Thermal Margin Evaluation for FELI Fuel Assemblies During an Accidental Vessel Draining

Safety requirements many times require specific evaluations for experiment operating conditions during periods of postulated off-normal operation. A unique experimental facility in the Advanced Test Reactor was designed for enhancement of the neutron flux in an irradiation position, large “I”, in the reflector region. Requirements for the facility necessitated analysis of the enhancement fuel to demonstrate that melting of the fuel element cladding would not occur during a loss of coolant event during reactor shutdown. The response of the fuel elements was evaluated using computer software that allowed detailed evaluations of the gamma heating magnitude and deposition fraction, natural convection cooling, prediction of heat transfer coefficients, and detailed finite element modeling for prediction of the temperature magnitudes and profile.