Transport of Methane Pellets for Advanced Cold Moderators

73071-Existing and planned neutron facilities, such as the Spallation Neutron Source, generate pulses of cold neutrons for materials research. The efficiency of the beam line components, which convert the fast neutrons to a cold neutron beam, determines the usefulness of the facility. Existing solid methane moderators have a high efficiency, but they can¿t be scaled to work on planned high power sources. However, a cold moderator using solid methane pellets should be capable of high power operation, and the technology for producing methane pellets has recently been demonstrated. This project will extend the technology to allow circulation of the pellets into and out of a remote moderator cell. In Phase I, methods were developed to improve the flow characteristics of the pellets, which tend to stick together. A cryogenic rotary drum hopper was developed, which allowed the pellets to be stored without sticking. In Phase II, a full scale cryogenic pellet storage and transport system will be developed. The system will include a larger rotary drum with an indirect pellet cooling system. A pellet discharge chute will be designed to rapidly transfer the pellets to a remote prototype moderator. Commercial Applications and Other Benefits as described by awardee: Compared to a conventional hydrogen moderator, a methane moderator using this cryogenic pellet technology would double the output of cold neutrons. The pellet technology also could be used for improving commercial dry ice pellet blasting machines.