The results of a December inspection at Ameren Missouri's Callaway Energy Center include one violation of "very low safety significance."
According to the document, the U.S. Nuclear Regulatory Commission wrapped up a routine inspection at the plant on Dec. 31. The inspection began in early October.
While the NRC inspection didn't identify any safety violations, it did document a minor violation identified by the plant's licensee.
It involved the failure to perform a particular test after doing maintenance work on a specific valve, the report said. The test, called a "seat leak" test, should have been pre-planned and performed in accordance with regulatory guidelines.
This valve was part of the water-carrying system in what's known as the "ultimate heat sink cooling tower," the report said. It's a cooling system that, for example, would come into play if the plant experienced an unexpected shutdown, a paper published by the International Atomic Energy Agency explained.
In mid-November, operators discovered the valve was leaking at a rate of 3,900 gallons per minute; however, the report said, the leak was not severe enough to adversely affect the function of the ultimate heat sink.
After evaluation, the licensee determined that the issue was of very low safety significance.
The licensee entered it into the "corrective action program," which tracks issues until they're resolved, the NRC said.
The NRC recorded the issue as a non-cited violation, meaning it doesn't require a response from the licensee.
To view the complete report, visit adams.nrc.gov/wba/ and search for the Callaway plant.