Analysis Of Radioactive Source Of Water Cooled Blanket For Fusion Plant And Study Of Accurate Shutdown Dose Rate Calculation Method

During the operation of the Chinese Fusion Engineering Testing Reactor(CFETR),a large amount of high energy neutrons are generated.The neutrons penetrate the system and activate both the solid material and coolant in the fusion facility.The secondary ra-dioactive source,which leads to radioactive safety issues such as the shutdown dose rate(SDR)fields and the transport of the radioactivity,is caused by the activation.There-fore,the estimation and analysis of the radioactive source term is of great importance to the fusion engineering and radioactive safety.This thesis performed research on fusion radioactive source and accurate shutdown dose rate calculation method based on the 2015 design of CFETR with Water Cooled Ceramic Breeder(WCCB)blanket.The Monte Carlo particle transport code MCNP and DAG-MCNP5 were used to get the detailed neutron flux.The inventory calculation code FISPACT-? and ALARA were used to perform the activation calculation to get the activation responses such as activity,decay heat,decay photons,and damage under the given irradiation scenario.The PyNE sub-voxel R2S method for shutdown dose rate calculation was developed based on open source code DAGMC,ALARA,and PyNE.The current workflow of activation analysis is inefficient and error-prone as it in-volves a complex workflow and a tremendous amount of data keywoprocessing.There-fore,the NAMF,a coupling code of MCNP and FISPACT-?,was developed for the activation responses calculation and the radioactive waste classification of the solid ma-terials.The activation of the CFETR in-vessel components was calculated with NAMF performed according to the given MCNP input/output files,component cell list,irradia-tion scenario,and the specific radioactive waste classification standard.All the CFETR in-vessel components can be recycled with advanced remote system after a short period of storage.Compared to the UK and US standards,China's standard of high level waste(HLW)includes more types of waste.Consequently,part of the CFETR in-vessel com-ponents which do not produce long-term high-level radioactivity are temporarily clas-sified to HLW and decay to intermediate level waste(ILW)or low level waste(LLW)very soon.Therefore,a more comprehensive management strategy for fusion radioac-tive waste should be developed and applied for the purpose of radwaste minimization,based on the characteristics of fusion radwaste and the consideration of the clearance and recycling.The waste classification should be regarded as an index for management with the least priority.Neutron flux of water coolant of WCCB in CFETR was calculated using MCNP ac-cording to coolant system design.The flow-time weighted neutron flux average method was used to get the average flux of each blanket module.A one-dimension flow method was used to calculate the water activation products along the coolant stream.CATE code was used to evaluate the activation corrosion products(ACPs)distribution of the WCCB coolant system,which is the basis of radiation safety analysis of the coolant system.The current mesh-based rigorous two-step(R2S)has relatively low accuracy due to the adoption of the homogeneous mesh voxel method,which neglects the local geometry effects.In order to obtain better accuracy,the sub-voxel method,which mitigates the local geometry effects,was creatively introduced to mesh-based R2S.The sub-voxel R2S was implemented based on Python for Nuclear Engineering(PyNE)toolkit and DAG-MCNP5.It was proved with the FNG-ITER benchmark problem that PyNE sub-voxel R2S has the advantage of faster convergence speed and more accurate results compared to the previous PyNE R2S.PyNE sub-voxel R2S was applied to the SDR calculation of CFETR in-vessel components.The dependence of shutdown dose rate tools on MCNP,a code with restricted accessibility,usage,and prohibited modification in China,was the obstacle to the further development and application of Chinese tools.This research developed PyNE R2S with open source DAG-OpenMC,to replace the DAG-MCNP5,as an alternative reliable shutdown dose rate calculation method for CFETR.