Pressures may be too high in some uranium hexafluoride (UF6) storage cylinders at the Nuclear Fuel Services, Inc. plant in Erwin, Erwin-based NFS has reported to the Nuclear Regulatory Commission.

That, according to a Jan. 20 "event notification report" posted on a Nuclear Regulatory Commission (NRC) Web site, apparently could pose a fire hazard and the company is taking precautions as a result.

But NRC Spokesman Joey Ledford said the problem is not believed to pose an immediate hazard to either workers or the public.

Ledford noted that NFS officials discovered the apparent pressure problem while making calculations as part of an investigation related to a Nov. 14 fire at the NFS plant.

He said there are "several hundred" of the cylinders that are about seven inches in length, or "about test-tube size." In addition, he said, there are five larger UF6 storage cylinders that are about a foot tall.

Ledford noted that 40 of the cylinders are "potentially at risk" from the pressure problem.

Ledford noted the NRC also is continuing an investigation into the Nov. 14 incident at the NFS plant and noted that it is "too early" to draw any conclusions into whether it was related to the suspected cylinder-pressure situation.

He also said some of the UF6 cylinders date to the 1950s and that most have been stored at the NFS plant for a number of years.

He noted that the NRC is expected to hold a public meeting in Erwin in March to discuss the results of an augmented inspection team's investigation into an earlier problem at the NFS plant.

Ledford said he did not know if the NRC's investigation into the UF6 cylinder pressure problem would be available by the March public meeting.

Uranium hexafluoride (UF6) is a chemical compound consisting of one atom of uranium combined with six atoms of fluorine, according to a U.S. Department of Energy Web site dedicated to management of the material.

"It is the chemical form of uranium that is used during the uranium enrichment process. Within a reasonable range of temperature and pressure, it can be a solid, liquid, or gas. Solid UF6 is a white, dense, crystalline material that resembles rock salt."

"The UF6 is contained in the cylinders, which are in Department of Transportation (DOT) shipping containers," the text of the Jan. 20 event notification report says. "Calculations were performed that indicated that the theoretical pressure in some of the cylinders exceeds the service pressure (200 pounds per square inch) and some exceed the hydrostatics test pressure (400 psi)."

DOE literature, according to the event notification report filed by NFS with the NRC, indicates that the "burst pressure" in the cylinders is estimated to be [approximately] 8,000 psi.

The report also notes that the cylinders "potentially contain fluorine gas."

"Fluorine reacts violently and decomposes to hydrofluoric acid on contact with moisture," according to the Environmental Health & Safety Web site of Princeton University. "Fluorine is the most powerful oxidizer known. It reacts with virtually all inorganic and organic substances. Fluorine ignites in contact with ammonia, ceramic materials, phosphorus, sulfur, copper wire, acetone and many other organic and inorganic compounds."

"There were no actual safety consequences to workers, the public, or the environment," the event notification report says.

"The potential consequences are minimal due to restricted access to the areas [where the cylinders are stored] and the stable condition of the cylinders [i.e. cylinders, shipping containers, building containment]."

The report went on to say that the storage arrangements "provide mitigation," as do sprinklers, smoke detectors and security cameras.

However, according to the report, "other compensatory measures are being considered that include providing uncharged fire hoses to the [affected] areas [of the plant]."

The proposed compensatory measures, according to the event report, that have been, or will be, put in place include:

* verified operability of smoke detection;

* verified operability of the sprinkler system;

* established fire patrol inspection;

* restricted access;

* hot work restricted in restricted areas;

* staging on one 150-pound dry chemical fire extinguisher; and

* briefing incoming plant superintendent on status during shift change.

The event notification report also notes that NFS has developed a specific pre-fire response plan for the areas where UF6 cylinders are stored.

"This plan has been reviewed with the Erwin City Fire Chief," the report states. "NFS plans to provide one trained fire brigade member on each shift who will coordinate the Erwin Fire Department's response to a fire incident involving a UF6 cylinder."

Many operations at the Nuclear Fuel Services, Inc., plant in Erwin currently are shut down while the company completes a number of safety-related actions.

NFS, according to a January letter from the NRC, has committed to:

* obtaining independent reviews of restart actions as well as company event investigation processes;

* changing the way the company handles materials based on lessons learned from the Oct. 13 event;

* making permanent improvements in the methods for identifying, documenting, evaluating and communicating all changes at the facility;

* re-evaluating certain accident scenarios to ensure the appropriate level of safety; and

* changing the NFS management structure to ensure separation between production goals and safety priorities.

NRC Region II Administrator Luis Reyes, wrote, "This letter clearly lays out the NRC's expectations for both short and long-term actions that NFS will take to address the concerns our inspectors have identified.

"We believe suspending operations is appropriate given the current situation, and the lines will not restart until NFS meets its commitments."