On March 11th, 2011, the Fukushima Daiichi nuclear power plant complex suffered damage from an earthquake and ensuing tsunami that caused multiple nuclear reactor core meltdowns and melt-throughs, explosions, and major releases of radioactive material into the air and the sea. In addition to the reactor meltdowns and melt-throughs spent fuel storage tanks were also damaged and probably contributed to the release. It took about a year for the plant to reach a condition that was stable enough that we stopped checking it every day to see if new bad things were happening. Heroic efforts were implemented by the utility and the workers, but in the end, very little that was done aside from the initial flooding of the reactors with sea water really had much effect. Basically, the plant just cooled down and stopped being as dangerous because the nuclear material in the plant escaped into the environment or just settled down to a less reactive level over time.
A handful of news items have come up recently mainly pertaining to contamination and other issues, so we thought an update was in order.
There have been a number of points where it looked like conflicts of interest between the regulators and the regulatees (as it were), or at least the appearance thereof, were in effect since the time of this disaster. It is happening again.
A commission was formed late last month, including six experts, to set up new safety standards for nuclear reactors in Japan. Four of the six members of the commission have received various amounts of money from Japan’s Nuclear Regulation Authority (NRA). This is not necessarily a bad thing, or unexpected, as experts get hired and one needs experts on a commission like this. Also, these individuals were required to report these associations and payments. Nonetheless, the time has passed when people (the victims in nuclear disasters) can easily be told “Don’t worry, we’re acting in your best interest” by any nuclear regulatory agency or by any utility operating nuclear plants, or, for that matter, “experts” in the field in general who have in the recent past demonstrated an almost cult-like adherence to untenable pseudoscience regarding nuclear safety.
The journal Nature has the story.
Much of the uproar over the handling of the Fukushima disaster came from the public perception that conflicts of interests led regulators … to favour cost-savings over safety. … It seems that Japanese policy-makers, despite the many public demonstrations, still haven’t got to grips with the tendency for conflicts of interest to lead to bad decisions and, even if they don’t, to breed mistrust.
Similarly troubling is the rush with which the government reopened two of the country’s shuttered nuclear reactors in July without fully evaluating the seismology of the ground beneath. Last week, at its second meeting, a subcommittee of the NRA could not confirm whether a fault line running under a seawater-intake channel — used to cool the reactors in an emergency — is active.
At stake is whether the fault is a landslide fault or a more dangerous, deeper tectonic one. …
Large sectors of the public opposed the reactor restarts with demonstrations of a fervour not seen in Japan in decades. The country had already proved that it could get by, at least in the short term, with no nuclear power. Some scientists had pointed out the uncertainty over the seismic fault, and suggested how to deal with it, before the reactors were restarted. Japan was supposed to emerge from the Fukushima crisis with a new respect for reactor safety and better awareness of the need to convince people of that safety. It hasn’t made a very good start.
US Nuclear Regulatory Commission to recommend new rules for Mark I and Mark II reactors
The Fukushima plant used Mark I and Mark II reactors, an early General Electric product, which are also used in several other plants around the world including at the two nuclear plants in Minnesota. These systems have a core that includes the nuclear fuel, surrounded by a primary containment vessel, which in turn is enclosed in a building which serves as secondary containment. During certain kinds of nuclear accidents, gasses can escape the primary containment, possibly through cracks or pipes being blown off from pressure build up, and fill the secondary containment area. These gasses would consist of water vapor, hydrogen in concentrations sufficient to explode, and radionucleotides. Under these conditions, the secondary containment can explode, spreading nasty nuclear stuff around the landscape in an uncontrolled way.
One way to reduce the likelihood of this happening is to install vents to relieve the pressure. This allows a plant operator to open the vent and avoid a catastrophic explosion. The down side of this, of course, is that radionuceotides are released into the atmosphere.
One way to reduce mitigate against this effect is to filter the vents. This is technologically difficult and expensive, costing in excess of abut $16 million dollars per plant. The filter designs are diverse and interesting but beyond the scope of this post.
Most Mark I reactors have had vents installed, and some Mark II have as well, but most of these vents are not filtered.
The Nuclear Regulatory Commission is poised to recommend that filtered vents be installed on all US based plants. Here’s what is interesting about this: Using their own method of determining cost benefit ratios, adding a $16 million dollar plus filtered vent to each plant is way more expensive than the estimated cost of cleaning up after a release from an unfiltered event, given their estimates of the likelihood of such an event happening. But the are recommending the change anyway, stating that this fits with the policy of “deep protection” against disaster. It is an overt and clear response to Fukushima. In the post Fukushima world, at least parts of the nuclear power industry are willing to spend mucho extra dollars on safety, even beyond what the usual cost-benefit risk assessments tell them to do.
This story is addressed HERE by the New York Times.
Radionucleotides are Accumulating in Lake Kasumigaura in Ibaraki Prefecture
Kasumigaura is a system of lakes forming an artificially closed basin (with presumed underground communication with the sea?) near the Fukushima plant. The catch basin for this lake was blanketed in nuclear fallout from the disaster, and it can be assumed that this material has to some extent eroded into the lake. This material is moving into the lake very slowly and will continue to do so for a long time, possibly decades.
Most of the material in question is cesium–134 and cesium–137. Cesium is very sticky, so it adheres to surfaces very well. This probably means that much of the cesium moved into the lake while stuck to various size sediments. Kilo for kilo, then, a given mass of gravel would contain a certain amount of cesium, sand much much more owing to the extra surface area, silt even more, and clay even more, all else being equal.
