When the NRC Senior Resident Inspector at the Perry Nuclear Plant in Ohio arrived at the plant on April 22, he stopped first at the outage control office, which oversees work being done during the plant’s refueling and maintenance outage.
One job of interest – removing a neutron detector that was lodged in the reactor core – had not been completed during the night as scheduled. The inspector inquired further and learned that the job had been halted when higher-than-expected radiation levels were encountered during the work.
After gathering more details, he conferred with the NRC’s Region III Office in Lisle, Ill., and began the process that led to a special inspection into the circumstances surrounding the incident.
The NRC has two or more resident inspectors assigned to each nuclear plant on a fulltime basis to assure the plant is operating safely. Their efforts are supplemented by inspections performed by specialists from the regional office or NRC Headquarters in Rockville, Md.
When something unexpected happens at the nuclear plant, particularly an event with safety implications, the NRC may dispatch inspectors to begin a special inspection to review the circumstances surrounding the incident and determine what additional agency action, if any, is called for.
The inspection is called a “special inspection” when it is managed by the regional office, and an “augmented inspection team” when the significance of the event warrants additional staff from the headquarters or other regional office. An inspection can also be headed by an “incident investigation team” for major issues that bring in NRC experts not previously involved with the plant and headed by a senior NRC manager.
The Perry incident led to a special team inspection with two Region III radiation specialists at the Perry site backed up by three inspectors working in the regional office.
Special team inspections occur several times a year at reactor sites across the country. In the past five years there have been 42 special inspections at 31 reactor sites. Thus far there have been nine special inspections in 2011.
Once the regional staff determines that an event warrants a special inspection a “charter” is prepared that lays out the plans for the inspection.
The inspections typically involve interviews of plant personnel involved with the event, review of documents associated with it, and assessment of the causes and consequences of the event. The inspectors also look at the plant staff’s response to the event and make sure the plant promptly addresses any immediate safety concerns
Once the inspection is completed – and the preliminary results presented to plant management – the inspectors prepare a written report to be issued within 45 days. Like all NRC inspection reports, the special inspection report is promptly made available on the NRC website.
The results of the inspection determine the NRC’s next steps. If violations are found, there may be further inspections and increased oversight to assure that the problems are corrected.
The Perry special inspection report was issued July 6 and it documents the preliminary finding that the event was of “low-to-moderate safety significance,” a “white finding” in the NRC’s assessment of findings ranging from “green” for minor safety significance and continuing through “white,” “yellow,” and “red” for increasing safety significance. (It is available via ADAMS using MLML11187A121.)
The inspectors identified three apparent violations associated with the event – failing to appropriately evaluate the radiological hazards associated with the work, failing to have adequate procedures in place, and failing to properly control work in a high radiation area.
The radiation exposures received by the workers involved were a small fraction of the NRC’s limit for nuclear plant workers, but the NRC inspectors determined that it was “fortuitous” that more significant radiation exposures did not occur.
After reviewing the NRC inspection report, the Perry plant may accept the NRC’s findings or provide additional information in writing or in a “regulatory conference,” which would be open to the public. The NRC would then review the response before making its final determination on the issue. A final “white” determination would lead to a detailed inspection to evaluate the causes and corrective actions for the event and the plant’s efforts to prevent of recurrence of the violations.