No abstract

A fixed radiation portal monitors (RPM) deployed at border, seaport, airport or key traffic checkpoints has played an important role in preventing the illicit trafficking and transport of nuclear and radioactive materials. However, the RPM usually is large and heavy and can't easily be moved to a different location. An intelligent terrorist may also circumvent the fixed RPM to avoid being detected. These reasons motivate us to develop a mobile radiation detection system. The objective of this paper is to report our experience on developing the mobile radiation detection system for the search and detection of nuclear and radioactive materials during road transport. Measurements were performed at various speeds and distances between the radioactive isotope(RI) transporting car and the measurement car. Results of our measurements and the detection limits of the system is described in this paper. The mobile radiation detection system developed should contribute to defending public's health and safety and the environment against nuclear and radiological terrorism by detecting nuclear or radioactive material hidden illegally in a vehicle.

A Monte Carlo simulation-based optimization of a SERS-based thermal neutron detector is aimed at improving detection efficiency for thermal neutrons. The moderator and collimator have been designed for a 241Am-9Be source to maximize the thermal neutrons flux in the irradiation area. Simulated thermal neutron detection efficiency can be increased to approximately 50.5% when polyethylene is added as neutron reflector and 10B enriched 4-MPBA is used. With Monte Carlo software GEANT4, the SERS-based thermal neutron detector has been proven to have almost no effect on original thermal neutron flux as well as the distribution and could be used for thermal neutron detection accurately.