A method for measuring deposition source term in pressurized water reactor nuclear power plants

Abstract

The present invention discloses a method for measuring the deposition source term at a pressurized water reactor nuclear power plant, comprising the following steps: initially establishing a deposition point arrangement plan; determining the radioactive nuclides to be measured, obtaining the activity concentration of the radioactive nuclides deposited on the inner wall of the pipe at each measurement point, and sorting the measurement points according to the activity concentration; determining the installation conditions of the proposed deposition source term online measurement device, measuring the on-site space dimensions of each measurement point, and excluding measurement points that do not meet the installation conditions; determining whether there are additional measurement points and priority factors; if there are no additional measurement points and priority factors, the order of the deposition point arrangement plan remains unchanged; if there are additional measurement points and / or priority factors, the additional measurement points are added and the measurement points are reordered; and according to the number of deposition source term online measurement devices, redundant measurement points are excluded, and finally the deposition point arrangement plan is determined. The deposition point arrangement method of the present invention is highly operable and can provide a reference for determining the on-site gamma spectrum online measurement point arrangement plan for various nuclear power plants.

Description

Technical Field

[0001] The invention relates to a method for measuring and distributing deposition source items in a pressurized water reactor nuclear power plant. Background Art

[0002] Activated corrosion products deposited on the surfaces of primary circuit piping during outages are known as deposition sources. They are the most significant radiation source and contributor to the collective dose in pressurized water reactor (PWR) nuclear power plants. According to domestic and international statistics, deposition sources contribute approximately 80%-95% of the collective dose in PWR nuclear power plants. Measuring deposition sources during overhauls is a crucial task. It helps understand the distribution of deposition sources within the primary circuit of a unit, the contribution of each nuclide to the irradiation field, and their deposition and migration characteristics, enabling targeted source control efforts.

[0003] Measuring the sediment source term is difficult using traditional direct sampling methods. Therefore, a primary method has emerged: a single-loop sediment source term measurement system employing nondestructive in situ gamma spectroscopy. During measurement, a probe is positioned at a distance outside the pipeline, and an in situ gamma spectrum is measured using a multichannel analyzer. This in turn yields the full-energy peak net count rate for gamma rays of varying energies. After determining measurement conditions such as the detector and collimator geometry, pipeline dimensions, and probe-to-pipe distance, the surface activity within the pipeline can be calculated based on the type of radionuclides within the pipeline, combined with the gamma full-energy peak detection efficiency and the gamma ray branching ratio. In situ gamma spectroscopy of the sediment source term can be performed using either a mobile / portable measurement device, which theoretically allows measurement at all locations but only provides discontinuous data at a single time point. Alternatively, multiple online measurement devices can be used for multi-point online measurement. This method, however, only provides data from a limited number of key locations. However, it allows for long-term online measurement, providing continuous data on the sediment source term over time, which is more valuable for studying its changing trends, influencing factors, and deposition and migration characteristics.

[0004] Domestic overhaul sediment source term surveys have been conducted, and efforts are underway to conduct online gamma-ray spectrometry measurements of multiple locations for these sediment source terms. To achieve this, the locations of these measurement points must be determined. Different PWR types have different system structures and sediment source term characteristics, and even different units within the same type may exhibit variations. Therefore, it is necessary to establish a method for measuring sediment source term locations in PWR nuclear power plants. Summary of the Invention

[0005] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a method for arranging measurement points for sediment source items in a pressurized water reactor nuclear power plant, so as to provide a reference for determining the measurement positions when each nuclear power plant carries out multi-point on-site gamma spectrum online measurement of sediment source items during overhaul.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for measuring the deposition source term of a pressurized water reactor nuclear power plant comprises the following steps:

[0008] Determine the measurement points based on the pipelines in the reactor coolant system, chemical and volume control system, residual heat removal system, and reactor boron and water supply system of the primary circuit of the pressurized water reactor, and preliminarily formulate a point layout plan;

[0009] Determine the radionuclides that need to be measured, use a mobile gamma spectrometer to obtain the activity concentration of the radionuclides deposited on the inner wall of the pipeline at each measurement point in the initial point layout plan, and sort the measurement points from high to low based on the activity concentration;

[0010] Determine the installation conditions of the proposed sediment source item online measurement device, measure the on-site space dimensions of each measurement point, eliminate measurement points that do not meet the installation conditions, and reorder the remaining measurement points;

[0011] Determine whether there are additional measurement points and priority factors. If there are no additional measurement points and priority factors, the order of the measurement points remains unchanged. If there are additional measurement points and / or priority factors, add the additional measurement points and reorder the measurement points.

