The Cook nuclear power plant in Michigan, owned by American Electric Power Co (AEP), has violated Nuclear Regulatory Commission (NRC) safety rules, the Commission has announced. The violation, relating to the plan cooling water system, was of low to moderate importance to safety, the NRC adjudged. AEP violated the regulations when it failed promptly to fix an equipment problem which led to the failure of a pump in the plant’s backup cooling water system. The pump did not work properly during testing in August 2001 and again in January of this year.