The NRC identified an
NCV of Title 10 of the CFR, Part 50, Appendix B, Criterion III, Design Control, for failure to establish and implement adequate design control measures to assure that the reactor building (
RB) fan assemblies were capable of performing their design function to mitigate a design basis loss of coolant accident (
LOCA) event. Specifically, testing and design calculations used a non-conservative
RB ventilation system alignment to determine the brake horsepower of the
RB fan motors during a
LOCA. As a result, engineers had not evaluated the capability of the
RB fan motors to operate above their nameplate full load rating to perform their intended safety function. Additionally,
RB fan motor electrical overload protection analyses were incorrect. Immediate corrective actions included interim calculations which demonstrated that the
RB fan assemblies would remain capable of performing their safety functions and that the
emergency diesel generators were capable of supplying the additional electrical load requirements. Exelon entered the issues into their corrective action program as IRs 2458932, 2458929, and 2451855. This finding was more than minor because it was associated with the design control attribute of the
Barrier Integrity cornerstone and adversely affected the cornerstone objective of ensuring the operational capability of the containment barrier to protect the public from radionuclide releases caused by accidents or events. Additionally, the finding was similar to example 3.j in
Appendix E of IMC 0612, in that the engineering calculation error resulted in a condition where there was reasonable doubt of the operability of the
RB fan assemblies to perform their safety function during a design basis
LOCA. The team determined the finding was of very low safety significance because it: did not affect the
reactor coolant system (
RCS) boundary; did not affect the radiological barrier function of the control room, auxiliary building, or spent fuel pool systems or boundaries; and did not represent an actual open pathway in containment or involve a reduction in the function of
hydrogen igniters. This finding was not assigned a cross-cutting aspect because the underlying cause was not indicative of current performance in that the non-conservative calculation error occurred in 1993.
