Neutron shielding for the RIKEN SSC

Calculation of neutron shielding by a hemi-spherical concrete covering at the center of which a point source is located was carried out by taking into account the effect of the inelastically scattered neutrons, and the dose rate multiplied by the square of the distance from the source to the observing point was obtained as a function of the depth of the shielding material. Rough estimation of skyshine for a point source enclosed by a cylindrical covering was also performed using the empirical equation of Thomas. On the basis of the calculated results, shielding consideration for the wall, roof and beam dump was given to get the external neutron dose below tolerance levels. (author)