Excess carbon found in JCFC steam generator components in reactors supplied by AREVA to reactors owned by EdF in France are estimated to have reduced the toughness of the steel by up to 50 percent, failing the minimum specified standard.This dramatically increases the risk of complete failure of the nuclear pressure circuit by fast fracture. Such a failure would lead to a rapid reactor core meltdown and the potential for a massive release of radioactivity into the environment.
All 12 reactors in France with steam generator components supplied by JCFC have been ordered to shutdown or undergo examination and further investigation. Steam generator components believed to be from JSW supplied to France are also under investigation, because of the potential for similar excess carbon content and reduced toughness. At this time, JCFC are manufacturing two full-size, new steam generator components at its Kitakyushu works for destructive testing and analysis, under the supervision of the French nuclear safety regulator ASN. Representatives from Edf, AREVA, the French regulatory bodies ASN and IRSN and Mitsubishi Heavy Industries, as well as the NRA, spent two days at the JCFC plant in mid-November investigating the excess carbon problem.
The Greenpeace-commissioned report reviewed submissions to the NRA from the Japanese nuclear reactor operators and the three steel forging companies over the past three months, as well as AREVA documents obtained directly from the French regulator. The report concludes that flawed components during the 1980s-1990s could have entered and remain in the Japanese nuclear equipment supply chain undetected by the discredited regulator of the time, Nuclear and Industrial Safety Agency (NISA).
“This situation is very disturbing” said Chartered Consulting Engineer John Large. “Whereas the NRA dismissed the possibility of carbon excess in these components, mainly on the basis of the methods of manufacture, the submissions of JCFC, JSW and JFE clearly show that macro-segregation heterogeneity formed in the pre-forged steel ingots, and that JCFC and JSW have used a carbon content prediction model that is flawed. This is quite contrary to the experience in France where it is now irrefutably established that reliance upon the manufacturing records alone is wholly insufficient. The French crisis shows that the only way to realistically determine the presence of such flawed components in operational reactors is to undertake inspections and tests, otherwise the flawed components, if such exist, are likely to remain undetected. ” said Large (2).
The JCFC, JSW and JFE submissions to the NRA include contradictions, anomalies and misleading statements. For example: virtually all of the steam generator components are excluded from any assessment whatsoever, simply on the basis that they could not possibly include zones of segregate heterogeneity, although this claim is entirely baseless. Contrary to the NRA claim, JSW acknowledges that positive macro segregation exists in the steel ingot with a residual amount remaining in its finished reactor pressure vessel components(3).
JCFC documents submitted to the NRA show that they predicted and measured levels of carbon in excess of French regulations on components destined for export to French reactors – yet they were approved for export and installed in 12 reactors operated by EdF. The JCFC quality control data and test results could not have reflected the actual conditions in the steel: if they had, the steam generator components would not have passed French regulations and would have been scrapped. Between 1989 and 1997, JCFC manufactured for EdF 36 bottom channel heads for steam generators.
Component data manufactured by the AREVA le Creusot Forge company in France have now been revealed to be based on fraudulent records submitted to the nuclear safety regulator. Last week, the Paris prosecutor opened criminal proceedings against the AREVA forging company: a case has already been opened by the prosecutor following a Greenpeace France’s complaint against AREVA and EdF over failure to disclose fraudulent activities for components installed in the Fessenheim reactor.
The risk of reduced toughness in steel is a fundamental issue of nuclear reactor safety – assurance and guarantee of its quality is the basis for the operating license granted to nuclear reactors by the regulator, ASN in France and the NRA in Japan. The Class 1 pressurized components from JCFC, JSW and JFE are not permitted to fail due to the radiological consequences. The risks include when a reactor is scrammed in response to a small leak in the primary circuit and when cold emergency core make-up water is injected into the circuit, there is a risk that the normally hot steam generator channel head will encounter a cold slug of water, this thermal effect woud cause the head of the steam generator to catastrophically fail. There is a similar risk of failure when the steam generator head encounters a hot slug of water traveling round the primary coolant circuit, for example, during reactor start-up transients.
Since June 2016 a series of physical non-destructive tests of EdF reactors, including those with JCFC components has revealed high carbon content. The NRA has so far failed to order such tests in Japan; however, under questioning in the Japanese Diet last week, the NRA revealed that it would request tests on the permanently shutdown Genkai 1 reactor, and assess the steel issue for Genkai 2 before any restart. Only three reactors are currently in operation in Japan, with Sendai unit 2 scheduled for maintenance shutdown at the end of this week.
“The scale of this crisis is almost beyond comprehension. Japanese critical components which are not permitted to fail have been supplied to nearly one-quarter of the 58 nuclear reactors in France and have been found to violate regulations. They are at the heart of this unprecedented crisis. There remains no credible explanation as to how such components passed through the checks that should have seen them rejected. In contrast to the physical inspections ordered on 18 reactors in France, no checks have been conducted on the three reactors operating in Japan. By not ordering urgent physical checks on these reactors, as well as those under restart review, the NRA has demonstrated a complacency verging on incompetence that is reminiscent of its discredited and disbanded predecessor, NISA. This is a nightmare for the nuclear industry in Japan and the regulator – they don’t want to look because they are afraid of what they will find. They are right to be – but ignoring it will solve nothing,” said Shaun Burnie, senior nuclear specialist at Greenpeace Germany, in Japan.
The French utility EdF is seeking authorization to restart reactors with JCFC components as early as 20th December, depsite not having demonstrated that it is safe to do so. Eight reactors are currently shutdown, with an additional four to be shutdown in the coming 10days.
1 – Irregularities and Anomalies Relating to Nuclear Reactor Primary Coolant Circuit Components Installed in Japanese Nuclear Power Plants,
Large&Associates, 10th December 2016, commissioned by Greenpeace Japan/Germany.
2 – Large&Associates note that at minimum the NRA should have received certificates verifying that the zones of segregates had been removed at the appropriate intermediate stages of the forging process – this could have been in the form of the certified ‘forging ratio’; a record of the discard weight; and chemical analysis of swarf and other small discards yielded during the interim rough and final finish machining stages, none of which has been provided in the submissions of power utilities or JCFC, JSW or JFE.
3 – JSW reported to the NRA that “. . .Carbon segregation tends to occur in the top side riser of the ingot core. The riser is cut away and discarded in order to remove this region. . . .. The final component is located in a region where there is no increased component concentration zone, therefore, carbon segregation in excess of 0,26 wt.% does not remain” see “BWR Reactor Pressure Vessel Material: Manufacturing processes and measures to prevent remnant carbon segregation October 17, 2016 JSW.”
For further information:
Shaun Burnie, senior nuclear specialist, Greenpeace Germany, firstname.lastname@example.org, +81 (0)80-6647- 8503
Chisato Jono, communications officer, Greenpeace Japan: email@example.com, +81 (0)80-6558-4446