Tuesday, March 15, 2011

Chernobyl as a Worst Case for Japan


I am absolutely not an expert on nuclear disasters, so take this for what it's worth.

It appears to me that the situation at the Fukushima-Daiichi nuclear plant is slipping out of control.  After multiple explosions and fires, radiation levels are getting high enough that it's becoming increasingly unsafe to work in the area:
The radiation levels at Fukushima Daiichi are now too high for staff from the Tokyo Electric Power Company, which operates the nuclear power plant, to stay in control rooms there
Meanwhile, radiation levels on site have been up to 400miSv/hr in the worst spots.  Here's a helpful scale from the BBC:


In consequence, the Tokyo electric company has withdrawn all but 50 workers from the site.  However, there are at least three reactors that were operating, as well as at least six pools containing spent fuel that need to be maintained.  All have the potential to boil off their cooling water and melt down or explode if not maintained.

That motivates me to wonder about the worst case here: suppose the company cannot contain the situation and it devolves into a Chernobyl-style release of radioactivity.  I found this map of the closed and contaminated areas at Chernobyl at the Wikipedia:


The pink/purple areas are the worst hit.

Then I superimposed this map on a map of Japan, with the scales matched, and the Chernobyl point matched to Fukushima.  That looks like this:



Obviously, this is an extremely rough exercise: not only do we not know the scale of the Japanese disaster yet, but prevailing winds will be different, and carry the contamination in an unknown direction. Still, I think this map makes it clear that a Chernobyl scale disaster could cause huge problems for a sizeable fraction of northern Japan.

I note also that there's one way in which Chernobyl might not be a worst case.  The Soviet authorities were willing and able to sacrifice hundreds of emergency workers who got acute radiation sickness while putting out the fires and building the emergency sarcophagus over the site of Chernobyl reactor 4.  Is a democratic country like Japan going to do the same?  And if not, then what?

I sincerely hope the Japanese authorities are able to bring this situation under control in the next few days.  If not, it may be many decades before anyone builds any more nuclear power plants.

24 comments:

rjs said...

i cant cite it, but in one of the articles ive read it was noted that a chernobyl style accident was impossible with the japanese reactors, being of a different design...chernobyl was a graphite reactor...

Stuart Staniford said...

rjs:

There's no question that the reactor designs are different. But it seems to me that with the #2 reactor container breached and a fire in at least one of the stored fuel ponds, the situation is now well outside of the designed-for envelope, and an uncontained melt-down cannot be ruled out.

ric davis said...

Without the scope for a graphite fire, and with the reactors at much lower energy levels than Chernobyl, I don't think there's the scope for a plume of radionucleides getting high enough in the atmosphere to reach the level of dispersal that Chernobyl achieved.

yt said...

Yes and what is amazing is the number of guys the USSR managed to put at work on the site, in between 600 000 to 800 000 !!!

yt said...

A question I have regarding this accident is that, considering that it is much more the tsunami than the quake that has caused problems, could these plant have been built higher/more in land ? (even if losing some efficiency related to water pumping)

Lucas said...

I think that the plant being next to the ocean was generally seen as a safety measure-they'll never run out of water(Indeed, this did turn out to be an option that has been keeping the core from a meltdown)
As for Rjs's comment, the only significance of the graphite was in the immediate vicinity of chernobyl, meaning the plant(and it helped to cause the meltdown, but thats irrelevant if were talking about an already melted down plant.
The real radioactive 'stuff' that got spread around after chernobyl was the reactor byproducts that were vaporized or shot into the air by the explosion. These bypruducts, such as iodine, caesium, and strontium are what caused the majority of the contamination, and all Nuclear fission reactions in nuclear power plants have resulted in these byproducts

Lars-Eric Bjerke said...

Countries like France, Sweden and Finland back fitted severe accident mitigation systems during the 80-ties on all nuclear plats in order to handle loss off all power and all core cooling systems leading to core melt. Swedish plants for example have reactor containment pressure relief via a water scrubber, redundant containment spray and a large number of passive hydrogen recombiners inside the reactor containment. As far as I know Japan and the US have not installed such systems in the old plants.

Mercury4 said...

It's silly comparing Chernobyl with the disaster unfolding in northern Honshu. In Japan we have a whole complex of reactors at or near failure, since neither cores nor spent fuel rod pools can be adequately cooled.

Also, the potential for radiation fallout is of an order of magnitude far greater, somewhere between 2 and 5 times higher.

Finally, the area just to south (the Kanto Plain) is where the majority of of all Japanese live. It would as if 100-120 million Russians and Ukrainians being at risk.

Hal said...

Good job, Stuart. I've been picturing Japan as a lot smaller in relation to the contaminated area from Chernobyl. Thanks for the reality check. Still not good, of course.

John said...

Lars, thanks for the info. I'm trying to find out if UK nuclear plants have this level of safety?

John

Fixed Carbon said...

Can we get more info on Lars-Eric's claim about Sweden and other Nordic countries increasing safety. Been reading lots and watching CNN (Spizer and Cooper are pretty good). No mention of this increased saftey.
Thanks Lars-Eric!

