Three Mile Island Unit 2 Reactor Building Basement Concrete Activity Distribution

Sample and measurement data used to determine the quantity of radioactive material in the concrete walls and floor of the Three Mile Island Unit 2 (TMI-2) reactor building (RB) basement are given. The layout of the RB basement, types of concretes and surface coatings, measurement methods, and final assessment are described. It was found that the radioactive material (primarily ¹³⁷Cs) did not significantly penetrate into poured concrete walls and floors, but did penetrate completely through concrete block. The activity distribution in the walls varied strongly with elevation above the floor. Of the estimated 975 (±25%) TBq (26400G) in the RB basement, ∼72% is contained in the concrete block, ∼23% in the low-compression-strength concrete walls, ∼2% in the low-compression-strength concrete floor, and ∼3% in the high-compression-strength walls.