As the world anxiously watches for signs of progress at the crippled Fukushima Daiichi nuclear complex, the focus of the repair has turned to removing radioactive water from in and around the reactor buildings, as the poison pools prevent workers from doing other tasks. Yet more than a week after the problem was first discovered, very little water has been removed.
Three factors have caused the delay: structural damage to pipes and other reactor parts crucial for water movement; radiation dangers blocking workers from performing essential steps; and a shortage of safe places to put the water.
Also, government and company officials seem to be moving methodically in this phase, concluding it is better to get things right than to rush. They appear to have the time, as the reactors seem to have stabilized and the amount of atmospheric radiation they have released has declined over the past two weeks.
'Obviously, it would be better if we were able to show a clear timetable,' Hidehiko Nishiyama, a top nuclear regulator said at a news conference Friday. 'But we do not want to lose trust by setting ambitious targets and missing them.'
The buildup of radioactive water, however, presents problems, as shown over the weekend, when officials confirmed it is leaking into nearby groundwater and the ocean.
When the water problem was first discovered March 24 after three workers got burned stepping in it, officials made the solution sound swift and simple: They would begin pumping the water out of the flooded buildings.
It turned out that wasn't so easy. They needed a place to put the water, and the logical places already were full.
The past week has been devoted largely to creating a three-link chain of repositories that will allow drainage of the reactors. Success now is measured not in actual removal of the water, but in clearing a space for it.
The key links in the chain begin with the most important task of attaching the electric cooling systems to reactors No. 1, 2 and 3, so the internal cooling process can begin. Absent that, operators are relying on injecting water to keep the reactors from overheating, a process that has stabilized the fuel rods, but doesn't seem likely to bring them to the desired cold shutdown. And it has the dangerous side effect of creating a large buildup of radioactive water in nearby groundwater and seawater.
Workers, however, can't hook up the cooling pumps now, because the turbine buildings that power the machinery are flooded. They first need to pump the water out of those turbine buildings. But they can't do that now either, because the closest place to move that water is the 'condenser unit,' so-called because during normal operations it takes the steam that runs the turbines and condenses it into water.
Those units are currently full. So the water there needs to be moved to second nearby tanks, called condensate storage tanks, located in front of the turbine buildings. When workers discovered the problem a few days ago, those tanks also had water in them. The water in those tanks needed to be drained into third tanks, called surge tanks, farther from the buildings.
2011-04-06 11:40 编辑：icetonado
TOKYO, Mar 17 （Reuters） - Japan may build robots to play the violin, run marathons and preside over weddings, but it has not deployed any of the machines to help repair its cripp