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Abstract
The RETRAN-01 code has a point kinetics model to describe the reactor core behavior during thermal-hydraulic transients. The principal assumption in deriving the point kinetics model is that the neutron flux may be separated into a time-dependent amplitude function and a time-independent shape function. Some transients cannot be correctly analyzed under this assumption, since proper definitions for core average quantities such as reactivity or lifetime include the inner product of the adjoint flux with the perturbed flux. A one-dimensional neutronics model has been developed for RETRAN-02. The ability to account for flux shape changes will permit an improved representation of the thermal and hydraulic feedback effects for many operational transients. The model is based on a space-time factorization method in which the neutron flux behavior is factored into a time-dependent amplitude function and a more slowly varying (in time) shape function. Results from simple slab geometry problems indicate good agreement with known solutions. Calculations that represent larger systems show that correct trends are predicted.