APR: your source for nuclear news and analysis since April 16, 2010

Friday, April 22, 2011

Friday morning update.... it's Earth Day

Plant data from Fukushima Daiichi remains fairly constant, with the reactor plants showing continued slow cooling. In fact, it's been released that the latest NRC consideration of the situation is that it is "stable, but fragile." This of course refers to both the potential for either loss of cooling to the cores, or else further possibly sudden release of contamination to the environment, which most likely would be a release of contaminated water.

TEPCO continues to pump water out of No. 2 plant, as reported everywhere, and intends to double pumping capacity within about a week.

As Earth Day 2011 progresses, we also find in the headlines in Japan the stories that the remaining reactor plants at Kashiwazaki Kariwa, the largest nuclear generating station in the world, will not be allowed to restart until the Fukushima situation is resolved (being stopped apparently by local government) and we also see the hint that Fukushima Daini will not be allowed to restart until certain safety guarantees are made (this stoppage by the prefecture's governor.) TEPCO certainly has its hands full, and will be very short of power come the summer if all of these reactor plants are kept shut down.

Having said that, it is of course imperative, given Fukushima Daini's closeness to the now highly-active earthquake zone off the northeast coast, that TEPCO perform major modifications to the plants at that site and improve tsunami protection before those plants can be allowed to restart. The case against idle reactors at Kashiwazaki Kariwa, where some reactors have never shut down (there are seven on site) is much less easy to make considering that it's on the opposite coast.

Also, given that it's Earth Day, we might expect a horde of articles to appear today against nuclear energy in the United States. The more informed authors might target boiling water reactors. However, it's important to note the modifications and alterations made to all US BWR plants that use Mark I containments, as delineated by the NRC site and given some analysis by your author:

1. In 1979, backup safety systems were separated. This means that backup systems like diesel generators were made fully and totally independent in all aspects. This might include ensuring completely separate water cooling for the diesels, it might include totally separate buses the diesels power, and even separated locations. What this step did was eliminate the chances that a problem in one backup safety system could have a negative effect on the operability of another.

2. In 1980, control rooms were reconfigured to improve operability and analysis of information by plant operators.

3. In 1980, the suppression chambers were strengthened. It had been recognized that the strength of the torus section of the Mark I containment could be considered a weak point of the design, regarding ability to hold structural integrity against severe accidents and a backfitting / rebuilding program was performed to strengthen this portion of the physical containment. (This might have helped Fukushima Daiichi No. 2, whose suppression chamber is damaged.)

4. In 1988, more batteries were added at all stations to protect against SBO or Station Blackout. As readers here now know, longer battery life delays core damage if there are no sources of AC or DC available either offsite or from EDG power.

5. In 1992, vents were added to vent the primary containment directly to atmosphere if necessary. These vent pipes, with valves in the vent path to maintain primary containment integrity while still allowing a direct vent path through a high point stack if necessary, are intended to vent hydrogen directly to atmosphere instead of allowing it to build up inside the primary and possibly leak to spaces in the reactor building. (This might have aided No. 1, 2 and 3 plants at Fukushima Daiichi.)

6. In 2002, plants added another spare portable diesel generator and water pump. The need for this is obvious, given the events at Fukushima Daiichi. These have been present at US plants now for a number of years.

We can see then that there are many things that might be considered superior points in the construction and operation of US BWR plants as compared to those at Fukushima Daiichi, and in fact these are just a few of the differences. The nuclear power establishment in this country has learned from past accidents and incidents, and many many reactor-years of operation in a number of programs. We need to all keep this in mind as Earth Day 2011 progresses, and the environmental voices begin to rise in volume.

Just six months ago, nuclear energy was one of the darlings of the green movement and environmentalists and climatologists in many places the world over. We must thus also remember that what's happening in Japan is the 'worst case' scenario, in which a major natural disaster overwhelms all active and passive core safety protections. Knowing the differences here in the USA compared with Japan, we can.. and should.. rest very comfortably at night.

10:00 AM Eastern Friday 4/22


  1. Another illuminating post.
    It might be worth adding that the Japan situation is a 'worst case' managerially as much as technically.
    A power plant operator who relies on a flock of competing subcontractors to build and maintain the sites is confronted by a huge crisis. Confusion and symptom suppression ensue, while the problem goes unresolved.
    There needs to be an international emergency response structure to provide politically acceptable authoritative expertise to manage this kind of event before it turns into a complete disaster.

  2. http://en.wikipedia.org/wiki/Historic_tsunamis#1983:_Sea_of_Japan_.28.E6.97.A5.E6.9C.AC.E6.B5.B7.E4.B8.AD.E9.83.A8.E5.9C.B0.E9.9C.87.29
    were on the sea of Japan side of Japan and had tsunamis of 10m and 31m respectively. There's no trouble seeing why the plant would be offline until ensuring the plant is tsunami proof.
    Like Ted Rockwell I'm amazed the Japanese left their plants unable to cope with tsunamis of the size that have occurred well within living memory.
    Your website is an absolutely excellent news site by the way.

