Design and testing of an irradiation room with low room-scattering for neutron calibration

This laboratory plans to establish neutron reference radiation fields with three neutron sources to calibrate neutron-measuring devices. To perform calibration at multiple dose rates, neutron ambient dose equivalent rate H˙^*(10) needs to range 1 μSv/h to 10 mSv/h. The lower limit requires that the maximum available calibration distance should be at least 4.5 m.

To reduce room-scattered neutrons and extend the available calibration distance, MC simulations were conducted to determine the material and size of the irradiation room. A 3″ Bonner sphere and a LB6411 environmental neutron dosimeter were used to characterize the irradiation room.

A 14.32 × 14.32 × 12.00 m³ irradiation room was built based on simulation results. Floor, roof, and walls are made of 75 cm concrete covered by a coating layer of 2 cm BPE and 3 cm PE. Experimental maximum available calibration distance reaches 4.65 m. The range of H˙^*(10) for calibration covers 1 μSv/h to 10 mSv/h. Neutron and photon H˙^*(10) outside the room are within 0.19 μSv/h and 0.22 μSv/h, respectively.