Dosimetry and biological results of mice irradiations in mixed neutron-gamma fields

Abstract Mice irradiations have been carried out for many years in the biological irradiation facility of the light water research reactor of the Central Research Institute for Physics, Budapest. The neutron/gamma dose ratio can be varied by altering the thickness of the bismuth filter placed between the reactor core and the irradiation facility. The dose intensities are calibrated after fuel replacement by the use of activation, track and thermoluminescent detectors. During irradiation the exposure is monitored by a GM counter. The actual doses are then calculated from the reactor power, irradiation time and the monitor response. The inhomogeneity of the dose distribution within the body of a single mouse/due to absorption and scattering of the neutrons/ was calculated by a Monte Carlo code and measured in a lucite mouse phantom. The main biological consequences found in the animals irradiated in utero are brain weight decreases, damage to protein synthesis, and changes in the function of the central nervous system.