Research On Comprehensive Risk Assessment Methodology For Off-site Transportation Of Nuclear Power Plant Spent Fuel Based On PSA

Spent nuclear fuel(SNF)transportation has the potential risk of releasing radioactive materials,which may cause severe radiological hazard to the public and the surrounding environment.The risk assessment of spent fuel transportation is crucial to ensure the safety and economy of the back-end cycle of nuclear fuel.Probabilistic Safety Assessment(PSA)is a mature and systematic method applied in the safety evaluation of nuclear power plants.However,it is still in the preliminary research stage in the field of radioactive material transportation.In this paper,the study on the integrated probabilistic risk assessment(IPRA)methodology for SNF road-sea-rail multimodal transportation based on PSA and the comprehensive probabilistic risk assessment methodology for SNF road and maritime transportation are systematically conducted.The IPRA method is a general method that envelops comprehensive risk assessment methods for road and maritime transport.The three aspects that will be future explored in this work are shown as follows:(1)An integrated probabilistic risk assessment method for spent fuel multimodal transport by road-sea-railway is proposed.Firstly,the comprehensive probability index system and consequence index system are constructed based on the identified"sociotechnical-environmental" risk factors.Secondly,the radionuclide dispersion model in different media under complex environment are established.Finally,the quantitative IPRA methodology considering both accident occurrence probability and associated radiological consequence comprehensively for SNF road-sea-rail multimodal transportation is proposed.The IPRA method provides a comprehensive and systematic approach to the quantification of SNF multimodal transport risks,as well as a new technical approach for the design optimization and risk management of transportation systems.(2)A comprehensive probabilistic risk assessment method for road transportation of spent fuel based on PSA is proposed.Firstly,an event tree-fault tree coupling model based on the comprehensive probability index system of PVCRES(Personnel,Vehicle,Cask,Road,Environment,Supervision)is constructed for the occurrence frequency analysis of road transportation accidents.Secondly,a k-ε turbulence model based on the Computational Fluid Dynamics(CFD)method is established to simulate the atmospheric dispersion concentration of radionuclide under complex environments.Thirdly,the evaluation of the severity of radiological consequences and the quantification of radioactive risks based on the comprehensive consequence index system are obtained.Finally,based on the radioactive risk obtained and combined with the transportation time cost and economic cost,the multi-objective path optimization method under the risk guidance is studied,which is helpful to improve the safety and economy of the SNF transportation.(3)A comprehensive probabilistic risk assessment method for maritime transportation of spent fuel based on PSA is proposed.Firstly,an event tree-fault tree coupling model based on the comprehensive probability index system of SMCETC(Ship,Management,Crew,Environment,Tank,Channel)is constructed for the occurrence frequency analysis of marine transportation accidents.Secondly,considering the influence of source term,ocean current,tide and decay,a hydrodynamic model based on Shallow Water Flow(SWF)is established for dynamic simulation of radionuclide concentration in coastal seawater.Finally,the evaluation of radiation consequences and the quantification of radioactive risks based on public internal and external exposure doses are realized,which could provide reference for the prevention of SNF maritime transportation accidents and nuclear emergency decision-making.The IPRA method proposed in this paper provides a systematic and comprehensive approach for quantifying the radioactive risk of SNF transportation accidents,and also provides new insights for the design optimization and risk management of the SNF transportation system.This approach improves and develops the risk assessment method system for spent fuel transportation,which is beneficial for decision makers to examine the safety of transportation system from the perspective of probability theory and system theory.