March 2016

Fukushima Daiichi nuclear accidentManagement of radioactive water from the damaged
reactors
Situation in March 2016
This document is based on publicly available information on the situation of the Fukushima Daiichi plant.

I.

Background: accumulation and continuous inflow of water into thebuildings

During the accident that affected the Fukushima Daiichi nuclear plant on the 11 th of March 2011, thenatural phenomena that caused it resulted in the flooding of the site, generating an accumulation ofwater in the basements of the power plant buildings.
In addition, since the accident, water injected for cooling the damaged cores of the reactors has
been flowing into the basements of the buildings, from where it is pumped to cool the reactors again,
after treatment; Currently, around 325 m3 of water flow daily into the basements. This water flows
into the primary and containment vessels and cools the core. It becomes radioactive by dragging inparticular the most mobile elements in the corium. In this regard, while uranium and the transuranicelements are not very soluble, some fission or activation products are more readily dispersible inwater (caesium, strontium, antimony, tritium, etc.).
TEPCO has thus found an activity of the order of several GBq/m3 or tens of GBq/m3 for caesium in thewater accumulated in the basements of the "turbine" buildings. The dose rates in some of thebuilding basements, due particularly to the presence of radioactive water, but also to the reactor
circuits located there, can reach a Gray per hour.
Furthermore, the groundwater seeps into the basements increasing the volume of water present (thewater inflow is estimated at about 200 m3 per day). TEPCO indeed keeps the water level in thepremises lower than that of the groundwater, thereby limiting the transfer of radioactivity, but also
promoting the inflow of water.
Given that the water contained in the basements of buildings is radioactive and that the volumes
being added daily are very significant, in the first weeks following the accident their treatment
and storage seemed to be important challenges for resuming control of the facilities, in order tocontrol the releases into the environment.
The accumulated volumes (storage tanks and basements of buildings) have now reached nearly
900 000 m3.

II.

Treatment of radioactive water

Water treatment has two objectives: desalination and removal of radionuclides.
Water desalination is necessary, particularly to limit corrosion phenomena: in addition to seawaterfrom the wave that submerged the site at the time of the accident, TEPCO also injected seawater
into the reactors to cool them in the days following the accident. Reverse osmosis and evaporation
processes were quickly developed and implemented a few months after the March 2011 accident.
TEPCO also desalted the water of the spent fuel pools in which it had also injected seawater.

1/4Furthermore, TEPCO quickly implemented several radionuclide removal systems: three devices
were operational a few months after the accident in March 2011. One of them is no longer usedbecause it generated a large volume of radioactive sludge. The two remaining systems only allow apartial removal of the radionuclides contained in the treated water, essentially caesium. TEPCO
gradually added strontium processing modules to them.
TEPCO has also developed a system for a more complete treatment, which it calls "multi-nuclide
removal equipment" or "advanced liquid processing system” (ALPS). This system consists of threesubsystems with a capacity for treating 250 m3/day. Tests in actual configurations were carried out
during the second quarter of 2013 and the system proved to be very efficient in decontaminating for
all radionuclides present in the water except for tritium. Indeed, to date no industrial means capableof extracting tritium from the water exists. After having encountered various problems during thetesting phases, the ALPS entered its industrial operation phase in November 2013.
TEPCO strengthened its water treatment capacity with the construction, during 2014, of a second
similar ALPS unit and a "high performance" ALPS unit equipped with a line allowing the treatment of
500 m3/day.
In addition, to treat the water already stored, TEPCO has deployed two new mobile strontium
treatment systems, called "Kurion Mobile Processing Systems" (KMPS), with a processing capacity of
300 m3/day, which were commissioned in October 2014 and in February 2015.
It should be noted that TEPCO also set up a system for the treatment of the groundwater after it ispumped1 and before its release: this system has two lines with a capacity to process 1 200 m3/day.
The year 2015 was a major milestone for TEPCO in terms of water decontamination. Since May 2015,
all of the water stored has undergone treatment, either complete by one of ALPS systems (around
600 000 m3 of water stored to date), or to remove caesium and strontium before future complete
treatment (around 150 000 m3 of water stored to date)2.
The waste from the treatment processes (resins, zeolites, etc.) have led to the filling of nearly
3 000 containers of radioactive waste, which are stored at the site.
The figure below gives an overall view of the treatment chain for the water from the FukushimaDaiichi
reactorbuildings
afterthecommissioningofallofthesystems.

Source TEPCO – General path of the water accumulated at Fukushima Daiichi
1

See the information note regarding the site groundwater for the objectives of this pumping.
Only a few thousand m3 of water pass, without having undergone complete treatment, into buffer tanks prior to theirinjection into the reactors.
2

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III.

Water Storage

Water treatment is only a first step towards managing the water accumulated on the site. Indeed,
it is necessary for TEPCO to obtain authorisations for the release of treated water still containing
residual radioactivity (mainly tritium).
In the meantime, TEPCO should store ever increasing volumes of water. The combined current
storage capacity is now about 1 000 000 m3.
In order to meet the growing need for storage capacity, TEPCO has implemented all types of storage:
vertical tanks with bolted flanges, welded horizontal or vertical tanks, welded cubic tanks,
underground tanks, etc., on available land within the perimeter of site. Since 2013 it has also mademany improvements to the radioactive water storage means and conditions by learning from various
events of varying importance.
These events had multiple origins, due both to the design of the first equipment used (leaks in theflanged tanks, valve failure, overflows, etc.) and to the work being performed at locations that wereprepared in an emergency (lack of retention, soil settlement, lack of isolation of the rainwatercollection network, etc.).
TEPCO now prefers the construction of welded tanks and has begun the gradual dismantling of tanks
assembled with bolted flanges. It has also initiated a vast retention area renovation and improvement
programme.
These developments, combined with the tightening of surveillance, have significantly improved
the site water storage management.

Source TEPCO – 1) cubic welded tanks – 2) vertical tanks assembled with bolted flanges and welded horizontal
tanks – 3) welded vertical tanks – 4) underground tank

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Source Google - Storage areas of the water accumulated at Fukushima Daiichi

In conclusion, the storage of contaminated water remains an important issue for TEPCO, sinceTEPCO should rapidly increase its storage capacities while simultaneously achieving the complete
treatment of the stored water. This topic will remain an important challenge, until TEPCO is able
to release the treated water. However, the very drastic reduction of the radioactivity containedin the water thanks to the treatments carried out, combined with improved storage facilities(tank design, retention barriers, monitoring) allow better management of this water.
Furthermore, their treatment generates large volumes of secondary waste in addition to thosegenerated by the storage of rubble or the dismantling of the damaged facilities. The operational
management of such waste on the site is an important challenge, both in terms of safe
sustainable storage and of further processing.

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