40 degrees Celsius, humidity over 90 percent (in the previous survey by the robots). 50 millisieverts/hour radiation, and the Spent Fuel Pool is apparently very warm.
At one spot, the steam (highly radioactive) from the Spent Fuel Pool was condensing and falling like raindrops. But TEPCO says it will be easier to work in the Reactor 2 than in the Reactor 1, because the radiation is lower. 50 millisieverts/hour sure seems infinitely lower than 1,000 or 2,000 millisieverts/hour in the Reactor 1.
(Take a look at the photos that the workers took, in my previous post. Link opens new window.)
From Nikkei Shinbun (5/19/2011):
東京電力/async/async.do/ae=P_LK_ILCORP;bg=0002021;dv=pc;sv=NXは 19日、福島第１原子力発電所２号機の内部を調べた詳細を発表した。原子炉建屋内は温度と湿度が高く「体力の面から15分以上の作業は困難」と説明した。 放射線量も最大で毎時50ミリシーベルトだった。新しい工程表では１～３号機の原子炉を「循環注水冷却」の新方式で冷やすとしたが、作業が難航する可能性 が出てきた。
TEPCO disclosed the details of the survey of the interior of the Reactor 2 reactor building [done on May 18]. According to TEPCO, the temperature and humidity were too high for the workers "to work for more than 15 minutes". The radiation level was also high, at 50 millisieverts/hour at the maximum. In the revised "roadmap", the reactors 1, 2 and 3 are to be cooled with the external water cooling systems, but the condition inside the reactor buildings may jeopadize the work [outlined in the "roadmap"].
Workers entered the Reactor 2 reactor building in the morning of May 18. There were three water puddles inside the building. According to TEPCO, "there was one spot where the steam from the Spent Fuel Pool condensed inside the building and was falling like small raindrops."
As the workers proceeded from the entrance, the temperature rose, making long works impossible. In the previous survey using the robots, the temperature registered 40 degrees Celsius.
Nonetheless, TEPCO was of the opinion that "it would be easier to work in the Reactor 2 reactor building as long as the high humidity can be dealt with, than to work in the Reactor 1 reactor building where the radiation level was measured at 1,000 millisieverts/hour". TEPCO said it would install a system to cool the Spent Fuel Pool, and come up with some form of ventilation.
What's left unsaid by the article or TEPCO is the now-admitted fact that the Containment Vessels of these reactors are damaged and leaking. How could they construct a cooling system that would circulate water that leaks from the RPV into the Containment Vessel back into the RPV, if the Containment Vessel is leaking? Could they fix the leak?
Mainichi Shinbun (link is in Japanese) says one worker in his 40s fell ill after the work inside the Reactor 2 reactor building, and was treated for heat exhaustion.