An open calculation of RD-14M small-break LOCA experiments using CATHENA code

The open calculations of two Small Break Loss of Coolant Accident (SBLOCA) experiments in the RD-14M integral test facility are performed as an International Atomic Energy Agency (IAEA) activity of International Collaborative Standard Problem (ICSP) with the objective to benchmark and validate the thermal–hydraulic analysis code against qualified data for Heavy Water Reactor (HWR) systems. This ICSP started with the first meeting of the participants in Vienna in 2007 November. Two tests were selected for this activity, test B9006, a 7-mm inlet header break experiment with pressurized accumulator emergency coolant injection, performed in 1990, and test B9802, a 3-mm inlet header break experiment, performed in 1998, to provide data with full channel power to study boiling in the channels and condensation in the steam generators. The previously performed blind simulations demonstrated that the CATHENA code is capable of adequately predicting the primary pressure depressurization, channel flow rate, channel voiding for tests B9006 and B9802, and the high pressure core injection flow by CATHENA accumulator model and switching time from high pressure to low pressure injections for test B9006. However, several significant discrepancies between the code predictions and the measurement data were noted, and attributed to the input errors and the code models relevant to post-dryout (PDO) heat transfer phenomena in the heated channels of test B9802. Therefore, the open calculations are performed to allow correction of previous blind calculations in the present study. These open calculations include the Senaratne and Leung model with the optimized coefficients of its correlation for the test B9802, which can predict more accurately the onset of sustained dryout on the surface of the heater rods. The improvement of the open calculation results are shown by comparing them with the test data and also with the blind calculation results.

► We present CATHENA code simulation for SBLOCA in the RD-14M facility.
► Modification of PDO model in the open calculation improved the previous blind simulation results.
► Slowing the heatup in PDO regime is achieved by tuning the developing PDO model.
► The “STM-GEN-COND” option was found to have an important effect on pressure evolution.