TEPCO’s Falsely Optimistic Predictions
Nice article from two reporters in Tokyo on how TEPCO underestimated the possibility of a quake such as the one that hit two weeks ago. TEPCO engineers only predicted what could happen based on what has been observed in recent history, ignoring archaeological evidence that every thousand years or so Japan is hit by giant tsunamis which sweep miles inland–and the previous one hit only a bit over a thousand years ago. Many American nuclear plant scenarios take into account extreme situations, like a quakes and tsunamis more powerful than ever recorded, at time when storms drive waters even higher. TEPCO, however, lowballed their estimates:
A TEPCO reassessment presented only four months ago concluded that tsunami-driven water would push no higher than 18 feet (5.7 meters) once it hit the shore at the Fukushima Dai-ichi complex. The reactors sit up a small bluff, between 14 and 23 feet (4.3 and 6.3 meters) above TEPCO’s projected high-water mark, according to a presentation at a November seismic safety conference in Japan by TEPCO civil engineer Makoto Takao.
“We assessed and confirmed the safety of the nuclear plants,” Takao asserted.
However, the wall of water that thundered ashore two weeks ago reached about 27 feet (8.2 meters) above TEPCO’s prediction. The flooding disabled backup power generators, located in basements or on first floors, imperiling the nuclear reactors and their nearby spent fuel pools.
Scientists in Japan have been aware of this possibility since long before the TEPCO assessments:
As early as 2001, a group of scientists published a paper documenting the Jogan tsunami. They estimated waves of nearly 26 feet (8 meters) at Soma, about 25 miles north of the plant. North of there, they concluded that a surge from the sea swept sand more than 2 1/2 miles (4 kilometers) inland across the Sendai plain. The latest tsunami pushed water at least about 1 1/2 miles (2 kilometers) inland.
The scientists also found two additional layers of sand and concluded that two additional “gigantic tsunamis” had hit the region during the past 3,000 years, both presumably comparable to Jogan. Carbon dating couldn’t pinpoint exactly when the other two hit, but the study’s authors put the range of those layers of sand at between 140 B.C. and A.D. 150, and between 670 B.C. and 910 B.C.
While it may be satisfying to see reports that TEPCO may be held liable for the damage caused by the plant’s crisis, it doesn’t take any engineering reassessment or scientific study to figure out where that money will be coming from.
yeah, fining TEPCO is just fining TEPCO’s users in the end. Well, 国 can take the dividend away, but TEPCO’s been paying about $1B/yr in dividends after the 2007 quake so it’s going to take TEPCO a long time to pay.
TEPCO’s stock price has fallen from over 2000 to 720 now, so the market is taking this somewhat seriously at least.
TEPCO’s 2002 study suffered from ex-post-facto justification pressure — the plants had already been built so perhaps there was a built-in bias to minimize the risk with their location.
The company would lose face it if it had to admit #1 had been built too low vs. the threat it was facing. Plus they wanted to fuel up with MOX, and admitting the risk of a station black out due to tsunami would have made that fight more difficult.
Well, American hurricane scenarios apparently didn’t take into account extreme situations, like Katrina -that the University of California Berkeley’s Dr. Raymond B. Seed called “the worst engineering disaster in the world since Chernobyl”. Shit happens!
Thing is, TEPCO’s “shit happening” has just wiped out ~$50B of wealth, $1000 per Japanese taxpayer, not to mention the hundreds of thousands of people who have been directly affected by this crisis.
It behooves us to endeavor to limit such failures to mitigate damage caused by human stupidity. (I’m sure I could word that better but it’s late)
“Shit happens” is no way to preserve a functional modern society, quite the opposite in fact.
That $50B worth of stupidity could have been used for $50B of good.
Shit need not necessarily happen.
But it does, Troy: it does! And when it does, the thing to do is learn from it so that it doesn’t happen again -rather than witch hunting. The notion of a fail-safe world is unreal. I bet you are not an engineer: when one talks about archaeological evidence, … there is also archeological evidence that meteorites hit the Earth. Maybe civil engineers and architects should take note of that.
Not just “archeological evidence” or once every 100,000 year mass-casualty events.
The plant’s backup facilities were simply too vulnerable to the thousand-year tsunami that this region of Japan was known to be vulnerable to.
That should be the standard — looking at the maximal known possibility, not just what has happened in the past 100 years — when you want to operate nuclear plants for 50 years or more. With an arrival rate of 1/900, particular disaster had a cumulative probability of occurrence of ~5% after 40-50 years. Plus given the stress nature of subduction events, modeling tsunami events as a poisson arrival is probably incorrect, ie. the longer we go without one the more likely one is to come.
TEPCO’s own analysis last year showed they only had a 2 meter seawall safety margin vs the tsunami of 2010 that came from Chile.
The study TEPCO should have made was what happens with a Indonesian-style tsunami — the Pacific Plate subducting under Japan is an obvious generator of tsunamis. TEPCO had the data but refused to incorporate it into their safety models.
The question is why. Perhaps the answer will come out.
Troy, … “nolo contendere”.