Tokyo Electric Power Co. (TEPCO), the Japanese utility that took on the behemoth task of controlling and decommissioning the six-unit Daiichi nuclear power plant in Fukushima prefecture after the March 11, 2011, accident, recently released a video showing progress at the site.
The disaster began as a 15-meter (49-foot) tsunami inundated and disabled the offsite power supply (12 of 13 backup generators located in the basements of the turbine buildings) of Units 1, 2, and 3 at Daiichi, interrupting critical cooling functions. The tsunami also disabled their heat exchangers and electrical switchgear. All three units consequently saw explosions that damaged their reactor buildings. It was also later established that the cores of Daiichi 1, 2, and 3 had largely melted within the first three days of the crisis.
At Unit 4, where the reactor had been shut down for periodic inspection, the nuclear fuel had been transferred to a spent fuel pool. But after the tsunami, both cooling and feedwater functions were lost, forcing crews to spray water over the pool. On March 15, the reactor building of that unit also exploded, blowing out the walls above the bottom of the operation floor. According to TEPCO’s July 18 video, “all units have been brought under control, and are being stably cooled.”