Neil Sheehan with the NRC wouldn't say exactly what was wrong, but says it was of low-to-moderate significance.
Constellation Energy, which operates the two reactors about 40 miles south of Annapolis, said the deficiencies were promptly corrected.
The special inspection was the second at the plant in two years. An inspection was also conducted last year after a leaking roof allowed melting snow to drip onto electrical equipment, causing both reactors to automatically shut down.
The problems found during the latest visit could trigger a complete examination of the plant's security systems by a larger team of inspectors.