Workers have entered the unit 1 reactor building of Japan's damaged Fukushima Dai-ichi nuclear plant for the first time since a hydrogen explosion hit the facility a day after the devastating March earthquake and tsunami. Twelve staff members stepped in to install duct pipes to six ventillation machines that will filter out the radioactive material in the air, Tokyo Electric Power Company (TEPCO) said May 5. High radiation levels inside the plant have kept workers from entering the facility to repair the plant's cooling systems. The workers—equipped with protective suits, masks and air tanks—entered through a special tent set up to prevent radiation leaks. They are to work in 10-minute shifts. The operation is expected to take four or five days. (AlJazeera, May 5)

TEPCO has now announced a plan to bring the reactors under control within the next six to nine months. The company said: "By bringing the reactors and spent fuel pools to a stable cooling condition and mitigating the release of radioactive materials, we will make every effort to enable evacuees to return to their homes and for all citizens to be able to secure a sound life."

In the plan's first step, TEPCO expects a decline in radiation levels around the plant to take three months. This will entail preventing further hydrogen explosions inside the primary containment vessels (PCVs) of units 1, 2 and 3. Cooling the reactor by injecting fresh water into the reactors increases the chance of steam condensation, potentially triggering hydrogen explosions. TEPCO will inject nitrogen gas into each unit's PCV to keep the concentration of hydrogen and oxygen below flammability levels. TEPCO also said it must prevent further release of contaminated water from the reactors.

In April, Hitachi—which supplied one of the plant’s six reactors—submitted a long-term plan to TEPCO to decommission the Fukushima Dai-ichi reactors. Working with General Electric, Exelon Corp. and Bechtel Corp., Hitachi said the plan would include removing the fuel rods from the reactors and spent fuel pools, cleaning the contaminated facilities, disposing of all nuclear waste and dismantling the reactors and buildings. Hitachi spokesman Masanao Sato told Nikkei News that such a process could take "about 30 years" to complete.

Hitachi has sent more than 300 employees to the site to help with re-establishing electricity supplies to the plant, and draining water from the turbine buildings and tunnels. Toshiba, which supplied two reactors as the main contractor and jointly supplied two others with GE, also submitted a long-term decommissioning plan. With help from the Babcock and Wilcox Co., the Shaw Group Inc. and Westinghouse Electric, Toshiba said its plan could take at last 10 years. (Power-Gen Worldwide, May 5)

See our last post on the Fukushima disaster.

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