Calculation of the Total Absorbed Dose of the BNCT Method in a Water Phantom at the Dalat Research Reactor

In this paper, the distribution of absorbed dose components of the BNCT method in a water phantom at the Dalat Nuclear Research Reactor (DNRR) was calculated using the MCNP5 code. The configuration of horizontal neutron channel No.2 of the DNRR, which contains a cylindrical collimator with neutron filters of 20 cm Si and 3 cm Bi, was simulated. The thermal neutron flux and gamma dose rate in the water phantom at the DNRR have been calculated; there is a good agreement between the calculated and experimental values. In the phantom, the gamma dose mainly from the ¹H(n,γ)²H reaction has the maximum value of 2.41×10^-6 Gy at the 0.5 cm depth, and reduces to 7.78×10^-7 Gy at the 3 cm depth. The gamma dose is about 400 times greater than that from the reactor but is about 2 times smaller than the thermal neutron dose. Besides, the total absorbed dose has a maximum value of 6.84x10^-5 Gy and decreases rapidly to 1.50×10^-5 Gy at depths 0.5 cm and 3 cm, respectively. It strongly depends on the boron and thermal neutron doses. Total absorbed dose of the BNCT method in a phantom mainly depends on the thermal neutron flux, the concentrations of ¹⁰B and ¹⁴N. (author)