Abstract
Researches for biological effect to fast neutrons have been done using NASBEE (Neutron Accelerator System for Biogical Effect Experiment) in NIRS. Neutron beam is produced by 4 MeV deuteron bombarding to thick berylium target. Neutron beam is irradiated to whole body of mice. At the next step, in rder to examine lung cancer of rat, neutron beam was locallized irradiation to rat. The beam is collimated within 4 cm slit width and shielded with iron and polyethylene blocks. Neutron beam specification in the neutron exposured and shielded areas were examined with exposure and absorbed dose rates of neutrons and photons, dose rate profiles, and suvival fraction of colony creation of epithelium cell (new born rat).
The exposured neutron dose rate is 0.05 Gy/min and neutrons are shielded to be decreased to less than 10% on the absorbed dose rate. Gamma rays are produced from the target via the neutron production. In the neutron beam, gamma rays are contaminated to be about 15%. Based on measured microdositry distributions of neutron and photon, RBE value at 2 Gy for endpoint crypt cell survival is obtained to be 3.3.
Now, the locallized neutron irradiation to rat lungs is prepared, (starts at the September 2009). The collimated neutron beam is useful tool to study neutron effect in locallized area.
