Nuclear safety officials have concluded that a fluke mishap last year at Progress Energy's Brunswick nuclear plant near Wilmington was caused by the lack of worker qualification for more than a decade.
The Nuclear Regulatory Commission issued its preliminary findings yesterday, but the federal safety agency is continuing its investigation to determine the safety significance of the incident.
The unusual mishap that shut down the Brunswick Unit 2 reactor last November may be the only such incident in U.S. nuclear history.
The Brunswick plant's boiling water nuclear reactor vessel functions like a giant teapot, producing steam to power an electric generator. The steam builds up under pressure contained by a tightly sealed lid.
But last November, mildly radioactive water bubbled out of the chamber rather than boiling inside under pressure to form steam. At one point the water was flowing out at a rate of over 10 gallons a minute, about 100 times more volume than would flow out under normal circumstances.
NRC investigators concluded the lid was improperly attached after a refueling outage because the maintenance workers were not trained in reactor vessel disassembly and reassembly. Qualification for this kind of work hadn't been provided since 2000, the NRC said in its assessment.
Nine of the 12 workers who performed the reactor vessel assembly were not qualified. Some received "just-in-time" (i.e., last minute) training before the Fall 2011 refueling outage, but not specifically in stud tensioning.
The workers didn't know how to read the instrumentation and torqued the reactor vessel lid's studs at 1,300 pounds per square inch instead of 13,000 psi. In other words, there were off by one zero, and screwed the studs at 1/10th the required pressure.
Some the bolts were left so loose they could be turned by hand, the NRC said. Others turned easily with a wrench.
Fortunately for Progress, the mistake did not cause damage to the reactor vessel.
John Murawski has been a full-time newspaper reporter since 1991, with stints at Legal Times and The Chronicle of Philanthropy (both in Washington, DC), The Philadelphia Inquirer and The Palm Beach Post (in South Florida) before arriving at the N&O in December 2004. At the N&O he covers energy (nuclear, coal, renewable, efficiency), utilities (electric, natural gas, telephone) and telecommunications. His beat includes such publicly traded companies as Progress Energy, Duke Energy, PSNC Energy, Piedmont Natural Gas, PowerSecure International, Tekelec, Cisco Systems, AT&T, among others. You can reach him at 919-829-8932 or 
Comments
observation
Fri, 01/27/2012 - 12:50 — EcriticThis is certainly an event that should not have happened. But one complicating factor is that the crew used "new" (at least to them) autoranging equipment for the discharge pressure of the hydraulic pump that supplies the force that tensions the head bolts and for the measurement of the elongation of the studs to ensure that the bolts had been truly tightened. These have certain idiosycrocies (like sometimes having a decimal, sometimes not, displaying 4 digits vice 3, depending on where you are in the scale) and user set differentials so that you don't measure the entire length of the stud, but just the difference between starting length and the completion length. If you are not familiar with the equipment, it could be easy to misinterpret the results, or to operate the equipment improperly in setup. That's really why they needed training. The scenario is not nearly as simple as the article leads you to believe. The people doing this job were educated, and very sharp people. We all have to guard against seeing what you expect to see as opposed to being open minded. Even when you read a newspaper article.
OUR HIGHLY EDUCATED COMMENTERS...
Thu, 01/26/2012 - 22:05 — frmckenzyDon't most people learn the difference between "fourth" and "forth" before the fourth grade?
Sorry, I didn't mean to make
Thu, 01/26/2012 - 23:20 — outhousecatSorry, I didn't mean to make you dyspeptic with a typo.
But then again, I don't get overly concerned with anal-retentive OCD perfectionist-type people.
?
Thu, 01/26/2012 - 18:49 — capefearFortunately for Progress, the mistake did not cause damage to the reactor vessel.
What about the damage to the people and the surrounding environment? This was a serious "mistake".
our highly educated employees...
Thu, 01/26/2012 - 18:23 — outhousecatDon't most people learn the difference between 1,300 and 13,000 in like, the forth grade?
I have to wonder about the education level of these people. Or does "qualification" merely consist of being able to count past your fingers and toes?