In a recent revelation in France, a nuclear power company there discovered ‘anomalies’ in the steel of the pressure vessel, leading to serious concerns. Now, six Japanese utility companies have confirmed they used steel from the Japanese steel company, JCFC, in their pressure vessels, which could mean weaker strengths than expected. From The Japan Times:

Six utilities used steel from Japan Casting & Forging Corp. (JCFC), they all said in separate statements Friday. The company was identified by Japanese authorities last month as having supplied steel to the Flamanville nuclear plant, developed by Electricite de France SA and Areva SA, where the French safety authority last year found weaker-than-expected steel.

This is not a good development for the struggling Japanese nuclear industry as it highlights potentially serious issues with steel from reactors. The pressure vessel is the main component of a nuclear power plant, the large dome typical in most plants, and is responsible for containing the burning fuels and coolant. It needs to withstand significant temperature and pressure for many decades.

As the plant ages, the pressure vessel can be structurally weakened by the constant irradiation. Constant irradiation can weaken the steel and cause cracks, voids, and weak areas that can ultimately lead to accidents. The reactor pressure vessel is the component that limits the life of the nuclear reactor.

What these latest revelations show is that reactors could have been built with weaker steel from the beginning with certain anomalies. This clearly presents a safety issue and an investigation has been ordered by the Nuclear Regulatory Administration in Japan:

The Nuclear Regulation Authority asked utilities last month to examine reactor parts made by the same companies that supplied the Flamanville facility. Utilities must now evaluate whether their reactor pressure vessels meet national standards and report the results to the regulator by Oct. 31.

In addition, the French have discovered steam generator channel heads also have anomalies and is investigating, though the investigation has been delayed.

EDF has also determined that steam generator channel heads at 18 French reactors contain anomalies similar to those at Flamanville, Autorite de Surete Nucleaire, the safety regulator, said in June.

It is not uncommon for nuclear power plants to be plagued by bad steel, and shows the bathtub effect is real: as the plants age, they need to be maintained and inspected well because they suffer issues from the harsh conditions. See this recent article on the bathtub effect.

Sources

http://www.japantimes.co.jp/news/2016/09/04/national/jcfc-steel-troubled-french-reactor-also-used-13-japanese-nuclear-power-plants/#.V8wurjVT6J0

http://allthingsnuclear.org/dlochbaum/cracked-steam-generator-tubes-at-san-onofre