Optimization of the cold moderator for the new pulsed reactor NEPTUN

Abstract

The Frank Laboratory of Neutron Physics (FLNP) at the Joint Institute for Nuclear Research (JINR) has begun designing a new research reactor, NEPTUN, to replace the IBR-2M (pulsed fast reactor - the name in russian) reactor, which is expected to be out of service between 2032 and 2036. The IBR-2 reactor is a third-generation neutron source that started working in 1982 at Dubna, Russian Federation. The IBR-2M reactor was successfully modernized in 2012. The NEPTUN reactor is a fourth-generation neutron source that will use Np-237 as a nuclear fuel for the first time. It was studied if mesitylene (1,3,5-trimethylbenzene), which is now being utilized effectively in the reactor IBR-2M, might be used as a cold moderator in the new research reactor NEPTUN with an average thermal power of 15 MWt. A study of five materials used as a cold neutron moderator at various temperatures was also conducted. Longer working times for cold moderator material were another goal of optimization. According to the findings, mesitylene at a temperature of 20 K should be used as a cold moderator to get the greatest neutron flux at a wavelength of 3 ≤ λ ≤ 10 Å. Additionally, ortho hydrogen at 20 K could increases the cold neutron flux with wavelengths, λ ˃ 10 Å.