The Nuclear Regulatory Commission (NRC) has determined that a “yellow” violation of NRC regulations was carried out at Calvert Cliffs 1.

NRC inspectors found that workers did not adhere to maintenance instructions during maintenance on an auxiliary feedwater pump and applied too much sealant to the bearing housing, contaminating the bearing oil, resulting in the bearing failure.

Under the NRC’s new reactor oversight process, the significance of inspection findings are assigned a colour. Findings with very low safety significance are labelled “green”; low to moderate importance to safety, “white”; substantial safety significance, “yellow”; and “red” findings have high safety significance.

Constellation Nuclear, operators of Calvert Cliffs, has corrected the problem and the pump has been tested satisfactorily. An additional NRC inspection will be scheduled to follow-up on the repair work.