Second Explosion Damages Japanese Nuclear Plant; Third Blast Could Follow

On the fourth day after Japan's massive earthquake, the nuclear emergency continues to worsen

3 min read
Second Explosion Damages Japanese Nuclear Plant; Third Blast Could Follow

Editor's Note: This is part of our ongoing news coverage of Japan's earthquake and nuclear emergency. John Boyd is an IEEE Spectrum contributor reporting from Kawasaki, Japan.

On day four of Japan's nuclear emergency, a second explosion has struck the Fukushima Dai-1 nuclear power plant, and officials warn that a third explosion is possible.

Japanese television screens around the country showed a huge plume of gray smoke billowing up. Today at around 11 a.m. local time a hydrogen explosion rocked the Fukushima Dai-1 nuclear plant. The detonation occurred in the structure housing the unstable No. 3 reactor; this came two days after a similar explosion occurred at the plant's No. 1 reactor structure. Judging by the size of the new smoke plume and visible damage to the structure's framework, today's explosion was of much greater strength.

According to Masashi Goto, a former design engineer of nuclear containment vessels with Toshiba Corporation, the increased intensity of the explosion was likely due "in part to the larger size of the reactor." The No. 3 reactor has a capacity of 784 megawatts, compared to the 460 megawatts for the No. 1 reactor—that means the No. 3 reactor probably produced a larger cloud of hydrogen gas, which interacted with steam escaping from the reactor to cause the explosion.

The government had warned that this explosion was possible. Pressure had been building in the reactor since its cooling system failed and a hydrogen cloud began forming in the space between the reactor and the inner walls of the outer structure. The plant is located in the area hit by the massive 9.0 earthquake and devastating tsunami on Friday. Three of the plant's reactors were in operation at the time, with three more closed for maintenance. All three active reactors automatically shut down when the cooling systems developed problems, but the shut-down didn't contain the ongoing disaster.

Japan's Chief Cabinet Secretary Yukio Edano told reporters that the new blast had not damaged the containment vessel protecting the reactor itself (officials have also said that the explosion around the No. 1 reactor didn't damage that reactor's containment shell). Edano said that radiation monitoring after the blast had not shown a significant increase in radiation.

Tokyo Electric Power Company (TEPCO), which operates the plant, had been pumping seawater into the No. 3 reactor to cool it down, but the operation ran into unspecified trouble, apparently resulting in the explosion. Nuclear expert Goto explains that using seawater "was a stopgap fix, and not as efficient as the original cooling system because it takes longer to cool the fuel rods."

Now the government is warning that a similarly dangerous situation is building in the No. 2 reactor.

TEPCO announced today that cooling efforts in its No. 2 reactor had failed and pressure was building, so operators were making preparations to pump seawater into the reactor. Japan's national television broadcaster and Kyodo News Service later reported that the water level in the No. 2 reactor had fallen to fully expose the fuel rods, which likely caused some of them to partially fuse.

Goto said that based on the reports it seems the mobile pump being used to push seawater into the No. 2 reactor had run out of fuel. He didn't know what kind of pump was being used. Goto, who earned his Ph.D. by evaluating the stress that reactor container vessel can endure, quit his job with Toshiba Corporation due to his concerns over reactor safety. "I came to the conclusion that the vessels being built were not adequate enough to be the last line of defense," he says. "They weren't designed to withstand the kinds of problems currently being experienced in the Fukushima plants." He now teaches design engineering at Shibaura Institute of Technology in Tokyo.

However, the government sounded one cautiously optimistic note today: Edano claimed that none of the troubled reactors were likely to experience a total meltdown.

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Smokey the AI

Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires

7 min read
Smokey the AI

The 2021 Dixie Fire in northern California is suspected of being caused by Pacific Gas & Electric's equipment. The fire is the second-largest in California history.

Robyn Beck/AFP/Getty Images

The 2020 fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. These West Coast fires killed at least 37 people, destroyed hundreds of structures, caused nearly US $20 billion in damage, and filled the air with smoke that threatened the health of millions of people. And this was on top of a 2018 fire season that burned more than 700,000 hectares of land in California, and a 2019-to-2020 wildfire season in Australia that torched nearly 18 million hectares.

While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection (Cal Fire) calculates that nearly 100,000 burned hectares of those 2018 California fires were the fault of the electric power infrastructure, including the devastating Camp Fire, which wiped out most of the town of Paradise. And in July of this year, Pacific Gas & Electric indicated that blown fuses on one of its utility poles may have sparked the Dixie Fire, which burned nearly 400,000 hectares.

Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure. Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis.

However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires. In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a 40-year lifespan, are entering their final decade.

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