No abstract

A large amount of radioactive waste liquid is generated in the spent fuel reprocessing process, and high-level waste is stored in a high-level waste tank. During storage, a hydrogen explosion accident may occur, resulting in the leakage of radioactive materials. This article reviewed the basic situation of high-level waste liquid and high-level waste storage system. The safety analysis of the hydrogen explosion accident was conducted, from the source and generation mechanism of hydrogen, the accumulation process of hydrogen in the tank, the possible ignition source and the possibility of explosion in the tank, the pressure generated by the hydrogen explosion, and the probability of tank failure due to hydrogen explosion are discussed. Suggestions were made on the design, operation, and safety analysis of high-level waste tanks in China, which provided a reference for the safe development of high-level waste storage facilities in commercial reprocessing plants.

Criticality safety needs to be considered carefully during the transport of nuclear fuel assemblies. Several factors should be taken in to account, such as package arrays, container damages under hypothetical accident condition, water moderation conditions and so on. In this work, criticality safety analysis has been carried out for a Westinghouse XL shipping container loaded with AP1000 fuel assemblies. The fuel assembly and transport container have been modeled and simulated using the MCNP code. The results of MCNP show that the Westinghouse XL package is subcritical, if the number of packages meets the requirements in the approval of the competent authority.

The isotopes of uranium and their daughter nuclides inside the UO2 pellet emit mono-energetic electrons and beta rays, which generate rather high dose rate near the UO2 pellet and could cause exposure to workers. In this work calculations of electron dose rates have been carried out with Monte Carlo codes, MCNPX and Geant4, for a UO2 pellet and a fuel rod. Comparisons between calculations and measurements have been carried out to verify the calculation results. The results could be used to estimate the dose produced by electrons and beta rays, which could be used to make optimization for radiation protection purpose.

China has been attaching greater attention to the safety supervision on the transport of radioactive material packages, one key part of which is the radiation monitoring to the radioactive material packages and vehicles. Issues on the radiation monitoring and safety supervision of radioactive material packages transportation discussed include: (1) Determination of proper monitoring location close to package surface; (2) Neutron radiation monitoring; (3) Choosing proper detectors for complicate radiation field monitoring; (4) Optimization of surface contamination monitoring. The requirement in Chinese standard and solution on above issues during practice are also given.