Lucas Hixson has posted a recent photo (left) at Enformable Nuclear News showing the significant change of appearance going on at Fukushima Daiichi Unit 4. Tokyo Electric Power Company is now removing large debris, such as destroyed walls, from the Unit 4 reactor building, nearly 16 months after a hydrogen explosion severely damaged it.
The yellow vessel is the visible portion of the primary radiological containment structure surrounding the reactor pressure vessel, which fortunately had been defueled and was not operational on March 11, 2011.
However, the high-level radioactive waste storage pool, located under the green-colored crane structure, is still of global concern. The pool holds 1,331 irradiated nuclear fuel assemblies. It remains vulnerable to a cooling water drain down, due to a large earthquake, setting the high-level radioactive waste on fire. A slow motion cooling water "boil down" could lead to the same catastrophic radioactivity release, if cooling systems are disrupted for a long enough period of time, even from simple mechanical breakdown, as have occurred repeatedly over the months.