A Separate Effect Test for a Low Reflooding Rate Condition during the Reflood Phase of a LBLOCA using the ATLAS

A thermal-hydraulic integral effect test facility, ATLAS, has been constructed at KAERI. It is a 1/2 reduced height and 1/288 volume scaled test facility based on the design features of the APR1400. The present LB-CL-15 test was performed to validate the RELAP5 reflood models for a core quench phenomenon under a low flow rate ECC injection condition. A separate effect test data peculiar to the APR1400 could be obtained by using the ATLAS, which has the DVI injection, reverse heat transfer from steam generators and steam binding effect, etc. In the present test the ECC water from a safety injection pump was supplied through four SI lines. The openings of the flow control valves were adjusted to give a pre-determined flow rate of 0.3 kg/s each. The containment simulator pressure was fixed at around 0.10 MPa and the initial outer wall temperature of the RPV was determined to be 150 .deg. C when the effect of down-comer boiling was negligible. The experimental results showed a gradual reflooding in the core and a cooling of the core heater rods and the reactor pressure vessel down-comer. The experimental data could be used to evaluate and revise the reflood models of safety analysis codes such as RELAP5/MOD3