The purpose of considering design extension conditions (DEC) is to further improve safety by enhancing the plant’s capability to withstand the conditions generated by accidents that are more severe than design basis accidents (DBAs). The paper first provides example lists of DEC. Then, the existing research for beyond design basis accidents with non-degraded core (i.e. DEC A) for existing reactors is presented. The tests performed include total loss of feedwater, station blackout, small break without high pressure safety injection, steam generator tube rupture with no high pressure safety injection etc. Finally, simulations of few experiments (representing DEC A) performed on integral test facilities, which have been analysed at Jožef Stefan Institute have been presented. The review of beyond design basis accidents performed on integral test facilities and simulations suggest that selected DEC scenarios were studied even before the requirements on DEC analyses were introduced.
COBISS.SI-ID: 33019175
The purpose of this study is to propose and demonstrate the fast Fourier transform based method by signal mirroring (FFTBM-SM) for judging the impact of given parameter uncertainty in deterministic safety analysis on plant response. The plant parameters and corresponding uncertainties are classified into two main categories, external and internal parameters. The proposed method is applied on the station blackout (SBO) event of the two-loop pressurized water reactor (PWR). This is done with the utilization of the RELAP5/MOD3.3 Patch 04 computer code simulations of the SBO scenarios. Obtained results demonstrate that larger source of uncertainties are external (i.e. operator actions) than internal parameters. Therefore, in the context of deterministic calculations in support of the PSA priority should be made on sources of uncertainties from external parameters, followed by sources of uncertainties from internal parameters.
COBISS.SI-ID: 33175591