Tokyo Electric Power Co. (TEPCO) is struggling to treat a massive amount of water contaminated with radioactive substances at its crisis-stricken Fukushima No. 1 Nuclear Power Plant.
The problems stem from persistent instability in a system that went into full operation on July 2 to purify highly radioactive water and use it to cool down the plant’s reactor cores. As a result, the amount of radioactive water in the reactor buildings and other areas of the plant grounds is in fact increasing.
The water purification and recycle system must be stabilized to bring the crippled power plant under control if the evacuation orders issued in areas around the plant are to be lifted anytime soon.
“The number of technical problems has decreased, but we still can’t say operations have been stabilized,” Junichi Matsumoto, deputy head of TEPCO’s nuclear power division, told a news conference on Aug. 3.
The purification rate of the system was about 74 percent over the week ending Aug. 2 because there were no major problems. The figure is well above the 58 percent of the previous week and the 54 percent of the week before that. Still, the overall purification rate over the past month stands at about 65 percent, far below the initial goal of 90 percent and the current goal of 70 percent set in July.
Apparently because the purification system was built in a hasty manner, however, it has been plagued by a series of technical problems, including a leak of a chemical solution to remove radioactive substances from contaminated water on July 10, an automatic shutdown as a result of a power failure on July 21, and a pumping system stop on July 24.
The system’s capacity to treat contaminated water has wavered as sludge sticks to the inner walls of its some four kilometers of pipes. TEPCO is set to begin work to install a new pipe to bypass a section about 100 meters long believed to be clogged with sludge.
As the system’s efficiency remains relatively low, the amount of radioactive water at the plant has in fact been increasing gradually. As of Aug. 2, contaminated water accumulating in buildings housing the No. 1 to 4 reactors and their turbines totaled 120,770 cubic meters — 120 cubic meters more than last week.
TEPCO attributes the rise to heavy rain on July 19 and 20 brought by a typhoon, and the use of fresh water from a nearby dam when the purification system stopped.
After confirming the system’s purification rate increased over the past week, TEPCO announced on Aug. 3 that it would raise its target from 70 percent back to 90 percent.
TEPCO expects it will finish treating all contaminated water at the facility in early December if efficiency is kept at more than 70 percent, and complete the work in late November if it achieves the target rate of 90 percent.
If the operation of the water purification and recycle system is stabilized, TEPCO could achieve its goal of finishing treating the radioactive water by the end of this year. If the rate declines to the 50-percent level, completion of the work could be delayed until late January 2012 or later. (By Takuji Nakanishi and Shinji Kanto, Science and Environment News Department)