Sodium Pool Combustion Codes for Evaluation of Fast Breeder Reactor Safety

Abstract

For the evaluation of thermal consequences of a sodium leak accident in the auxiliary buildings of the LMFBRs, the sodium pool combustion codes SOFIRE-MII, ASSCOPS and SPM have been developed. In SOFIRE-MII and ASSCOPS, assumptions are made that the combustion occurs at a pool surface, and the process is controlled solely by the turbulent oxygen transfer from atmospheric gas to the pool surface. Combustion heat is dissipated by turbulent and radiation heat transfers to the gas and surrounding walls. On the contrary, a flame over the pool is modeled in SPM, in which the combustion is controlled by sodium vapor and oxygen supplies by the diffusion from the pool surface and the turbulent mass transfer from the atmospheric gas, respectively. These codes were validated using experimental results obtained in the large-scale sodium fire test facilities; SAPFIRE (PNC, japan) and FAUNA (KfK, Federal Republic of Germany). The comparison revealed that agreements between the codes and the test results are reasonably well.

Development of PIRT and Assessment Matrix for Verification and Validation of Sodium Fire Analysis Codes

“…Evaluating tools for sodium fire consequences have been developed since around the 1980's in Japan both for sodium fire behavior and sodium aerosols behavior. (2)- (5) After that, a set of sodium leak and fire analysis code system has been developed to be summarized in the structure as shown in Fig. 1.…”

Development and validation of key aerosol models for source term predictions in sodium-cooled fast reactors during beyond design basis accidents

“…17, in which the Na pool is displayed as a hot flat plate. As observed, the pool nearby can be split into three layers: sodium vapour, right over the pool; a flame region, above and adjacent to the Na layer; and the bulk gas overlying the flame and feeding the flame region with oxygen by natural convection (Miyake et al, 1991;Newman, 1983;Newman and Payne, 1978).…”

“…In this model the combustion rate depends on heat and mass transfer of Na and O2 to the flame (flame sheet approach). The vapour-phase sodium-combustion model has been included in numerous combustion codes as the SPM code by Miyake et al (1991), SOPA code developed by Lee and Choi (1997) or more recently in multidimensional numerical analysis codes such as the SPHINCS code (Yamaguchi and Tajima, 2003) or AQUA-SF code (Takata et al, 2003).…”

“…The first one, named as surface combustion model (Beiriger et al, 1973), is one in which Na vaporization rate is slow and Na-O2 reactions occur at the pool surface. The second one, a gas-phase reaction model, was developed by Sagae and Suzuoki (1985) and later used by Doda et al, 2003;Karthikeyan et al, 2009;Lee and Choi, 1997;Miyake et al, 1991;Yamaguchi and Tajima, 2009 and more recently by Sathiah and Roelofs (2014).…”

“…Based on the information found in the open literature on sodium pool fire analytical models (Karthikeyan et al, 2009;Lee and Choi, 1997;Marimuthu, 1996;Miyake et al, 1991;Sagae and Suzuoki, 1985), two reactions are considered in the Na-O2 chemical modelling:…”