Dose equivalent due to cosmic-ray neutrons in a ferroconcrete building

Dose equivalent rates due to natural neutrons are estimated at sea level in Fukuoka (geomagnetic latitude 210 N) from the neutron energy spectra obtained by Hess et al. and are measured to be 0.39 μrem/h by a neutron rem-counter. Both the estimated and the measured values agree well with each other. Neutron dose rates are also measured at several places on each floor in a six-storey ferroconcrete building. The measured values of dose rates are distributed between two values on a floor. The smaller one corresponds to a dose rate due to neutrons attenuated through concrete floors above a room where the dose rates are measured. The larger one is that induced by neutrons which penetrate the building wall from the outside atmosphere. (author)