In addition to the radioactive air removal effort within the building, 500 million Becquerel of activity was discharged from the "upper part of the reactor" within the last few days, probably due to the venting observed via live video on May 8th. From Xinhuanet:
"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."TEPCO needs to catch a break. A lot was riding on being able to cleanse the air within the unit. They were expecting a +/-96% reduction in exposures from Iodine after the operation, among other isotopes. This proves that high radiation levels within the building are primarily coming from point sources, ie, the reactor itself, radioactive debris among other objects, and not from radioactive isotopes in air.
Edit: The Daily Yomiuri is out with an almost contrarian release to the above article, stating that temperatures are "low enough for full-scale work to begin" with the new cooling system for the unit 1 reactor. A further working example of positive press:
"The nine workers were found to have been exposed to radiation of up to 10.56 millisieverts during their time in the reactor building, posing little threat to their health."
Workers received this dose in less than an hours time. If exposures remain consistent at these levels, they can technically be allowed about 25 more rounds of work under similar circumstances before workers hit their maximum allowable doses and are cycled out of the workforce for at least the next year.
10.56 mSv whole body in under an hour is nothing to feel comfortable with, and it is a bit indulgent for the press to deign this exposure as one "posing little threat" when their own reproductive organs are not at irradiative risk.