Report on “Radiation Disaster Recovery Studies”
Course : Radioactivity Environmental Protection
Name : Herry Wijayanto○ Regarding“Radiation Disaster Recovery Studies”
On March 11, 2011, the strongest earthquake ever recorded in Japan occurred in PacificOcean, east of Tohoku Region. Immediately after the earthquake, a powerful tsunami came andcaused flooding in the emergency power supplies of the Fukushima Daiichi Nuclear Power Plant(FDNPP) facing the Pacific Ocean. It led to cooling system interruption which induced the nuclear
reactors to melt followed by the release of large amounts of radioactive substances into theenvironment. Consequently, more than 70% of municipalities in Fukushima Prefecture were
designated as high-level radiation areas.1,2
In order to reduce the impact of high radiation levels on human health, Japanese government
had been implemented decontamination work since the enactment of Special Measures Act inJanuary 2012 regarding the handling of contaminated areas.3 Decontamination work that includes
removal of radioactive topsoil, grass, branches, leaves, etc. was completed on March 19, 2018.1
Therefore, the radiation dose level in Fukushima Prefecture has been decreasing significantly due todecontamination efforts as well as natural dispersion. Accordingly, as of April 1st, 2017, mostevacuation orders had been lifted and the residents had been able to return to their hometowns,
except the Difficult-to-Return Zones (DRZ) where the annual cumulative radiation doses are over 50
mSv, which covered southern part of Iitate Village, northeast part of Katsurao Village, Namie Town,
Okuma Town, Futaba Town, and some part of Tomioka Town.4
The most recent news informed that finally for the first time, partial evacuation order has
been lifted in Futaba town (DRZ) on August 30, 2022—11 years since the accident, particularly 5.55
km2 of area surrounding Futaba Station.5 Even though the residents have been allowed to come back,however, more than 80% of the town is still considered as DRZ. In addition, many residents arereluctant to return home. A survey conducted by Reconstruction Agency in 2021 showed that only
11.3% of residents wanted to return, while 60.5% of them decided not to return. The remaining
residents (24.8%) had not yet decided.6 It is because former residents have already found jobs andrestarted new lives in other cities in Japan. Another reason is that the current situation in Futaba
town is still lack of employment and poor facilities such as schools, shops, hospitals or other publicservices. The similar condition also happened in Katsurao Village although evacuation order has been
lifted on June 12, 2022. In fact, previous studies revealed that public anxiety (self-stigma) about
health effects of radiation exposure when living in the ex-radioactive contaminated area is also
inhibiting factor for residents to come back.7,8 It seems the residents are pessimistic as well as
traumatic about the future of their hometowns.
1Indeed, Japan has advanced technology and financial capability to clean up radiationaffected areas quickly, nevertheless, the social problems faced by residents are very complex and moredifficult to recover. In other words, it should be realized that there are "tangible" and "intangible"
problems as the result of nuclear disaster. Contaminated land due to radioactive pollution is one of
the tangible problems, but intangible problem like distrust and psychological issues is prolongedproblems. For that reason, it is important to pay more attention to the social problem treatment by,for example, giving them more empathy and intense public consultation.
On the other hand, however, decontamination work produces high amount of radioactive
contaminated waste. Basically, there are two kinds of waste: combustible (leaves, grass, branches,trees, etc.) and non-combustible which is cesium-contaminated soil. The combustible materials canbe burned to reduce its volume, then the ash will be stored at waste storage facility at the Interim
Storage Facility (ISF).1 But, soil is difficult to be burned for volume reduction. Moreover, the volumeof soil being stored in ISF is approximately 14 million m3 (equivalent to 11 times Tokyo Dome)acquiring 1,600 ha of land area.1To reduce the amount of contaminated soil in final disposal after 30 years of storing at ISF,
the government actively proposes soil recycling.1 The soil containing less than 8,000 Bq/kg can beused for embankment materials for roads, and other building levees, not only in Fukushima but allover Japan. However, this project faced protests from residents who doubted its safety level, especially
its effects of radiation on health.9 Meanwhile, according to survey of nation’s prefectural governors(except Fukushima Prefecture), 7 governors opposed or rejected the use of radioactive soil, whileothers decided not to answer.10
In terms of storage space and cost saving, soil washing treatment can be considered as oneof the possible choices to reduce soil volume that is stored at ISF, including supporting government
projects about soil recycling by decreasing radiation levels in soil. In my research, I conducted very
basic experiment about cesium desorption using cationic surfactant from clays and clay minerals of
the soil by analyzing Cs desorption efficiency and its mechanism involved. The results obtained fromthis study hopefully afford new insights for surfactant selection in the washing remediation
technology of cesium-contaminated clays and clay minerals including soil.
References
1

Ministry of the Environment, Japan. Off-Site Environmental Remediation in Affected Areas inJapan. August 2020.
2

NHK News. 2022. Contaminated soil piles up in vast Fukushima cleanup project.
https://www3.nhk.or.jp/nhkworld/en/news/backstories/1942/

3Ozawa, S. 2021. Progress on Off-Site Cleanup Efforts in Fukushima. Originally published in
Journal of the Atomic Energy Society of Japan, 2015, 57 (6), 399-402 in Japanese.

