Research On Radiation Intensity Reconstruction And Radiation Monitoring Plans Of Radioactive Waste Liquid Storage

Nuclear power plants have been in operation in China for more than 30 years,and some nuclear facilities have been in operation for even longer,so more and more nuclear facilities(including nuclear power plants)near or beyond their life cycle are facing decommissioning.Research related to the decommissioning of nuclear facilities has received a lot of attention,among which the radiation monitoring and protection of post-decommissioning treatment plants is a hot issue.In nuclear waste reprocessing plants,there are special storage bodies for storing radioactive waste,and the plants need to classify the radioactivity of their storage contents for subsequent treatment,and also need to take relevant samples and send them to the laboratory to test the correctness of the classification.How to use computer simulation technology to infer the radioactive intensity of the contents of the storage body by measuring the dose value at a certain point without contact,and to carry out preliminary classification of medium and low emission waste liquids is a research topic with important engineering significance.If technicians can understand the source intensity of unknown radiation sources and the distribution of radiation fields around them through simulation results,they can not only effectively carry out path planning and reduce the irradiation dose to relevant personnel,but also address the needs of different scenarios based on engineering for sampling and detection of waste liquid storage pools,selecting suitable detectors and designing monitoring systems.In the context of the above engineering requirements,this thesis conducts an in-depth study on how to use the dose value at a point to infer the radiation source strength and use the inferred source strength to reconstruct the radiation source strength at the specified point of the radiation field,as well as the sampling and detection of the wastewater pool in the following aspects.(1)Based on the classical point kernel integration theory,a new algorithm of reduceddimensional point kernel integration using area fraction to calculate the particle flux of a bulk source is proposed,which can be used for the inverse calculation of the source intensity of a bulk source.This algorithm can calculate the source intensity of the radioactive source by inputting the source term and the information at the detection point in reverse.In order to verify the reliability of the algorithm,simulations are performed and the results are compared with the experimental data of the plant,and the difference between the two is small,which means that the algorithm can invert the source term intensity more accurately.Meanwhile,after getting the inverse source intensity and then using the program to calculate the dose value distribution of the forward radiation field,a point-to-point comparison was performed using MCNP5,and the error of the obtained data was within an acceptable range.(2)On the basis of in-depth analysis of detector principles and data from a reprocessing plant,the sampling and radiation monitoring schemes for waste liquid storage bodies are studied,a research method for the classification of medium and low discharge wastewater is given,several schemes that can be used for waste liquid sampling and radiation monitoring are determined,the sampling volume and the corresponding detector selection,and the radiation protection design is carried out for different sampling schemes to provide theoretical guidance for future radiation protection work in nuclear facility decommissioning projects.