Research on Multi-objective Optimization of Flow Distribution in Natural Circulation Reactor Whole Life-Cycle

The design of core flow distribution is the key content of core structure optimization of natural circulation reactor, which is highly valuable for improving core economy and safety. In this paper, the local optimal flow distribution calculation model is constructed based on the reactor closed parallel multi-channel model, and the existing flow distribution scheme is analyzed. Aiming at its limitations, a multi-objective comprehensive evaluation method based on the optimal time zone is proposed, which can realize the optimization calculation of the whole life-circle multi-objective reactor flow distribution. According to the proposed theory, combined with the TOPSIS comprehensive evaluation method, the maximum output power under natural circulation, the maximum temperature difference at the outlet during the reactor life-circle, and the standard deviation of the maximum temperature difference over time are used as attribute values to develop the optimization of core flow distribution scheme for a small long-life natural cycle lead-bismuth fast reactor SPALLER-100. The research results show that the flow distribution scheme of SPALLER-100 reactor core is the best based on the power distribution of 3182 d running time. Compared with the flow distribution scheme based on the power distribution at the beginning of life circle, the maximum temperature difference at the core outlet is reduced by 30 K, the standard deviation of the maximum temperature difference at the core outlet with time is reduced by 41%, and the maximum output power of the reactor natural cycle is increased by 2.35%.