[ad_1]
OKUMA, Japan — Eleven years after the Fukushima Daiichi nuclear power plant was devastated by a meltdown following a major earthquake and tsunami, the facility now looks like a sprawling construction site. Most of the radioactive debris detonated by the hydrogen explosions has been cleared and the torn buildings repaired.
During a recent visit by journalists from the Associated Press to see firsthand the cleanup of one of the world’s worst nuclear disasters, the helmeted men wore regular work suits and surgical masks instead of the previously mandatory hazmat overalls and full-face masks when digging nearby. a recently fortified oceanfront seawall.
Workers were preparing to construct an Olympic-sized pool the size of a well to begin in the spring of 2023 to phase out the purified radioactive water, and be used in a highly controversial plan – currently more than 1.3 million tons stored in 1,000 tanks – so officials are taking the other necessary steps to decommission the facility. can make room for facilities.
Despite progress, large amounts of radioactive molten fuel remain inside the reactors. There are concerns about the fuel, as not much is still known about its condition, even with clean-up officials.
About 900 tons of molten nuclear fuel remain inside the three damaged reactors, and removing it is an unprecedented challenge, involving 10 times the amount of damaged fuel removed in the Three Mile Island cleanup following the 1979 partial core meltdown.
The government has set a decommissioning roadmap that aims to be completed in 29 years.
The challenge of removing molten fuel from reactors is so daunting that some experts say it is now impossible to set a completion target, especially since officials still have no idea where to store the waste.
Toyoshi Fuketa, Chairman of the Nuclear Regulatory Authority, said recently that extra time will be needed to determine where and how the highly radioactive waste from reactors should be stored.
Japan does not have a final storage plan, even for highly radioactive waste from normal reactors. Of the country’s 60 reactors, 24 will be decommissioned, mostly due to the high cost required to meet the safety standards established in the wake of the Fukushima disaster.
On March 11, 2011, a magnitude 9.0 earthquake caused a tsunami 17 meters (56 feet) high and struck the coastal facility, destroying its power supply and cooling systems, causing reactors 1, 2 and 3 to melt and erupt in large quantities. caused. radiation. Three other reactors failed and survived, but a fourth building suffered hydrogen explosions.
The emitted radiation caused about 160,000 people to evacuate. Part of the surrounding neighborhood is still uninhabitable.
The molten cores in Units 1, 2 and 3, along with the control rods and other equipment, largely fell to the bottom of the primary containment containers, some possibly penetrating or mixing with the concrete foundation, making cleaning extremely difficult.
Probes of the molten fuel must be based on remotely controlled robots carrying equipment such as cameras and dosimeters that measure radiation, because radiation levels in these areas are still deadly high for humans.
In February, a remotely controlled submersible robot entered the Unit 1 primary containment vessel, its first internal probe since a failed 2017 attempt. It captured limited footage of what are believed to be piles of molten fuel rising from the concrete floor.
Probes have advanced in Unit 2, where TEPCO plans to send an extendable robotic arm to collect melted fuel samples later this year.
Akira Ono, TEPCO Chief Decommissioning Officer, said in a recent online interview that the robotic probes in Units 1 and 2 are a big “step forward” in decades of cleanup this year.
“We’re finally at the starting line,” Ono said. “Before, we didn’t even know which way to go.”
Ono said Unit 2 molten fuel test extraction will start with one or two granules, and all of these will be sent for lab analysis, meaning a storage facility won’t be necessary until larger quantities are drawn. He said even a small amount would provide valuable data for research and development of fuel and debris removal technology for all three reactors.
Hideyuki Ban, co-founder of the Citizens’ Nuclear Information Center, who has previously served on government nuclear safety panels, suggests burying solidified treated water underground for stable long-term storage while burying the three reactors for several decades – like Chernobyl. and waiting for radioactivity to subside for better safety and access for workers rather than rushing for cleanup.
Since the disaster, contaminated coolant has continually escaped from damaged primary containment vessels to reactor building basements, where it mixes with groundwater and seepage rainwater.
The water is pumped and treated, partially recycled as cooling water, and the rest is stored in the 1,000 giant tanks that fill the facility. TEPCO says the tanks will be filled with 1.37 million tons by next spring.
The government has announced plans to release the water well below legally releasable levels after purification and dilution through an undersea tunnel planned at about 1 kilometer offshore. The plan met with fierce opposition from local residents, especially fishermen, who were worried about further damage to the area’s reputation.
TEPCO and government officials say small amounts of non-harmful tritium are inseparable from water, but all 63 other radioactive isotopes selected for treatment can be reduced to safe levels, further diluted with seawater before being tested and released.
Scientists say the health impact of consuming tritium along the food chain may be greater than drinking it in water, and more research is needed.
At one of the water treatment plants, where radiation levels are much higher, a team of fully protective workers handled a container filled with highly radioactive slurry. It had been filtered from the polluted water that had continually leaked from damaged reactors and pumped from their basements since the disaster. In addition, large quantities of slurry and solid radioactive waste accumulate at the facility.
After decontamination since the disaster, radiation levels have dropped significantly and full shielding is only needed in limited areas, including inside and around reactor buildings.
On a recent visit, AP journalists used cotton gloves, goggles, headscarves and surgical masks to tour low-radiation areas.
When journalists entered the Unit 5 primary containment container and the authorities introduced the concept of robotic probe No. 1 and 2 reactors.
TEPCO discharged spent fuel from reactor pools 3 and 4, but removal in reactors 1 and 2 was delayed for several years due to high radiation and contaminated spillage, raising concerns about spent fuel melting on another occasion. The great earthquake caused water loss and overheating.
Futaba Mayor Shiro Izawa said the Fukushima Daiichi plant must be safely and completely decommissioned “to make our hometown a safe and habitable place again.” Izawa said he wanted the government to “erase (the area’s) negative image” by tackling safe cleanup, a prerequisite for the town’s rebuilding.
[ad_2]
Source link