Fukushima
Daiichi
Update
By Kenji Tateiwa, Tokyo Electric Power
Company.
Kenji Tateiwa
Kenji Tateiwa is Manager of Nuclear
Power Programs at TEPCO’s
Washington Office,
where he leads
collaborative
efforts with U.S.
organizations.
Kenji received
his bachelors and
masters in nuclear
engineering from
Kyoto University.
He began his career
at TEPCO in 1996
at Fukushima
Daini NPP, then at
the headquarters,
specializing in severe
accident analysis. After receiving MBA
from Stanford, Kenji led TEPCO’s
involvement in the plan to construct 2
ABWR units at the South Texas Project
site.
Kenji has coped with the Fukushima
accident from day one, playing a key role
as liaison between TEPCO and nuclear
experts around the world.
An interview by Newal Agnihotri, Editor
of Nuclear Plant Journal, at the Nuclear
Regulatory Commission’s Regulatory
Information Conference in North
Bethesda, Maryland on March 12, 2015.
1.
What is the current status of
contaminated water?
TEPCO has been able to stably cool
the reactors of Units 1-3 by establishing
a closed-cycle water injection loop
shortly after the accident. However,
water injected into the reactors becomes
highly contaminated with radioactivity
and requires treatment by multiple
sophisticated water treatment facilities.
Contaminated water accumulating
in various buildings is first treated with
either the “Cesium adsorption apparatus
(Kurion)” or “2nd Cesium adsorption
apparatus (SARRY),” where the majority
of Cs-134 and Cs-137 are removed. Both
Kurion and SARRY systems have been
recently modified to
enable removal of
Sr-90 as well. The
second step is using
the reverse osmosis
(RO) apparatus to
remove
chloride
originating
from
sea water injection
during the early
phase of the accident
response. Desalinated
water is re-injected
to the reactor and
the RO-concentrated
water, with high
chloride
content
and radioactivity, is stored in above-
ground tanks. RO-concentrated water
is then treated with the Multi-nuclide
Removal System (ALPS: Advanced
Liquid Processing System) to remove the
remaining 62 radionuclides to below or
near detectable level (except for tritium.)
In addition to the existing ALPS, an
improved ALPS and high-performance
ALPS have been installed and are
currently operating.
In order to augment the three ALPS
systems and to reduce the risk of leakage
of RO-concentrated water, additional
systems have been deployed to remove
Sr-90, including the mobile and stationary
Sr-removal systems.
Water treated with the Sr-removal
systems will eventually be further
treated by the ALPS systems to remove
remaining radioactivity. The above
mentioned 7 water treatment systems,
or “Seven Samurai”, have contributed to
significantly reducing the risk of leakage
of contaminated water stored onsite in the
approximately 1,000 tanks.
Ingress of large volume of
groundwater into the various buildings
continues to pose grave challenges to the
water treatment system, as it increases the
amount of contaminated water that needs
to be treated and stored on site. Multiple
measures have been implemented to
reduce the amount of groundwater ingress
and the rate has gone down from 400 m
3
/
day to 300 m
3
/day.
One of the significant steps has
been the installation and operation of the
Groundwater Bypass system. We have
installed a series of groundwater bypass
wells upstream from the buildings and by
pumping up water from these wells, we
have been able to lower the groundwater
level near the buildings, thereby reducing
the volume of ingress into the buildings.
Groundwater pumped up from the bypass
wells is discharged to the sea after being
confirmed that it meets the strict water
quality standard agreed by various
stakeholders.
In addition, we have been restoring
the Subdrain system. It is comprised of
multiple wells surrounding the buildings
to pump up groundwater and a water
treatment facility to remove radioactivity
from the water. Operating the Subdrain
system will enable us to actively control
the groundwater level and thus allow
greater control of groundwater ingress.
Another major ongoing effort is
installation of the land-side impermeable
wall, or the frozen soil wall. We have been
installing freezer pipes about 100 feet
deep underground surrounding the Units
1-4 buildings with a perimeter of about
1 mile. The concept is to circulate very
cold brine (-30°C) in the freezer pipes and
freeze the soil to form an impermeable
barrier. This will stop groundwater from
entering into the buildings. Test operation
of the brine circulating system has begun
in April 2015.
Various other measures are also
being implemented to minimize the
32
NuclearPlantJournal.com Nuclear Plant Journal, May-June 2015
