INDIANAPOLIS -- Army contractors are pressing ahead with the destruction of a deadly nerve agent stored in western Indiana after installing sturdier valves in the base's two chemical reactors to prevent a repeat of a June spill at the complex.

Destruction of the VX nerve agent began in May but was halted in early June after a polymer-based component in one of the reactors' injection valves failed, allowing a mixture of about 30 gallons of VX, sodium hydroxide and water to spill in a contained area.

Both reactors now have new valves that use a ball bearing system that can better withstand the caustic materials that course into the reactors, said Jeff Brubaker, the Army's on-site manager at the Newport Chemical Depot about 30 miles north of Terre Haute.

The valves are used to inject water, sodium hydroxide and VX into each 1,000-gallon reactor, where a heating and mixing process destroys the nerve agent's chemical structure.

Aside from the mechanical upgrade, Brubaker said the Army's contractor, Parsons Technology Inc., is confident it has overcome a potentially bigger problem that resulted in the initial batches of the chemically neutralized VX being far more flammable than tests had predicted.

That problem was addressed by lowering the temperature in the reactors about an hour into the treatment process from 194 degrees to 150 degrees Fahrenheit, and also by venting away a chemical called diisopropylamine that accumulates in the chambers during the reaction.

In May and June, the initial batches of VX destroyed produced a caustic wastewater called hydrolysate with a flash point of between 68 and 88 degrees.

That low flash point raised questions about the feasibility of the Army's plans to ship the waste to a DuPont Inc. plant in New Jersey for final treatment and disposal. The flash point is the lowest temperature at which the vapor of a combustible liquid can be made to ignite.

Brubaker said the revised neutralization process has consistently resulted in hydrolysate with a flash point of no lower than 141 degrees. And most of the batches have flash points greater than 200 degrees, he said.

"It has worked and it's worked repeatedly. We've now been able to clear 17 batches in total since we resumed operations," Brubaker said.

As of Friday, Parsons had chemically neutralized 6,067 gallons of VX -- or about 2.5 percent of more than 250,000 gallons of VX stored at Newport.

Brubaker said Parsons' 575 workers at Newport are continuing to ramp up operations. By early December, the Army hopes to be processing three to four 180-gallon containers of VX each day, he said. About 1,600 hardened steel containers of VX are stored at Newport.

Craig Williams, director of the Chemical Weapons Working Group, said members of the Berea, Ky.-based advocacy group are pleased that the Army is being cautious in destroying Newport's stockpile of VX, a single droplet of which can kill a healthy adult.

"They're taking it slow and as things go wrong they're stopping and fixing them and then going on. That's the right way to do it," he said.

Williams' group opposes the Army's plans to ship Newport's hydrolysate to a DuPont plant in New Jersey for treatment and disposal in the Delaware River. That plan has generated strong opposition in both New Jersey and Delaware.

The Centers for Disease Control and Prevention is studying DuPont's proposed method for treating the hydrolysate, which is being stored at Newport as it is produced.

John Florence, a CDC spokesman, said the agency anticipates completing its final report on DuPont's treatment process by the first quarter of next year.