A Measurement Method for Cesium Contamination Distribution on the Bottom of a Top Shield Plug from the Operation Floor of the Fukushima Daiichi Nuclear Power Plant

For the decommissioning of the Fukushima Daiichi Nuclear Power Plant, Cs-137 contamination distribution on the bottom of a top shield plug must be estimated.Gamma rays emitted from the surface of an operation floor and inner walls of a reactor building, however, disturb the contamination distribution measurement.This paper proposes a direct measurement method of Cs-137 contamination distribution on the other side of a concrete shield plug with a gamma ray pinhole camera based on deterministic calculations.