Measures for Contaminated Water at Fukushima Daiichi Nuclear Power Station
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Timescale
At the Fukushima Daiichi Nuclear Power Station operated by TEPCO, the Tokyo Electric Power Co., the problem of contaminated water has been a concern since soon after the earthquake and tsunami of March 11, 2011. On April 2, 2011, highly irradiated water was found flowing into the sea from cracks in the concrete near the intake port of the Unit 2 reactor. This was the first leak to be discovered.
In April 2013, leaks were detected from underground tanks for storage of water that had been contaminated through use in cooling the damaged reactor cores. In July, it was confirmed that some 300 tons of underground water, which included contaminated water, were flowing into the sea every day. In August, it was discovered that some 300 tons of contaminated water had leaked from a water storage tank above ground.
TEPCO has taken a purely responsive approach to all the problems that have occurred, which has only exacerbated the situation. On August 21, 2013, Japan’s Nuclear Regulation Authority categorized the leakage of contaminated water as level 3 (a “serious incident”) on the International Nuclear and Radiological Event Scale. Concerned that the situation was impacting the global community’s confidence in Japan, on September 3 the Japanese government announced the formulation of a basic policy for measures to deal with the contaminated water and integrated countermeasures. Prime Minister Abe Shinzō declared that the government “will not leave it up to TEPCO, but will stand at the forefront and resolve the issue,” and his government has embarked on full-scale measures to tackle the problem.
Grey: Events that occurred or were detected
Blue: TEPCO responses
Yellow: Government’s responses
| Date | Event |
|---|---|
| 2011 | |
| March 11 | Earthquake strikes. Unit 1, 2, and 3 reactors shut down automatically. Emergency core cooling systems of Unit 1 and 2 reactors taken offline by the tsunami. |
| March 12 | Hydrogen explosion in Unit 1, blowing off top part of building. Seawater injection into Unit 1 commences. |
| March 13 | Supply of cooling water stops in Unit 3 reactor following battery failure. |
| March 14 | Hydrogen explosion at Unit 3 destroys the upper part of the reactor building. In Unit 2, fuel rods are completely exposed above water. |
| March 15 | An explosion is heard from Unit 2. Fire breaks out in the spent fuel pool in Unit 4. |
| March 17 | Two Ground Self-Defense Force helicopters drop 7.5 tons of water on Unit 3. Self-Defense Force fire trucks pump water into the reactors from ground level. |
| March 24 | Three workers suffer radiation exposure when they step in puddles of water that have accumulated in the Unit 3 reactor building. |
| March 27 | Water containing radioactive material detected in maintenance tunnels of Units 1, 2, and 3. |
| April 2 | Highly radioactive water is discovered to have leaked into the ocean from cracks in the Unit 2 reactor. |
| April 4 | Water contaminated with low levels of radiation is released into the sea around the power station for the first time. |
| April 5 | Announcement that radioactive iodine at 7.5 million times Japan’s legal limit and radioactive cesium at 2.0 million times the legal limit have been detected in seawater near Unit 2. |
| April 6 | Radioactive water leak into the sea from the Unit 2 reactor is blocked by pouring a fast-hardening glassy liquid containing sodium silicate into the cracks in the reactor. |
| April 14 | Installation of silt fences to partition seawater near intake port completed. |
| April 17 | Work schedule for resolution of accident announced. |
| April 18 | Transfer of highly contaminated water from pools in Unit 2 reactor building basement and maintenance tunnels commences. |
| May 11 | Highly radioactive water is found to have leaked into the ocean from the intake port near the Unit 3 reactor. |
| June 17 | Revised schedule announced for bringing the nuclear disaster under control. The “Mid- and Long-Term Roadmap” future challenges include installation of impermeable walls. |
| August 1 | Announcement that construction of seaward impermeable walls will commence before landward walls. Completion scheduled for September 2014. |
| October 26 | Postponement announced of installation of landward impermeable walls. |
| December 16 | Prime Minister Noda Yoshihiko announces state of cold shutdown; states that the accident itself has been resolved. |
| 2013 | |
