The support structure for the Reactor 4 building is now just as high as the reactor building itself.
TEPCO, pressured by the government (particularly the current Abe administration officials), is making haste in building the structure so that they can start removing the fuel assemblies in the Spent Fuel Pool starting November this year.
I hate to say it but a hasty job often fails in an unexpected way. But if that happens, no government official will take responsibility anyway, TEPCO gets the blame, who in turn blames the lead subcontractor (probably Kajima), who then blames its subcontractor, who then.... (down to 7th level or so).
From TEPCO's Photos and Videos Library (3/13/2013):
(Click to enlarge)
Speaking about hasty job, all those tanks at Fukushima I Nuke Plant that contain water treated to remove radioactive cesium and other gamma nuclides but not beta (like strontium) and tritium will need extensive maintenance in about three years. Those tanks are made of steel sheets bolted together, not welded, with rubber packing. The rubber packing lasts 5 years.
Workers have been patrolling among these tanks, and tightening the bolts to prevent the leak.
TEPCO/government chose those materials and the construction method as they needed those tanks as soon as possible, back in the first several months of the accident. The plan was that the contaminated water would be all treated clean by Kurion's and AREVA's systems (which did claim to remove more than just cesium) by the end of the year (2011) and these tanks would not be needed.
With 400 tonnes of water still seeping from the ground into the turbine building basements every day, TEPCO continues to have a huge water problem.
But instead, let's worry about a potential earthquake and let's remove fuel assemblies in haste. That will show to the world how serious Japan is in dealing with the accident. (The world yawns.)