Radioactive water issue cannot be resolved by ice wall project alone

From today’s Yomiuri Shimbun

Tokyo Electric Power Co. has launched the construction of ice walls, a project aimed at curbing the buildup of radioactive water at its crippled Fukushima No. 1 nuclear power plant.

Halting the increase of contaminated water is the major task for the moment to end the crisis at the plant. Therefore, the project must be steadily promoted.

Pipes to circulate liquid coolants will be buried over a 1.5-kilometer perimeter around the plant’s Nos. 1 to 4 reactor buildings, thereby freezing the soil to a depth of 30 meters below ground to construct ice walls. The government and TEPCO expect the envisaged ice walls to help prevent groundwater from flowing into the reactor buildings, which has caused an increase of contaminated water at the plant.

Many essential pipes and electrical cables are installed underground around the reactor buildings. If such equipment is accidentally damaged, it could impair the cooling functions of the reactors.

Given the high radiation levels at the construction site, it is necessary to minimize workers’ radiation exposure. Due care must be taken in carrying out the work.

Installation will cost ¥32 billion. The government will bear the cost as a research and development project. Power consumption equivalent to that of 13,000 ordinary households, running more than ¥1 billion annually in simple calculation, will be needed to keep the underground walls frozen.

Such massive spending aside, the question is whether the ice walls will ensure that groundwater will not flow into the reactor buildings.

Ice walls have been used as a temporary method of halting the flow of groundwater when tunnels are constructed. The installation of ice walls on the currently planned scale is unprecedented in Japan.

Fears of subsidence

There are fears that if the soil is not frozen evenly, it could cause subsidence. Experts have warned that if the ice walls melt due to problems with cooling functions, there could be a widespread danger of radioactive water flowing outside the reactor buildings.

There is no reason to place overly high expectations on the ice walls.

Considering the fact that there has been constant trouble with the countermeasures taken so far to deal with radioactive water, it is essential to carry out several measures in parallel.

The amount of contaminated water has increased by 300-400 tons a day. Storage tanks built on the plant’s premises already number about 900, leaving no choice but to assign many workers to maintenance and surveillance duties.

This hinders work to repair the crippled reactors, which must be given top priority to end the crisis at the plant. This must be taken seriously.

Sooner or later, there will be no more sites available for the construction of storage tanks at the plant.

It is vital to reduce the amount of rainwater infiltrating the soil as one of the countermeasures. The decision was made to pave the plant’s site, but little progress has been made due to a delay in land leveling.

New highly radioactive leak at Japan’s Fukushima plant

TOKYO (Reuters) – The operator of Japan’s Fukushima nuclear plant said on Thursday that 100 tonnes of highly contaminated water had leaked out of a tank, the worst incident since last August, when a series of radioactive water leaks sparked international alarm.

Initial measurements of the latest incident showed the leaked water had a reading of 230 million becquerels per litre of beta-emitting radioactive isotopes, including strontium 90.

The legal limit for releasing strontium 90 into the ocean is 30 becquerels per litre.

full article:

Radiation doubles to new high in No. 1 plant water ditch

Tokyo Electric Power Co. said Thursday that radiation rose to a new record in water collected from a drainage ditch at its stricken Fukushima No. 1 nuclear plant.

Tepco said it detected a maximum of 140,000 becquerels per liter of beta ray-emitting substances, including strontium, from a water sample collected Wednesday from the ditch, which extends to the sea beyond the plant’s port.

The figure is 2.3 times higher than the previous record of 59,000 becquerels detected in water sampled at the same location Tuesday, and was more than 11 times the previous day’s reading.

The measurement location is about 600 meters from the open ocean and close to the storage tank that leaked some 300 tons of radioactive water in August.

Tepco said rainwater may have carried radioactive materials in surrounding areas into the drainage ditch.

Sandbags were placed downstream, but heavy rain may have caused the water in the ditch to overflow them and enter the ocean.

Also on Thursday, Tepco started transferring radioactive water that has built up inside the tanks’ flood enclosures to a covered reservoir ahead of heavy rain expected from fresh typhoons approaching Japan.


Fukushima: Tanks’ enclosures swamped by downpours; strontium level soars, radiation in rainwater overflow spikes

Kyodo, Jiji Reports

Rainwater that overflowed Sunday from the concrete-ringed enclosures around the water storage tanks at the Fukushima No. 1 nuclear plant had excessively high radiation readings, Tokyo Electric Power Co. disclosed Monday.

Strontium-90 in the rainwater, which had accumulated from recent downpours, was above the limit of 10 becquerels per liter near six tank clusters, with the reading in one area reaching 710 becquerels, Tepco said.

It said some of the radioactive water has seeped into the ground, but noted that most of the affected surface water probably didn’t flow to the Pacific Ocean because barrier mounds have been built outside the flood enclosures to prevent water from entering the drainage channels that lead to the sea.

Yet Tepco couldn’t totally rule out that surface water had reached the sea.

The concrete flood fences, about 30 cm high, were built to keep water from spreading if a tank leaks. There are 23 enclosed tank clusters. The tanks store highly radioactive water that was used to cool the melted cores of the three crippled reactors.

When rainwater accumulates in an enclosure, Tepco transfers it to other containers and checks the radiation level before discharging it. But Sunday’s rainfall was so heavy that it overflowed.

The rainwater that day overflowed the fences of 11 of the tank enclosures, Tepco said.

Simultaneous overflows had never taken place at so many clusters before.

Tepco also found water leaks from a concrete joint in a barrier at another tank cluster where excessively radioactive substances were found in the past. As a result, tainted water in such barriers has leaked from over half of the plant’s 23 tank enclosures.

In the past, radioactive materials in excess of the provisional limits set by Tepco have been detected in water in some of the tank cluster enclosures.

The overflows and leaks are the latest in a series of the Japanese government’s water problems at the plant.

On Sunday, the utility started draining water from inside the barriers at six tank areas, including five of the 11 overflowed areas, after confirming that radiation levels had fallen below the provisional limits.

At two other tank areas, Tepco transferred the enclosure water to sunken reservoirs. Although the utility stopped using the reservoirs to store the highly radioactive coolant after discovering in April that they were leaking, it took the emergency step this time because of the looming rainfall threat when Typhoon Wipha approached last week.

The total amount of water that overflowed and leaked Sunday is not known, the company said.

In one location among the 11 tank areas, a maximum of 29,000 becquerels per liter of strontium and other radioactive materials emitting beta-ray particles were detected in the past.

Tepco’s provisional limit on radiation is 10 becquerels per liter for strontium-90, a substance linked to bone cancer that is also believed to account for about half of beta ray-emitting radioactive materials. Airborne radioactive materials have fallen into the enclosures, while tainted tank water is thought to have leaked into some of the areas.