Tokyo Electric Power Co. (TEPCO) on Monday detected radiation levels in the building housing the faltering No. 1 reactor that far exceeded expected levels reaching as high as 700 millisieverts per hour, the utility firm said.

The latest readings for the troubled reactor has lead Japan's Nuclear and Industrial Safety Agency to embark on new radiation shielding measures so that work to bring the crisis under control can go ahead with risks of massive doses of deadly radiation poisoning hopefully being lessened for the TEPCO workers and their affiliates as they attempt to embark on a massive project to install a nuclear fuel cooling system.

TEPCO is currently mulling ideas to protect its workers -- some who have only had a single medical check since the March 11 triple disasters and many who have been exposed to levels of radiation far exceeded legal levels -- such as constructing a metal tunnel for people to walk through, or using lead sheeting to provide increased protection against radioactive substances and increase safer mobility for the workers moving around in high-radiation areas.

An area with a double-digit millisievert level, let alone three-digit figures, is quite tough as a working environment. So we have to do the work by using some shielding,'' Hidehiko Nishiyama, a spokesman for the Nuclear and Industrial Safety Agency, told a press conference.

TEPCO during the press conference were unable to confirm whether the latest measures would be a success and could not say unequivocally whether Asia's largest utility's well-publicized schedule to stabilize the plant's troubled reactors by October would be met.

TEPCO said that as 10 to 70 millisieverts per hour were detected in areas where workers would be expected to spend prolonged periods of time inside of the No. 1 reactor, restoration work is possible.

But the utility firm opened the main access points to the reactor and in doing do freely released 500 million becquerels of radioactive substances into the atmosphere, where it had gathered in the upper part of the reactor following a massive hydrogen explosion on March 12.

Seven TEPCO representatives and two from the nuclear agency entered the reactor in the early hours of Monday morning and measured radiation, working and safety conditions inside the reactor for roughly 30 minutes.

Following the reconnaissance mission, the nine people involved were exposed to radiation ranging from between levels of 2.7 millisieverts and 10.56 millisieverts, according the Nuclear and Industrial Safety Agency.

The installation of such cooling equipment is likely to be hampered by high radiation, as the group found several radiation " hot spots," especially around pipes suspected to be clogged with highly radioactive material.

The nuclear agency and the Environment Ministry on Monday also began taking readings from highly contaminated rubble from the vicinity of the stricken No. 1 nuclear plant and remove some of the debris and bring it back to laboratories in Tokyo for further tests.

The radioactive rubble continues to emit radiation into the atmosphere, the ministry said.