Void measurement of BWR fuel assembly

Steam void fraction measurement test in a BWR fuel assembly has been carried out to prove the current BWR void prediction method. This report describes the experimental apparatus, experimental data, and evaluation results. The test was carried out in an out-of-pile test facility that can simulate the high pressure and high temperature conditions of BWRs. Water was used as a coolant. The void distribution in a BWR fuel assembly under BWR operating conditions was measured for the first time by an X-ray CT scanner, using an electrically heated test assembly which simulated a BWR fuel assembly on a full scale. Void fraction under steady and unsteady conditions was measured by an X-ray CT scanner and an X-ray densitometer. In steady state void test, 476 data were obtained. These data were compared with the current BWR void prediction method. Unsteady void test data were evaluated with the unsteady analytical code. It has been proved from these evaluation results that the verification of the current BWR void prediction method and unsteady analytical code has been accomplished.