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Table 1: Estimates of radioactive releases into the atmosphere
Amount released (PBq 1 )
Rare gas I-131 Cs-134 Cs-137
TEPCO (24 May 2012) 2 ~500 ~500 ~10 ~10
Japan Atomic Energy Agency, Nuclear Safety Commission
(12 April 2011-12 May 2011)
- 150 - 13
Japan Atomic Energy Agency, Nuclear Safety Commission
(22 August 2011)
- 130 - 11
Japan Atomic Energy Agency (6 March 2012) - 120 - 9
Nuclear and Industrial Safety Agency (12 April 2011) - 130 - 6.1
Nuclear and Industrial Safety Agency (6 June 2011) - 160 18 15
Nuclear and Industrial Safety Agency (16 February 2012) - 150 - 8.2
Releases from the Chernobyl nuclear power plant accident 6 500 1 800 - 85
1. 1 PBq (peta Becquerel) = 1 000 trillion Bq = 1 015 Bq.
2. The value estimated by TEPCO is rounded off to one decimal place and was originally reported in Bq.
Sources: www.tepco.co.jp/en/press/corp-com/release/2012/1204659_1870.html and
www.tepco.co.jp/en/press/corp-com/release/betu12_e/images/120524e0201.pdf.
Table 2: Estimates of radioactive releases into the ocean
TEPCO
(Central Research Institute of Electric Power Industry)
Japan Atomic Energy Agency
Period of
assessment
Released amount in PBq
I-131 Cs-134 Cs-137
26 March 2011-
30 September 2011 1 11 3.5 3.6
21 March 2011-
30 April 2011 2 11.4 - 3.6
1. The amount released from 21 March 2011, when the measurement of the concentration of radioactive materials in seawater near the
water discharge canals was started, to 25 March 2011, was tentatively calculated to be about 0.1 PBq for Cs-137. The ratio of I-131
and Cs-137 suggests the predominance of releases into the atmosphere.
2. Includes the releases into the atmosphere.
Source: www.tepco.co.jp/en/press/corp-com/release/betu12_e/images/120524e0202.pdf.
Since the time of the accident, the status of
contaminated areas has evolved. Based on a decision
by the Japanese government once the safety of
the plant was considered stable, and following the
government’s recovery plan of 26 December 2011,
access to certain previously restricted areas has
been reinstated in a phased manner. Allowing for
a transition period and for tasks such as confirmation
of infrastructure and security, the areas for
which evacuation orders had been issued have been
organised into three areas responding to the annual
cumulative doses since April 2012 as follows:
1. 1mSv~20 mSv: Areas for which evacuation
orders are ready to be lifted.
2. 20mSv~50 mSv: Areas in which residents are
not permitted to live.
3. 50 mSv~: Areas where it is expected that
residents will face difficulties in
returning for a long time.
In response to the accident, the Fukushima prefectural
government developed and implemented
the Fukushima Health Survey to facilitate suitable
healthcare in the future. The results from this survey
will be used to estimate individual external exposures
received between 11 March 2011 and 11 July
2011. These estimates will be used as basic data in
health exams scheduled to be conducted for former
residents of evacuated areas, as well as for future
long-term health care. The survey is being conducted
in the form of a self-report questionnaire.
This health survey was first issued to the residents
of three towns (Namie, Iitate and Kawamata)
near the Fukushima Daiichi nuclear power plant and
was then extended to all residents of Fukushima
prefecture. By 5 December 2012, the health survey
had been sent to 361 906 residents in Fukushima
prefecture. For 354 736 residents (all residents except
for radiation workers), this survey showed that
most received less than a few mSv of exposure. The
highest effective dose was 25 mSv as shown below.
8 The Fukushima Daiichi Accident and NEA Follow-up