Containment Integrity of SEP Plants under Combined Loads

by T. Lo, Lawrence Livermore Natl Lab, Livermore, CA, USA,
T. A. Nelson, Lawrence Livermore Natl Lab, Livermore, CA, USA,
P. Y. Chen, Lawrence Livermore Natl Lab, Livermore, CA, USA,
D. Persinko, Lawrence Livermore Natl Lab, Livermore, CA, USA,
C. Grimes, Lawrence Livermore Natl Lab, Livermore, CA, USA,

Document Type: Proceeding Paper

Part of: Structural Engineering in Nuclear Facilities


The containment designs analyzed consisted of three inverted light-bulb shaped drywells used in boiling water reactor (BWR) systems, and three steel-lines concrete containments and a spherical steel shell used in pressurized water reactor (PWR) systems. These designs cover a majority of the containment types used in domestic operating plants. The results indicate that five of the seven designs are adequate even under current design standards. For the remaining two designs, the possible design weaknesses identified were buckling of the spherical steel shell and over-stress in both the radial and tangential directions in one of the concrete containments near its base. These issues are being pursued in greater detail under the SEP. Despite these possible design weaknesses, we generally found that the margins of safety in these containment designs were larger than expected. The possible design weaknesses identified are mainly related to the high temperature and pressure conditions resulting from conservative LOCA and MSLB analyses; i. e. , those resulting from an instantaneous double-ended guillotine break (DEGB). In a separate research study, the probability of a DEGB in PWR reactor coolant loop piping has been found to be rather small under all plant conditions including seismic events. It is likely that the probability of MSLB is also small in PWR plants. In view of the small probability of having a DEGB in the large piping inside the containments, one would tend to conclude that the existing margins of safety in these older plants are rather comfortable.

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