At congressional hearings earlier this year, Bernard Roser, manager of the Department of Energy's nuclear weapons building program, said the Pantex nuclear weapons plant near Amarillo, Tex., "doesn't meet the latest safety or safeguard criteria.... Significantly upgrading of that plant is not only appropriate, but we think is very necessary."

Uppermost in Roser's mind was an explosion at Pantex on March 30, 1977, that killed three workers. Although the accidental blast, set off while a high explosive was being machined, did not take place in the nuclear weapons assembly area, it did force a closer look at the aging plant.

According to plant officials, new Pantex construction will include more safety engineering and a master plan is being drawn up to renovate the plant.

Meanwhile, however, two new assembly cells are to be built, for $10 million, to help handle the increased workload over the next five years.

The 1940s-vintage buildings are not the only carryover from World War II days at Pantex.

The workers and their attitudes seem to reflect the defense plant atmosphere of that era.

In the administration building, visitors are greeted with a large poster showing a woman with her finger on her lips. "Shh," reads the caption, "no classified discussion here." The same poster is in the cafeteria.

What's more, employes floolw that direction. They refuse to discuss their work with reporters. Part of that attitude is a throwback to the past. Although Pantex has assembled nuclear weapons ince 1951, it wasn't until 1963 that its function was made public.

When a network camera crew recently did some filming at Pantex, the employes covered up their identification badges. A security officer said they feared someone would enlarge the film and make counterfeit badges.

Managers of Pantex like to portray the facility in terms of "just another defense plant." They point to the line of cars prior to the 8 a.m. plant opening as a sign that their 1,900 workers are just like any other factory employes.

"They work here on the line just the same way they do at Ford or General Motors," one official said recently.

They do recognize though that handling high explosives and nuclear components makes a difference.

The Pantex "line" is primarily made up of bays -- small, high-ceiling rooms with thick cement doors, and often heavy steel doors.

Mechanical assemblies and explosive work is done in such bays. A high explosive part in a weapon, for example, is made into a hardened form by a pressing operation.

Then it is put on a machine that resembles a potter's wheel and cut by a machine tool into the shape for the weapon involved.

In both the pressing and machining operations, the number of people on a bay is limited, normally to only or two workers.

When the pressure is being applied to the high explosives, no one is allowed in the bay. The room is also cleared when the machining requires holes to be drilled in the explosive. The operation is run from a control room with a television camera in the bay showing how the work is going. Security has been tightened, particularly within the weapons assembly line area. Some of that has to do with fear of terrorists, some with last year's accident. plant at Amarillo, Tex.

Outsiders are not allowed in the double fenced assumbly areas. Even government and neclear laboratory officials have been barred from entering unless their business requires it.

A staff member of the Senate Armed Services Committee, for example, was recently kept from the assembly area while on a tour of nuclear production facilities on behalf of committee cochairman John C. Stennis (D-Miss.). What particularly irritated the staff member was that he had formerly worked in the Pentagon as the top adviser to the defense secretary for atomic matters and had been associated with the nuclear weapons program for almost 20 years.