Officials say a Holtec employee was splashed with radioactive water in late February at the Oyster Creek nuclear power plant.
Spokesperson for the Nuclear Regulatory Commission Neil Sheehan said that a test of a lid seal resulted in a leak through the cask’s vent.
The spill occurred when a device used to seal the casks became disengaged after snap rings failed, according to Sheehan.
The contaminated water also spread to two levels of the reactor building.
Officials say the employee, who was exposed to a radiation dose of less than 10 mrem, or millirem, was wearing protective gear and was checked for contamination.
According to the Nuclear Regulatory Commission, exposure from a chest x-ray is about 10 millirem.
The plant was cited by federal regulators for a low-level safety violation and is undergoing decommissioning, the Asbury Park Press reported Wednesday.
During stoppage in spent fuel loadings, Holtec modified a valve design, revised loading procedures and held additional training, according to Holtec spokesperson Joseph Delmar.