Feasibility Studies and Development of NDA Technologies for NM in the Melted Fuels of Fukushima-Daiichi NPP

摘要

This paper presents, at first conceptual methods for the removal of melted fuel in the reactorand containment vessels of Units 1 - 3 of Fukushima-Daiichi NPP. By making the removalmethods clear, several strata of removed MF could be categorized into slab type debris,cylindrical debris, small rock-like debris and particle-like debris. Two possible NDAtechnologies are described in terms of feasibility studies.One of the two is Neutron Resonance Densitometry (NRD) based on NRTA (NeutronResonance Transmission Analysis) and NRCA (Neutron Resonance Capture Analysis)utilizing the TOF (Time of Flight) method, which is intended for the analysis of particle-likedebris. This paper describes the proposed NRD very roughly, while another paper shows thedetails of this method [1].The other NDA technology uses LCS (Laser Compton Scattered) gamma-rays(mono-energetic gamma-rays) to analyze other types of debris. The application of LCSgamma-rays by the Nuclear Resonance Fluorescence (NRF) method and is presented hereroughly. The measurement technique of the scattered method with NRF is shown. A noveltransmission measurement using NRF is also shown roughly, which has the advantage ofbeing insensitive to the radioactive nature of the fuel and is completely insensitive to thegeometry of the fuel. The techniques are discussed in other papers in more detail [2] [3].