TEPCO starts injecting nitrogen into No. 3 Fukushima reactor+

TOKYO, July 14 Kyodo -
The operator of the crippled Fukushima Daiichi nuclear power plant said Thursday it started to inject nitrogen into the No. 3 reactor to reduce the risk of further hydrogen explosions, a move marking further progress toward containing the four-month-old nuclear crisis.
The injection of the substance into the plant's three troubled reactors has been one of the key goals Tokyo Electric Power Co. has intended to achieve by mid-July, and the No. 3 reactor was the only remaining one that was not receiving the inert gas.
As Tokyo Electric has also started to operate a new system that enables water to circulate around the three reactors to stably keep the nuclear fuel inside cool, the utility and the government believe they are basically moving ahead with the restoration work as planned in a roadmap.
Under the roadmap, the utility, known also as TEPCO, would aim to bring the crippled reactors to a stable condition by mid-July as a first step, and to a further stable ''cold shutdown'' by January at the latest as a second step.
TEPCO and the government will announce a new roadmap Tuesday that will highlight their work schedule to be implemented during the second step and beyond.
Nitrogen injection into the reactor's primary containment vessel is important to prevent an explosion from occurring inside the vessel, which may lead to the release of massive amounts of radioactive substances outside. The step is intended to keep the ratio of hydrogen inside the vessel to a certain low level.
The move may cause radioactive substances to further leak out from the containment vessel, but the utility said that the amount would not be at a level to affect the surrounding environment.
Nonetheless, TEPCO decided to strengthen radiation monitoring inside the plant.
Hit by a magnitude-9.0 earthquake and massive tsunami on March 11, the six-reactor Fukushima complex lost nearly all of its power sources, and thus the cooling functions of many of the reactors and spent fuel pools.
Hydrogen explosions occurred at the Nos. 1 and 3 units in the early days of the nuclear crisis, blowing off the walls and roofs of the buildings housing the reactors and leading to the release of radioactive materials into the environment.