First neutron computed tomography with digital neutron imaging systems in a high-radiation environment at the 250 kw neutron radiography reactor at idaho national laboratory

The Neutron Radiography Reactor (NRAD) at Idaho National Laboratory (INL) was designed for thermal and epithermal neutron radiography for examination of highly-radioactive irradiated nuclear fuel elements. Radioactive samples are remotely lowered into the East and North Radiography Stations (ERS and NRS, respectively), and a rail transfer system remotely positions radiography cassettes into the detector position for indirect radiography. The indirect transfer method with film has been used at NRAD for around forty years, but recent efforts seek to develop digital camera-based neutron imaging systems. Two initial camera detector systems were built using an inexpensive but high-quality scientific CMOS camera with robust shielding, and tests were performed in collaboration with Heinz Maier-Leibnitz Institut of Technische Universität München. The first measurements in the ERS provided valuable experience that informed the design of an improved neutron imaging system that was tested in the NRS. The first successful digital neutron computed tomography at INL was acquired, consisting of 421 neutron radiographs acquired in 4 hours. These first tests with camera-based neutron imaging systems have demonstrated the potential to both increase the throughput of radiography by two orders of magnitude and provide higher quality spatial information with three-dimensional tomographic reconstructions compared to two-dimensional radiographic projections, which represent a significant improvement compared to current film radiography capabilities.