21 Responses to Japan’s effort to cool nuke fuel has itself led to massive releases of radioactivity
Tokyo Electric to scrap Reactors 1 to 4, probably 5 and 6, too
… a deluge of contaminated water, plutonium traces in the soil and an increasingly hazardous environment for workers at the plant have forced government officials to confront the reality that the emergency measures they have taken to keep nuclear fuel cool are producing increasingly dangerous side effects. And the prospect of restoring automatic cooling systems anytime soon is fading.
Hiroto Sakashita, a professor in nuclear reactor thermal hydraulics at Hokkaido University, said of the fuel rods, “Handling this situation is getting increasingly difficult.”
The NY Times explains how the very efforts to stop a full meltdown have themselves had serious consequences:
The setbacks have raised questions about how long, and at what cost, Japan can keep up what experts call its “feed and bleed” strategy of cooling the reactor’ fuel rods with emergency infusions of water from the ocean and now from freshwater sources.
That cooling strategy, while essential to prevent full meltdowns, has released harmful amounts of radioactive steam into the atmosphere and set off leaks of highly contaminated water, making it perilous for some of the hundreds of workers at the plant to further critical repair work.
Moreover, the discovery of radioactive elements that experts say could come only from the core of a reactor suggest that the government’s strategy may not be working and that partial fuel melting has not been completely halted.
Some of the well-meaning, but ineffective strategies, may have backfired entirely.
Compounding the matter, the government said Tuesday that the recent discovery of plutonium in the soil at the plant provided new evidence that at least one reactor was experiencing melting of its nuclear fuel, as happened in the early days of the crisis.
While the source of the plutonium found at the plant was unclear, all three kinds of nuclear fuel at the complex could leak plutonium.
Fresh signs of radiation leaks have raised questions about the sustainability of the government’s feed-and-bleed approach.
One major problem, said Murray E. Jennex, an associate professor at San Diego State University with 20 years of experience in examining nuclear containment structures, was that all the water the Japanese were spraying had soaked important machinery like generators and pumps, further hampering efforts to restore the reactors’ electricity supply. The use of helicopters in the first week to drop water on the rectors from above was especially ineffective in hitting the target and may have done more harm than good, he said.
“They dumped water all over the place,” he said. “They keep on generating more contamination. That’s the consequence of doing it. They got water on things that shouldn’t be wet.”
Hiroto Sakashita, an associate professor in nuclear reactor thermal hydraulics at Hokkaido University, said that though the fuel rods in the nuclear reactors had already lost over 99 percent of their heat, they were still giving off enough heat to evaporate an estimated 200 tons of water a day.
And the remaining heat, from isotopes with long half-lives, will take years to cool. “They will just have to keep on pouring and pouring,” Mr. Sakashita said, “but contaminated water will keep leaking out.”
Separately, the NYT reports today, “High Radiation Levels Found in Seawater Near Japanese Nuclear Plant”:
Seawater near the crippled Fukushima Daiichi nuclear power plant shows significantly higher levels of radioactive iodine than in recent days, Japan‘s nuclear safety agency reported Wednesday, and the operator of the plant publicly acknowledged for the first time that at least four of the six reactors at the multibillion-dollar complex would have to be scrapped….
Estimates of the costs of decommissioning a single reactor under normal circumstances run upward of $500 million, and the company faces the likelihood of enormous liability claims from a disaster that has forced the evacuation of tens of thousands of people.
“We have no choice but to scrap” the Nos. 1, 2, 3 and 4 units at the Fukushima Daiichi Nuclear Power Station, Tsunehisa Katsumata, chairman of Tokyo Electric, said at a news conference.
He said the Nos. 5 and 6 units were still operational, but said any restart of those would depend on consultation with the government and local residents.
Yukio Edano, the chief government spokesman, appeared skeptical of reviving the Nos. 5 and 6 units, saying at the news conference that “the decision is pretty obvious.”
That’s Japanese for, “duh.”