THE DISCHARGE OFALPS TREATED WATER:ENSURING SAFETY AND PAVING THE WAY
TOWARD DECOMMISSIONING

At Tokyo Electric Power Company Holdings’ Fukushima Daiichi Nuclear Power Station, where efforts for decommissioning
and reconstruction have been underway ever since the accident caused by the Great East Japan Earthquake of March 11,
2011, the discharge of “ALPS treated water” into the sea started in August 2023. The process is being undertaken with safety
as the top priority, under strict safety management and in partnership with third-party organizations. Why is the discharge
taking place, and what future is envisioned beyond it?
Since the accident at Tokyo
Electric Power Company Holdings’
Fukushima Daiichi Nuclear PowerStation (NPS), which occurredshortly after the Great East Japan
Earthquake struck the area on
March 11, 2011, the company has
been advancing decommissioning
work to reduce the risk fromradioactive materials to local
people and the environment. Suchefforts are now reaching a major
turning point. Concentrationsof radioactive materials inthe surrounding sea area havesufficiently decreased, and so havethe radiation levels measured
at monitoring posts at the siteThe discharge of ALPS treated water into the sea
has begun at Tokyo Electric Power Company
Holdings’ Fukushima Daiichi Nuclear Power
Station (center). Decommissioning work has been
conducted carefully, with safety as the top priority.
THE ASAHI SHIMBUN COMPANY/JIJI PRESS PHOTO

boundary. Although at the timeof the accident it was impossible
to enter the site without wearing
protective clothes, workers can
now wear regular work clothes inabout 96% of the area.
“The major challenge from now
on will be the retrieval of ‘fueldebris,’ which is a mixture of melted
fuel inside the reactor and reactor
materials that have solidified,” says
Professor OKAMOTO Koji of theGraduate School of Engineering,
the University of Tokyo, who
has been involved from the startin the decommissioning process.
Fuel debris retrieval is one of themost difficult challenges duringthat process, but according to
the professor, “it is necessary to
overcome this challenge in orderfor decommissioning to proceedfurther.”An essential step in taking on
this difficult task is the dischargeof ALPS treated water into the sea,
which began in August 2023. Thisis water that contains radioactive
materials from inside the buildingsof Fukushima Daiichi NPS, andhas been purified and treated by
the Advanced Liquid Processing
System (ALPS) until it satisfies
safety standards for all radioactive
materials other than tritium.
The tanks for storing ALPS
treated water on the site are large
and their number is increasing,already exceeding a thousand. Inorder to safely proceed with thedecommissioning work, the space
occupied by the tanks is needed forthe construction of new facilities.
It thus became necessary todischarge the water and reduce thenumber of tanks.
The ALPS treated water isdischarged under strict safety
management and monitoring. Allradioactive materials are removed
by ALPS to meet the regulatory
standards, with the exceptionof tritium. And for the level oftritium to also fully satisfy safety
standards, the water is diluted withseawater before discharge to reduce
the tritium concentration to under
1,500 Becquerels/L, which isapproximately one-seventh of
the World Health Organization(WHO) standards for drinking
water.
“Japan has made a huge effort
to ensure that radiation doses forpeople and the environment areextremely low,” says Jim Smith, aprofessor of environmental scienceat the University of Portsmouth inEngland, who studies the effectsof radioactive materials on theenvironment and people. “Therelease will be conducted over
30 years, which is much longer
than would strictly be needed tomeet safety standards. This meansthat annual radiation doses topeople and the environment arevanishingly small.”In addition to thoroughconfirmation prior to dischargethat the ALPS treated watersatisfies the discharge limit, theconcentration of tritium andother nuclides in the surrounding
seawater and marine products aremonitored both before and after
the start of the discharge, with theresults posted on the Internet.*
To further ensure transparency,
the International Atomic Energy

Left: On August 22,
2023, IAEA personnel
witnessed the sampling ofwater treated by ALPS
and diluted with seawater,prior to its first discharge
at the Fukushima Daiichi
NPS. In July, the IAEA
released a comprehensive
report on the safety
review of the ALPS
treated water, concludingthat Japan’s approach andactivities regarding thedischarge of the water into the sea are “consistent withrelevant international safety standards,” and that thedischarge “will have a negligible radiological impact onpeople and the environment.” TEPCO/AFP/AFLO
Right: Professor Jim Smith of the University of Portsmouth,
England, is an environmental scientist who has long studied
the impacts of the nuclear accidents at Chernobyl andFukushima on people and the environment. SAM SHAW

Top: Storage tanks containing ALPS treatedwater line the grounds of the Fukushima
Daiichi NPS. Reducing the number of tanks bydischarging the water into the sea will make itpossible to build the facilities needed forfurther decommissioning work. JIJI
Bottom: Professor OKAMOTO Koji has held
his post at the Graduate School of Engineering,
the University of Tokyo, since 2004. While
conducting research on decommissioning, heregularly visits the Fukushima Daiichi NPS,
and discusses and advises on issues faced in thefield. Since 2018, he has concurrently been
serving as the Director General of theCollaborative Laboratories for Advanced
Decommissioning Science of the Japan Atomic
Energy Agency.

Agency (IAEA) has been and will
be conducting monitoring—inaddition to setting up an office inthe Fukushima Daiichi NPS areawith personnel on site—and willcontinue to review the safety of thedischarge.
Under this system, the firstdischarge of about 7,800 m3 ofwater was fully implemented from
August 24 to September 11, 2023.
Tritium concentrations confirmed
by monitoring were well below theregulatory standard. “The fact thatthe discharge was carried out safely
is a very big step forward in termsof paving the way to fuel debris
retrieval,” says Okamoto. To protect
people and the environment, Japan
will progress, step by step, with thedischarge of ALPS treated waterand decommissioning efforts, withsafety as the top priority.

*For detailed information on the monitoring of ALPS treated water
Fisheries Agency (https://www.jfa.maff.go.jp/e/inspection/index.html)
Ministry of the Environment (https://shorisui-monitoring.env.go.jp/en/)
Nuclear Regulation Authority (https://radioactivity.nra.go.jp/en/list/309/list-1.html)
Ministry of Economy, Trade and Industry (https://www.meti.go.jp/earthquake/nuclear/hairo_osensui/english/shirou_alps/monitoring/)