Three accelerator experiments on source term and radiation shielding performed by the staffs of Japan Atomic Energy Agency (JAEA) to validate the accuracy of the radiation behavior simulation code PHITS (Particle and Heavy Ion Transport code System) are reviewed. In the measurement of neutron spectra from a thin beryllium target bombarded with [approximately]10-MeV protons, measured peak energies and values of the cross section were the same as those in the Evaluated Nuclear Data File ENDF/B-VII. In the measurements of forward-direction neutron spectra from thick targets bombarded with 140-, 250-, and 350-MeV protons, the calculated spectra from an iron target by the PHITS code agreed well with the measured spectra. In the measurement of neutron spectra from a tungsten target bombarded with [approximately]400-MeV protons, the shape of neutron spectra and its intensity are compared with that in Los Alamos Neutron Science Center/Weapons Neutron Research.