Tepco reschedules water purification target

Monday, 16 March 2015

More than 90% of the contaminated water stored on the Fukushima Daiichi site will be treated by the end of May, two months later than originally planned, Tokyo Electric Power Company (Tepco) announced today.

Water storage tanks on the Fukushima Daiichi site (Image: Tepco)

Tepco said it still aims to achieve the goal of reducing the radiation dose at the site boundary attributed to the water storage tanks to below 1 millisievert per year by the end of this month. It said that meeting this target "reduces the overall risk created at the premises, something it recognizes as being very important to the site workers and people of the surrounding communities."

The company had originally planned to treat all contaminated water on the site by the end of March, but in January it announced that it would need more time. It attributed the longer time frame to the challenges of implementing new technologies to clean the water and to a "safety first" approach.

The revised scheduled now calls for most of the remaining water to be treated by the end of May. This includes water that has had strontium and other contaminants removed through the ALPS multi-nuclide removal system, as well as water that has had strontium removed but not the other contaminants. It also includes water that was processed by the ALPS systems whilst they encountered performance issues and which now needs to be treated again to further remove contaminants.

The remainder of the water is that containing relatively high levels of seawater components, such as calcium and magnesium. In the days immediately following the March 2011 accident, the damaged reactors were cooled with seawater until a freshwater system was in place. Tepco said several more months will be needed to complete the treatment of this water as it must be fed through the treatment system at a slower rate than the other types of water to ensure the strontium is removed effectively.

The company said that residual water at the bottom of storage tanks - expected to total some 20,000 tonnes - is not included in the treatment target amount. However, it will be removed and treated as each storage tank is dismantled in the future.

Tepco noted that about 300 tonnes of groundwater entering the reactor building on a daily basis, together with the roughly 100 tonnes of water drawn up from well points and transferred to the reactor buildings will continue to be treated as part of the overall process.

Tepco's chief decommissioning officer Haohiro Masuda said, "We are re-evaluating the risks of not just contaminated water, but all factors including solid waste, liquid and airborne risks. Even if some contaminated water remains, I feel that we can reduce a substantial amount of risk."

Researched and written
by World Nuclear News