[0012] According to the number of online measurement devices for sedimentation source items, redundant measurement points are eliminated and the final measurement point layout plan is determined.

[0013] According to some preferred embodiments of the present invention, the primary circuit of a pressurized water reactor (PWR) primarily includes the reactor coolant system (RCP), the chemical and volumetric control system (RCV), the residual heat removal system (RRA), the reactor boron and water replenishment system (REA), the reactor and spent fuel pool cooling and treatment system (PTR), the safety injection system (RIS), and the containment spray system (EAS). Sedimentation sources are primarily distributed in the RCP, RCV, RRA, and REA systems. The distribution of these sedimentation sources often changes after the coolant passes through key equipment such as filters, resin desalination beds, heat exchangers, and pumps. Therefore, for the deposition source term, RCP should focus on the hot section, transition section, cold section pipelines, and stabilizer surge pipe; RRA should focus on the waste heat removal pump downstream header, waste heat removal pump upstream header, waste heat exchanger downstream header, and waste heat exchanger downstream header; RCV should focus on the regenerative heat exchanger upstream pipeline, regenerative heat exchanger downstream pipeline, secondary heat exchanger upstream pipeline, secondary heat exchanger downstream pipeline, purification filter upstream pipeline, purification filter downstream pipeline, resin desalination bed upstream pipeline, resin desalination bed downstream pipeline, top-up pump upstream pipeline, top-up pump downstream pipeline, control box upstream pipeline, and control box downstream pipeline; REA should focus on the filter upstream pipeline and filter downstream pipeline. When the initial layout plan is set, measurement points are set for these pipelines.

[0014] According to some preferred embodiments of the present invention, in the step of determining the radionuclides to be measured, the radionuclides to be measured include Co-58 and / or Co-60. When only Co-58 or Co-60 needs to be measured, the measurement points are sorted from high to low based solely on the activity concentration of the corresponding radionuclides. When both Co-58 and Co-60 need to be measured at the measurement points, the activity concentrations of the two radionuclides at each measurement point are added together, and then the measurement points are sorted from high to low based on the activity concentration.

[0015] According to some preferred implementation aspects of the present invention, the installation condition of the deposition source term online measurement device is the footprint of the deposition source term online measurement device, which includes the height, width and length of the deposition source term online measurement device.

[0016] According to some preferred implementation aspects of the present invention, the measurement points that do not meet the installation conditions include measurement points whose on-site space size is smaller than the footprint of the deposition source item online measurement device.

[0017] According to some preferred implementation aspects of the present invention, the additional measurement points include locations contaminated by radioactive nuclides Ag-110m and / or Sb-124.

[0018] According to some preferred embodiments of the present invention, the priority factor includes pipelines that require replacement and / or modification in the initial measurement point plan. When a pipeline in the RCP, RCV, RRA, or REA system that is located in the initial measurement point plan requires replacement or modification, the pipeline requires special attention, and the measurement point is generally prioritized.

[0019] According to some preferred implementation aspects of the present invention, if there are additional measurement points, the measurement points are reordered after the additional measurement points are added to the point layout plan, and the order of the additional measurement points is placed before the order of other measurement points.

[0020] According to some preferred implementation aspects of the present invention, if there is a priority factor, the measurement point corresponding to the priority factor is placed before the order of other measurement points.

[0021] According to some preferred implementation aspects of the present invention, if there are additional measurement points and priority factors, the additional measurement points are first added to the point layout plan, and then all measurement points are reordered, and the order of the additional measurement points and the order of the measurement points corresponding to the priority factors are placed before the order of other measurement points, and the order of the measurement points corresponding to the priority factors is placed before the order of the additional measurement points.

[0022] According to some preferred embodiments of the present invention, the method for eliminating redundant measurement points according to the number of online measurement devices for deposition source items is as follows: according to the ranking of each measurement point, the measurement points with the lowest ranking are removed, and the number of retained measurement points is less than or equal to the number of online measurement devices for deposition source items.

[0023] Due to the adoption of the above technical solution, compared with the existing technology, the benefits of the present invention are: a method for measuring the deposition source term of a pressurized water reactor nuclear power plant of the present invention is highly operational, and the determined measurement points of the deposition source term are highly representative. The method is applicable to all pressurized water reactor units and can also be used as a reference for other reactor types. It is universal and widely applicable, and can provide a reference for determining the measurement locations when conducting multi-point on-site gamma spectrum online measurements of deposition source terms for overhaul in various nuclear power plants. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0025] A method for measuring and arranging deposition source terms in a pressurized water reactor nuclear power plant according to the present invention comprises the following steps:

[0026] The locations of various measurement points are determined based on the pipelines in the reactor coolant system, chemical and volume control system, residual heat removal system and reactor boron and water supply system of the primary circuit of the pressurized water reactor, and a preliminary distribution plan is formulated.

