Transport of Methane Pellets for Advanced Cold Moderators

73071S03-I 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, the existing methane pellet machine will be modified to improve the flow characteristics of the pellets, which tend to stick together. The pellets will be sub-cooled to temperatures below 50 K and accumulated in a fluidized bed, capable of rapidly filling a moderator with a charge of pellets. A prototype pellet moderator system will be designed for construction and testing in Phase II. 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.