An assessment of helium gas behavior in SP-100 class reactors

A theoretical investigation into the behavior of helium gas in the primary heat transport system of the SP-100 space nuclear power system is performed. Results indicate that helium gas dissolved in the primary coolant will most likely diffuse out of solution directly into existing bubbles in the system accumulators/gas separators before reaching a concentration sufficient to drive a nucleation process elsewhere in the loop. Differences in individual loop flow rates of only a few percent are demonstrated to have a significant impact on the relative gas diffusion rates in the loop accumulators