Environmental Engineering Reference
In-Depth Information
all electric equipment in reactors 1-4 were rendered useless (IAEA
2011
). Venting
operations had to be undertaken; hydrogen explosions in reactors Nos. 1 and 3
occurred, spewing more radioactive material such as cesium (
137
Cs and
134
Cs) and
iodine (
131
I). Special measures were taken in the damaged reactors to avoid spent
fuel meltdown (NISA and JNES
2011
).
The total amount of released
131
I was calculated to be around 1.2−1.6 × 10
17
Bq
while in the case of
137
Cs was 0.8−2.0 × 10
16
Bq; the highest release estimates were
after the hydrogen explosions around 10−15 × 10
16
Bq per hour for both. In Onagawa
city (Miyagi), about 150 km from the Fukushima plant, the dose rate was measured
to be up to 15
Svh
−1
) on 13th March 2011, although in
Minamisoma City the level near the plant reached 20
ʼ
Sieverts per hour (
ʼ
Svh
−1
. The deposition map
of
137
Cs showed that the radiation plume was large, covering most of Miyagi and
southern Iwate, albeit in low quantities (Masamichi et al.
2011
; Masamichi
2012
).
The majority of the released radiation dispersed over the Pacifi c Ocean.
On the other hand, a study done in 2011 based on cesium (
137
Cs) and xenon
(
133
Xe) readings stated that the amount of radiation from the nuclear plant was much
higher than reported (Stohl et al.
2011
; Brumfi el
2011
). A study done by Yasunaria
et al. (
2011a
,
b
) on soil contamination estimated that large areas in eastern and
northeastern Japan, particularly in Fukushima and nearby prefectures had partially
(
137
Cs) estimated depositions larger than 100,000 and 10,000 MBq km
−2
respectively.
The Nuclear Regulation Authority of Japan (NRAJ
2012
) published the results
of radiation monitoring of soil in a number of towns in Fukushima Prefecture after
the nuclear accident focusing of strontium and plutonium (
90
Sr and
238
Pu). This
agency concluded that the highest contamination from
90
Sr occurred in Ottozawa in
the town of Okuma and Koriyama in the town of Futaba being 3,070 Bq/m2
(80.8 Bq/kg-dry soil) and 502 Bq/m2 (14.9 Bq/kg-dry soil) respectively. In the case
of plutonium (
238
Pu) only Ottozawa in Okuma seemed to have been only slightly
contaminated. The same authority provides detailed information about the events,
damage and measures taken due to radiation exposure of different isotopes
(NRAJ
2013
).
Comprehensive information about emergency monitoring readings of environ-
mental radiation levels throughout 2011 is provided by the Ministry of Education,
Culture, Sports, Science and Technology of Japan (MEXT
2011
). The Japan Reishi
Association (JRA
2012
), an international NGO supported by industries and govern-
ment organizations provided the radiation (air dose) levels in various prefectures in
eastern Japan from 2011 to 2012, and their analysis showed that while making
comparisons with radiation-exposure levels found in other cities around the world,
levels in Fukushima City were only slightly higher than in other locations.
In the case of Miyagi Prefecture, the Radiation Information Site of Miyagi
Prefecture provides detailed, up-to-date information about radiation dosage rates
considering air, tap water, agriculture, forest and marine products (MPG
2013b
).
As result of the nuclear accident, a variety of agricultural and forest products in
northern Miyagi, including mushrooms, aralia sprout and bamboo shoots have
recorded radioactive cesium (MPG
2013b
). Moreover, reports by citizens watch on
radioactivity in Japan showed that domestic house dust from vacuum cleaners
ʼ
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