Directional neutron surveys on a semiautonomous mobile robot for a radiological vault

Monitoring of stored nuclear materials is time consuming and can expose human workers to high levels of radiological risk. The use of robotics in the nuclear complex has the ability to provide increased monitoring while lowering dose. Radiation detectors are essential tools for assessing the hazards present in everyday work and need to be incorporated with robotic systems. However, since there are often many materials collocated in storage areas, the ability to determine the direction and thus source of radiation in a crowded room would provide a better understanding of where the radiological hazards are. A Bridgeport Instruments boron-10 neutron scintillator detector was well characterized to determine inherent directional dependencies. Modeling of a neutron shield to create an artificial aperture around the neutron detector was performed in MCNP. Once the shielding was fabricated, the performance of the aperture was evaluated with a Cf-252 neutron source. The shielding resulted in a maximum 21.75% difference in radiation coming directly through the aperture versus from a different direction. A Pioneer LX robot was successfully approved for operation in the main plutonium facility at Los Alamos National Laboratory. The neutron detector was integrated with a Waypoint Robotics Vector platform, and performed an autonomous survey of storage containers with sealed radioactive sources. This work has been reviewed and issued LANL LA-UR-19-31470.