This document outlines the measurement of neutron flux distribution for decommissioning in the Tokai Power Station. An activation foil method and direct measurement using a gas filled neutron detector were used for this purpose. A wide range of data could be obtained before stopping its commercial operation, from areas to be controlled as radioactive waste to areas that do not require treatment as radioactive waste. From the viewpoint of practical use, it was confirmed that these types of detection methods were sufficiently effective.