Monitoring of Intermediate-Energy Neutrons

In working areas around reactors and accelerators, neutrons In the Intermediate-energy range can contribute a substantial fraction of the total neutron dose-equivalent. Instruments available at present for monitoring intermediate -energy and fast neutrons make use of a thermal neutron detector surrounded by a suitable moderator. Such Instruments can be unwieldy and can also give rise to large errors in dose measurements Involving a predominantly Intermediate- energy spectrum of neutrons. This paper describes a method of monitoring thermal and Intermediate-energy neutrons up to 300 keV by means of a cadmium-covered boron-trlfluoride counter. The intermediate-energy spectrum is assumed to be of 1/E type from 0.3 eV to 10 keV, 1/E08 type from 10 keV to 100 keV and 1/E05 type from 100 keV to 300 keV This Instrument is (a) more portable, and (b) reasonably accurate, since the calibration factor In the present case is derived from an exact fit of the dose-equivalent values at various energies. The paper also discusses preliminary results obtained with a personnel monitoring device for Intermediate-energy neutrons, which consists of a cadmium-boron filter and a track recording plastic. For this device, the contribution due to the backscattered spectrum from the body has also been taken into account. (author)