coolant system and entering the sample bottle;

[0008] Step 2: Decay treatment of the primary coolant sample, and measurement of the sample nuclide specific activity in the high-purity germanium gamma spectrometer analysis input system settings.

[0009] Step 2.1: Place the sample in the laboratory and allow it to decay to time T1. Input the sampling end time into the high-purity germanium gamma spectrometer and input the value to time T0-t. Measure the I-134 specific activity using the high-purity germanium gamma spectrometer.

[0010] Step 2.2: Place the sample in the laboratory to decay to time T2. Input the sampling end time into the high-purity germanium gamma spectrometer and input the value as time T0-t. Measure the specific activity of I-131 using the high-purity germanium gamma spectrometer.

[0011] Step 3: Calculate the FRI value using the specific activity data of nuclide I-134 and nuclide I-131.

[0012] In some embodiments, step one specifically includes: reading and recording the sampling pipeline flow rate f, then opening the primary loop sampling valve to obtain the primary loop coolant sample, filling a specific sampling bottle with the sample to complete the sampling, and recording the sampling start time T0; using formula (1) to calculate the time interval t from when the coolant sample leaves the ideal water body of the primary loop coolant system to when it enters the sample bottle, where V is the sampling pipeline volume and f is the sampling pipeline flow rate;

[0013] t = V / f (1);

[0014] In some embodiments, the settings of the high-purity germanium gamma spectrometer include: sampling end time, sample vial volume, scale, and nuclide library.

[0015] In some embodiments, time T1 is one hour after time T0-t.

[0016] In some embodiments, time T2 is 3 days after time T0-t.

[0017] In some embodiments, the actual decay time of the sample placed in the laboratory until time T1 is 1 h-t; the actual decay time of the sample placed in the laboratory until time T2 is 3 days-t.

[0018] In some embodiments, step three includes: after measuring the specific activity of I-131, substituting the specific activities of I-131 and I-134 into the fuel reliability index calculation formula to obtain the fuel reliability index value.

[0019] The implementation of this invention has the following beneficial effects:

[0020] This invention provides a method for sampling and analyzing gamma spectra of primary coolant in nuclear power plants. This method, by inputting the HPGe sampling time as T0-t, reduces the storage time of highly radioactive RCP samples in the nuclear island laboratory, improves overall analysis speed, and lowers the collective chemical radiation dose for each unit. This method also reduces systematic errors caused by sampling, obtaining more accurate iodine specific activity data and more reliable FRI values ​​in the coolant. Furthermore, this method reduces FRI value deviations and the need for subsequent repeated sampling and analysis verification, as well as reducing primary coolant leakage and highly radioactive wastewater, thus reducing analytical work time and costs, and lowering personnel radiation dose. Attached Figure Description

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Figure 1 This is a schematic diagram of a method for sampling and analyzing gamma spectra of primary coolant in a nuclear power plant, as proposed in an embodiment of the present invention.

[0023] Figure descriptions: 1. Reactor pressure vessel; 2. Steam generator; 3. Main pump; 4. Delay coil; 5. Flow meter; 6. Boron meter; 7. Sampling valve; 8. Sampling bottle. Detailed Implementation

[0024] like Figure 1 As shown, a method for sampling and analyzing the gamma spectrum of the primary coolant in a nuclear power plant is described. The method includes:

[0025] Step 1: Obtain a primary coolant sample; and calculate the time interval t from when the sample leaves the ideal water body of the primary coolant system to when it enters the sample bottle. Specifically, this includes: reading and recording the flow rate f of the sampling pipeline, then opening the primary sampling valve 7 to obtain the primary coolant sample, filling the sample bottle 8 with the sample to complete the sampling, and recording the sampling end time T0; using formula (1) to calculate the time interval t from when the coolant sample leaves the ideal water body of the primary coolant system to when it enters the sample bottle, where V is the volume of the sampling pipeline and f is the flow rate of the sampling pipeline.

[0026] t = V / f (1);

[0027] Step 2: Decay treatment of the primary coolant sample, and measurement of the sample nuclide specific activity in the high-purity germanium gamma spectrometer analysis input system settings.

[0028] Step 2.1: Place the sample in the laboratory and allow it to decay to time T1. Input the sampling end time value as T0-t into the high-purity germanium gamma spectrometer and measure the I-134 specific activity using the high-purity germanium gamma spectrometer. The settings for the high-purity germanium gamma spectrometer include: sampling end time, sample vial volume, scale, and nuclide library.

[0029] Step 2.2: Place the sample in the laboratory to decay to time T2. Input the sampling end time into the high-purity germanium gamma spectrometer and input the value as time T0-t. Measure the specific activity of I-131 using the high-purity germanium gamma spectrometer.

[0030] Step 3: Calculate the FRI value using the obtained specific activity data of nuclides I-134 and I-131. Specifically, this includes: after measuring the specific activity of I-131, substituting the specific activities of I-131 and I-134 into the fuel reliability index calculation formula to obtain the fuel reliability index value.

[0031] In some embodiments, time T1 is 1 hour after time T0-t. Time T2 is 3 days after time T0-t. The actual decay time of the sample in the laboratory until time T1 is 1 h-t; the actual decay time of the sample in the laboratory until time T2 is 3 days-t.