Fixed Carbon said...

Another thought. I am a faculty member at the Bodega Marine Lab of the University of California. The property came to UC in the 1960's as a result of Pacific Gas and Electric attempting to put a nuclear power plant on Bodega Head, which is right on top of the San Andreas Fault. The "Hole in the Head" is still there. It is the excavation for the plant, which was moved to Diablo Canyon to the south after a huge public protest. So think about the degree of care that went into siting and planning of the plants in the US...Gawd

Robert said...

Chernobyl - 25 years later. (one opinion)

http://ageconsearch.umn.edu/bitstream/100713/2/Simmons%20P.pdf

porsena said...

I've been wondering about this topic. Reinforcing the first comment be rjs about the design difference between Chernobyl and the reactors at Fukushima. The UK's chief scientific advisor, John Beddington, is quoted in the 1:16 PM comment in The Guardian's blog as saying that it's wholly wrong to compare the two situations. More info here.

kjmclark said...

Looks like we'll find out. It's around 11pm eastern, and BBC and AP are reporting that the remaining 50 workers are being evacuated due to a large radiation spike.

Mercury4 said...

Ok, here's a reality check for you;

Tuesday's explosion at the Dai-ichi plant likely caused damage similar to what was seen at Chernobyl;
The explosion (at No:2 reactor) probably damaged the main protective shield around the uranium-filled core inside one of the plant's six reactors. Such a breach would be the first at a nuclear power plant since the Chernobyl catastrophe 25 years ago in what was then the Soviet Union.

JCamasto said...

442 nuclear power plants operating worldwide. 3 significant failures to date. Those are some ugly odds...

If we're going to keep playing this game, it's time for a radical increase in engineered factors-of-safety, given the calamitous scale of errors/unaccounted for scenarios.

JCamasto said...

Or, better said: Design for failure.

Stuart Staniford said...

There's a piece here in the NYT looking at Chernobyl as a worst case, and also comparing to 3 mile island:

“We’re in uncharted territory here,” said Robert Alvarez, a nuclear expert and adviser to the secretary of energy during the Clinton administration. “But in very general terms, the worst-case scenario would be a catastrophic release of radiation that will not necessarily happen all at once.”

That would make the event similar to, and perhaps worse than, the Chernobyl accident in 1986, in which large amounts of radioactivity were released and hundreds of square miles of land in Ukraine were left uninhabitable. But without such a catastrophic release, the events would likely be closer in scale to the partial meltdown in 1979 at Three Mile Island in Pennsylvania, where the plant’s containment structure held and a relatively small amount of radioactivity was released.

So far, the problems at the Fukushima Daiichi plant in Japan are more severe than at Three Mile Island but less so than in Chernobyl.


The thing I keep thinking about (after reading about the new explosions and fires overnight) is - what is it going to take to bring the situation under control? No-one can now work there safely and legally. So either the Japanese adopt something like the Soviet system (where they conscript a massive labor force and rotate them through, as well as de-facto suspending the rules about radiation exposure), or the thing is just going to sit there with no-one going near it, spewing radioactive fumes for miles around, for months on end, until it settles down by itself.

I guess a key question would be whether there's much flammable in the structure of those buildings (like the graphite at Chernobyl)? So far, it seems hydrogen from denatured cooling water is capable of quite a bit of fire. However, if the site becomes totally unapproachable, presumably they will stop cooling it. Then how big a fire will there be?

Stuart Staniford said...

There's some very helpful discussion of the issues with the spent fuel ponds at the UCS All Things Nuclear blog.

Stuart Staniford said...

Also, just to confirm what kjmclark said above, this story confirms that all workers have been withdrawn from the plant. So, as far as I'm able to determine at present, nothing is now being down to contain the situation (which seems to make it likely that it will get worse before it gets better).

It seems to me this is now a key test of the leadership of the Japanese prime minister. This has spiralled way beyond the ability of a single company to control, given the need to suspend laws. And it's a threat to the welfare of the entire country to have this thing sitting there uncontrolled, spewing unknowable amounts of radioactivity in random directions, depending on the shifts in the wind.

Stuart Staniford said...

Well, now comes word that the number of workers at the plant has been doubled to 100. So reports are confusing and contradictory, I guess...

I can't imagine doing that job. They have to know their lives are at serious risk, and are doing it anyway because it's clearly the right thing to do. Heroic, for sure.

Lars-Eric Bjerke said...

John and Fixed Carbon,

Regarding severe accident mitigation in the UK none of the plants including Sizewell B have a filtered containment vent system, however severe accidents were considered in the Sizewell B design and some design features were implemented. A short summary of measures taken in the European plants is summarized in

http://www.ansn.org/Documents/Pakistan/Workshop%20on%20EOPs%20SAMGs%20Feb%202004/Vayssier/Acceptance%20Criteria%20for%20Severe%20Accidents.ppt

Stuart Staniford said...

Looks like China has also suspended approvals on new plants pending further study of safety issues:

http://www.nytimes.com/2011/03/17/world/asia/17china.html?hp