Session: 14-17 Student Paper Competition

Paper Number: 65504

Start Time: August 6, 2021, 04:45 PM

65504 - Influence of Fuel Pellets’ Thermal Expansion on Temperature Feedback Regulation for Megawatt-Class Space Gas-Cooled Fast Reactor 

As human beings explore the outer space, the demand for the nuclear sources in space missions is increasing. Almost all the existing space nuclear reactors have adopted the design of gas-cooled fast reactor, and the temperature feedback effect of the fuel of the small fast neutron reactor is different from that of the traditional pressurized water reactor. For the space fast reactors, they are designed to be compact and with a long operating lifetime to accomplish the long-term space missions. Due to the high-level enrichment of U-235 in the fuel, the Doppler effect of U-238 has little impact on the reactor reactivity. In the present paper, based on the design of the 1.15MWt space gas-cooled fast reactor, the overall temperature feedback adjustment capability of the core, and the overall temperature coefficient of the core including fuel, structural materials, and coolant are investigated. The calculation results show that the temperature of the coolant has little effect on the reactivity. The temperature coefficient of the fuel is positive, and the structural material with a large negative temperature feedback coefficient. At the same time, the deformation of the fuel pellets due to thermal stress at high temperatures and the reactivity changes caused by the deformation are analyzed. Calculate the temperature distribution of the fuel pellets by numerical simulation, and then use the results in the calculation of thermal stress in the way of mapping. Thermal stress will cause the fuel pellet to deform, which will expand in the axial direction. Due to the large number of fuel pellets in the core, the expansion of the pellets has a greater impact on the reactivity. The deformation results of the pellets at different temperatures were analyzed, and the reactivity changes of the reactor at different temperatures were calculated. Integrate the calculated results and fit the results into a curve to better describe the law between temperature and fuel pellet deformation. Finally, based on the temperature feedback results obtained from the above calculations, the physical characteristics of the reactor core are re-evaluated.

Presenting Author: He Yuhao Harbin Engineering University

Authors:

He Yuhao Harbin Engineering University
Yuan Dongdong Harbin Engineering University
Qiu Zhifang Nuclear Power Institute of China
Ning Kewei Harbin Engineering University
Wang Xiaoyu Nuclear Power Institute of China
Fulong Zhao Harbin Engineering University
Tan Sichao Harbin Engineering University