Radiation transport in a liquid metal fast breeder rector during a loss of sodium coolant reactor core disassembly

The time-dependent, neutron radiation transport equation for a liquid metal fast breeder reactor undergoing a loss of sodium coolant reactor core disassembly accident is analyzed and the models being used evaluated. Time-dependent neutron transport is calculated using both a discrete ordinates and a diffusion theory solution for the real flux shape. It was found that diffusion theory would underpredict reactivity levels by about $6 using referenceable material properties when compared to discrete ordinates. It was also found that the use of an initial adjoint neutron flux throughout the transient as a reactivity weighting function could seriously underpredict reactivity levels for a severely degraded reactor core. The uncertainty due to being limited to two fuel fields for an end-of-equilibrium cycle reactor core during the transient was grader than that due to microscopic cross-section shielding factor iteration and interpolation schemes. Fifty energy group reactivity coefficients were best duplicated in collapsing to a ten energy group set with an entire reactor integrated bilinear neutron energy flux spectrum. Comparison is also made with a second discrete ordinates time-dependent computer code of reactivity coefficients. Finally, a comparison of the equation of state analytical formulation used in the transient calculations is made with that of Hicks and Menzies