Fukushima Dai-ichi’s Messy Future
How do you take apart a power station that experienced a triple meltdown?
By John Boyd and Eliza Strickland
Editor's Note: This is part of the IEEE Spectrum special report: Fukushima and the Future of Nuclear Power.
The nuclear accident at Fukushima Dai-ichi occurred nine months ago, but the cleanup and decommissioning of the power station has only just begun. We asked the experts what will be happening at the site when the one-year anniversary of the accident rolls around in March, and what to expect from the 10-year and 100-year milestones.
|1 YEAR||10 YEARS||100 YEARS|
|The damaged reactor 1 building has been surrounded by a steel frame with a protective plastic covering to prevent radioactive emissions.||
The reactor buildings 1, 3, and 4, which were all shattered by explosions during the accident, have been covered to prevent radioactive emissions.
All radioactive debris has been removed from the buildings’ interiors and radioactive particles have been scrubbed from walls and floors to allow the decommissioning effort to go forward.
Option 1: The damaged reactors have been left in place and entombed in huge concrete shells. Radiation levels will decrease gradually over time.
Option 2: The reactor cores have been removed, and the reactor buildings have been dismantled and transported to a radioactive waste storage facility.
|Meltdowns occurred at the three reactors active at the time of the accident (units 1, 2, and 3). These reactors’ damaged nuclear cores, made of a congealed mix of uranium and other metals, are now kept at a stable temperature of below 100 °C.||The protective primary containment vessels have been flooded with water to help block radiation during work. Lids of the inner pressure vessels have been opened to allow workers to determine the exact location of the damaged cores.||
Option 1: The damaged cores have been left in place inside the entombed reactor buildings.
Option 2: The damaged cores have been removed. While submerged in water, they were broken into pieces by drills, sucked up into containers, and transported to an off-site waste storage facility.
|Construction is under way on an underground iron wall between the reactor buildings and the sea to prevent radioactive water from leaking into the ocean. The wall will be made of 22-meter-long iron pipes sunk into the ground.||
The underground wall is complete.
The demolition of damaged auxiliary structures is complete. Debris removal is complete.
Option 1: The entombed reactor buildings are still off-limits.
Option 2: The grass grows over the site where Fukushima Dai-ichi once stood.
|A system to decontaminate radioactive cooling water is in place, which can clean up to 1200 metric tons of water each day.||Leaks in the primary containment vessel have been sealed to simplify the water decontamination and circulation system.||Not applicable|
|Water circulation has been restored in all six reactors’ pools to keep the spent fuel rods at a stable temperature.||All spent fuel has been removed from the pools, transferred to dry cask storage, and taken to an off-site disposal facility.||Not applicable|
Evacuees have returned to the voluntary evacuation zone that’s between 20 kilometers and 30 km of the plant.
Fukushima City has begun washing all 110 000 houses in the city to remove radiation.
Areas within 3 km of the plant are still off-limits. The government bought this land to use for temporary storage facilities for contaminated debris and sludge from the plant, and for contaminated soil from surrounding areas.
Other areas within the 20-km mandatory evacuation zone have been cleaned by an arduous process of topsoil removal from farmland, forests, and residential areas. Up to 5 cm of topsoil was removed from an area covering as much as 2400 square km. This cleanup resulted in up to 30 million cubic meters of contaminated waste.
|While the site of the Fukushima Dai-ichi plant itself is still off-limits, the towns within 3 km of the plant have been decontaminated. However, it seems doubtful that anyone will choose to live there again.|
Sources: TEPCO’s “Roadmap Towards Restoration from the Accident at Fukushima Daiichi Nuclear Power Station”; Akio Yamamoto, professor of energy engineering at Nagoya University; Muneo Morokuzu, professor of energy and environmental technology at University of Tokyo’s Graduate School of Public Policy; Harold Denton, former director of the office of nuclear reactor regulation at the U.S. Nuclear Regulatory Commission and President Jimmy Carter’s personal adviser for the Three Mile Island accident.