A fast-sorting measurement technique to determine decontamination priority

Recovery of large contaminated buildings, such as the Three Mile Island Unit 2 (TMI-2) reactor building, are complicated by ceilings that can be 12 to 13 m high. Much of the overhead space is filled with conduits, pipes, cable trays, ventilation ducts, and steel structures. The total complex surface can greatly exceed the total surface of walls and floors. Concrete pedestals, heavy steel stands, embedded steel rails, refueling mechanisms, and other similar structures complicate normally accessible areas and impede exposure reduction efforts. Initial recovery of contaminated spaces tends to involve treatment of hot spots and accessible spaces such as floor and wall surfaces. Subsequent decontamination may be less efficient since untreated surfaces, such as in overhead spaces, may be beyond the reach of ordinary decontamination tools. To conserve radiation exposure of recovery personnel, it is important to prioritize the effort so that early work provides maximum exposure reduction. Subsequent exposure reduction can then be carried out with less total exposure to recovery personnel. This favorable scenario depends on identification of key surfaces that most affect the exposure rate. The quick-sort method that was developed is based on the Eberline HP 220A directional survey system