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Probe Design for the Eddy Current Inspection of Cooling Tubes in the Blanket of a Fusion DEMO Reactor

Mizuki KAKO¹⁾, Takuma TOMIZAWA¹⁾, Jiuhao GE^1,2), Takashi NOZAWA³⁾ and Noritaka YUSA¹⁾

1)

Graduate School of Engineering, Tohoku University, 6-6-01-2 Aramaki Aza Aoba, Sendai 980-8579, Japan

2)

Nondestructive Detection and Monitoring Technology for High Speed Transportation Facilities, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, 211106, China

3)

National Institutes for Quantum Science and Technology, 2-166 Obuchi Omotedate, Rokkasho-mura 039-3212, Japan

(Received 20 December 2021 / Accepted 13 September 2022 / Published 24 November 2022)

Abstract

This study investigated the applicability of eddy current testing (ECT) to the non-destructive inspection of cooling tubes in the blanket of a fusion DEMO reactor. Pipes made of F82H steel with inner and outer diameters of 9.0 and 11.0 mm, respectively, were prepared, and slits imitating cracks were fabricated on the pipe surfaces. ECT was performed using a differential type bobbin probe having one exciting and two detecting coils designed in this study. The results of the inspections and subsequent three-dimensional finite element simulations revealed that a bobbin probe is effective in detecting cracks appearing on the inner surface of a pipe. Moreover, the detectability does not deteriorate significantly when cracks oriented in the circumferential directions are targeted, unlike in the case of ECT of the heat exchanger tubes of the steam generators of the pressurized water reactors. This indicates that a probe with a more complicated structure, such as a plus-point probe, would be unnecessary to detect flaws on the inner surface of a pipe. In contrast, the ECT signals from a non-penetrating slit on the outer surface were buried in noise even though the slit was as deep as 0.9 mm.

Copyright (c) 2022 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

ECT, F82H, blanket, prototype reactor, cooling tube, ferromagnetic, bobbin probe

DOI: 10.1585/pfr.17.2405102

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