4

Fukushima Prefectural Government. 2019. Transition of evacuation designated zones.
https://www.pref.fukushima.lg.jp/site/portal-english/en03-08.html
25

The Japan Times. 2022. Evacuation order finally lifted for Fukushima nuclear plant town.
https://www.japantimes.co.jp/news/2022/08/30/national/futaba-evacuation-order/

6

The Japan Times. 2022. Fukushima town ready to lift evacuation order but only 10% ofresidents wish to return. https://www.japantimes.co.jp/news/2022/07/27/national/fukushimatown-residents-not-returning/
7

Matsunaga, H., Orita, M., Iyama, K., Sato, N., Aso, S., Tateishi, F., Yasuyuki T., Kudo, T.,
Yamashita, S., and Takamura, N. J. Radiat. Res., 2019, 60 (1), 51-58.

8Orita, M., Hayashida, N., Nakayama, Y., Shinkawa, T., Urata, H., Fukushima, Y., Endo, Y.,
Yamashita, S., and Takamura, N. PLoS ONE, 2015, 10 (6), e0129227.

9NHKNews.

2019.

DisposingofFukushima’s

contaminatedsoil.

https://www3.nhk.or.jp/nhkworld/en/news/backstories/399/
10The Asahi Shimbun. 2021. Survey: Not a single prefecture backs reuse of radioactive soil.
https://www.asahi.com/ajw/articles/14311546○ Title of Doctoral Thesis
Cationic surfactant for remediation of 137Cs-contaminated soil and the influence of its headgroup structure on the Cs desorption from clays and clay minerals○ Summary of Doctoral Thesis
Substantial amounts of radionuclides released following the 2011 Fukushima Daiichi
Nuclear Power Plant accident have contaminated lands in the Fukushima area of Japan. Of theradionuclides found in Fukushima soil, radioactive cesium (137Cs) is still of major concern because of
its long half-life (t1/2 = 30.1 years), consequently, being major contributor to public health impact oflong-term effect. Particularly, deposited 137Cs in the soil takes part in the internal exposure whencrops cultivated from contaminated land are consumed. It has been observed that Cs ions are strongly
bonded to clay minerals of the Fukushima soil, causing their retention in the upper 5-cm soil layer.1

Hydrophilic part(head group)

Hydrophobic part(chain group)3

Fig. 1. Structure of (a) benzyldodecyldimethylammonium bromide (BDAB) and (b)dodecyltrimethylammonium bromide (DTAB)
Cs was mainly adsorbed to micaceous clay minerals1 and probably also presented inkaolinite-, and smectite-like clay minerals.2 In order to overcome the issues, soil remediation strategy
is necessary both to reduce radiation effect on public health and to recover the land. The soil washingmethod by cationic surfactants (R–N(CH3)3+; R=long hydrocarbon chain group; N(CH3)3+ = headgroup) has been widely used as desorption agent (desorbent) to effectively desorb Cs from clay
minerals via ion exchange between positively charged amine groups with Cs ions. Moreover, thelength of their hydrocarbon chain group plays essential role in enhancing Cs desorption. The longer
the surfactant chain length, the more Cs were released from kaolinite due to the stronger affinity oflonger chain with kaolinite surfaces.3 In the case of montmorillonite, a longer hydrocarbon chain
increased its interlayer distance, therefore enhancing Cs desorption efficiency.4 Although theinfluence of different surfactant chain lengths on the Cs desorption from clay minerals has beenstudied extensively, the contribution of their head group to such desorption mechanism has not been
well understood. This study aims to examine the effectiveness of cationic surfactant ofbenzyldodecyldimethylammonium bromide (BDAB) to desorb Cs from actual 137Cs-contaminated soil
taken from Fukushima Prefecture and to investigate the influence of cationic surfactant head groupon the desorption of Cs from specific clays and clay minerals by comparing two kinds of surfactants
having the same 12 hydrocarbon chain lengths but different head group types. In this case, BDAB
which has bulky head group was compared to dodecyltrimethylammonium bromide (DTAB) withlinear structure (Fig. 1). The clays used in this study included Na- and Ca-bentonite, which are
dominantly composed of montmorillonite. Clay minerals such as kaolinite and illite were also used.
To examine the effectiveness of cationic surfactant for soil remediation, first we compared
BDAB with hydrochloric acid (HCl; strong acid), the commonly used desorbent in the soil washingmethod.

