The low-enriched uranium core design of a MW heat pipe cooled reactor

•Methods to reduce the fuel enrichment in a heat pipe cooled reactor was researched.•A conceptual design of a heat pipe cooled reactor using low-enriched uranium fuel was proposed.•The performance of schemes using high-enriched uranium fuel and low-enriched uranium fuel was compared.•The effect of adding moderator rods on the reactor core parameters was studied. The heat pipe cooled reactor usually has compact core and fast neutron spectrum, which requires highly enriched fuel. For better nuclear non-proliferation performance, a low-enriched uranium reactor core design, UPR-SL, has been proposed on the basis of the existing heat pipe cooled reactor core design UPR-S in this paper. A high-density UN fuel was used to replace the original UO2 fuel to reduce the fuel enrichment. The core diameter of 1 m and the 1 MW thermal power were inherited from UPR-S. The new reactor has a total of 109 heat pipes, 436 fuel rods, and 88 moderator rods in the active zone. The core length and control system were redesigned using the SARAX code system. The lifetime, power distribution, control rod worth and reactivity feedback were analyzed. The results show that using high-density fuel, increasing the axial length of the active core and introducing local neutron moderation into the active core are effective to reduce the fuel enrichment for a heat pipe cooled reactor with no degradation of core performance. The softened neutron spectrum brought stronger feedback to the core.