Epithermal Neutron Time-of-Flight Facility Using Research Reactor at Penn State

An epithermal neutron time-of-flight (TOF) facility is being developed at the Penn State Breazeale Reactor (PSBR). Various novel designs of a mechanical neutron chopper are being explored to produce nearly monoenergetic pulses of neutrons up to 40 eV. These neutrons will be used for epithermal neutron activation analysis (ENAA) for material samples from various stages of nuclear fuel cycle, as well for epithermal-neutron imaging (ENI). Specifically, four different mechanical chopper designs are currently being investigated and each design is intended to act as a mechanical shutter to pulse a continuous neutron beam at PSBR. Fermi choppers and disc choppers are compared to two novel design approaches; pistons and rings. The piston chopper offers the ability to carry a sufficient amount of absorbing material at the expense of a small slit width. The ring chopper is able to act as a monochromator due to its inherent geometry; however, the inertial stresses of a rotating ring impose theoretical limits for pulse intensity and energy resolution.