Design and optimization of the new LEU MNSR for neutron radiography using thermal column to upgrade thermal flux

In this article, the preliminary feasibility of using the new miniature neutron source reactor (MNSR) with unique thermal column (TC), as a neutron source for neutron radiography (NR), is investigated. The new reactor core is designed based on the Isfahan MNSR with high density low-enriched uranium (LEU) UO2 fuel instead of high-enriched uranium (HEU) UAl4-Al fuel. The safety of the LEU reactor is studied by the calculation of important neutronics parameters such as core excess reactivity, central control rod worth, shut-down margin (SDM) and effective delayed neutron fraction. The vertical collimator dimensions, the materials to be employed in the collimator, and the collimator position are optimized using MCNP Monte Carlo code. The results showed that presence of the graphite thermal column increases thermal neutrons flux and reduces gamma-ray dose that can satisfy the requirements for neutron radiography. Therefore there is no need for extra gamma filters, fast neutron filters, and neutron moderators at the collimator. We emphasize here that the current designed LEU MNSR can be applied for NR and neutron activation analysis (NAA).