A 5,000-pound batch of nitroglycerine exploded at the Radford Army Ammunition Plant this morning, killing one worker, leaving another one missing and presumed dead, and turning the building where they worked into a half-acre crater.

One of the workers, James Ernest Brookman, 41, was talking on the telephone with a colleague about transporting a shipment of nitroglycerine when the explosion occurred at 8:53 a.m. Brookman was blown out the building, where his body was found. The body of another employe, Earl Ray Burcham, 41, was not found -- a common occurrence in blasts involving a highly volatile substance.

In the last 15 years there have been nine major explosions at Radford, the nation's largest military munitions plant, resulting in seven deaths, more than 115 injuries and millions of dollars in damage. But Army officials said today that the plant has a safety record unmatched in the munitions industry.

The cause of today's explosion is not known, said Capt. Michael Coleman, the plant's executive officer. An Army board of inquiry is looking into the blast, he said.

The explosion blew out windows and roof shingles at the 4,000-acre site, and it was heard up to 10 miles away in Blacksburg.

The accident was the first at the plant's manned nitroglycerine mixing unit, where some of the most volatile work is performed, Army officials said.

"The arsenal," as it is called in this small town on the edge of the Blue Ridge Mountains 40 miles southwest of Roanoke, is this rural region's largest employer, providing jobs for 4,000 persons. Since the plant was built in 1940, those who have lived in its shadow have come to view the danger of working there as a fact of life. Even the sound of explosions is taken for granted.

"They're always testing powder, so we're used to it," said Louise Keister, a secretary at an elementary school about a mile from the arsenal, "but this was a little louder than usual."

Hercules Inc., a Delaware-based company, operates the plant under contract with the Army. It manufactures the explosive substance used to propel bullets, rockets and artillery shells.

Most of the plant's functions are performed in small buildings surrounded by high wooden earth-filled barriers, designed to "vent" any accidental blasts upward. To minimize danger, only small numbers of employes work in each unit.

The small, three-story wood building where the blast occurred was surrounded on three sides by a barrier that was almost totally destroyed by the blast. Little else was left in the crater, except for pieces of wood and other fragments.

Workers at the building mix glycerine with nitric and sulphuric acids in large stainless steel vats, where the compound is purified to make nitroglycerine.

Investigators plan to question the employe at the plant's storehouse who was talking to Brookman on the phone about plans to transport the substance when the blast occurred.

"She's pretty unsettled," Coleman said, "and we haven't been able to get a good statement from her."

Army officials estimate the damage at $4 million, and said layoffs are probable because some work at the plant will have to be halted until the investigation is finished.

Today's explosion was the first serious accident at the plant since July 28, 1982 when a fire caused $2.7 million in damage but resulted in no serious injuries. The most recent fatality occurred on June 10, 1982, when an explosion killed one worker and injured seven others.

"We do feel the things we do here are safe," Coleman said. "The most hazardous thing we do is driving to work." He said that before this explosion, the plant functioned for 18 million man hours without a work-related injury.

"If it was grossly unsafe to work here, we couldn't pay people to work," he said.

Army officials said there is a backlog of several thousand applications for jobs at the plant.

* Furniture Factory Explosion Injures Four Va. Workers ---Associated Press

MADISON, Va., Feb. 6 -- Four men were injured today, three seriously, in a fiery explosion at the E.A. Clore Sons Inc. furniture factory in this town about 15 miles southwest of Culpeper, authorities said.

The 11:50 a.m. blast apparently was triggered by sawdust being ignited, according to Madison County Sheriff Harry O. Tinsley and Fire Chief Willie Coppage.

"I presume that dust caused it. It tore down a cinder block bin that they store sawdust to fuel the boiler with," Tinsley said.

Coppage said a spark from the boiler apparently was sucked into the sawdust bin, ignited and blew a portion of the roof off the building. A wall collapsed as well, he said.

Tinsley said three of the men were taken to U-Va. Medical Center.