[0032] This method, by converting the HPGe sampling time to T0-t, reduces systematic errors introduced by sampling, resulting in more accurate coolant iodine specific activity data and more reliable FRI values. It also reduces deviations in fuel reliability indicators and the need for subsequent repeated sampling and analysis, as well as primary coolant leakage and highly radioactive wastewater, thereby reducing analytical workload and personnel radiation dose. Furthermore, by converting the static decay time to T1-t, this method reduces the storage time of highly radioactive RCP samples in the nuclear island laboratory, improving overall analysis speed and lowering collective chemical radiation dose.

[0033] Specific Implementation: Step 1: Obtain a primary coolant sample and calculate the time interval t between the sample leaving the ideal water body of the primary coolant system and entering the sample bottle. This specifically includes:

[0034] The primary coolant flows out of reactor pressure vessel 1, passing sequentially through steam generator 2, main pump 3, delay coil 4, flow meter 5, boron gauge 6, and sampling valve 7. Readings and records are then performed. Figure 1 The flow rate f of the flow meter 5 in the sampling pipeline is generally 150-200 L / h. Then, the sampling valve 7 is opened to complete the sampling, and the sampling end time T0 is recorded.

[0035] The sampling pipeline volume V is fixed, so the time interval t = V / f is obtained when the coolant sample leaves the ideal water body in the primary coolant system and enters the sample bottle. In comparison, the original technology only includes: sampling in step one and recording the sampling end time T0.

[0036] Step 2: Decay treatment of the primary coolant sample, and measurement of the sample nuclide specific activity in the high-purity germanium gamma spectrometer analysis input system settings.

[0037] The time interval t from when the coolant sample leaves the ideal water in the primary coolant system to when it enters the sample bottle is included in the sample decay time. In step two, after static decay to T0-t+1h, the actual decay time is 1h-t, and the I-134 specific activity is measured. In step two, after static decay to T0-t+3 days, the actual decay time is 3 days-t, and the I-131 specific activity is measured. For example, if the time interval from when the ideal water in the primary coolant system enters the sample bottle is 15min, and the gamma spectrum of the sample is measured at T0+1h, the actual static decay time is: 1h-15min = 45min. Similarly, when measuring the gamma spectrum after 3 days of cumulative decay, the actual static decay time is: 3 days-15min.

[0038] In contrast, current technology: in step two, 1 hour is used as the decay time to measure the specific activity of I-134; and 3 days are used as the decay time to measure the specific activity of I-131.

[0039] Step 3: Calculate the FRI value using the specific activity data of nuclide I-134 and nuclide I-131.

[0040] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for analyzing the gamma spectrum of a primary coolant sample from a nuclear power plant, characterized in that, The method is performed using a detection device, which includes a time delay coil, a flow meter, a boron meter, a sampling valve, and a sampling bottle. The time delay coil is connected to the flow meter, the boron meter, the sampling valve, and the sampling bottle in sequence through a pipeline. The primary coolant flows out from the reactor pressure vessel and passes through the steam generator, the main pump, the time delay coil, the flow meter, the boron meter, the sampling valve, and the sampling bottle in sequence. The method includes: Step 1: Obtain a primary coolant sample and record the sampling end time T0; calculate the time interval t from when the sample leaves the ideal water body of the primary coolant system to when it enters the sampling bottle; Step 1 specifically includes: reading and recording the sampling pipeline flow rate f, then opening the primary sampling valve, obtaining the primary coolant sample, filling the sampling bottle with the sample to complete the sampling, and recording the sampling end time T0; using formula (1) to calculate the time interval t from when the coolant sample leaves the ideal water body of the primary coolant system to when it enters the sample bottle, where V is the sampling pipeline volume and f is the sampling pipeline flow rate; t=V / f (1; Step 2: Decay treatment of the primary coolant sample, and measurement of the sample nuclide specific activity in the high-purity germanium gamma spectrometer analysis input system settings; Step 2.1: Place the sample in the laboratory and decay it to time T1. Input the sampling end time into the high-purity germanium gamma spectrometer and input the value to time T0-t. Measure the I-134 specific activity using the high-purity germanium gamma spectrometer. Step 2.2: Place the sample in the laboratory to decay to time T2, input the sampling end time value as time T0-t into the high-purity germanium gamma spectrometer, and measure the I-131 specific activity using the high-purity germanium gamma spectrometer; Step 3: Calculate the FRI value using the obtained specific activity data of nuclides I-134 and I-131. Step 3 includes: after measuring the specific activity of I-131, substituting the specific activities of I-131 and I-134 into the fuel reliability index calculation formula to obtain the fuel reliability index value.

2. The method for sampling and analyzing the gamma spectrum of the primary coolant in a nuclear power plant according to claim 1, characterized in that, The settings for the high-purity germanium gamma spectrometer include: sampling end time, sample vial volume, scale, and nuclide library.

3. The method for sampling and analyzing the gamma spectrum of the primary coolant in a nuclear power plant according to claim 1, characterized in that, The time T1 is one hour after time T0-t.

4. The method for sampling and analyzing the gamma spectrum of the primary coolant in a nuclear power plant according to claim 1, characterized in that, The T2 time is 3 days after the T0-t time.

5. A method for sampling and analyzing the gamma spectrum of a primary coolant in a nuclear power plant according to claim 3 or 4, characterized in that, The actual decay time of the sample placed in the laboratory until time T1 is 1 h-t; the actual decay time of the sample placed in the laboratory until time T2 is 3 days-t.

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