The Nuclear Regulatory Commission is sending a special inspection team to the Global Nuclear Fuel Americas commercial nuclear fuel processing plant near Wilmington, N.C. after an incident last week in which moisture was detected in a vessel containing uranium -- a situation that can lead to a dangerous radiation release. Fortunately, no release occurred.

According to an NRC press release, plant officials declared an alert last Wednesday after alarms indicated the president of moisture in a vessel holding about 63 pounds of low-enriched uranium. At the time, the vessel was supposed to have been empty for maintenance. The presence of moisture allows a nuclear reaction to take place with less fissionable material.

While the NRC's Incident Response Center in Atlanta monitored the situation, workers at the plant removed the uranium from the vessel and put it into a safe container. Plant officials said they determined the moisture level in the vessel was too low to cause "criticality," which occurs when material undergoes fission and emits radiation either in a "burst" or a sustained release. They are now investigating how moisture got into the vessel in the first place.

Here's more on "bursts" from Dave Lochbaum, a nuclear engineer with the Union of Concerned Scientists:

In general, "bursts" are bad things but primarily bad things for the workers. "Bursts" occur when too much fissile material is brought together. A chain reaction starts -- the "burst." The energy released by the "burst" tends to spread the material apart and ending the chain reaction. And harming any one in the vicinity.

While the amount of material might be as much or more than the amount of material in an atomic bomb, the "burst" cannot become a "cloud" because the energy disperses the material before all of the atoms can split and release energy. The key to atomic bombs is maintaining the material together long enough to split as many of the atoms as possible.

Last month the NRC proposed a $32,500 fine against the Virginia-based Babcock & Wilcox Co. (formerly BWXT) for failing to adequately test a uranium-handling procedure that had the potential to cause a burst. In the July 2007 incident at the company's Lynchburg, Va. facility -- one of only two in the nation licensed to process high-enriched uranium -- a special vacuum cleaner spilled a solution of high-enriched uranium into a plastic bag used for contamination control. Fortunately, the amount of materials involved was not enough to reach criticality.

Nuclear facility workers have been killed by bursts before. In 1964, Robert Peabody -- a 37-year-old father of nine -- died as a result of an accident at a United Nuclear Corp. facility in Rhode Island that occurred when he was handling liquid uranium that was more concentrated than he realized and went critical, starting a reaction that exposed him to radiation at 1,000 times the lethal dose. And in 1999, an accident at a small nuclear fuel processing facility in Tokaimura, Japan led to a reaction that irradiated 119 workers, two of whom died as a result.

As we all know, accidents happen. But in the nuclear industry they can be especially disastrous.