nuclear-news

Fukushima and ‘The Devil’s Scenario’ – the bullet that Japan dodged

60,000 tons of dangerous radioactive waste sits on Great Lakes shores   Keith Matheny, Detroit Free Press Oct. 19, 2018  “……… Fukushima and ‘The Devil’s Scenario’

On March 11, 2011, following a magnitude-9.0 earthquake and an ensuing, 50-foot tsunami, the Fukushima Daiichi nuclear power plant in Japan lost cooling capabilities for four of its six reactors. The cores became damaged and radiation was released into the atmosphere, making it the world’s second-worst nuclear power industry accident after Chernobyl.

But it’s what happened — or almost happened — at the plant’s Unit 4 spent-fuel pool that gives nuclear watchdogs nightmares.

A hydrogen explosion four days into the disaster left the building housing the Unit 4 spent-fuel pool in ruins. The pool was seven stories up in a crumbling, inaccessible building.

It “was so radioactive, you couldn’t put people up there,” von Hippel said. “For about a month after Fukushima, people didn’t know how much water was in the pool. They were shooting water up there haphazardly with a hose, trying to drop it by helicopter.”

Two weeks after the earthquake and tsunami, the Japanese Atomic Energy Commission secretly conducted a worst-case scenario study of the ongoing disaster. The biggest fear that emerged: that a self-sustaining fire would start in the Unit 4 spent fuel pool, spreading to the nearby, damaged reactors. That, they found, would release radiation requiring evacuations as far away as 150 miles, to the outskirts of Tokyo and its more than 13.4 million residents.

“That was the devil’s scenario that was on my mind,” Chief Cabinet Secretary Yukio Edano said during a special commission’s 2014 investigation of the accident.

“Common sense dictated that, if that came to pass, then it was the end of Tokyo.”

The worst-case-scenario report was not released for nearly a year. “The content was so shocking that we decided to treat it as if it didn’t exist,” the Japan Times quoted a senior Japanese government official as saying in January 2012.

What kept the spent fuel rods covered with water in Unit 4 was a miraculous twist of fate: The explosion had jarred open a gate that typically separated the Unit 4 spent fuel pool from an adjacent reactor pool.

“Leakage through the gate seals was essential for keeping the fuel in the Unit 4 pool covered with water,” a 2016 report on the Fukushima accident by the U.S. National Academies of Sciences, Engineering and Medicine concluded.

“Had there been no water in the reactor well, there could well have been severe damage to the stored fuel and substantial releases of radioactive material to the environment.”

It’s a startling “very near-miss,” said Gordon Thompson, executive director of the Institute for Resource and Security Studies in Cambridge, Massachusetts.

“Given wind directions that are common in Japan, they could have been looking at removing the population of Tokyo for decades, or centuries,” he said. “You’re talking tens of millions of people that would have to relocate. That’s the bullet that Japan dodged.”……..https://www.freep.com/story/news/local/michigan/2018/10/19/nuclear-waste-great-lakes/1417767002/

October 20, 2018 - Posted by Christina Macpherson | incidents, Japan