Prince William county was offered a nonpolluting growth industry yesterday willing to build an $18 million plant on a secluded site, hire 310 people and dispense a $4 million annual payroll.

County Supervisor T. Clay Wood's reaction to that proposal was, "If I'm going to stay in Prince William there's no room for it,"

Absolutely not in my district," said Board of Supervisors Chairman Donald L. White, and three other supervisors said there just is not enough space available in their districts, although it might be all right in somebody else's.

The problem is the industry - a medium-security state prison for 504 inmates.

Elilee Pate, the State Corrections Department's assistant director for Physical facilities, had come to Manassas to explain the state's plans to build five more medium-security prisons in Virginia, with two in the populous north.

The prison would want at least 400 acres "to do a little farming" and "keep a buffer zone," Pate said, presenting figures that showed about five or six escapes a year from similar existing facilities.

Supervisors James J. McCoart said, "The only thing I can compare it to is Lorton," the District of Columbia's often criticized prison complex in Fairfax County near the Prince William line.

Pate said, "I was afraid of that."

And McCoart said, "They have a beaten path to I-95 and hitchhike back to the District . . . can you assure us we wouldn't have that problem?"

"I can assure you it won't be that large," Pate said, "but you can't build unsinkable ships. Five hundred men over a period of years can outsmart the man who built the prison."

Pate assured the board that relations between the state's prisons and neighboring communties were generally good and said no prison would be built if a jurisdication's elected official opposed it. Caroline County, south of Fredericksburg, and several Shenandoah Valley counties have shown interest in having a prison, said Pate, who invited the Prince William board to visit one of the state's prisons.

"We spend all of our time trying to stay out," said Supervisor Alice E. Humphries.

"We wouldn't want to keep you," said Pate.

The board decided to defer its decision on inviting the state to put a prison in Prince William County until after supervisors have a chance to visit one.

But polled later, only Supervisors James Byrd and Andrew J. Donnelly said they would be willing to have it in their own districts.

Wood, the most vocal foe, said, "I think we can attract some of the better things the world has to offer."