Theexperimental

results

indicatedthatcationicsurfactant

ofbenzyldimethyldodecylammonium bromide (BDAB) was more effective in desorbing 137Cs fromcontaminated soil of Fukushima even by using a low concentration in comparison to HCl. It should
be noted that performance of desorbents for soil remediation depends on contaminants and soil
characteristics, including the content of clay minerals, the content of other metals in soil, organic
matters, etc.5
Therefore, in the next experiment, we used specific clays and clay minerals to investigate theinfluence of cationic surfactant head group on the Cs desorption. Clays and clay minerals samples
were initially contaminated by Cs solution with maximum adsorption capacity, followed by desorption
experiment using desorbents. Batch desorption experiment indicated that, in general, desorption
efficiency for all studied samples increased by increasing surfactants concentration. In swelling
bentonites that highly contain montmorillonite, Cs desorption was accompanied by interlayers’
4expansion. In the case of Na-bentonite, BDAB showed higher Cs desorption efficiency than DTAB due
to larger Na-bentonite interlayers expansion after intercalation of BDAB (bulkier ammonium headgroup structure). In contrast, Cs desorption efficiency from Ca-bentonite was relatively similar, whichcorresponded to the identical interlayers’ expansion after intercalation of both surfactants. It wasbecause divalent cation of Ca2+ must associate with two negatively charged interlayers, limiting
interlayer expansion of Ca-bentonite. Cs desorption from kaolinite was more governed by surfactant
micelles. In comparison to surfactant ions, surfactant micelles had a stronger affinity to the clay
surface, enhancing Cs desorption efficiency.

Fig. 2 shows that as the surfactant micelle formed

earlier for BDAB, a faster Cs desorption was achieved. Thus, BDAB desorbed Cs more efficiently than
DTAB due to formation of surfactant micelle at low concentration in BDAB solution. Fig. 3 displays
possible mechanism of Cs desorption from kaolinite based on surfactant micelles formation. For Cs
desorption from illite, both surfactants even showed relatively similar performance with HCl used asa desorbent control. This was due to the existence of frayed edge sites in illite, which provokes strong
cesium retention. Desorption kinetic model of pseudo-second order fitted well to all studied samples
by BDAB and DTAB suggested that desorption process was ion-exchange process.

Fig. 2. Cs desorption from kaolinite

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(b) Slightly below CMC(a) Far below CMC

Cs+

Cs+

Cs+Cs+Cs+Cs+Cs+ Cs+ Cs+ Cs+ Cs+

TT

𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿OOTT𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿OO(c) At/slightly above CMC

Cs+ Cs+ Cs+

𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿-𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿-(d) Far above CMC+Cs+ Cs

Cs+Cs++Cs+ Cs

Cs+Cs+TO
TO

Cs+Cs+Cs+Cs+ Cs+

T

𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿-OT

𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿-OCs+

𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿-𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿- 𝛿-Fig. 3. Schematic diagram of Cs desorption from kaolinite based on micellar formation
References
1

H. Mukai, T. Hatta, H. Kitazawa, H. Yamada, T. Yaita and T. Kogure, Environ. Sci. Technol., 2014,48, 13053–13059.

2

N. Kozai, T. Ohnuki, M. Arisaka, M. Watanabe, F. Sakamoto, S. Yamasaki and M. Jiang, J. Nucl.

Sci. Technol., 2012, 49, 473–478.
3

C. Willms, Z. Li, L. Allen and C. V. Evans, Appl. Clay Sci., 2004, 25, 125–133.

4

B. H. Kim, C. W. Park, H.-M. Yang, B.-K. Seo, S.-J. Park and K.-W. Lee, J. Nucl. Fuel Cycle Waste

Technol., 2017, 15, 27–34.
5

S. M. Park, J. G. Kim, H. Bin Kim, Y. H. Kim and K. Baek, Environ. Geochem. Health, 2021, 43,3263–3272.

○ Other theses published in academic research journals
1. Wijayanto, H., Tsujimoto, M., Basuki, T. & Nakashima, S. Comparison of cationic surfactant
and acid solution for remediation of actual 137Cs-contaminated soil from Fukushima
Prefecture. AIP-CP. 2381, 020107 (2021).
2. Wijayanto, H. & Nakashima, S. Influence of head group structure of cationic surfactants onthe desorption of cesium from clays and clay minerals. Appl. Clay Sci. 228, 106649 (2022).
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