An accident-tolerant control drum system for a small space reactor

• An accident-tolerant control drum system for space reactor was proposed.
• The neutronic performance of the proposed control drum system was investigated.
• The new system improved reactor safety during various launch accidents.
• A mass reduction can be achieved as well by adopting the new system.

In this paper, an accident-tolerant control drum system was proposed to enhance the safety of space reactors in various launch accidents and the safety enhancement was demonstrated for a LEU-fueled and a HEU-fueled space reactors. The space reactors with an accident-tolerant control drum system remain subcritical even when all the control drums are missing while the reactors with a control rod system become supercritical when a control rod is missing without any damage in reflector. The heterogeneous LEU-fueled space reactor with an accident-tolerant control drum system remains subcritical even when it is immersed in dry sand, wet sand, or water with two adjacent control drums are rotated to the operation position. The HEU-fueled space reactor with an accident-tolerant control drum system remains subcritical even when it is immersed in various surrounding materials with one or two control drums rotated to the operation position depending on the thickness of the reflector. Besides the safety enhancement, a reduction of the total reactor mass was achieved by adopting an accident-tolerant control drum system instead of a control rod system.