Inspectors from the U.N.'s International Atomic Energy Agency (IAEA) arrived in Japan this week to monitor the ongoing cleanup and look into the continued leaking of contaminated water at the Fukushima Daiichi nuclear power plant.
This as the Tokyo Electric Power Co. (TEPCO), the company nominally in control of the crippled facility, has again postponed the start of procedures to remove highly radioactive fuel rods from a severely damaged storage pool inside what used to be the Fukushima plant's reactor No. 4.
Three reactors at Fukushima suffered core meltdowns after a massive earthquake and tsunami compromised containment and damaged cooling systems in March 2011.
The three molten cores have now likely melted through the floors of their containment buildings and are somewhere underground, though plant and government officials have no clear picture as to exactly how deep.
At the time of the Tohoku quake, the reactor at unit 4 had been emptied for maintenance, but its active fuel and decades of older "spent" fuel rods were stored in pools of water suspended above the core, inside the reactor building.
Under normal operation, water must be kept constantly circulating through the spent fuel pools to keep the uranium and plutonium rods cool and away from contact with the air. The 2011 disaster, however, not only disabled the cooling systems, but also left the structure holding the pool dangerously weakened.
A team from the IAEA is expected to sample water from around the plant, including seawater off the Japanese coast in an attempt to better gage the level of radioactive contamination.
A series of admissions by TEPCO and the Japanese government over the summer revealed that groundwater seeping into the damaged reactor buildings and seawater being continuously dumped over the damaged reactors and spent fuel storage had been leaking into the surrounding grounds and eventually into the Pacific Ocean.
Plant officials also discovered that several of the hastily built tanks used to contain the radioactive effluent were also leaking. Leaks from the tanks were estimated at 300 metric tons in August, and an additional 300 metric tons of contaminated water were said to have been leaking from the plant into the sea every day.
In September, radiation readings around some tanks, which now number in the thousands and hold enough radioactive water to fill well over 130 Olympic-sized swimming pools, climbed to hazardous levels. All this as Japan pledged a full cleanup in advance of the 2020 Olympic Summer Games, which were awarded to Tokyo that same month.
The situation in reactor 4's spent fuel pool has troubled nuclear engineers and environmental activists since the earliest days of the crisis. Removing the large nuclear fuel rods is daunting task, as the assemblies need to remain properly spaced, cool and submerged in water to prevent the possibility of increased fission activity, overheating, melting, and possible fires — and the crane originally built for the task was destroyed in the 2011 quake.
A newly constructed gantry, built around unit 4 over the past two years, was supposed to start the slow process of transferring fuel rods out of the damaged pool on Friday, but TEPCO officials said earlier this week that the system needed more testing, and that the actual removal of spent fuel would not happen until next Friday at the earliest.
The activity around Fukushima comes as Chinese government officials appealed to the U.N. nuclear watchdog to compel Japan to provide better information on how it is handling the ongoing Fukushima disaster.
"We urge the Japanese side to spare no effort in minimizing the subsequent impact of the accident and provide timely, comprehensive and accurate information to the international community," said China's U.N. ambassador Wang Min in a debate before the IAEA.
China's criticism of Japan has grown as revelations about the leaks of contaminated water and TEPCO's inept management of the entire Fukushima crisis have mounted this year.