Monte Carlo determination of gamma-ray dose rate with the GEANT system.

Conversion factors for the dose rate 1 m above the ground level from the measured activities for different gamma-ray emitters in soil are calculated using the Monte Carlo method. The calculations are based on the GEANT system developed at CERN, Geneva. Results for the uniform and surface distribution of the emitters in the soil are given for gamma-ray energies in the interval between 20 keV and 3 MeV. They are similar to those of the recent report of ICRU that indicates that GEANT system is suitable for application in health physics problems. For 137Cs the dose rates for plane sources at different depths are given, which allow for the calculation of the dose rate for any depth distribution of the activity in the soil.

Chromosome aberrations induced in human lymphocytes by U-235 fission neutrons. Part II: Evaluation of the effect of the induced Na-24 activity on the chromosomal aberration yield.

Blood samples were spiked with Na-24 to study the separate effect of this nuclide on the incidence of chromosomal aberrations in neutron irradiated blood samples. A delay of 96 h was allowed before cultivation, so the results of chromosomal aberration analysis could be compared with the results obtained by direct irradiation of blood samples with U-235 fission neutrons [7]. The absorbed dose was calculated using a simple conservative model. From the results obtained we can conclude that Na-24 alone was not the reason for the difference in the incidence of chromosomal aberrations between blood samples cultivated immediately after "in vitro" irradiation by U-235 fission neutrons and samples which were cultivated after 96 h storage.