This video was released by TEPCO on 4 June 2011. It shows radioactive steam venting somewhere in the Unit 1 reactor building. [Update: Ex-SKF has the scoop] Packbot video was taken on 3:30PM on June 3. It looks as if the water was boiling. From Yomiuri Shinbun (1:14PM JST 6/4/2011):

東京電力は４日、福島第一原子力発電所１号機の原子炉建屋１階南東部の床を貫通する気体輸送用の配管周辺の隙間から湯気が上がっているのを、調査に入った米国製ロボット「パックボット」で確認、撮影したと発表した。 On June 4, TEPCO announced that the US-made robot “Packbot” confirmed and photographed the hot steam gushing through the space around the air duct that goes through the floor in the southeast corner of the 1st floor of the reactor building of the Reactor 1 at Fukushima I Nuclear Power Plant. 湯気が立ち上っている周辺の放射線量は、最高で毎時４０００ミリ・シーベルトで、３月１１日の事故発生後に測定された中では、最も高い数値だった。３分余りで作業員の被曝(ひばく)限度である２５０ミリ・シーベルトを超え、１５分間続けて作業すると、吐き気など急性放射線障害の自覚症状が出るレベルだ。 The radiation level near the steam was 4,000 millisieverts per hour at the maximum, the highest level ever measured since the start of the accident on March 11. The 250 millisieverts radiation exposure limit for the workers would be exceeded in 3 minutes, and acute radiation poisoning would occur after 15 minutes of work. …

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