Variation of environmental neutron flux with the depth of water and soil

金沢大学環日本海域環境研究センター金沢大学自然計測応用研究センター自然計測研究部門As a part of interest in the study of the neutron flux in biological environments, variations of slow neutrons with depth of water and soil were measured through the radioactivity induced in gold by 197Au(n,γ)198Au interaction. The measurements made for 0-100 cm in fresh water and 20-400 cm in sea water showed that the thermal neutron flux showed peak at around 10 cm depth and then gradually decreased with depth in water. The depth profiles in seawater were almost the same profile as freshwater. In the case of soil made for 0-60 cm, thermal neutron flux showed a peak at 5 cm then through a shoulder-like decrease during 10~30 cm range and decreased with depth gradually rapidly to 60 cm

Some Applications of the Gold Activation by Environmental Neutrons

金沢大学自然計測応用研究センター自然計測研究部門金沢大学環日本海域環境研究センターThe activation of gold by environmental neutrons was used to study the effect of concrete buildings at our laboratory (LLRL) on the neutron flux, and to estimate the thermal neutron flux in and around the building of Kinki University Training Reactor (UTR-Kinki). The results showed that three ceilings of thickness (34 g/cm2 each) decrease the fast neutrons to 26 %. However, the same reinforced concrete decreases the slow flux to only 62 %. On the other hand, the thermal neutron flux at 283m from the reactor center was two times higher than the environmental background. These results can give attention to the effect of concrete walls as a shielding around the reactors, especially those that have been hold near to the living environments