Research on prevention and detection technology of flow channel blockage accident of plate-type fuel elements

[Background] Plate-type fuel element exhibits excellent irradiation properties in research reactor while the grid spacing between the fuel element plates is usually very small. Most of the blockage accidents are caused by foreign matters entering the flow channel or fuel swelling due to the narrow coolant flow channel in the core. [Purpose] This study aims to analyze the process of blockage accidents, and put forward effective preventive measurements and detection methods. [Methods] Based on the investigation of some typical accidents abroad, China advanced research reactor (CARR) was taken as a feature research object, and the thermal hydraulic simulation calculation of CARR core, reactor body, single fuel assembly and cooling circuit outside the reactor was carried out by using the RELAP5/MOD3.2 thermal calculation program. Modeling and analysis of the specific flow channel blockage accident process on CARR was finished. [Results] Simulation results show that the temperature of the fuel assembly in the blocked flow passage will increase when the reactor power is raising, then the coolant will begin to boil, and the power will fluctuate significantly. [Conclusions] It is necessary to strictly control the quality of core operation. The monitoring of neutron flux rate and reactor power, and analyzing fuel temperature are helpful to detect and prevent the further development of the blockage accident. (authors)