Tokyo Electric Power Co. (TEPCO) is struggling to carry out its plans to fill the containment vessel of the Fukushima No. 1 Nuclear Power Plant's No. 1 reactor with water to control radiation emissions, it has emerged.

Workers have already pumped in more than enough water to fill the containment vessel, but they have not actually seen a rise in the water level. Furthermore, when workers increased the amount of water pumped into the containment vessel, pressure inside the vessel fell, threatening a hydrogen explosion. As a result, workers had to once again reduce the amount of water. When pressure inside the containment vessel falls to a level near regular atmospheric pressure, oxygen can enter the container from outside and react with hydrogen inside to produce an explosion.