The US Nuclear Regulatory Commission (NRC) has issued a finding to the LaSalle nuclear plant Unit 2 for failing to adhere to a procedure that led to a manual shutdown.

Identified by NRC inspectors during a September 2013 inspection at the plant, the finding involved the failure of the plant staff to perform certain procedural steps in accordance with existing procedures, which resulted in influx of a foot of circulating water flowed into a small area in the turbine building.

The excess water influx triggered intake pumps to shut off and a loss of normal heat removal, which led to a reactor shutdown.

NRC Region III Administrator Cynthia Pederson said the organization expects plants to make conservative decisions when planning or executing work activities, even though the issue did not had an impact on the public.

”They need to follow procedures in order to ensure the safety of plant workers, the public and environment,” Pederson added.

A special inspection will be carried out by the NRC to review the plants corrective actions, such as additional training activities for operators, procedure revisions and whether plant staff understood the cause of the problem.

Operated by Exelon Generation, the two-unit plant is located in Marseilles, Illinois, US. The company has 30 days to contest the finding.