Construction on the underground ice wall around Fukushima is now underway. its aim is to prevent water that’s been contaminated with radioactive materials from escaping and entering the broader water supply. The ambitious government funded project project intends to freeze the ground around four reactors, as well as other related buildings, to a depth of 30 meters. In total, the frozen wall of earth will stretch for 1.5km and will reach temperatures of minus 40 degrees Celsius. A series of pipes carrying coolant will be used to freeze the land. Beyond preventing water from escaping the area, the AFP reports that the hope is that it will also prevent contamination of the huge volume of groundwater that flows into the plant from nearby hillsides daily. Construction is expected to finish in March of 2015 with an expected cost of about 32 billion yen ($314 million).
In Japan ground freezing projects have already been used in the construction of tunnels and subways for short periods of time. An underground ice wall has also been used to isolate radioactive waste at the U.S. Department of Energy’s former site of the Oak Ridge National Laboratory in Tennessee that produced plutonium, but only for six years, according to the MIT Technology Review magazine.
Some experts are still skeptical about the technology and say the running costs will be a huge burden. Atsunao Marui, an underground water expert at the National Institute of Advanced Industrial Science and Technology, said a frozen wall could be water-tight but is normally intended for use for a few years and is not proven for long-term use as planned in the outline. The decommissioning process is expected to take about 40 years.
A group of reporters were permitted into the Fukushima plant last Friday to visit key working areas to tackle the radioactive water. They were accompanied by Masato Kino the Natural Resources and Energy Agency’s director for management of the contaminated water at the plant and Tokyo Electric Power Co. officials.
Kino emphasized the importance of improving working conditions for the roughly 6,000 workers at the crippled nuclear plant during the tour.
“I sincerely felt the hardships workers have experienced, as what’s going on here is different from ordinary construction work in terms of the severe heat due to protective suits and high radiation level,” he said.
The water buildup is a major headache for TEPCO and the government as they work toward decommissioning all six reactors at the complex. The contaminated water is increasing at a rate of around 400 tons per day as groundwater flows into the damaged buildings for reactors 1 through 4.
Tepco began constructing the huge underground ice wall early this month. It will surround reactor buildings 1 through 4 in an attempt to prevent more groundwater from seeping into their basements and mixing with heavily contaminated water. Under the unprecedented government-funded project, 1,550 pipes will be inserted deep into the ground to circulate coolant and freeze the nearby soil. However, the work is taking place in conditions of high radiation. “A worker is permitted to continue to do his job for about three hours a day due to legal limits on radiation exposure,” said Kino.
The scale of the project is immense. “Look at that crane! Three out of only six or seven of that supergiant kind existing in Japan are operating here,” Kino said. “The current work is dominated by construction.” In addition to the huge cranes, various kinds of heavy machinery and trucks are operating in the area, which is now a large-scale construction site. Everyone on site has to wear white protective suits and full face masks. A signboard reads “Highly contaminated water here.”
Since May, Tepco has employed a “groundwater bypass system” in which it has dumped thousands of tons of groundwater into the Pacific Ocean collected from wells dug near the reactor buildings. The utility claims the water’s radiation level meets safety guidelines.The system is designed to pump out the groundwater before it reaches the heavily contaminated area near the reactors. “We will not be sure whether this measure is working effectively until one or two months have passed,” said Kino.
An Advanced Liquid Processing System, or ALPS, has been developed to reduce the radiation level of the highly contaminated water accumulating at the plant.ALPS is reportedly capable of removing 62 different types of radioactive substances from the contaminated water, but not tritium. The system has been plagued by glitches and is still in the trial stage, with all three of its lines resuming Sunday for the first time in about three months.
TEPCO is also constructing an offshore wall of steel panels to keep contaminants from spreading further into the sea. The utility says radioactive elements have mostly remained near the embankment inside the bay, but experts have reported offshore “hot spots” of sediments contaminated with high levels of cesium.
Sources:The Japan Times,The Huffington Post, The Verge.com
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