Pressurized water reactor primary coolant circuit boundary leakage monitoring method and system as well as monitoring instrument

Abstract

The invention discloses a pressurized water reactor primary coolant circuit boundary leakage monitoring method and system as well as a monitoring instrument. The method comprises the following steps:on a sampling point, acquiring sampling gas in a safety shell by virtue of a sampling pipeline, and transporting the sampling gas into a sampling container; detecting gamma-gamma coincidence countingof gamma-gamma photons opposite to the emitted direction of beta+ decay of 13N in the sampling gas of the sampling container by virtue of a coincidence detection apparatus, and calculating and outputting a gamma-gamma coincidence counting rate, wherein the coincidence detection apparatus comprises at least two coincidence detectors; and according to the gamma-gamma coincidence counting rate in thesampling gas, determining a leakage rate of cooling agent water on the pressurized water reactor primary coolant circuit boundary, so that the pressurized water reactor primary coolant circuit leakage can be accurately and efficiently monitored.

Description

technical field [0001] The invention relates to the field of radiation leakage monitoring of nuclear power plants, in particular to a method, system and monitoring instrument for monitoring boundary leakage of a primary circuit of a pressurized water reactor. Background technique [0002] Nuclear safety is the life of nuclear power. The most important thing to develop my country's independent nuclear power technology is how to improve safety. Although nuclear power is a clean energy source, it still has the possibility of nuclear leakage due to the emission of radioactive substances. In order to ensure the stable development of nuclear power and the situation of going global, the safe operation and monitoring of nuclear power plants is one of the keys related to the stable development and going global of nuclear power. The primary circuit pressure boundary leakage monitoring of nuclear power plants is the core component of nuclear power plant safety monitoring. Because the ...

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Problems solved by technology

[0006] In the process of realizing the present invention, the inventors found that: due to the aerosol, 131 Both I measurement and inert gas are nuclear fission products leaked from the cladding of nuclear fuel elements, and their source terms depend on the degree of damage to the cladding of the nuclear fuel and the degree of nuclear reaction of the nuclear fuel. When exposed to water, a certain degree of corrosion damage, stress damage, etc. will occur, resulting in trachoma (ie small holes) or defects in the nature of fine cracks. The damage of nuclear fuel cladding cannot be quantified. Therefore, through aerosol, 131 I measurement and the measurement method of inert gas can only monitor whether there is leakage of fission products, but cannot quantitatively calculate the leakage of fission products, so it can only be measured qualitatively; 13 N radioactivity measurement, since the radioactive source item is a product of neutron activation, the source item can be accurately calculated, compared with aerosol, 131 I measurement and the measurement of the three fission products of inert gas (i.e. PIG) can not only know whether there is leakage, but also can accurately calculate the leakage amount according to the source item, which can be used for quantitative measurement, but using 13 N radioactivity measurement, although it can give quantitative leakage rate information within the error range of ±20%, has been developed at home and abroad. 13 N leakage monitoring is carried out by using the low-background gamma energy spectrum method, which is to put the sampling container into the low-background lead chamber and then use the detector to measure the gamma energy spectrum. However, due to 13 The concentration of N nuclides in the containment is relatively low, which causes the detector to 13 The detection count of N is relatively small, and these monitoring equipment will encounter a high detection limit in the actual use process, which is currently about 10L / h. However, in practical applications, the specific use departments of nuclear power plants hope that the The lower limit of detection can reach the leakage rate of 1L / h, because the normal level of leakage in the primary circuit of the pressurized water reactor nuclear power plant is about 40 liters to 120 liters per day, and the existing detection lower limit of the leakage rate is 10L / h 13 The N monitor intelligently detects prominent and relatively large leakage accidents, which cannot reflect the situation of the leakage; and the low-background gamma energy spectrum method is used to measure through stable spectra 13 beta of N + The method of leak monitoring with 0.511 Mev gamma photons emitted by decay requires high long-term stability of the instrument. Due to long-term on-line monitoring, if the energy spectrum drifts, the measured 0.511 Mev gamma count rate will not be stable. Accurate, affecting the accuracy of measurement results

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