Beamline improvements to the MInes NEutron Radiography (MINER) facility

Abstract

The Colorado School of Mines designed and installed a neutron radiography system at the United States Geological Survey TRIGA reactor (GSTR) in 2012. Several potential improvements to this system have since been identified, particularly with respect to the neutron beamline. This thesis details the design of a new beamline to address some of the drawbacks of the present system. Computational analysis using MCNP determined that a 7.32 m long, un-lined, square aluminum beam tube with a 1 m circular pre-collimator produces a neutron beam with a lower divergence than an equal length collimator that has a neutron absorbing liner and no pre-collimator. The placement of graphite around the pre-collimator can boost beam intensity by up to 15%. The new beamstop will require an additional 720 kg shielding to keep the radiation dose rates comparable to the present beamline. Structural analysis also showed that the new beamline design has a smaller tendency to bend (by ~90%) than the current tube, and has a maximum buoyant force of 29.5 kg that will need to be overcome through the addition of ballast.