12.199. Continuing research and studies contribute to a large body of severe accident information for various reactor types. The work has been carried out under the auspices of the Nuclear Regulatory Commission, the Nuclear Management and Resources Council (NUMARC), which serves as liaison between industry and the NRC, and the Electric Power Research Institute. NUMARC has a group that coordinates severe accident activities.

12.200. Basic research has been directed toward understanding the physical mechanisms occurring during severe accident scenarios, such as those described earlier (§12.95 et seq.) and to model the various steps analytically. Many projects are thermal-hydraulics oriented. For example, the thermal behavior of a pool of molten core debris at the bottom of a reactor pressure vessel can affect the practicality of preserving the vessel integrity by external cooling.

12.201. The assessment of severe accident risks carried out under the NUREG-1150 Program (§12.234) can identify areas of vulnerability specific to individual plants. Such work can then serve as the focus of further studies which can then lead to the subsequent development of appropriate remedial actions.

Supporting Instrumentation

12.202. During a severe accident, plant instrumentation must provide the operating staff with an indication of the plant condition. The program must therefore address the need for additional instruments, the surviva­bility of vital instruments during an accident, and the interpretation of readings.