USE OF A BORON DOPED SPHERICAL PHANTOM FOR THE INVESTIGATION OF NEUTRON DIRECTIONAL PROPERTIES: COMPARISON BETWEEN EXPERIMENT AND MCNP SIMULATION

摘要

A boron doped 19 cm diameter spherical phantom was constructed to give information on the direction of neutrons inside the Ringhals 4 containment. The phantom was made of 40/100 paraffin and 60/100 boric acid.~10B contributes 2/100 of the total phantom weight. The phantom was tested for its angular sensitivity to neutrons. The response was tested with a ~252 Cf source and with a Monte Carlo calculation (MCNP) simulating a ~252Cf source. In these investigations the phantom showed a strong directional response. However, there was only a fair correspondence between the experiment and the simulation. The discrepancies are, at least in part, due to the difference in energy and angular response of the dosementers as compared with the idealised response characteristics in the MCNP calculation. In the MCNP calculation the experimental conditions were not fully simulated. The investigations also showed that the addition of boron to the phantom reduces the leakage of thermalised neutrons from the phantom,and the production of neutron induced photons in the phantom to insignificant levels.