[0027] Determine the radioactive nuclides that need to be measured, use a mobile gamma spectrometer to obtain the activity concentration of the radioactive nuclides deposited on the inner wall of the pipeline at each measurement point in the initial layout plan, and sort the measurement points from high to low according to the activity concentration.

[0028] Determine the size of the sedimentation source online measurement device to be used, including length, height and width, and then measure the on-site space size of each measurement point. After excluding the measurement points whose on-site space size is smaller than the size of the sedimentation source online measurement device, reorder the remaining measurement points.

[0029] Determine whether there are additional measurement points and priority factors. If there are no additional measurement points and priority factors, the order of the layout plan remains unchanged. If there are additional measurement points, reorder the measurement points after adding the additional measurement points to the layout plan, and the order of the additional measurement points is before the order of other measurement points. If there are priority factors, place the measurement points corresponding to the priority factors before the order of other measurement points. If there are both additional measurement points and priority factors, first add the additional measurement points to the layout plan, and then reorder all measurement points, and place the order of the additional measurement points and the order of the measurement points corresponding to the priority factors before the order of other measurement points, and the order of the measurement points corresponding to the priority factors is before the order of the additional measurement points.

[0030] According to the number of online measurement devices for sedimentation source items, the measurement points with the lowest ranking are removed, and the number of retained measurement points is less than or equal to the number of online measurement devices for sedimentation source items, and the point layout plan is finally determined.

[0031] Example 1 The process of determining the measurement point arrangement plan for the deposition source term of a certain nuclear power plant is as follows:

[0032] Preliminary layout plan: The measurement points include the hot section pipeline, transition section pipeline, cold section pipeline and stabilizer surge pipe of the RCP system of the primary circuit of the pressurized water reactor; the upstream pipeline of the regenerative heat exchanger, the downstream pipeline of the regenerative heat exchanger, the upstream pipeline of the secondary heat exchanger, the downstream pipeline of the secondary heat exchanger, the upstream pipeline of the purification filter, the downstream pipeline of the purification filter, the upstream pipeline of the resin desalination bed, the downstream pipeline of the resin desalination bed, the upstream pipeline of the upper charging pump, the downstream pipeline of the upper charging pump, the upstream pipeline of the containment control box, and the downstream pipeline of the containment control box of the RCV system; the downstream collecting pipe of the waste heat discharge pump, the upstream collecting pipe of the waste heat discharge pump, the downstream collecting pipe of the waste heat exchanger, and the downstream collecting pipe of the waste heat exchanger of the RRA system; the upstream pipeline of the filter and the downstream pipeline of the filter of the REA system, a total of 22 measurement points.

[0033] A mobile gamma spectrometer was used to measure each of the above-mentioned measurement points. The activity concentrations of the radionuclides Co-58 and Co-60 deposited on the inner wall of the pipe at each measurement point were obtained. The sum of the activity concentrations of the two radionuclides at each measurement point was calculated. The measurement points were then ranked from high to low based on the sum of the activity concentrations. The order of the measurement points is shown in Table 1 below.

[0034] Table 1 Ranking of measurement points in the initial layout plan

[0035] Sorting system Point <![CDATA[Activity concentration (Bq / cm 2 )]]> 1 RCP Cold section pipe <![CDATA[8.6×10 4 ]]> 2 RCP Hot section pipeline <![CDATA[5.8×10 4 ]]> 3 RCP Transition pipe <![CDATA[4.2×10 4 ]]> 4 RCV Pipeline downstream of secondary heat exchanger <![CDATA[1.3×10 4 ]]> 5 RCV Purify filter upstream pipeline <![CDATA[8.0×10 3 ]]> 6 RCV Secondary heat exchanger upstream pipe <![CDATA[7.2×10 3 ]]> 7 RCV Regenerative heat exchanger downstream piping <![CDATA[6.9×10 3 ]]> 8 RCV Regenerative heat exchanger upstream piping <![CDATA[6.5×10 3 ]]> 9 RCV Purify filter downstream pipeline <![CDATA[6.1×10 3 ]]> 10 RCV Resin desalination bed upstream pipeline <![CDATA[5.6×10 3 ]]> 11 RCV Resin desalination bed downstream pipeline <![CDATA[5.0×10 3 ]]> 12 RCV Upstream pipeline of the control box <![CDATA[4.5×10 3 ]]> 13 RCV Downstream pipeline of the control box <![CDATA[3.5×10 3 ]]> 14 RCV Upstream pipeline of charging pump <![CDATA[3.1×10 3 ]]> 15 RCV Downstream pipeline of charging pump <![CDATA[2.8×10 3 ]]> 16 REA Filter upstream pipe <![CDATA[2.1×10 3 ]]> 17 REA Filter downstream pipe <![CDATA[1.4×10 3 ]]> 18 RCP Voltage stabilizer surge tube <![CDATA[1.1×10 3 ]]> 19 RRA Downstream header of exhaust heat exchanger <![CDATA[8.2×10 2 ]]> 20 RRA Downstream header of exhaust heat exchanger <![CDATA[6.0×10 2 ]]> 21 RRA Waste heat removal pump downstream header <![CDATA[4.4×10 2 ]]> 22 RRA Waste heat removal pump upstream header <![CDATA[2.2×10 2 ]]>