  3. @lawr: Interesting, and thank you for the compliment! However I'd like to point out one little thing: Around here, we don't quote Wikipedia and in fact we never look at it. It's the world's most dangerous source of total misinformation.

  4. I don't worry about the safety systems at US plants. I worry a little about aging factors.

    We know relatively less about the implications of aging, as far as I have been able to find out.

    Do you know of any studies/resources on aging?

    Great post, btw.

  5. @maxedoutmama: Thank you. Yes, we have plenty of information on aging.. all sorts of things, from reactor pressure vessels to plant systems. That will be coming in the future!

  6. Will, looking forward to it! Thanks, keep up the great work.

  7. Great post, and great addition to the discussion on the continuing lessons learned. But I have several points that I take issue with in one way or another. I have been reading a lot and have found the issue less than clear-cut. Let me address by number:

    4. The U.S. fleet may have added more batteries, but as the NYTimes was pointing out, the majority of our plants have 4-hour batteries as opposed to 8-hour batteries at Japanese plants. It seems toxic for us to claim this as a safety benefit of our fleet.

    5. Do we have any indication that hard pipe vents were not installed at Fukushima Daiichi? I've read many mentions of such vents but when it comes to what THEY had, the best I've got is "we don't know". And do we even have this? The NEI fact sheet shows this:
    Indicating a pump in front of the filters, which is exactly what went wrong at Fukushima - no power to power the pump.

    I agree that the rest of them are very significant. But I am intensely interested in the flood event measures that have been taken which were not mentioned in your post. The 1999 flooding of the Blayais plant in France was apparently very significant and caught the attention of the NRC.

    The flood-worthiness of equipment seems to be one of the most major take-aways I've read about.

  8. @alan: Is the battery life that the NY Times quoted an average over all plants, or is it just for BWR plants? At the BWR plants (as I am sure you know) SBO is far more dangerous with no natural circ capability, and it's these that I imagine the NRC was indicating in that data.

    I don't know the exact vent structure at the Fukushima Daiichi plants, but since the NRC has reiterated these changes/backfits to our plants here as a result of not only the specified unresolved safety issues found post-TMI but also as a result of continued compliance to the SBO rule I'd have to imagine ours are installed as illustrated at the NRC site by rule - and if they aren't there would be a good reason. Now, why Japan isn't right at the cutting edge with these developments either using information from the reactor vendors or the NRC is simply beyond me.

    Good point about the flooding issue! Being an ex-Navy nuclear man I'm quite familiar with spray-tight equipment enclosure and frankly I can't see why anything at a nuclear plant wouldn't be designed with at least spraydown if not long-term immersion in mind, at least a couple feet from ground level. However, if we're going to start saying that "everyone should have known that a 30 foot tsunami can happen" then we need to start putting all the I&C equipment in new enclosures on the turbine building roof.. and the control room with it.

    The content of that post was primarily driven by news features (freakouts?) of the day, and by the NRC's repeated assertions as to why our plants are better protected against SBO than the plants at Fukushima Daiichi. SBO is in the NRC fault tree sort of mentality the triggering event, but many many times I've said here that the triggering event is the tsunami. (Not the earthquake.) While the tsunami of course did lead to long-term SBO it also led to widespread equipment derangement that wasn't on anyone's radar screen, at least in Japan. This type of derangement IS on our screens here, since 9/11, it would seem -- at least judging by the NRC's statements and required actions / backfits.

    Great comments; thanks for writing!

  9. There is absolutely room to argue that an event resembling Fukushima would not happen here. Like every nuclear power plant meltdown, there was a sequence of failures and stopping it at any given stage would have prevented offsite consequences. I think the U.S. has at least one stage covered (meaning that it wouldn't happen), but we would like to know that every single item in the failure chain has been locked down. I've been going through several lessons learned posts and I hope to summarize and write my own post about it.

    Here is the reference for the batteries. I know, batteries at Fukushima lasted longer than 8 hours and this is a terrible simplification in some senses, but that doesn't change the fact that a bill has been considered to mandate having 72 hour batteries. The claim is that 93 of our 104 plants have 4-hour batteries, so this isn't limited to BWRs, but certainly includes BWRs.

    NEI specifically stated that Fukushima may have had hardened vents, per National Geographic. If we discover they HAD them and that they didn't work that would be disastrous of course, although I doubt this is the case and I also don't understand what the spectrum of technology available for this is.

  10. @alan: Of course, since TMI we've all known that almost any CONCEIVABLE accident scenario is actually POSSIBLE... hence, for example, the struggle to try to figure out if any of the fault tree analyses of WASH-1400 actually predicted the events at TMI-2. In other words, the event taught us that reality was a shade more nuanced than even the still-new fault tree analysis could handle. I don't think anyone has let up on that end since that time, whether it be the reactor vendors or the NRC or the operating entities.

    NEI seems to say that it has no idea whether they had these vents at Fukushima Daiichi, and frankly I'm going to have to guess "no" or there would not have been any hydrogen explosions inside the reactor buildings. It says NEI "struggled to get a firm answer," so that seems to say "probably not" in and of itself.