Nominally Reflected Pipe Intersections Containing Fissile Solution

Monte Carlo calculations for pipe intersections containing highly enriched, concentrated uranyl nitrate solution and reflected by a concrete room provide safe pipe diameters for a range of room sizes. The pipe-wall material (steel, aluminum, or Plexiglas) has a small effect on k_eff for 0.125-in.-thick pipes. Replacing the uranyl nitrate solution by uranyl fluoride results in a large increase in k_eff, and using plutonium nitrate (3% ²⁴⁰Pu) lowers k_eff Reflector savings curves for water and for concrete around an infinite cylinder of uranyl nitrate solution show that thick concrete is a much better reflector than an equal thickness of water. The calculational data are summarized in the form of a table and a set of rules for the use of the table in the calculation of safe dimensions for a system of intersecting pipes. This method is also applicable to plutonium systems if the plutonium contains at least 3 wt% ²⁴⁰Pu and no ²⁴¹Pu.