Destruction of the deadly Cold War nerve agent VX will halt this week while the U.S. Army and a contractor replace a faulty valve that allowed about 30 gallons of the chemical to spill late Friday.

The spill occurred at the Newport Chemical Depot, about 30 miles north of Terre Haute, as VX was being fed from a holding tank into a reactor of sodium hydroxide and water. The mixture is heated in the reactor to destroy the agent.

Officials determined over the weekend that a valve feeding the agent from the holding tank malfunctioned, allowing VX to spill onto the floor, Army spokeswoman Terry Arthur said Sunday. The agent, which drained into a sump in the sealed concrete floor, was destroyed after workers sprayed the area with sodium hydroxide and let it sit for several hours, Arthur said.

The area was being cleaned with water Sunday, and she said it would be retested before workers tried to replace the valve.

The work stoppage, one of several breaks planned to consider ways to improve the process, was scheduled before the spill occurred, so Arthur said the incident probably won't delay destruction.

"There is no good time for something like this to happen, but it (coincidentally) happened right before a pause in work," she said.

Workers never were in danger from VX -- so lethal a single drop could kill a person in minutes -- because the spill occurred in an area known as the Toxic Cubicle, which nobody enters unless there is a problem and only while wearing protective gear, Arthur said. The cubicle is pressurized, so air cannot escape the building.

"All the thousands of hours workers spent training to respond to situations like this have paid off," Arthur said. "That's why we have backup (warning systems) because things like this can happen."

More than 250,000 gallons of VX have been at Newport, the only place it was manufactured, for more than 35 years. The agent was developed to deter the Soviet Union during the Cold War.

Army officials said almost 2,900 gallons of the agent have been destroyed safely since operations began May 5.

Under an international agreement, the United States is to destroy its chemical weapons stockpile by 2007. Chemical weapons, including VX-loaded weapons, still are stored at seven U.S. sites.

The Newport plant was built in 1962. The U.S. never used the agent, and President Richard Nixon ordered the plant shut down in 1969.

The byproduct of the VX destruction will be stored in special containers in Newport until a final decision is made on where it will go.

Army officials want to ship the byproduct to a DuPont Co. plant in New Jersey, where it would be treated and released into the Delaware River, but opposition in New Jersey and Delaware has stalled the plan.

Call Star reporter Tammy Webber at (317) 444-6212.