To provide a reliable and comprehensive data reference for core geometry design of graphite-moderated and low-enriched uranium fueled molten salt reactors, the influences of geometric parameters on the temperature coefficient of reactivity (TCR) at an assembly level were characterized. A four-factor formula was introduced to explain how different reactivity coefficients behave in terms of the fuel salt volume fraction and assembly size. The results show that the fuel salt temperature coefficient (FSTC) is always negative owing to a more negative fuel salt density coefficient in the over-moderated region or a more negative Doppler coefficient in the under-moderated region. Depending on the fuel salt channel spacing, the graphite moderator temperature coefficient (MTC) can be negative or positive. Furthermore, an assembly with a smaller fuel salt channel spacing is more likely to exhibit a negative MTC. As the fuel salt volume fraction increases, the negative FSTC first weakens and then increases, owing to the fuel salt density effect gradually weakening from negative to positive feedback and then decreasing. Meanwhile, the MTC weakens as the thermal utilization coefficient caused by the graphite temperature effect deteriorates. Thus, the negative TCR first weakens and then strengthens, mainly because of the change in the fuel salt density coefficient. As the assembly size increases, the magnitude of the FSTC decreases monotonously owing to a monotonously weakened fuel salt Doppler coefficient, whereas the MTC changes from gradually weakened negative feedback to gradually enhanced positive feedback. Then, the negative TCR weakens. Therefore, to achieve a proper negative TCR, particularly a negative MTC, an assembly with a smaller fuel salt channel spacing in the under-moderated region is strongly recommended.

为了为石墨慢化和低浓铀燃料熔盐反应堆的堆芯几何设计提供可靠和全面的数据参考，表征了几何参数对装配级反应温度系数 (TCR) 的影响。引入了一个四因素公式来解释不同的反应性系数在燃料盐体积分数和组件尺寸方面的表现。结果表明，燃料盐温度系数（FSTC）总是负的，这是由于在过度缓和区域中更负的燃料盐密度系数或在欠缓和区域中更负的多普勒系数。根据燃料盐通道间距，石墨减速剂温度系数 (MTC) 可以为负或正。此外，具有较小燃料盐通道间距的组件更有可能表现出负 MTC。随着燃料盐体积分数的增加，负FSTC先减弱后增大，这是由于燃料盐密度效应从负反馈逐渐减弱到正反馈然后减小。同时，随着石墨温度效应引起的热利用系数恶化，MTC减弱。因此，负TCR先弱后强，主要是由于燃料盐密度系数的变化。随着组件尺寸的增加，由于燃料盐多普勒系数单调减弱，FSTC 的幅度单调减小，而 MTC 从逐渐减弱的负反馈变为逐渐增强的正反馈。然后，负 TCR 减弱。所以，