Transient Analysis Of The Spent Fuel Dry Storage And Cooling System Of HTR-PM

Dry-storage and cooling scenario is adopted in both the temporary and interim storage period of the spent fuel of High Temperature Reactor – Pebblebed Modules(HTR-PM).Considering the difference of residual heat power,forced ventilation and natural ventilation mode are used in the temporary and interim storage period,respectively.It's practically meaningful to the design basis verification and safety feature evaluation for the research of the residual heat removal characteristics of the dry-storage and cooling system under both normal condition and accident condition.Also,the spent fuel dry-storage system is a multi-scale and multi-physics transient ventilation system,thus the transient analysis can also provide useful guidance to study of large-scale ventilation system.This work firstly establishes a single-phase transient flow model on a multiple scale and a transient conjugate heat transfer coupling with thermal radiation model of the solid region.CFD method is used to study the local resistance and convective heat transfer feature.Coarse mesh is used to perform the transient process on the system scale.Transfer function is used to establish the one-way coupling between the local scale and system scale.Each of the storage wells is partitioned vertically such that the conjugate heat transfer with thermal radiation process in each layer can be solved separately.Secondly,this work studies the solving algorithm of the transient analysis model and develops a computer code TAC-DS.The governing equations is discretized spatially using finite volume method.Semi-implicit scheme for the convective heat transfer is used to decouple the flow process and the solid heat transfer process.The discretized flow equations are treated semi-implicitly and converted to linear algebraic equations system.The non-linear solid heat transfer equations are also treated semi-implicitly and then solved directly using Newton's method.A transient analysis computer code called TAC-DS is developed to realize the model and solving algorithm.Both experimental data and CFD simulation results are used to verify the analysis model and the TAC-DS code.Thirdly,by using the TAC-DS code,the heat removal characteristics of the buffer storage region and interim storage region of the HTR-PM spent fuel dry-storage system under multiple operation conditions are simulated and analyzed,respectively.Information about flow distribution and temperature profile under steady state,formation of natural ventilation and the solid temperature ascend process during blower failure accident are obtained.The results show that both the buffer storage region and the interim storage region can remove the residual heat effectively under normal operation condition and blower failure accident condition,and the maximum temperatures of the solid structures in the wells are lower than the temperature limits.The effect factors such as the canister inventory,environment temperature and surface emissivity of the solid structures are studied to extend the application range of the results.Finally,this work develops the transient analysis model and the TAC-DS code and applies into multicomponent flow.A case regarding smoke diffusion process in tunnel fire accident is simulated and analyzed.It shows that the transient analysis model can not only be applied to study the spent fuel dry-storage and cooling system but also be applied to analyze the gas component diffusion in the building ventilation system.