Development Of Three-Dimensional Monte Carlo-Discrete Ordinates Bidirectional Coupled Shielding Calculation Method

Radiation shielding design is importrant to the security and economy of the nuclear facilities. Selecting suitable shielding calculation method is the key to guarantee the quality of the system shielding design. Single discrete ordinates (i.e.SN) method has limitation in dealing with complex geometric, while single Monte Carlo (MC) method has weakness in deep-penetration. With the research and development of the advanced nuclear power system, the speed and precision of radiation shielding calculation are put forward to higher request. In order to solve the complex shielding problem with complex geometric and bulk shields effectively, the coupling scheme which combines the advantages of both the SN and MC approaches would be the natural choice to treat shielding problems of the advanced nuclear facilities. This work propses a three-dimensional MC-SN bidirectional coupled approach to handle different kinds of shielding problems. The ralative program system has been developed to realize three dimensional MC-SN bidirectional coupled shielding calculation ring for flexible using in complex shielding calculation of nuclear facilities.Firstly, the MC-SN bidirectional coupled method of cartesian and cylindarical coordinates is developed in this thesis. The mapping approach of particle flight direction of source particles to discrete quadrature directions is studied. The corresponding interface procedure are developed to realize the application of MC-SN coupled system in cartesian and cylindarical coordinates. Meanwhile, comprehensive research of the three dimensional SN-MC coupled method is carried out in this paper. The mapping algorithm is derived to calculate the probability density distribution function from the angular flux distribution, and the methodology of source sampling is developed to realize the three-dimensional SN-MC coupled method in both cartesian and cylindarical coordinates.Secondly, the three dimensional MC-SN bidirectional coupled shielding calculation programs are developed. By the bidirectional coupled method, different coupling way between MC and SN can be realized. The test problems of cartesian and cylindrical coordinate have been calculated by MC-SN,SN-MC and MC-SN-MC coupled methods. Satisfactory agreements are obtained among the results calculated by these coupled approaches and single MCNP and TORT calculated results. The result demonstrates that the coupling scheme with the bidirectional coupled program system is correctness and feasibility.Benchmark examples released by U.S. Nuclear Regulatory Commission are selected to verify the effectiveness of the coupled program system in complex model. The three dimensional MC-SN coupled program system MCNP-TORT is used for BNL NUREG/CR-6115PWR shielding validation calculation. The calculation results are performed with comparison to solutions of benchmark report and satisfactory agreements are obtained. The correctness of the MC-SN coupled method in application of complex model is proved. The HBR-2benchmark experiment is used as the calculated model for the TORT-MCNP couple program system calculation, and validate the three dimensional SN-MC coupled method effectiveness in large nuclear device shielding calculation. Good aggrement are obtained among the TORT-MCNP coupled results and the value of experimental and references.Finally, the three-dimensional MC-SN bidirectional coupled method is used for a reactor pit radiation flux distribution calculation. In this application, through MC-SN-MC two-step coupled calculation, the neutron and photon flux distribution in the reactor gallery and cabinet are obtained. At the same time, the MCNP result of reactor gallery is selected to compared to the coupled result. The results indicates that the three dimensional MC-SN-MC coupled system is suitable and effective for solving large-scale complicated geometry transport problems.A three dimensional MC-SN bidirectional coupled method has been developed in this paper. The corresponding calculation program system is developed and verified. The MC-SN bidirectional coupled calculation ring combines the advantage of SN and MC method to improve the accuracy and speed of shielding calculation. The coupled method is important for the current advanced nuclear system shielding design, and proved an effective radiation transport calculation tool in large and complex advanced nuclear facilities.