VERA Solution to the Watts Bar Benchmark Problem

The TVA Watts Bar Unit 1 Benchmark Problem is currently being developed by the OECD Nuclear Energy Agency (NEA).The benchmark problem is based upon models originally developed by the Consortium for the Advanced Simulation of Light Water Reactors (CASL) for use in validating the Virtual Environment for Reactor Applications (VERA).VERA includes a core simulator that models the reactor using an advanced 3D transport method coupled with a 3D full-core subchannel thermal-hydraulics model and a detailed cross section and depletion model.Watts Bar is a typical Westinghouse 4-loop reactor design that is operated by the Tennessee Valley Authority (TVA).In this paper, results are presented for Exercises 1 and 3 of the benchmark.Exercise 1 consists of zero-power physics test cases, which include ten measured critical rod positions and an isothermal temperature coefficient (ITC) measurement.Exercise 3 consists of the full-power depletion for cycle 1.The VERA results are quite accurate, and for the ten measured criticals in exercise 1, the average difference from measured criticality is 25 p cm.The full benchmark specification and results will eventually consist of the first three cycles of depletion data for Watts Bar Unit 1 reactor.