KENS Shielding Experiment (2): Measurement of the Neutron Spatial Distribution inside and outside of a Concrete Shield using an Activation Foil and an Imaging Plate Technique

The spatial distribution of neutrons inside and outside the concrete shield of KENS was measured by the combined use of activation detectors and an imaging plate. Aluminium and gold foils were used for neutron flux measurements of both high-energy and thermal neutrons, respectively. The obtained results concerning attenuation of the high-energy neutron flux show a good agreement with results obtained by a Monte Carlo simulation using the MARS 14 code. The thermal and epithermal neutron flux ratio on the beam axis was measured by the cadmium ratio method, and gave about 30, which almost constant inside the concrete shield. It is concluded that the method, which combined the use of activation detectors and an imaging plate, was very useful to measure the activity of many pieces of the detector simultaneously without any efficiency or decay correction. A wide dynamic range and a high sensitivity are also merits of this method.