Workers enter the Japan reactor nuclear building

Workers in one of the buildings damaged reactor at the nuclear plant disaster of Japan Thursday for the first time since it was rocked by an explosion in the days after a devastating earthquake, the country's nuclear security agencysaid.

The plant operator, Tokyo Electric Power Co., said workers are connecting ventilation equipment to the unit 1 in an attempt to absorb the radiation from the air inside the building. The work should take about four or five days.

The utility must lower the levels of radiation within the reactor before the key step of the installation of a cooling system is eliminated by the earthquake on March 11 and the subsequent tsunami that leaves the people of more than 25,000 dead or missing along the northeast of the Japan Coast.

Workers were unable to enter the buildings of the Fukushima Daiichi nuclear power reactor, about 140 km northeast of Tokyo, since the first days after the tsunami. Explosions of hydrogen to four of the buildings of the complex six-reactor in the early days destroyed some of their roofs and walls and dispersed radioactive debris.

In April, a robot recorded readings of radioactivity of approximately 50 millisieverts per hour building reactor of unit 1 - for workers to enter realistically a too high level.

The decision to send workers was made after the robots last Friday raised fresh data that showed radiation levels were sufficiently safe for workers to enter in some regions, said Taisuke Tomikawa, a TEPCO spokesman.

Two workers entered the reactor building autour from 11: 30 pm (0230GMT) for about 25 minutes. They were exposed to 2 millisieverts during this time, said Tomikawa.

A dozen workers split into teams had to enter the building on a rotation for short periods limit exposure to radiation.

"It is an effort to improve the environment inside the reactor building," he said.

Workers were equipped with protective and a reservoir of mask and air set similar to those used by the scuba divers, according to an official of the industrial and nuclear safety agency.

Before the building of the reactor, the utility erected a temporary tent designed to prevent radioactive air to escape.

TEPCO has a plan to bring the integrating plant a cold judgment within six to nine months.

Japanese authorities have more than double the legal limit of exposure to radiation from nuclear workers since the beginning of the crisis to 250 millisieverts per year. The United States nuclear industry workers are allowed to an upper limit of 50 millisieverts per year. Doctors say irradiation sets 1,000 millisieverts and includes nausea and vomiting.

Radiation leaks from the Fukushima plant has forced 80,000 people living within a radius of 12 miles (20 kilometres) out of their homes. Many live in gymnasiums and community centers.

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Associated Press Writer Mari Yamaguchi in Tokyo contributed to this report.