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.

NPR reports that iRobot is sending some of the robots it has developed for bomb disposal to the earthquake-damaged Fukushima nuclear power plant in Japan. The robots may be able to get inside the plant with cameras and radiation detectors to give workers a better idea of what's going on inside—high radiation levels and other dangers have forced people to keep a distance.

According to the story, this might be just the start of the use of robotics in the aftermath of the disaster at the plant.

Carnegie Mellon University robotics researcher Red Whittaker has assisted with robotic operations at nuclear accidents like Chernobyl. He says after that 1986 accident, at a nuclear power plant in Ukraine, radiation levels were too high for workers to conduct cleanup operations, so remote-controlled robots had to take over . . .

"I would anticipate that we are going to see a phenomenal enterprise of remote work systems that are brought to bear over the weeks, months and years of recovering Fukushima," he says.

Radiation levels and other hazards have complicated efforts to get the situation under control, or even allow workers to know what's going with the levels of water in spent fuel pools. So this seems like a perfect situation to have robots involved. Which raises a number of questions. Why weren't robots on the site faster? What can robots realistically do, and what can't they do? Should regulators establish quick response robot teams that can be dispatched overnight in the case of a disaster like this one?

I'll look into these questions—but if any of our readers have knowledge in this area, it would be great to hear from you.

The U.S. agency that last week raised alarm over the condition of spent fuel ponds at the earthquake- and tsunami-damaged Fukushima nuclear power plant in Japan said in a meeting this morning that the situation at the plant has nearly been stabilized. The Nuclear Regulatory Commission (NRC) also suggested no changes to guard against such damage to spent fuel pools at power plants in the U.S.

Last week, the head of the NRC said that damage to pools for storing and cooling spent nuclear fuel at the Japanese facility had allowed water to drain, exposing the fuel. That condition would eventually cause the fuel to overheat, generating explosive hydrogen, and releasing large amounts of radiation into the air. Workers at the plant in Japan have struggled to get water to these pools; high radiation levels have kept them from approaching the plant; and a lack of power and damage to the plant's cooling systems prevented them from using the plant's built-in safety systems. They've resorted to dropping water from helicopters that have been equipped with lead plates to shield against radiation, and spraying the pools from a distance with high-power water cannons.

This morning, William Borchardt, executive director of operations at the NRC, blamed radiation releases at the Japanese plant on the spent fuel pools, not the reactors themselves. But he said that the agency believes the the situation at the pools "has stabilized," after a "concerted effort" to get water into them. "The fact that offsite power is close to being available for use by plant equipment is perhaps the first optimistic sign that things could be turning around," he said. With power restored, cooling systems at the plant could be used, but it's not clear yet whether those cooling systems were damaged by the earthquake and tsunami.

Spent fuel cooling pools at power plants in the U.S. contain too much spent nuclear fuel, according to some researchers, who say that if water were to be lost from these pools, the results could be worse than Chernobyl, the worst nuclear reactor accident in history. They say that the amount of dangerous material in the pools is greater than what was contained in the damaged reactor at Chernobyl, and so more radioactive material could be released. A paper published in 2003 outlined the potential problem, pointing in particular to the danger posed by terrorist attacks. The researchers suggested that to reduce the risk, rules be changed to require power plant operators to more quickly move fuel out of the pools and into dry cask storage, which relies on air cooling rather than water. "We suggested a relatively inexpensive solution," says Allison Macfarlane, a professor of environmental science at George Mason University, and one of the authors of the paper. It would cost billions of dollars, she says, but that's cheaper than losing multi-billion nuclear reactors, as is happening in Japan. After a review, the NRC decided not to implement the proposed changes. "It is still a problem in the U.S.," Macfarlane says.

The NRC has not responded to requests for comment. But at this morning's meeting the agency briefly raised the issue of the ponds in the U.S. "It's a very simple problem. All you have to do is keep water in the pool," Borchardt said. After the 9-11 terrorist attack, the agency required that power plants have backup plans, such as extra generators, to respond to problems like those seen in Japan. He said that the NRC task force that is trying to draw lessons from Japan needs to look at whether the backup plans, "really would work under that scenario."

William Ostendorff, one of the NRC's commissioners, raised the question of the spent fuel pools at the meeting. Compared to the discussions on emergency core cooling systems, he said, "we don't spend a lot of time as a commission talking about that."