Japanese government considers underground wall to contain Fukushima radiation

The Japanese government is considering building an underground barrier near the Fukushima No. 1 nuclear power plant to prevent radioactive material from spreading far from the plant via soil and groundwater, a senior government official said.

Sumio Mabuchi, a special adviser to the prime minister, revealed the plan Friday at the Japan National Press Club building in Tokyo. The plan is the first attempt to address the risk of contaminated water spreading far from the plant through soil.

According to Mabuchi, the barrier would extend so far underground that it would reach a layer that does not absorb water. The wall would entirely surround the land on which reactors No. 1, 2, 3 and 4 stand.

Mabuchi is a member of the unified command headquarters set up by the government and Tokyo Electric Power Co. to deal with the nuclear crisis. He serves as the head of government representatives on a team dealing with medium- and long-term issues, including how to contain the spread of radioactive materials from the plant.

The process of filling the containment vessel of the Fukushima power plant’s No. 1 reactor with water is progressing steadily, according to Tepco.

Tepco plans to continue injecting water into the containment vessel until the fuel rods inside are fully submerged in what the power company has called a “water coffin.”

At a press conference held Friday, Tepco said it believed pressure suppression pools at the bottom of the No. 1 reactor’s containment vessel were full of water, and that the top section of the containment vessel was about half full. Under normal circumstances, the pressure suppression pools are about 50 percent full with water.

The pressure suppression pools help control the air pressure inside the reactor’s pressure vessel. Operators can open valves to release steam from the vessel into the suppression pools, where it is cooled and condensed to water.

According to Tepco, it has poured about 7,000 tons of water into the No. 1 reactor’s pressure vessel. The company said it believes almost all of that water is still inside the pressure vessel and the containment vessel. However, the firm said it has injected about 14,000 tons of water into the No. 2 reactor and 9,600 tons of water into the No. 3 reactor since cooling operations began. In both cases, the amount injected exceeds the about-7,000-ton capacity of the reactors’ containment vessels.

Tepco believes considerable amounts of water leaked from those reactors’ containment vessels into their turbine buildings through cracks in pressure suppression pools and other routes.

Meanwhile, at the No. 4 reactor, Tepco has attached cameras and other equipment to a concrete pump used to inject water into the pool containing spent nuclear fuel rods to monitor the water and radiation levels around the clock.

According to the company, water in the pool was 91 C (196 F) on Friday, and the water level was about 2 meters (about 6.5 feet) above the spent fuel rods. Those readings were about the same as those taken by the company on April 12, Tepco said.