Combined radiation source strength backward induction method and combined radiation source strength backward induction system for point source, linear source and surface source of nuclear power plant

Abstract

The invention discloses a combined radiation source strength backward induction method and a combined radiation source strength backward induction system for a point source, a linear source and a surface source of a nuclear power plant. The method is characterized in that dosage rates at a plurality of positions are acquired through a detector; a normalized radiation source strength is diffused in a space; an optical distance is calculated by means of a ray tracking method; an equation set coefficient is calculated according to information such as material and accumulation factor, thereby performing backward induction for obtaining source strength; then dosage rate calculation is performed on detector position; through performing linear regression analysis on a measured value and a calculated value, key parameters such as standard deviation, gradient and intercept are calculated, and furthermore a quality factor is calculated for measuring acceptance degree of a calculation result at each time. Furthermore the invention provides a weighted iteration method. An error which is introduced by a detector with relatively high uncertainty is reduced. The steps are repeated by multiple times in an iteration manner until the quality factor reaches a preset fixed value, and anticipated radiation source strength information is obtained.

Description

technical field [0001] The invention relates to a method and system for calculating radiation source intensity in a nuclear power plant, in particular to a method and system for reversing the strength of a composite radiation source for a combination of point source, line source, and area source in a nuclear power plant. Background technique [0002] The radioactivity in nuclear power plants comes from the active area of ​​the fuel assembly in the pressure vessel, and the radiation source is mainly composed of fission products, actinides and corrosion activation products. During the operation of the system, the radiation source flows with the coolant through the main system of the primary circuit (including pressure vessels, main pumps, voltage stabilizers, main pipelines, etc.), the chemical container control system, etc., and the radiation sources are distributed on the surface of the coolant and related equipment. The radiation source itself is highly radioactive, and the...

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Problems solved by technology

[0003] The distribution of radiation sources in nuclear power plants is relatively wide, especially after long-term use and overhaul, it is more and more difficult to infer the radiation intensity of radiation sources at various positions based on engineering experience, so when calculating many data, especially based on radiation source In the calculation of intensity, the accuracy and practicability are greatly affected because it is difficult to obtain accurate basic information. At the same time, the current domestic protective facilities and means are not very complete, which also greatly increases the risk of workers being exposed

[0004] In the prior art, when it is necessary to estimate the radiation source intensity, the source term analysis method is generally used. First, according to the production and disappearance pathways of radioactive substances, its production items (such as inflow items, decay production items, etc.) and disappearance items (such as filter items) are determined. , leakage items, etc.), and define the physical models of each item, then establish nucleon concentration balance equations (groups) for radioactive substances according to the above items, and finally solve the simultaneous equations (groups), but there are a lot of simplifications in these calculations and approximate calculation, so the result is often far from the real value, and there are many obstacles in practical application. In addition, considering the harm caused by the radiation source itself to the human body, the complex geometric structure inside the nuclear power plant, and the accuracy of radionuclides When the information is difficult to obtain, the uncertainty of the nuclear power plant detector measurement value and other factors, the above methods have problems in terms of safety and accuracy, and it is urgent to improve or propose a new way to obtain the intensity of radiation sources

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