On May 14, 2018, during evaluation of protection for Technical Specification (TS) equipment from the damaging effects of a
tornado generated missile, Calvert Cliffs identified a non-conforming condition in the plant design such that specific TS equipment is considered to not be adequately protected from a
tornado generated missile. A tornado could generate a missile that could strike the Unit 1 Saltwater system
header and associated piping. This could result in damage to the unit 1 Saltwater system
header which could affect the ability of the Unit 1 Saltwater subsystems to perform their design function if such a tornado would occur.
This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, and per 10 CFR 50.72(b)(3)(v)(D) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.
This condition is being addressed in accordance with NRC enforcement guidance provided in EGM 15-002 and DSS-ISG-2016-01. Compensatory measures have been implemented in accordance with these documents.
The NRC Resident Inspector has been informed of this notification.