[0036] The proposed online sediment source measurement device footprint was determined to be 60 cm long, 60 cm wide, and 130 cm high. The on-site space dimensions of each measurement point were measured, and those that were unsuitable for installation were excluded. These included the hot section piping and pressurizer surge pipe of the RCP system, as well as the downstream header of the exhaust heat exchanger, downstream header of the exhaust heat exchanger, downstream header of the exhaust heat pump, and upstream header of the exhaust heat pump of the RRA system, a total of six locations. These piping locations had limited on-site space and were therefore unsuitable for the online sediment source measurement device, so they were excluded. The remaining sixteen measurement points were reordered as shown in Table 2 below.

[0037] Table 2: The order of measurement points after removing those that do not meet the installation conditions in the initial layout plan

[0038] Sorting system Point 1 RCP Cold section pipe 2 RCP Transition pipe 3 RCV Pipeline downstream of secondary heat exchanger 4 RCV Purify filter upstream pipeline 5 RCV Secondary heat exchanger upstream pipe 6 RCV Regenerative heat exchanger downstream piping 7 RCV Regenerative heat exchanger upstream piping 8 RCV Purify filter downstream pipeline 9 RCV Resin desalination bed upstream pipeline 10 RCV Resin desalination bed downstream pipeline 11 RCV Upstream pipeline of the control box 12 RCV Downstream pipeline of the control box 13 RCV Upstream pipeline of charging pump 14 RCV Downstream pipeline of charging pump 15 REA Filter upstream pipe 16 REA Filter downstream pipe

[0039] It was determined that there were no additional measurement points in the primary circuit of the pressurized water reactor of this nuclear power plant that required special attention. However, there were priority factors. Since the filter of the REA system of this nuclear power plant was to be replaced, it was hoped to monitor the changes in the deposition source items in the pipeline upstream of the REA filter. Therefore, the order in Table 2 above was readjusted, and the pipeline upstream of the REA filter was placed first. The order is shown in Table 3 below.

[0040] Table 3 Ranking of measurement points in the initial layout plan after removing those that do not meet the installation conditions and considering priority factors

[0041] Sorting system Point 1 REA Filter downstream pipe 2 RCP Cold section pipe 3 RCP Transition pipe 4 RCV Pipeline downstream of secondary heat exchanger 5 RCV Purify filter upstream pipeline 6 RCV Secondary heat exchanger upstream pipe 7 RCV Regenerative heat exchanger downstream piping 8 RCV Regenerative heat exchanger upstream piping 9 RCV Purify filter downstream pipeline 10 RCV Resin desalination bed upstream pipeline 11 RCV Resin desalination bed downstream pipeline 12 RCV Upstream pipeline of the control box 13 RCV Downstream pipeline of the control box 14 RCV Upstream pipeline of charging pump 15 RCV Downstream pipeline of charging pump 16 REA Filter upstream pipe

[0042] Since the number of online sediment source measurement devices in this nuclear power plant is 8, the eight measurement points with the lowest ranking are removed according to the ranking in Table 3, and the final point layout plan is determined, as shown in Table 4 below.

[0043] Table 4: Measurement layout of deposition source items in nuclear power plants

[0044] Sorting system Point 1 REA Filter downstream pipe 2 RCP Cold section pipe 3 RCP Transition pipe 4 RCV Pipeline downstream of secondary heat exchanger 5 RCV Purify filter upstream pipeline 6 RCV Secondary heat exchanger upstream pipe 7 RCV Regenerative heat exchanger downstream piping 8 RCV Regenerative heat exchanger upstream piping

[0045] The method for arranging measurement points for sediment source items in a pressurized water reactor nuclear power plant of this embodiment is highly operable, universal, and widely applicable, and can provide a reference for determining measurement locations when conducting multi-point on-site gamma spectrum online measurements of sediment source items during overhaul in various nuclear power plants.