Scientist have been sampling the lake bottom mud as well as the water. From an article in the Japan Times
According to the latest round of monitoring, which was the fourth of its kind, and carried out in September and October, no traceable amount of cesium was detected in the water itself. The mud samples from the lake and the rivers, meanwhile, were found to contain up to 5,200 becquerels/kg of cesium–134 and cesium–137, compared with a maximum of 500 Bq/kg detected a year ago, a maximum of 5,800 Bq/kg in February this year and a maximum of 4,800 Bq/kg in July. The sludge sampled from the bottom of the lake registered cesium contamination ranging from 97 Bq/kg to 520 Bq/kg. That is lower than the maximum 1,300 Bq/kg registered in February, but higher than the 340 Bq/kg detected in the first round of monitoring a year ago. The government safety limit for cesium-tainted food is 10 Bq/kg for water and 100 Bq/kg for most other foods. The mud samples from Kasumigaura have surpassed these figures, but mud is usually not ingested as food. Government regulations state that soil containing more than 8,000 Bq/kg of cesium is considered to emit levels of radiation that pose a danger to human health and therefore must be sealed away.
So, the amount of contamination of the lake bottom seems to be both rising over the long term and variable, possibly leveling off. The problem is, given the nature of sediment flow into the lake, these numbers should be continuing to rise steadily. For this reason, there is some confusion and concern as to how to interpret these results.
Several species of fish that live on the bottom of the lake have been sown to regularly exceed the safe limits of contamination and their sale has been banned. The water is known to contain cesium but at levels designated as safe.
The density an intensity of sampling in this catchment has probably been insufficient, and is being criticized. Sampling has shown that some of the rivers and streams have a decreasing level of contamination while others are “hot spots” with very high levels. It has been proposed that one way to deal with the contamination is to use the Fukushima Method: Dump the water into the sea, in this case by opening the dam that separates the freshwater of the lake from the salt water of the sea. Ironically, the demand for water from this lake has dropped because the economy of the immediate area was ruined by the nuclear disaster, so this would have reduced effects.
Highly Radioactive Fish Have Been Found
Related to this, some interesting things have been discovered among the local fish. As noted, bottom feeders have been shown to be contaminated beyond usability. A different kind of fish, the Ayu, or Sweetfish (Plecoglossus altivelis) has a very rapid turnover and short lifepan, and is not a bottom feeder. This is a key element in the Japanese diet, and is the fish eaten by the famous Japanese Cormorants. These fish don’t live long enough, or feed enough on the bottom, to accumulate very much contamination and have been shown to be generally safe to eat. They form a special sort of sampling procedure whereby spontaneous levels of contamination in the water can be assessed. That they are not particularly “hot” is a good thing.
But other fish turn out to be highly contaminated. From Asia and Japan Watch:
…in August, two greenlings caught 20 kilometers north of the Fukushima plant were found to have cesium levels of 25,800 becquerels per kilogram, the highest level ever measured in fish since the nuclear accident. The government standard for food is 100 becquerels per kilogram.
And in March, tests recorded a level of 18,700 becquerels per kilogram in freshwater salmon in the Niidagawa river near Iitate, a village northwest of the nuclear plant.
Furthermore, the concentration of cesium in freshwater salmon and char caught since March has not been decreasing, leading to restrictions on the shipment of such fish from Fukushima Prefecture and surrounding areas.
Greenlings are “lingcod” and live in the sea, and tend to feed on the bottom and I believe they are relatively long lived. Freshwater salmon and char live in the freshwater streams feeding into the Lake Kasumigaura system, and eat a variety of foods and are much longer lived, depending on when caught, than the sweetfish.
The extremely high levels of contamination in these fish in waters that should be decreasing in contamination levels seems enigmatic, and a study is being launched to look further into this.
I have a hypothesis that explains many of these observations. Fish like trout, salmon, and char eat, among other things, insects on the surface, gorging on hatches. A hatch is a large number of insects flying around and spending time over water, or often, just falling into the water, after emerging from a body of water where they spent an aquatic phase. I’ve written before about the role that insects such as dragonflies and lake flies serve the role of moving nutrients from their “final” resting place at the bottom of ponds and lakes, out across the landscape. These animals start off as an egg, and then turn into their adult form underwater, accumulating nutrients …. and cesium? …. as they grow. Then they fly out of the water and die everywhere. Or, are eaten by selected species of fish. From clay-rich lake bottom, where radioactive cesium can accumulate in sufficient density to disqualify bottom feeders from human consumption, to the mouths of trout, salmon and char. I don’t know if the Japanese researchers are thinking about it this way, but I hope it is given some thought.
Previous updates on this disaster are archived HERE.
Thank you for this, I was wondering about the recent development of the Fukushima situation.
If memory serves, cesium is readily incorporated into bones where it will remain. A higher concentration in long-living fish would not seem surprising to me due to the potential for bio-accumulation.
Do you remember seeing any information about radiation levels in other foodstuffs? After Chernobyl I remember especially (wild)mushrooms and game as items of concern for accumulation of isotopes.
Prak: You are probably confusing cesium with strontium, which famously is a bone-seeker, being in the same chemical group as calcium (II, alkaline earth metals). Fortunately there was essentially no strontium released from Fukushima.
Greg: radionucleotide -> radionuclide.
Cesium substitutes for calcium in biologically active systems and bone, which is why it is a killer. It doesn't substitute well. As thether or not it can build up (bioaccumulate), there is debate. People generally think it is not good at that but the all this evidence came along and it seems to have been. So there is an argument that it does.
Thing is, something lie strontium is more abundant and easier to experiment with in a lab setting. I don't think sufficient research has been one with cesium.