SASSYS-1 balance-of-plant component models for an integrated plant response

The balance-of-plant (BOP) system of a nuclear power plant is a complicated thermal-hydraulic network involving several types of components interacting with one another. A first-principles analysis of such a complex system would be a formidable computation task. Such an approach appears to be the one represented by the mathematical models and numerical techniques of codes like RETRAN and RELAP, which are capable of performing elaborate analyses on plant transients. The approach taken for the SASSYS-1 BOP component models was deliberately different. Hard-wired component-specific models were developed. The stand-alone coding for the various types of SASSYS-1 BOP components can be said to be based on models that rely on simple conservation balances and extensive component data in the form of correlations. This should ensure a reasonable and adequate simulation and should not take extensive time in terms of computation and user setup. A validation program will be implemented to verify the capability of the models to generate results within an acceptable accuracy range. Models of power plant heat transfer components and rotating machinery have been added to the BOP model in the SASSYS-1 liquid-metal reactor systems analysis code. The models described in this paper extend the scope of the BOP model to handle nonadiabatic conditions along flow paths. The heat source term is treated with full explicitness. The seven types of heaters and the turbine model are discussed in this paper