PWR dry containment issue characterization

Severe accident issues have been characterized for pressurized water reactors with large dry containments. A description of PWR dry containment performance under severe accident conditions is provided. Reviews and discussions of early containment failure due to direct containment heating (DCH), in-vessel steam explosions, hydrogen burns and steam spikes, late containment failure due to gradual overpressurization and basemat meltthrough, and containment bypass (interfacing systems LOCA) events are included. An assessment of potential improvements such as RCS depressurization, reactor cavity reflooding, hydrogen control, containment venting and accident management strategy is presented. The review and discussion are largely based on existing information obtained from the nuclear industry and the NRC's severe accident research programs. Additional analyses related to operator actions were performed and are presented in the Appendices. 49 refs., 11 figs., 23 tabs.