| March 30 | Multi nuclide removal equipment ALPS begins trial operations (operations suspended in June due to problems). |
| April 5 | Leak of contaminated water discovered from an underground storage tank. |
| April 16 | Transfer of contaminated water to aboveground tanks commences (completed on June 9). |
| April 26 | Ministry of Economy, Trade, and Industry Committee on Countermeasures for Contaminated Water Treatment commences examination. |
| May 30 | METI committee coordinates policy for installation of landward impermeable walls using frozen soil method. |
| June 19 | Detection of high concentration of tritium and strontium in underground water to the east of Units 1 and 2 turbine housings announced. Possibility of leakage into sea denied. |
| July 10 | Nuclear Regulation Authority says diffusion into ocean is strongly suspected. |
| July 22 | Previous denial reversed; admission of flow of underground water including contaminated water into open channels (the sea). |
| August 2 | First meeting of NRA contaminated water countermeasures working group. |
| August 7 | Agency for Natural Resources and Energy publishes results of calculations, finding that approx. 1,000 tons/day of underground water flow into Units 1–4, of which approx. 400 tons enter reactor buildings. Of the remaining 600 tons, 300 tons come into contact with sources of contamination in trenches and are discharged into the sea as contaminated water. |
| August 19 | Discovery of puddles believed to be water that has leaked from aboveground storage tank. |
| NRA gives water leak a provisional INES rating of level 1. | |
| August 20 | Amount of water leaked from aboveground tank announced to be 300 tons. |
| August 21 | Announcement of 6 millisievert/hour radioactivity detected in ditch near the leaking tank. “Undeniable possibility that contaminated water has flowed into the sea” admitted. Preliminary calculations show that a cumulative total of up to 10 trillion becquerels of strontium have flowed into the sea with underground water. |
| NRA discusses raising evaluation of contaminated water leak to INES level 3. | |
| August 22 | Pumping highly contaminated water out of trenches commences. |
| September 3 | Nuclear Emergency Response Headquarters determines basic policy for contaminated water countermeasures and overall measures. Prime Minister Abe announces policy that the government “will not leave it up to TEPCO, but will stand at the forefront and resolve the issue”; establishes a council of relevant ministers and unveils economic package worth ¥47 billion. |
| September 7 | Prime Minister Abe declares to International Olympic Committee general meeting that the situation at Fukushima is “under control.” Contaminated water measures now an international commitment. |
| September 18 | NRA commences measurements of concentration of radioactive cesium on ocean floor off Fukushima. |
| September 25 | Testing of fish caught in trawl nets off Fukushima resumes. |
| September 27 | ALPS 1 system commences trial operations (trials of 3 systems to be carried out by November). |
| The Diet’s House of Representatives Economy, Trade, and Industry Committee holds a meeting while the Diet is not in session to tackle the problem of contaminated water. | |
Three Principles for Contamination Countermeasures
- Remove the sources of contamination
- Isolate ground water from the contamination sources
- Prevent leakages of contaminated water
Emergency Measures
- Start removal of highly contaminated water from trenches (underground spaces for pipes and electric cables) (starting August 22, 2013)
- Firm up ground in the contaminated area with liquid glass (partially completed August 9, 2013), pave ground surface with asphalt, etc. (starting sequentially from October 2013), pump out ground water (starting August 9, 2013)
- Pump out underground water from mountainside (underground water bypass) (installation completed March 2013; work commencement currently being scheduled)
Drastic Measures (Over the Coming 1–2 Years)
- Pump out underground water using subdrains (wells near buildings) (installation scheduled for completion around September 2014)
- Install seaward impermeable wall (at present, installation is partially complete; scheduled for completion in September 2014)
- Install landward impermeable wall using frozen soil method (operation aimed to start during fiscal 2014)
- Provide equipment for cleaning up highly contaminated water with greater treatment efficiency
(Banner photo courtesy of TEPCO.)
Fukushima Daiichi Nuclear Power Plant contaminated water radioactive material