Dose Field Research of Analysis Room for In-Hospital Neutron Irradiator

Neutron equivalent dose rate and γ ray dose rate inside the analysis room of the inhospital neutron irradiator (IHNI) and outdoor were measured. The results show that γ ray dose rate inside the analysis room exceeds calculation value many times and γ ray dose rate outdoor is higher than supervision region dose limit of 7.5 μSv/h. According to the measurement results and the Monte Carlo simulation, the following shielding plan was adopted. Lead shielding with thinkness of 16 cm was installed on the wall, which faces the neutron beam, to shield γ ray, and lithium polyethylene plate with thinkness of 1 cm was installed on all the wall (not including ceiling and floor) to shield scattering neutron. After shielding transformation, the highest γ ray dose rate point inside the analysis room decreased 277 times, the neutron equivalent dose rate decreased 5.8 times, and the outdoor γ ray dose rate decreased nearly 90 times.