# Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2019, Vol. 30 ›› Issue (11): 166

• NUCLEAR ENERGY SCIENCE AND ENGINEERING •

### Influence of 235U enrichment on moderator temperature coefficient of reactivity (MTC) in a graphite-moderated Molten Salt Reactor (MSR)

Xiao-Xiao Li,1, 2 De-Yang Cui,3 Yu-Wen Ma,3 Xiang-Zhou Cai,3 Jin-Gen Chen3

1. 1 Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
2 CAS Innovative Academies in TMSR Energy System, Chinese Academy of Sciences, Shanghai 201800, China
3 University of Chinese Academy of Sciences, Beijing 100049, China
• Received:2019-02-28 Revised:2019-07-11 Accepted:2019-07-13
• Contact: Xiang-Zhou Cai E-mail:caixz@sinap.ac.cn
• Supported by:
This work was supported by the Chinese TMSR Strategic Pioneer Science and Technology Project (No. XDA02010000) and the Frontier Science Key Program of the Chinese Academy of Sciences (No. QYZDY-SSW-JSC016).
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Xiao-Xiao Li, De-Yang Cui, Yu-Wen Ma, Xiang-Zhou Cai, Jin-Gen Chen. Influence of 235U enrichment on moderator temperature coefficient of reactivity (MTC) in a graphite-moderated Molten Salt Reactor (MSR).Nuclear Science and Techniques, 2019, 30(11): 166
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Abstract: To optimize the temperature coefficient of reactivity (TCR) for a graphite-moderated and liquid-fueled molten salt reactor, the effects of fuel salt composition on the fuel salt temperature coefficient of reactivity (FSTC) were investigated in our earlier work. In this study, we aim to provide a more comprehensive analysis of the TCR by considering the effects of the graphite-moderator temperature coefficient of reactivity (MTC). The effects of 235 U enrichment and heavy metal (HM) proportion in the salt mixture on the MTC are investigated from the perspective of the six-factor formula based on a full-core model. For the MTC (labeled “ αTM ”), the temperature coefficient of the fast fission factors ( αTM(ε) ) is positive, while those of the resonance escape probability ( αTM(p) ), the thermal reproduction factor ( αTM(η) ), the thermal utilization factor ( αTM(f) ), and the total non-leakage probability ( αTM(Λ) ) are negative. The results reveal that the magnitudes of αTM(ε) and αTM(p) for the MTC are similar. Thus, variations in the MTC with 235 U enrichment for different HM proportions are mainly dependent on αTM(η) , αTM(Λ) , and αTM(f) , but especially on the former two. To obtain a more negative MTC, a lower HM proportion and/or a lower 235 U enrichment is recommended. Together with our previous studies on the FSTC, a relatively soft neutron spectrum could strengthen the TCR with a sufficiently negative MTC.