Neutron-induced radionuclides in soil from the JCO campus

Neutron-induced radionuclides in soil samples from the JCO campus were measured by non-destructive γ-ray spectrometry to estimate neutron fluence of a criticality accident. The soil samples were collected during the first and second surveys within the JCO campus. Radionuclides concentrations were measured by γ-ray spectrometry after dried, sieved through a 2 mm screen and homogenized in a molar. Neutron-induced radionuclides such as 24Na, 46Sc, 54Mn, 59Fe, 60Co, 65Zn, 82Br, 122,124Sb, 134Cs, and 140La were detected in their samples. All radionuclides detected were induced by the thermal neutron capture reaction except 54Mn, which was produced by (n,p) reaction with fast neutron. Specific activity with distances from precipitation tank, directional variation and depth profile in the soil samples were analyzed. Fast neutron fluence in the neighborhood of conversion building was estimated at 2.75-6.25x1010 (n/cm2) from value of 54Mn/Fe ratio at ground surface. (author)