Monte Carlo-point Kernel Coupling Calculation Method For Decommissioning Radiation Field Of Nuclear Facilities And Its Application

At present,a large number of reactors and other nuclear facilities around the world are in the stage of decommissioning or ready to be decommissioned.The decommissioning of nuclear facilities is a complex,extensive and content-oriented project.On the basis of considering the safety,economy and rationality of decommissioning of nuclear facilities,before the decommissioning projects of nuclear facilities are implemented,computer programs must be used to verify,evaluate and verify the decommissioning technical solutions and procedures to reduce radiation to the staff.And the surrounding environment causes unnecessary harm.Thus,the rapid and accurate calculation of the radiation field of a decommissioned nuclear facility is in line with the basic requirements for the decommissioning of nuclear facilities.The traditional calculation methods for the calculation of the three-dimensional radiation field of decommissioning of nuclear facilities have their own advantages and disadvantages in the actual radiation field shielding calculation:(1)The discrete ordinate method is suitable for solving the deep penetration problem,but it is not suitable for complex source and geometric regions.The calculation does not apply to the fast calculation of the radiation field;(2)the Monte Carlo method can be used to calculate complex source terms and geometric regions,but for large space shielding problems,it is impossible to give reliable results in a reasonable time;(3)The nuclear method for calculating the radiation shielding problem is suitable for deep penetration problems.Although it is fast,it is not suitable for the calculation of complex source terms and geometric regions.At the same time,the estimation of accumulation factors may bring large calculation errors and low reliability.In fact,there are two problems in the process of calculating the three-dimensional radiation field of nuclear facility decommissioning:(1)space,the calculation of the radiation field in the entire space of the entire plant;(2)time,with the removal of equipment as much as possible A new dose distribution is given in a short time.The three-dimensional radiation field of decommissioning of nuclear facilities is very complicated,and it is difficult to solve these two problems at the same time by the traditional single calculation method.Therefore,this paper selects the Monte Carlo-Point Kernel coupling method to calculate the three-dimensional radiation field of nuclear facility decommissioning,and the Monte Carlo-Point Kernel coupling calculation method is used to calculate the three-dimensional radiation field of nuclear facility decommissioning:(1)Give full space of the three-dimensional radiation field,solves the problems of the Point Kernel integration method in complex source and geometric regions;(2)Compared with the single method,a new dose field distribution can be given with the disassembly of the device in the shortest possible time.The Monte Carlo-Point Kernel coupling method is used to calculate the multi-point source radiation field model.The results show that the error calculation of the Monte Carlo-Point Kernel coupling calculation is about 1-2 orders of magnitude better than that of the single point kernel integral,compared to a single Monte Carlo calculation can save several times of time,and verify the feasibility of calculating the complex radiation field by the Monte Carlo-Point Kernel coupling method.At the same time,the calculation results of the Monte Carlo-Point Kernel coupling calculation for the single source model show that the coupling calculation ratio The calculation speed of a single Monte Carlo method is increased by several tens of times,and the maximum relative error is within 11%,and the calculation accuracy is high.The calculation results of the Monte Carlo-Point Kernel coupling calculation for the two-cylinder source model show that the coupling calculation is simpler than the single Monte Carlo method.The calculation speed is increased by several tens of times,and the maximum relative error is within 30%,and the calculation accuracy is high.The program of the three-dimensional radiation field of the nuclear facility decommissioned with the Monte Carlo-Point Kernel coupling calculation program are developed,and the three-dimensional visualization program of the radiation field are developed.The fast and accurate calculation program of the radiation field includes the source item database module,the radiation field calculation module and the interface program module,and the three-dimensional radiation field is visualized.The module enables visualization of the three-dimensional radiation field distribution of the nuclear facility decommissioning.The software is applied to the calculation of the decommissioning radiation field of Qinshan Phase I.The distribution of the whole radiation field is calculated by the coupling program.Compared with the calculation result of MCNP5,the maximum error is less than 1.5 times.The calculation accuracy and speed meet the calculation of the dynamic radiation field of nuclear facilities decommissioning claim.