Spray cooling heat transfer phase I test results ENC: 8 x 8 BWR fuel, 60 and 63 active rods. Interim report

The first-phase test results of a contemplated two-phase test program are presented. The purpose of the test program is to confirm the spray cooling heat transfer performance of the Exxon Nuclear Company (ENC) 8 x 8 BWR fuel design under conservatively represented loss-of-coolant-accident (LOCA) conditions. The test fuel assembly is a geometric mock-up of the 8 x 8 design with 63 potentially active rods, of which three rods located toward the center can be deactivated to simulate the ENC 8 x 8 design with four centrally located inert rods. The channel and adjacent hardware provide a mockup of the fuel assembly channel/control rod configuration. However, since the thermal boundary conditions that may exist in the reactor during a LOCA are not exactly simulated, the fuel assembly temperature achieved in these tests is not intended to be representative of the expected fuel assembly temperature during LOCA. The heat transfer coefficients and inert rod wetting front data derived from the tests should be representative of reactor coefficients and wetting because the difference in boundary conditions is taken into account in the models. Wherever possible, conditions expected to exist in the hot assembly during spray cooling have been simulated in the tests