The walkdowns are visual assessments at the plant conducted in response to the NRC's post-Fukushima flooding hazard re-evaluation requirements, said Neil Sheehan, NRC spokesman. Plant officials have described the observations as administrative, rather than substantive, issues.
From July 23 to 25, 2013, an NRC team reviewed the plant's own walkdown process which assess flood risks at the Lacey Township nuclear generating station.
In its audit of the plant's review process, the NRC made five observations, sent one to the NRC Resident Inspectors based at the plant for follow-up reviews and developed two potential requests for additional information, said Sheehan.
The observations "are neither findings nor violations; however, they will be used to inform the NRC staff assessment of the licensee's walkdown report," the audit, which was released this week, said.
The observations included a question of the flood height measurement on the roof of the plant's turbine building, indicating it is 23 feet, 6 inches. The listed height had "no physical meaning or relevance for a flood protection feature," according to the report.
"Although the discussions were helpful in understanding the thought process that went into the determination, the team believes that the physical meaning of APMs may not have been clearly understood," the audit said, referring to "available physical margin," which is represented by the "APM" acronym.
In another observation, the plant's operators referred to the turbine building doors as passive flood prevention features, though the doors themselves are non-watertight. Through discussions, the report said, the inspection team learned the designation referred to the door threshold rather than the doors themselves.
"This demonstrates that documentation of the relevant features in the walkdown form was not done properly," the audit said.
In its third observation, the inspection team learned that floor drain inspections were not typically performed using a company structural monitoring procedure. During a visual inspection, a 4-inch conduit at the plant was found "with extensive corrosion as well as very significant growth of stalactites," according to the audit.
The team also observed that APM was not calculated on several walkdown record forms, "particularly forms associated with penetration seals."
Finally, according to the audit, "in several instances, an evaluation was not performed on seals where the margin was small with potentially significant safety consequences."
The audit team found that flood protection features ocated on the southwest corner of the turbine building basement had water intrusion at about 40 drops per minute, and that a conduit containing cables that run to a second emergency diesel generator is located in a vault that could fill with water in the event that a drain clogs.
The NRC said in the audit that it will request additional information on APM calculations and, "moreover, the NRC staff may require additional information to clarify whether deficiencies were identified during the site walkdowns."