Irregularities in equipment manufacturing at Japan Steel Works

Published on 26/01/2023 at 16:48

Information notice

In May 2022, Japan Steel Works (JSW) published reports of irregularities in its Muroran plant in Japan, which mainly concerned turbines for thermal power stations. The irregularities consisted more specifically in the modification of chemical analysis results, residual stress measurements and hardness measurements.

JSW also manufactures numerous components for the nuclear industry across the world, in particular parts of steam generators and reactor pressure vessels, including for the EPR2 reactors. It also manufactures components of radioactive substance transport packages. According to the information initially communicated by JSW, the nuclear sector was not concerned by these irregularities, thanks to the presence of a dedicated independent quality department. Manufacturing at JSW was immediately suspended. A special investigation committee, including lawyers external to JSW, was set up and tasked with conducting an in-depth investigation.

ASN engaged in technical discussions with EDF and the nuclear pressure equipment manufacturers to assess the safety risks for the French installations. EDF, Orano and the manufacturers Framatome, Mitsubishi Heavy Industries (MHI), Westinghouse and General Electrics shared investigations to analyse the impacts of these irregularities. They conducted an audit of JSW in Japan, which did not reveal any irregularities in the manufactured products intended for the French nuclear installations.

However, on 14 November 2022, the special investigation committee submitted its report which was published on the JSW website. This report highlighted irregularities affecting twenty components of equipment intended for the nuclear industry, the oldest dating back to 2013. Six cases concerned EDF orders, including the nozzle support ring of a steam generator of the Cruas nuclear power plant reactor 1. EDF's analysis, which is currently being examined by ASN, shows that the integrity of the equipment is not jeopardized.

In December 2022, ASN carried out an inspection in the MHI manufacturing plants in Japan to examine the handling of the irregularities detected at JSW. In the presence of the Japanese nuclear regulator, the ASN inspectors met the company's senior management and asked them to send the French licensees and their manufacturers all the information necessary to establish an inventory of the equipment concerned.

ASN closely follows this file in order more specifically to determine the conditions for restarting the manufacture of products for the French nuclear installations.

ASN and several of its foreign counterparts will conduct a multinational inspection at JSW in the first half of 2023.

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Date of last update : 14/03/2023