On March 11, 2011 Japan suffered its worse earthquake ever, registering 9.0 on the Richter scale. This was followed by a tremendous tsunami that reached over 40 meters in height and lasted for more than six minutes.
The tsunami caused devastating damage, including the loss of 19,000 lives, 120,000 buildings totally destroyed and another 1,000,000 buildings partially damaged. The damage is estimated at $235 billion, making it the most expensive natural disaster in the history of the world. 
Damage at the Fukushima Daiichi and Daini Power Plants
The earthquake and tsunami not only damaged apartment dwellings and industrial buildings in the Northeast of Japan. Due to insufficient preparations on the part of the Tokyo Electric Power Company (TEPCO), there was also devastating damage to the Fukushima Daiichi power plant. The incident was given a rating of 7, the most severe on the International Nuclear Event Scale (INES).
The INES scale has existed since 1990. They rate non-military nuclear mishaps on a scale of 1 for a minor anomaly to 7 for a major accident. Similar to the Richter scale, every level is approximately 10 times more severe than the previous level. To put things in proportion, the accident at Three Mile Island in 1979 was rated 5 on the INES scale, while the only other accident with a rating of 7 was the Chernobyl meltdown in 1986. 
The first day of the tsunami three out of six nuclear cores melted down and, after five days, a fourth core melted down.  The Daini power plant, 10 kilometers south of Daiichi, shut down automatically when the tsunami hit and, despite the fact that there was no meltdown, to date the facility is still closed. 
Cooling Down the Reactors
Almost immediately fresh water and sea water started to be injected into the reactors. Unfortunately the water injection systems, as well as the backup systems, stopped working after three days
A few hours after the backup system broke down, water was being pumped again into the reactors, but steam had built up and wreaked havoc in all of the nuclear units. An estimated 40% of the water boiled off, while the rest leaked out of the bottom. 
A Million Tons of Radioactive Water
In order to keep the radioactive water that leaked to the bottom of the reactor from seeping into the ground or the Pacific Ocean, TEPCO filtered the water as best it could and pumped it all into 7-foot-high water silos. There are hundreds of these silos filled with contaminated water. It is an undisputed fact that these storage facilities will not last forever and there are different thoughts as what to do with the contaminated water.
Companies such as Veolia Nuclear Solutions claim that they can purify the radioactive water, but TEPCO is not willing to cover the multi-billion-dollar cost.
Dale Klein, the former head of the Nuclear Regulatory Commission, believes that the radiation in the water in the tanks is now low enough to allow TEPCO to further dilute the contents and release them gradually into the Pacific Ocean without causing any further damage to the environment. He went on to say that it is better to have a controlled released of the contaminated water than an accident that would spill all of the water directly into the ocean. 
The Final Note
It has been very difficult to convince the Japanese that the best solution is a controlled pumping of the water into the Pacific Ocean. The people no longer trust TEPCO, and those whose livelihoods depend on a pollution free ocean such as the fishing and tourist industries have been actively opposed to emptying the silos into the ocean. There have also been official objections from China, Korea, and Taiwan.
In the meantime TEPCO has made some efforts to contain the radioactive water such as the installation in 2016 of a subterranean “ice wall”, a $300,000,000 project involving cooling rods to contain the leaking water. However, a long-term plan to completely solve the problem is needed, sooner rather than later.
 Becky Oskin, Japan Earthquake and Tsunami of 2011: Facts and Information, September 13, 2017
 The Guardian, Nuclear Power Plant Accidents, October 9, 2015
 Mari Yamaguchi Japan Utility agrees nuclear crisis was avoidable, October 12, 2012
 Ranjay Gulati, How the other Fukushima Plant Survived, July, 2014
 World Nuclear Organization, Fukushima Accident, June, 2018
 Vince Beiser, Fukushima’s Other Big Problem: A Million Tons of Radioactive Water, April 27, 2018