An exhaustive analysis of data from nuclear plants nationwide reveals that critical safety components in both reactors at the San Onofre nuclear power plant — the damaged replacement steam generators — are in far worse shape compared to typical U.S. reactors than previously admitted by federal regulators and the plant’s operator.
San Onofre’s Unit 2 reactor has about 400 times as many damaged steam generator tubes as the median number at comparable plants over the same operational period, and Unit 3 has more than 450 times as many.
Each San Onofre reactor has greater than 1,000 times as many indications of wear on the tubes than the typical reactor in its first cycle of operation.
Each San Onofre unit has had to plug more tubes than all replacement steam generators nationwide combined.
Daniel Hirsch is a lecturer in Nuclear Policy at the University of California, Santa Cruz. He is the former Director of the Stevenson Program on Nuclear Policy at UCSC. Hirsch is also President of the Committee to Bridge the Gap, a nonprofit organization working for over four decades to reduce risks of nuclear accident, nuclear proliferation, nuclear terrorism, and problems of radioactive waste disposal. Shortly after the Fukushima accident began, Hirsch was asked to testify before the Select Committee on Earthquake and Disaster Preparedness, Response, and Recovery of the California Senate on the implications of the disaster for the Diablo Canyon and San Onofre reactors.
And we must remember the adverse effects of inhaling the significant radioactive emissions from the San Onofre stacks long-term. There are many people now whose homes are within the 5 mile zone where children should not be residing permanently.
And what civilized society would store toxic long life radiation above ground? The meteor strike in Russia last week landed close to their buried nuclear waste pile in Siberia.
Using filthy nuclear fission reactions to generate power was a bad idea in the first place and it is still a bad idea, but nothing in the world was going to stop people who label themselves as ‘nuclear engineers’.
Dr. Richard Sauerheber
If a major, non-isolatable, steam-line break (MSLB) event were to occur inside the Containment Building, the rapid depressurization of the affected Steam Generator would result in flashing of it’s liquid inventory. This would cause increased steam production, increased upward steam and liquid velocities, and increased flow-induced vibration effects within the steam generator tube bundle. This enhanced vibration, coupled with an increase in the differential pressure across the tube walls, might result in more than a few steam generator tube failures. The end result would be a combined steam-line break (MSLB) plus a loss of coolant accident (LOCA). The magnitude of the LOCA would depend on how many tubes actually fail.
The NRC appears to have addressed this safety concern in “Resolution of Generic Safety Issues: Issue 18: Steam-Line Break with Consequential Small LOCA.” However, it is not clear how many tube failures were envisioned for a “Small” LOCA. What if several hundred or perhaps a thousand or more tubes were to fail as a consequence of a steam-line break? Would that be a classified as a “Small” LOCA? See public reference document below.
Some other important considerations are the following:
For NSSS’s supplied by CE, as is the case for SONGS Units 2 and 3, postulated steam-line break accidents are quite severe, and they tend to result in Containment Building environmental pressures which exceed that of a worst case LOCA accident by a significant margin. This is because CE NSSSs utilize only two relatively large steam generators (as opposed to four smaller steam generators provided by W) and the liquid inventory in each of the two steam generators is relatively high.
As a comparison, the worst case LOCA for Songs Units 2 & 3 (at 102% power) is said to result in a peak containment environmental pressure of 45.9 psig, while the worst case MSLB (also at 102% power) is said to result in a peak pressure of 56.5 psig for a steam-line break size of 8.85 square feet. With a specified Containment Building design pressure of 60 psig for Songs Units 2 and 3, there is little design margin for a MSLB accident. See public document below.
Click to access ML013340271.pdf
When operating a CE NSSS Steam Generator at reduced power, such as at 70% power for five months or so as proposed by SCE, the liquid inventory in the steam generator will be significantly higher than it is at 102% power. This is because the void fraction (steam volume) in the tube bundle region will be reduced at lower power levels. Also, the level of liquid water in the downcomer annulus will be somewhat higher at reduced power levels. The bottom line here is that the amount of mass/energy release into the Containment Building atmosphere would be significantly greater at 70% power than it is at 102% power. So, with the assumption that all other factors are nearly equal, operating at 70% power would be a set-up for a more severe MSLB event… one which could result in a peak pressure that exceeds the Containment Building design pressure by a significant margin.
For a postulated accident which consists of a steam-line break (MSLB) and a consequential loss of coolant accident (LOCA) of a significant magnitude, due to rupture of perhaps 1000 steam generator tubes, who knows what the resulting peak pressure would be in the Containment Building?
If I’m not mistaken, I think it was Isaac Newton who made this statement around 300 years ago:
“I can calculate the motions of heavenly bodies, but not the madness of people”