Generation, Nuclear

SCE claims Mitsubishi generators led to SONGS retirement

Southern California Edison (SCE) has served a formal notice of dispute on Mitsubishi Heavy Industries, and Mitsubishi Nuclear Energy Systems, which seeks to hold Mitsubishi accountable for designing and manufacturing defective replacement steam generators at the San Onofre Nuclear Generating Station (SONGS).

Although Mitsubishi warranted the generators would operate reliably for 20 years, SCE was required to take SONGS offline in January 2012 when one of the Mitsubishi RSGs experienced a radioactive coolant leak after less than a year of operation. Although its contract with SCE required Mitsubishi to repair the generators “with due diligence and dispatch,” SCE’s notice of dispute alleges that Mitsubishi failed to do so.

Facing continued uncertainty about restoring SONGS to service at any level of power, SCE permanently retired the nuclear power plant as of June 2013. SCE alleges that Mitsubishi, as designer and manufacturer of the faulty defective replacement steam generators, is responsible for the enormous harm its failures have caused to California ratepayers, SCE, and the other SONGS owners.

When SCE contracted with Mitsubishi to replace the SONGS steam generators, it did so to extend the life of SONGS so that the plant could continue to provide safe, reliable and affordable power to over 1.4 million homes in Southern California.

However, SCE’s notice claims that Mitsubishi seriously breached the contract, totally and fundamentally failing to deliver what it promised. SCE alleges that Mitsubishi grossly failed to appropriately model the thermal hydraulic conditions in the generators, including the relative wetness of the steam/water mix in the defective replacement steam generators (“void fraction”) and the speed of the steam/water flow within the defective replacement steam generators (“fluid velocity”).

In addition, Mitsubishi is alleged to have failed to design tube support structures capable of withstanding the extreme thermal hydraulic conditions within the RSGs. As a result, the defective replacement steam generators experienced damaging flow-induced vibration that caused several types of excessive tube wear.

The tube-to-tube wear was so advanced in one of the four identically-designed generators that it caused a radioactive coolant leak, which SCE was able to address by promptly and safely shutting the plant down.

The notice claims that for over 16 months, SCE has asked Mitsubishi to make things right, but Mitsubishi failed to live up to its contractual obligations. SCE invoiced Mitsubishi for the money SCE was forced to spend investigating and attempting to repair the generators, but SCE claims that Mitsubishi has refused to even acknowledge responsibility for any of these costs, even after receiving thousands of pages of documents in support.