29/03 'Hot' water removal going slowly / Flooded steam condensers in reactors hamper workers' efforts

The Yomiuri Shimbun

Steam condensers at the Nos. 2 and 3 reactors of the crippled Fukushima No. 1 nuclear power plant are flooded, making it difficult for workers to remove highly radioactive water from inside the turbine buildings, Tokyo Electric Power Co. said Monday.

The turbine buildings house equipment indispensable to carrying out full-scale cooling of the troubled reactors.

Radioactive water has accumulated at the bottom of the buildings.

In the case of the No. 1 reactor, TEPCO could not ascertain when it would be able to completely pump out the water because of a huge quantity of water in the basement of the turbine building.

Referring to radiation of more than 1,000 millisieverts per hour that was detected on the surface of the radioactive water at the No. 2 reactor, Chief Cabinet Secretary Yukio Edano said Monday the high level of radiation was caused by water overflowing after coming in contact with nuclear fuel rods that had temporarily melted.

Earlier in the day, TEPCO said the concentration of radioactive substances in the water at the No. 2 reactor's turbine building was about 100,000 times higher than normal in water inside a reactor.

The utility said Sunday morning that the concentration of radioactive iodine-134 detected in water taken the previous day from the basement of the turbine building of the No. 2 reactor was 2.9 billion becquerels per milliliter, or 10 million times the normal concentration.

Later that day, TEPCO corrected that analysis, saying it was highly possible that cobalt-56 was mistaken for iodine-134 when compiling the earlier data. Early Monday, the company again made a correction, saying it should have referred to cesium-134, not cobalt-56.

The concentration of radioactive substances detected at the same place in the No. 2 reactor was 20 million becquerels per milliliter or 100,000 times that of the water inside a reactor, TEPCO said.

There was some good news. TEPCO reported that the spent nuclear fuel rod temporary storage pools at the Nos. 2 and 3 reactors were confirmed to be filled to their capacity Monday.

Despite this, restoration work at the plant is expected to take a long time, observers said.

Referring to the radiation-contaminated water at the basement of Reactor No. 2's turbine building, Edano said the contamination was regrettable but restoration work would continue at the plant while ensuring there was no health risk.

With regard to the Nos. 1 and 3 reactors, where concentrations of radioactive substances are lower than at Reactor No. 2, he said radioactive water that became steam in the reactor containment vessel was condensed or diluted as a result of water spraying.

Reactor No. 1's condenser has a capacity of 1,600 tons while those of the Nos. 2 and 3 reactors are almost twice that at 3,000 tons.

Work to remove radioactive water from the basement of Reactor No. 1's turbine building has started. Additional pumps have been installed to remove the radioactive water, but it remains to be seen when the work can be finished because of the large volume of water.

The condensers at the Nos. 2 and 3 reactors cannot take additional radioactive water because they are already full. TEPCO is looking into the possibility of transferring contaminated water to tanks located at other places. But new pipes will be needed to connect them, TEPCO said.

The amount of radiation in the air in the basements of the turbine buildings amounted to 25 millisieverts per hour at the No. 1 reactor, more than 1,000 millisieverts at the No. 2 reactor and 400 millisieverts at the No. 3 reactor.

The high radiation records at the Nos. 2 and 3 reactors made it difficult to make progress in removing radioactive water.

To help ensure safety in the dark working environment, TEPCO is considering bringing temporary lighting equipment into the basements of the turbine buildings of the Nos. 2 and 3 reactors and dividing workers into several groups so they can work for short periods.

As for pouring freshwater into Reactor No. 2, TEPCO has installed electric-driven pumps inside the turbine building to connect them with a power supply. On Sunday afternoon, water-spraying into the reactor started using water drawn directly from a freshwater tank installed about one kilometer away.

(Mar. 29, 2011)