Large-break loss of coolant accident LBLOCA

During 1988, new data was developed for the RVSS materials at Oak Ridge National Laboratory (ORNL) (References 2 and 3). This data indicated that low neutron flux at low temperatures caused greater embrittlement of the materials used in RVSS than previously anticipated. This increased material embrittlement or "upward shift" in NDTT reduces the fracture toughness of these materials and, under certain specific and conservative transient conditions such as an earthquake or Large-Break Loss-Of-Coolant Accident (LBLOCA), could conceivably result in the failure of the supports thus permitting the reactor vessel to move. 

Large Break Loss of Coolant Accident (LBLOCA)... 

Currently, there are three DBAs that appear enveloping and could potentially limit reactor power the large break loss-of-coolant accident (LBLOCA) and the loss of pumping accident (LOPA), which are judged to very low probability events and the loss of septifoil cooling accident, which has occurred twice during the life of the SRS reactors. 

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