Study on the Transport Mechanism and Troubleshooting Analysis of Spherical Fuel in High Temperature Gas Cooled Reactor
Authors: Wang Jinhua , Hao Yuchen , Li Yue , Wu Bin , Wang Haitao , Ma Tao 
Published: October 2021

Abstract
With the global warming, it is imperative to develop green and environmentally sustainable energy. Although wind and solar energy can meet the demand of civil power to a certain extent, the contribution of nuclear power is still indispensable for large-scale industrial development of power.
After several major nuclear power accidents, main countries in the world hope to develop more safe nuclear power technology, which can fundamentally avoid reactor core melting and large-scale radiation leakage accidents. At present, some units of the third-generation nuclear power technology have been put into operation, and its safety is greatly improved compared with the second-generation nuclear power technology. The fourth-generation nuclear power technology is still in the process of development. The Pebble Module High Temperature gas-cooled Reactor demonstration project (HTR-PM) with the fourth-generation nuclear power safety technology in China has been completed and is undergoing commissioning test and trial operation. After the completion of the research and design of high temperature gas cooled reactor demonstration project, the research and design of multi-module high temperature gas cooled reactor is currently under way to meet the economic requirements of the fourth-generation nuclear power technology.
The pebble bed high temperature gas cooled reactor developed in China adopts the method of continuous refueling without reactor shutdown to improve the operation rate of the unit. The spherical fuel elements of the reactor are continuously loaded into the core through stainless steel pipes, and the fuel elements reaching the burn up depth are discharged into the spent fuel storage tank through pipes for storage. Considering that the spherical fuel element of high temperature reactor has graphite material matrix, which may cause the element to be damaged due to some special reasons, the separation mechanism of the damaged elements is set at the bottom of the reactor and the bottom of the key equipment, which can separate the fuel elements that do not meet the size requirements for separate storage, so most of the elements in the fuel element transmission pipeline meet transportation requirements.
Considering that there are damaged elements in the fuel element transmission pipeline under extreme conditions, it is necessary to ensure that the damaged elements can still be transported in the pipeline. Therefore, it is necessary to study the transmission law of various possible damaged elements in the pipeline, to provide basis for the actual operation of the project. At the same time, if there is a smaller probability of damaged elements, fuel element may stuck in the pipeline, it is required to be able to judge the occurrence of the accident as soon as possible, and use simple and easy methods to remove the element stuck accident, providing the basis for the maintenance of the project. This paper focuses on the transmission law of the damaged elements in the pipeline, the element stuck law and the removal method after the element stuck, to solve the potential accident of the online refueling system of the high temperature reactor to a certain extent, which has an important role in the operation and maintenance of practical engineering projects.