A visit to the 'source' room

It is a trip that tons of food could soon be making. Dr. Martin Welt, president of Radiation Technology Inc. of Rockaway, N.J., agreed to take this reporter to what he calls the ''source'' room, where containers of food and other materials are irradiated.

The area is usually sealed off by several thick metal barriers. But now, those are removed and the radiation source shut down. We walk dowb a long hallway with concrete walls and floors. ''The walls are five feet thick, the floors six,'' Dr. Welt remarks. Alongside us runs a two-level conveyor belt that transports the material to be irradiated.

Down a second hallway and around a corner, we enter the source room. It has been surveyed for radiation. ''There's about as much radiation in this room right now as there is in your living room at home,'' Mr. Welt says. Cobalt 60 gamma radiation disintegrates instantly, but ''When the source is exposed, the radiation in the room would kill you in 30 seconds,'' he says.

We peer down into a tank of water 20 feet deep and 10 feet across. At the bottom, standing vertically, is the ''source plaque,'' a 5 by 6 foot grid containing 180 ribbons of radioactive cobalt 60. ''You are looking at one of the largest sources of cobalt 60 gamma radiation in the world,'' Mr. Welt says. It glows an eerie purplis(-blue. ''That's where they get the name cobalt blue,'' he says.

''The radiation is being absorbed by the water, causing it to be heated'' Dr. Welt says, as he dips his finger in the water.

Above the tank, standing on the two conveyor belts, are large metal containers. They are filled with products waiting to be irradiated. They might be mushrooms, wheat, or onions. But I am not allowed to look into the containers. Much of the work is confidential testing for food companies and other sources.

When the source is out of the water, Mr. Welt explains, the metal containers move around it, slowly, automated by a computer. As many as 12 containers can receive radiation at one time; the irradiation takes about a minute.

After a short time, we leave and return to the plant floor. There, forklifts stand idle, waiting to move the next containers to the belt. The doors shut down on the passageway. The operator activates the computer and, says Mr. Welt, ''The source is now being lifted out of the water by metal arms.''

A red light flashes and a horn sounds. Irradiation has begun again.