3 ms·

Japan tsunami was at least 23-metres high

8 points by erikstarck 16y ago

anigbrowl 16y ago
That's going to be rather awkward for California's coastal nuclear plants, which IIRC are about 80 feet above sea level. While I'm generally pro-nuclear, I've always doubted the wisdom of siting plants in earthquake-prone areas. Although the San Andreas fault in southern California is not thought to be capable of generating such a large quake, the Cascadia fault (off the coast of Washington state) probably is. Plus, the fact that they're operated by PG&E fails to fill me with confidence - the company has a mediocre public safety record, and both plants were beset with construction problems: in Diablo Canyon the seismic supports for one reactor were built backwards, while one of the reactors at the San Onofre plant was also installed backwards. both plants are said to be safe for anything up to a magnitude 7 quake right next to the reactor, but hearings that were due next month to extend operating lifetime have just been postponed pending resolution of the situation in Japan. The historically unusual size of the quakes at other locations around the 'ring of fire' (Chile, NZ, and now Japan) is naturally worrying to disaster planners in California, and the problems at Fukushima demonstrate the potential severity of a cascading failure. The 50 mile safety radius recommended by USG would include ~7.5 million people if applied to the San Onofre plant, which is midway between Los Angeles and San Diego, and right next to southern California's major freeway. Diablo Canyon is about 60 miles north of LA, albeit in a hilly area that is unlikely to be affected by a tsunami.
- ChuckMcM 16y ago
  It is important to understand that California earthquakes are extremely unlikely to generate tsunamis. That is because a tsunami (or tidal wave) is generated by a subduction fault where one plate is sliding over or under the other. When tension is released there is a sudden change in relative altitude on either side of the fault, that if it occurs under water results in lifting up (or dropping) a large mass of water. California has strike/slip faults, that is faults where two plates are moving past each other. They tend to create large horizontal dislocations along their fault rather than vertical dislocations. This does not result in massive water movement. That isn't to say that its not possible, at some level all things are possible. But locally generated tidal waves (from a California fault) are even more rare than earthquakes of magnitude 8 or higher. That being said, two things disaster planners can take away from the Japanese experience are; Storing more spent fuel in the pond than the pond is designed to hold is a huge deal, it should be on the inspection list, there should be mandatory fines if discovered and an immediate shutdown until the situation is corrected, and additional backup power options should be available, with infrastructure immune transport (aka helicopters), within a couple of hours.
  - anigbrowl 16y ago
    The Cascadia fault is a subduction fault, and this was the reason I mentioned in the context of risks facing commercial nuclear plants in California (there are none operating in Washington or Oregon). http://en.wikipedia.org/wiki/Cascadia_fault http://en.wikipedia.org/wiki/Cascadia_fault http://walrus.wr.usgs.gov/tsunami/research1.html http://walrus.wr.usgs.gov/tsunami/research1.html edit: I ought properly to be calling it the 'Cascadia subduction zone' rather than a fault, because it spans several named faults where the North American plate meets different pacific plates.
    - ChuckMcM 16y ago
      You will note I didn't mention that Oregon and Washington :-). If you look at the USGS analysis [1] of the tsunami risk it does not extend below the western most part of California (Eureka/Fortuna area). This is a bit of fortunate geologic structure on the part of California. You might also note that there are no US nuclear power plants near the coast between Eureka and the southern border of Canada [2] so for some definition of risk avoidance, no one has built reactors there. Point being, in California at least, there is a very very small chance that one of our reactor's disaster plans will be challenged by a combination 9.0 earthquake and a 30' tsunami. [1] http://pubs.usgs.gov/pp/pp1661b/ http://pubs.usgs.gov/pp/pp1661b/ [2] http://en.wikipedia.org/wiki/File:NRC_regions_and_plant_locations_2008.jpg http://en.wikipedia.org/wiki/File:NRC_regions_and_plant_loca...

8 points by erikstarck 16y ago

That's going to be rather awkward for California's coastal nuclear plants, which IIRC are about 80 feet above sea level. While I'm generally pro-nuclear, I've always doubted the wisdom of siting plants in earthquake-prone areas. Although the San Andreas fault in southern California is not thought to be capable of generating such a large quake, the Cascadia fault (off the coast of Washington state) probably is. Plus, the fact that they're operated by PG&E fails to fill me with confidence - the company has a mediocre public safety record, and both plants were beset with construction problems: in Diablo Canyon the seismic supports for one reactor were built backwards, while one of the reactors at the San Onofre plant was also installed backwards. both plants are said to be safe for anything up to a magnitude 7 quake right next to the reactor, but hearings that were due next month to extend operating lifetime have just been postponed pending resolution of the situation in Japan. The historically unusual size of the quakes at other locations around the 'ring of fire' (Chile, NZ, and now Japan) is naturally worrying to disaster planners in California, and the problems at Fukushima demonstrate the potential severity of a cascading failure. The 50 mile safety radius recommended by USG would include ~7.5 million people if applied to the San Onofre plant, which is midway between Los Angeles and San Diego, and right next to southern California's major freeway. Diablo Canyon is about 60 miles north of LA, albeit in a hilly area that is unlikely to be affected by a tsunami.

ChuckMcM 16y ago
It is important to understand that California earthquakes are extremely unlikely to generate tsunamis. That is because a tsunami (or tidal wave) is generated by a subduction fault where one plate is sliding over or under the other. When tension is released there is a sudden change in relative altitude on either side of the fault, that if it occurs under water results in lifting up (or dropping) a large mass of water. California has strike/slip faults, that is faults where two plates are moving past each other. They tend to create large horizontal dislocations along their fault rather than vertical dislocations. This does not result in massive water movement. That isn't to say that its not possible, at some level all things are possible. But locally generated tidal waves (from a California fault) are even more rare than earthquakes of magnitude 8 or higher. That being said, two things disaster planners can take away from the Japanese experience are; Storing more spent fuel in the pond than the pond is designed to hold is a huge deal, it should be on the inspection list, there should be mandatory fines if discovered and an immediate shutdown until the situation is corrected, and additional backup power options should be available, with infrastructure immune transport (aka helicopters), within a couple of hours.
- anigbrowl 16y ago
  The Cascadia fault is a subduction fault, and this was the reason I mentioned in the context of risks facing commercial nuclear plants in California (there are none operating in Washington or Oregon). http://en.wikipedia.org/wiki/Cascadia_fault http://en.wikipedia.org/wiki/Cascadia_fault http://walrus.wr.usgs.gov/tsunami/research1.html http://walrus.wr.usgs.gov/tsunami/research1.html edit: I ought properly to be calling it the 'Cascadia subduction zone' rather than a fault, because it spans several named faults where the North American plate meets different pacific plates.
  - ChuckMcM 16y ago
    You will note I didn't mention that Oregon and Washington :-). If you look at the USGS analysis [1] of the tsunami risk it does not extend below the western most part of California (Eureka/Fortuna area). This is a bit of fortunate geologic structure on the part of California. You might also note that there are no US nuclear power plants near the coast between Eureka and the southern border of Canada [2] so for some definition of risk avoidance, no one has built reactors there. Point being, in California at least, there is a very very small chance that one of our reactor's disaster plans will be challenged by a combination 9.0 earthquake and a 30' tsunami. [1] http://pubs.usgs.gov/pp/pp1661b/ http://pubs.usgs.gov/pp/pp1661b/ [2] http://en.wikipedia.org/wiki/File:NRC_regions_and_plant_locations_2008.jpg http://en.wikipedia.org/wiki/File:NRC_regions_and_plant_loca...