Neutron flux and gamma dose rate measurements in RMC's SLOWPOKE-2 reactor

A shielded sample enclosure in the RMC SLOWPOKE-2 reactor is being investigated for future studies of irradiation effects on I&C cables. To inform the construction of the enclosure, half-power (10 kW) MCNP simulations were performed Compared to aluminum, zircaloy-4 and tungsten, lead was found to be most effective at selectively shielding gamma rays for various enclosure designs. The neutron flux and gamma dose rates calculated in the selected enclosure model with 1 cm of lead shielding were 1.81⋅10 10 n⋅cm -2 ⋅s -1 and 37.9 krad⋅hr -1 , respectively. The neutron flux and gamma dose rates were then measured in the constructed enclosure. The neutron flux ranged from 1.80⋅10 10 to 2.81⋅10 10 n⋅cm -2 ⋅s -1 , while the gamma dose rate ranged from 91.5 to 111 krad⋅hr -1 . Additional trials were performed using cadmium and boric acid shielding on the probe to protect against neutron interference on the gamma probe and rectify differences between the modeling and experimental results. Using cadmium, the gamma dose rate increased between 10 and 29%, and using boric acid, was decreased by 13%.