[0046] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A method for measuring the deposition source term of a pressurized water reactor nuclear power plant, characterized in that: The steps include: Initial layout plan; Determine the radionuclides that need to be measured, obtain the activity concentration of the radionuclides deposited on the inner wall of the pipeline at each measurement point in the initial point layout plan, and sort the measurement points according to the activity concentration; Determine the installation conditions of the proposed sediment source item online measurement device, measure the on-site space dimensions of each measurement point, eliminate measurement points that do not meet the installation conditions, and reorder the remaining measurement points; Determine whether there are additional measurement points and priority factors. If there are no additional measurement points and priority factors, the order of the measurement points remains unchanged. If there are additional measurement points and / or priority factors, add the additional measurement points and reorder the measurement points. According to the number of online measurement devices for sedimentation source items, redundant measurement points are eliminated and the final measurement point layout plan is determined.

2. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The method for the initial layout plan is to determine the location of each measurement point based on the pipelines in the reactor coolant system, chemical and volume control system, residual heat removal system and reactor boron and water supply system of the primary circuit of the pressurized water reactor.

3. The method for measuring the sedimentation source term of a pressurized water reactor nuclear power plant according to claim 2, characterized in that: The measurement points of the reactor coolant system are located in the hot section pipeline, transition section pipeline, cold section pipeline and stabilizer surge pipe.

4. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 2, wherein: The measurement points of the chemical and volume control systems are located in the upstream pipeline of the regenerative heat exchanger, the downstream pipeline of the regenerative heat exchanger, the upstream pipeline of the secondary heat exchanger, the downstream pipeline of the secondary heat exchanger, the upstream pipeline of the purification filter, the downstream pipeline of the purification filter, the upstream pipeline of the resin desalination bed, the downstream pipeline of the resin desalination bed, the upstream pipeline of the upper charging pump, the downstream pipeline of the upper charging pump, the upstream pipeline of the capacity control box, and the downstream pipeline of the capacity control box.

5. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 2, characterized in that: The measurement points of the waste heat discharge system are located at the downstream collecting pipe of the waste heat discharge pump, the upstream collecting pipe of the waste heat discharge pump, the downstream collecting pipe of the waste heat exchanger, and the upstream collecting pipe of the waste heat exchanger.

6. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 2, characterized in that: The measurement points of the reactor boron and water supply systems are located in the upstream and downstream pipes of the filter respectively.

7. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 1, wherein: In the step of determining the radioactive nuclides to be measured, the radioactive nuclides to be measured include Co-58 and / or Co-60.

8. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 1, wherein: The method for sorting the measurement points according to the activity concentration is: sorting the measurement points from high to low according to the activity concentration of the measurement points.

9. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The installation condition of the deposition source item online measurement device is the floor space size of the deposition source item online measurement device, and the floor space size includes the floor space height, width and length of the deposition source item online measurement device.

10. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 9, characterized in that: The measurement points that do not meet the installation conditions include measurement points whose on-site space size is smaller than the footprint of the deposition source item online measurement device.

11. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 1, characterized in that: The additional measurement points include locations contaminated by the radioactive nuclides Ag-110m and / or Sb-124.

12. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 8, characterized in that: The priority factors include pipelines that need to be replaced and / or modified in the initial layout plan.

13. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 8, characterized in that: If there are additional measurement points, they will be reordered after being added to the point layout plan, and the order of the additional measurement points will be before the order of other measurement points.

14. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 12, wherein: If there is a priority factor, the measurement point corresponding to the priority factor is placed before the order of other measurement points.

15. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 8, characterized in that: If there are additional measurement points and priority factors, first add the additional measurement points to the layout plan, and then reorder all measurement points, placing the order of the additional measurement points and the order of the measurement points corresponding to the priority factors before the order of other measurement points, and the order of the measurement points corresponding to the priority factors before the order of the additional measurement points.

16. The method for measuring the deposition source term of a pressurized water reactor nuclear power plant according to claim 1, wherein: According to the number of online measurement devices for deposition source items, the method for eliminating redundant measurement points is as follows: according to the ranking of each measurement point, the measurement points with the lowest ranking are removed, and the number of retained measurement points is less than or equal to the number of online measurement devices for deposition source items.