Dosimetry for a Biological Irradiation Facility at a Thermal Reactor

A description is given of an irradiation cavity in which small biological objects can be exposed to mixed neutrons and gamma -rays. The neutron/gamma ratio can be varied by the use of easily replaceable filters. The neutron spectrum and kerma were measured by activation techniques and the gamma -ray dose measured by neutron-insensitive thermoluminescent dosemeters. The fast neutron flux could be varied between about 108 and 109 n cm-2s-1 and the fast neutron kerma-rate between 103 and 104 rad/h, while the gamma -ray dose-rate can be varied between 102 and 104 rad/h. The kerma due to thermal neutron contamination is less than 1% when B4C filters are used.