Occupational radiation exposure control analyses of 14 MeV neutron generator facility: A neutronic assessment for the biological and local shield design

The 14 MeV neutron generator facility is being developed by the Institute for Plasma Research India to conduct the lab scale experiments related to Indian breeding blanket system for ITER and DEMO. It will also be utilized for material testing, shielding experiments and development of fusion diagnostics. Occupational radiation exposure control is necessary for the all kind of nuclear facilities to get the operational licensing from governing authorities and nuclear regulatory bodies. In the same way, the radiation exposure for the 14 MeV neutron generator facility at the occupational worker area and accessible zones for general workers should be under the permissible limit of AERB India. The generator is designed for the yield of 1012 n/s. The shielding assessment has been made to estimate the radiation dose during the operational time of the neutron generator. The facility has many utilities and constraints like ventilation ducts, accessible doors, accessibility of neutron generator components and to conduct the experiments which make the shielding assessment challenging to provide proper safety for occupational workers and the general public. The neutron and gamma dose rates have been estimated using the MCNP radiation transport code and ENDF –VII nuclear data libraries. The ICRP-74 fluence to dose conversion coefficients has been used for the assessment. The annual radiation exposure has been assessed by considering 500 h per year operational time. The provision of local shield near to neutron generator has been also evaluated to reduce the annual radiation doses. The comprehensive results of radiation shielding capability of neutron generator building and local shield design have been presented in the paper along with detailed maps of radiation field. •Radiation doses surround the lab during the operation of the neutron generator has been assessed considering all constrains.•Local shield has been designed to control the radiation exposure and keeping the accessibility for maintenance.•HDPE local shield makes the significant reduction in dose rates and use of B4C and cadmium can further enhance the efficiency.•Radiation field maps have been generated in order to take preventive measures in instruments and control design.•The assessment will support to get the operational licensing of the neutron generator from atomic energy regulatory board.