论文部分内容阅读
With respect to a liquid-fueled molten salt reactor (MSR),the temperature coefficient of reactivity mainly includes the moderator temperature coefficient (MTC) and the fuel salt temperature coefficient (FSTC).The FSTC is typically divided into the Doppler coefficient and the density coefficient.In order to compensate for the potentially positive MTC,the FSTC should be sufficiently negative,and this is mostly optimized in terms of the geometry aspect in pioneering studies.However,the properties of fuel salt also directly influence the FSTC.Thus,the effects of different fuel salt compositions including the 235U enrichment,heavy metal proportion in salt phase (HM proportion),and the 7Li enrichment on FSTC are investigated from the viewpoint of the essential six-factor formula.The analysis is based on an undermoderated MSR.With respect to the Doppler coefficient,the temperature coefficient of the fast fission factors (αT(ε)) is positive and those of the resonance escape probability (αT(p)),thermal reproduction factor (αT(η)),thermal utilization factor (αT(f)),and total non-leakage probability (αT(∧)) are negative.With respect to the density coefficient,αT(P) and αT(η) are positive,while the others are negative.The results indicate that the effects of the 235U enrichment and HM on FSTC are mainly reflected in αT(ε) and αT(P),which are the dominant factors when the neu tron spectrum is relatively hard.Furthermore,the 7Li enrichment influences FSTC by αT(f) and αT(∧),which are the key factors in a relative soft spectrum.In order to obtain a more negative FSTC for an under-moderated MSR,the possible positive density coefficient,especially its αT(P),should be suppressed.Thus,a lower 235U enrichment (albeit higher than a certain value,5 wt％ in this article) along with a lower HM proportion and/or a higher 7Li enrichment are recommended.The analyses provide an approach to achieve a more suitable fuel salt composition with a sufficiently negative FSTC.