Imaging of Fast Neutrons and Gamma Rays from 252Cf in a Heavily Shielded Environment

A 75 MBq 252Cf neutron source stored inside a steel water tank was characterised using a compact fast-neutron and gamma-ray imaging system based on a passive slot modulation imaging technique. Radiation fields were imaged from a variety of positions with the source in the stored position (located in the center of the water tank: high shielding) and in the exposed position (located at the edge of the water tank: low shielding). It was possible to locate the 252Cf source in each image and gain additional information of the neutron and gamma-ray fields in the local environment including scatter contributions from the steel shield, floor and walls in proximity to the source. A long exposure image of the stored source, taken over thirty days, identified the location of the radiation source from the low dose ( < 1 μ Sv / h ) field penetrating through 46 cm of water in the storage tank

The potential of real time, fast neutron and gamma radiography for the characterization of low-mass, solid-phase media

Most techniques that are used for transmission imaging with ionizing radiation use X-rays, which have the advantage of providing quick, high-resolution images with a relatively small dose of radiation. However, they also have the disadvantage that their penetrating power can be limited in some forms of matter. This can make the discrimination of materials with a low atomic number particularly challenging. Of specific interest in this regard is the need to screen a diversity of manmade items that are heterogeneous and with the tendency to have many interfaces between components that can comprise a diversity of low-mass elements and compounds. These items usually have a compact geometry and a high density of components, which can make them less easy to be imaged quickly and effectively with X-rays. This limit of current screening technology necessitates further stages of examination reducing the ease with which this is done for manufacturing and quality assurance applications. The results presented in this paper demonstrate that, either via fast-neutron radiography or tomography, the potential exists to discern a variety of low-A compounds from one another. Via Monte Carlo simulations, it will be shown that fast-neutron radiography undertaken with a portable, isotopic radiation source (californium-252), absorption and scattering by the doped polymeric materials yields a degree of distinction from other substances. Considering these results, the state-of-the-art of the technique leading to the realization of a combined, real-time fast-neutron and gamma-ray radiography system will also be presented, as well as the first experimental results