Followup on last Fukushima post

22 Aug 2011 by Jim Fickett.

A scary possibility was raised in comments on my last Fukushima post, that contamination of the groundwater at the Fukushima plant could spread to freshwater aquifers used for cities or farms. In fact the flow of subterranean water at the site is very unlikely to be towards any freshwater aquifer. I would certainly like to know if there is really an additional catastrophe brewing – if so I need to sell some things! – but, so far, every big worry I've investigated in detail has turned out to be overdone.

My recent post on progress at Fukushima generated some animated discussion. Some readers seem to feel that I'm defending the industry and deliberately ignoring the bad news.

First let me speak to motivation. This site is primarily about investing. What I write about Fukushima is all about whether it makes sense to invest in nuclear power, or not. I have no ax to grind either for or against nuclear power, and if I were to see clear evidence that the outcome at Fukushima would be much worse than it appears so far, I would get out of nuclear power-related investments in an instant. One of the worst mistakes an investor can make is to become emotionally attached to a position, failing to take new evidence into account. That is why I regularly follow up on very negative headlines about Fukushima; if things are really going to hell, I want to know about it ASAP.

In the comment thread, the scariest possibility that came up was that Fukushima might be contaminating groundwater in a way that would eventually poison freshwater aquifers used for city water supplies or agriculture. There are many sites on the web describing such eventualities. For example, Classical Values writes,

From my crude measurements it appears that Fukushima is just outside the Tokyo aquifer. Or it might be close enough that it will be a problem if the radioactive sludge reaches the aquifer.

Contamination of freshwater aquifers would indeed be a first order disaster, so I decided to look into it. Classical Value's idea, of contaminating Tokyo's water supply, is far-fetched and easily refuted. Here is a detail from a Unesco map showing the water resource area for Tokyo:

And here is a snippet of a Google map showing the location of the Fukushima Daichi power plants:

(The plants were located based on information at the Tepco website: “The power station is located approximately 250 km (155 miles) north of Tokyo in the towns of Futaba and Ohkuma”.)

Comparing the two maps shows Fukushima is not near Tokyo's water supply.

More generally, worries about groundwater contamination became widespread after Arnold Gundersen, a former nuclear engineer who now teaches and runs a consulting business for anti-nuclear efforts, gave an interview in which he worried out loud about a contaminated aquifer:

“So ten to 15 years from now maybe we can say the reactors have been dismantled, and in the meantime you wind up contaminating the water,” Gundersen said. “We are already seeing Strontium [at] 250 times the allowable limits in the water table at Fukushima. Contaminated water tables are incredibly difficult to clean. So I think we will have a contaminated aquifer in the area of the Fukushima site for a long, long time to come.”

It is worth taking a moment to understand the exact nature of this radioactive strontium measurement. The power plant is constructed right at the edge of the sea, and the lowest basements of the buildings are actually below sea level. Because of this, a system of tanks below the level of the lowest basement was installed, which collects groundwater seepage below the site, and these were, before the accident, regularly emptied to the sea, thus keeping the basements dry. The complex of tanks, interconnecting pipes, and pumps is called the “sub-drain” system. In April radioactive iodine was found in the sub-drains, and in June radioactive strontium was found there. So indeed there is radioactive contamination in water on site. Since the emergency measures to cool the reactors and cooling ponds spilled large amounts of contaminated water, this is not too surprising (which does not make it less bad).

As an aside, a German analysis of the contamination in the sub-drains suggests that all the contamination may have come via one building, which would lessen worries around groundwater more generally.

The big question is where this contamination might go next. Keep in mind that the sub-drains are right next to the sea and well below sea level. That gives a somewhat different mental image than “contaminated water tables” and “contaminated aquifer”.

How likely is it that the contamination would spread inland to fresh water aquifers? Generally speaking, water flows from higher elevations to lower, and from inland to the sea. There are cases (one not far from where I live) where a freshwater aquifer connects with the sea, but these are the exception rather than the rule, and to really get worried about freshwater aquifer contamination, I would need to see some evidence that groundwater at Fukushima was flowing inland rather than seaward. In fact, all the evidence points the other way.

Hiroaki Koide, an assistant professor at Kyoto University, has made known his worries that a melted core may escape from the building entirely, by melting through the various steel and concrete barriers and going into the bedrock below. He is worried about groundwater contamination, but not inland; he is worried about the sea:

“As far as I can tell from the announcements made by Tokyo Electric Power Co. (TEPCO), the nuclear fuel that has melted down inside reactors at the Fukushima nuclear plant has gone through the bottom of the containers, which are like pressure cookers, and is lying on the concrete foundations, sinking into the ground below. We have to install a barrier deep in the soil and build a subterranean dam as soon as possible to prevent groundwater contaminated with radioactive materials from leaking into the ocean.”

I will not address at the moment any worries about seawater contamination. One thing at a time and, at the moment, I'd like to address worries about freshwater aquifer contamination.

In a newsletter of the International Association of Hydrogeologists, Professor Shimada, vice president of the Japanese Association of Groundwater Hydrology, does mention the possibility of contamination at the site, but seems to be more worried, at a practical level, about salt brought inland by the tsunami and rendering freshwater aquifers brackish. I checked later editions of the newsletter, after the strontium readings, and there is no further comment.

The German analysis mentioned earlier, entitled “Radiological Consequences of the Fukushima Event via Water Pathways”, concludes that seaweed and fish contamination should be monitored, but does not mention freshwater aquifers.

One Physics Forum thread translates an article in the German newspaper Die Welt showing that there are hundreds of meters of impermeable rock under the Fukushima site, and no aquifer.

Another Physics Forum post, from a geologist, supports the idea that any subsurface water flow is likely towards the sea. And in a third the poster says he has consulted with a Japanese professor of geology, who was unable to find any information on the local hydrology, but also supported the idea that water would very likely be flowing towards the sea.

All told, I could find no evidence that contaminated groundwater at the site would be likely to damage freshwater sources, and considerable indirect evidence that that outcome is unlikely.

I have investigated in some detail perhaps 20 claims of an impending major disaster at Fukushima, and in every case the outcome has been the same – the evidence crumbles on inspection. That does not mean everything is going to be hunky dory, or even that major disasters will be averted. It is worrying that cooling is not yet under control and there is still a great deal of nuclear material in the cooling ponds, open to the sky. And good information is very hard to come by. Tepco and the Japanese government have clearly downplayed the situation and, at the same time, very worried people have repeated scary stories without really checking the facts. So far, though, I have yet to see any serious indication that the situation will get any worse than it currently appears to be.