Passive Safety Small Reactor for Distributed Energy Supply: Heavy Water Mixing Core Available to Purchase

The purpose of this paper is to study the core performance of passive safety small reactor for distributed energy supply by changing the heavy water (D₂O) concentration in the mixed coolant together with the fuel pitch. The long core life with conditions of the excessive reactivity of 2 %Δk/k, the reactivity shutdown margin of 1 %Δk/k and the negative coolant temperature reactivity coefficient is attained for the case of D₂O concentration of 60 % with 10 % enrichment gadolinia (Gd₂O₃) doped fuel rods. This D₂O core has a shorter core life 4.14 years than the original light water (H₂O) core 4.76 years, while it needs a larger core size. However, changing the D₂O concentration on the way during the burn-up shows a possibility of extending more the core life than that of the original H₂O core.