The Long-Term Impact of Fukushima

The journal Nature is publishing several articles today looking at the long term impact of the nuclear disaster at Fukushima in Japan. They’re all available to the public.

One news report considers what it will take to fully decommission the damaged plant, a process that could take more than a decade,

After the tsunami on 11 March knocked out backup generators — preventing cooling water from circulating around the hot cores of reactors 1-3 — the fuel rods inside began to warp, split and at least partially melt. Steam reacted with the rods’ outer sheath of zirconium, creating hydrogen gas that caused a sequence of massive explosions (see Nature 471, 417-418; 2011).

But data from Japanese regulators and TEPCO suggest to some researchers that conditions inside the core could be far worse than a partial meltdown. Some believe that molten fuel may have flowed into the outer concrete containment vessel, whereas others suggest that nuclear chain reactions are still happening inside the fuel.

One looks at the impact of long-lived cesium-137,

Three weeks after the Fukushima accident, a clearer picture is beginning to emerge of possible long-term environmental consequences. The US Department of Energy (DOE) aerial survey of radiation doses was a crucial development. A clear trace reaching out 30-40 kilometres northwest of the plant marked a zone of dose rate above 125 microsieverts per hour, a level at which immediate evacuation is often advised. Already, external doses are rapidly declining as a result of the decay of short-lived isotopes. But, as with the 1986 Chernobyl accident, it is caesium-137, with a half-life of 30.2 years, that will determine the long-term impact on the contaminated region and its residents.

In another, an expert on radiation bemoans how little is known about the dangers of the sort of low-doses of radiation people in much of Japan are receiving,

The continuing and disturbing releases of radioactivity from the damaged nuclear reactors at the Fukushima Daiichi plant in Japan raise questions in everyone’s minds. What are the risks for the nuclear plant workers? For the local population? For the rest of Japan? Worldwide?

Although the scientific community is doing what it can to estimate these risks, the reality is that we really don’t know. More specifically, the uncertainties associated with our best estimates of the health effects of low-doses of radiation are large¹. And not knowing the risks means that we really don’t know what is a reasonable evacuation zone, whom to evacuate, when to evacuate or when to allow people back.

Finally, one report details some of the changes in nuclear design since Fukushima was built in the 1970s, changes that address key vulnerabilities that led to the disaster there,

The Fukushima blueprint is decades old, and reactor design has evolved significantly in the interim. So much so, that many of the battles faced by the Fukushima team could never have arisen in a new plant.