estimation of radioactive leakages into the pacific ocean due to fukushima nuclear accident

ORIGINAL ARTICLE

Estimation of radioactive leakages into the Pacific Oceandue to Fukushima nuclear accident

R. N. Nair • Faby Sunny • Manish Chopra •

L. K. Sharma • V. D. Puranik • A. K. Ghosh

Received: 22 October 2012 / Accepted: 15 April 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract High concentrations of several radionuclides

were reported in the sea near the Fukushima Daiichi

Nuclear Power Station (FDNPS) in Japan due to the

nuclear accident that occurred on 11 March 2011. The

main source of these concentrations was leakage of highly

radioactive liquid effluent from a pit in the turbine building

near the intake canal of Unit-2 of FDNPS through a crack

in the concrete wall. In the immediate vicinity of the plant,

seawater concentrations reached 68 MBq m-3 for 134Cs

and 137Cs, and exceeded 100 MBq m-3 for 131I in early

April 2011. These concentrations began to fall as of 11

April 2011 and, at the end of April, had reached a value

close to 0.1 MBq m-3 for 137Cs. Following the nuclear

accident, the Tokyo Electric Power Company (TEPCO)

had initiated intense monitoring of the environment

including the Pacific Ocean. Seawater samples were col-

lected and the concentrations of few radionuclides were

measured on a wide spatial and temporal scale. In this

study, the measured concentrations of different radionuc-

lides near the south discharge canal of the FDNPS were

used to estimate their leakages into the Pacific Ocean. The

method is based on estimating the release rates that

reproduce the concentration of radionuclides in seawater at

a chosen location using a two-dimensional advection–dis-

persion model in an iterative manner. The radioactive

leakages were estimated as 5.68 PBq for 131I, 2.24 PBq for134Cs and 2.25 PBq for 137Cs. Leakages were also esti-

mated for 99mTc, 136Cs, 140Ba and 140La and they range

between 0.02 PBq (99mTc) and 0.53 PBq (140Ba). It was

estimated that about 11.28 PBq of radioactivity in total was

leaked into the Pacific Ocean from the damaged FDNPS.

Out of this, 131I constitutes 50.3 %; 134Cs 20 %; 137Cs

20 %; 140Ba 4.6 %; 136Cs 2.6 %; 140La 2.3 % and 99mTc

0.2 % of the total radioactive leakage. Such quantitative

estimates of radioactive leakages are essential prerequisites

for short-term and local-scale as well as long-term and

large-scale radiological impact assessment of the nuclear

accident.

Keywords Fukushima � Daiichi Nuclear Power Station �Nuclear accident � Pacific Ocean � Advection–dispersion

model � Radionuclide concentration � Radioactive leakage �Radioactive release � Source reconstruction

Introduction

The Tohoku earthquake and tsunami of 11 March 2011

caused extensive damage to the Fukushima Daiichi nuclear

Electronic supplementary material The online version of thisarticle (doi:10.1007/s12665-013-2501-1) contains supplementarymaterial, which is available to authorized users.

R. N. Nair (&) � F. Sunny � M. Chopra �L. K. Sharma � V. D. Puranik

Environmental Assessment Division, Bhabha Atomic Research

Centre, Mumbai 400 085, India

e-mail: [email protected]

F. Sunny


M. Chopra


L. K. Sharma


V. D. Puranik


A. K. Ghosh

Health, Safety and Environment Group, Bhabha Atomic

Research Centre, Mumbai 400 085, India


123

Environ Earth Sci

DOI 10.1007/s12665-013-2501-1

http://dx.doi.org/10.1007/s12665-013-2501-1

power station (FDNPS) in Japan. This severe nuclear

accident had resulted in large amounts of radioactive fall-

out over land and the sea that peaked in the middle of

March 2011 (Chino et al. 2011; Morino et al. 2011;

Yasunari et al. 2011; NISA 2011; TEPCO 2011). In addi-

tion to radioactive fallout over the sea, water used to cool

the nuclear reactor cores leaked from the reactor buildings

to the Pacific Ocean with large amounts of radioactivity of

a spectrum of radionuclides (IAEA 2011; IRSN 2011;

MEXT 2011; Tsumune et al. 2012). Other sources of

marine radioactive contamination were the voluntary dis-

charge of low contaminated water from the reactor build-

ings to increase the on-site storage capacity for highly

contaminated water and transport of radioactive material

by rainwater runoffs of contaminated soils (Bailly du Bois

et al. 2012). A leak of highly contaminated water to sea

from a pit adjacent to Unit-2 of FDNPS through a crack on

the wall was confirmed on 2 April 2011, which was sealed

off on 6 April 2011 (TEPCO 2011). On 4 April 2011, a

planned discharge to sea commenced from FDNPS of

11,500 tonnes of low-level radioactive water that had been

stored on site awaiting treatment to create storage capacity

for the highly radioactive water that had collected in var-

ious parts of the site. Nearly 70,000 tonnes of heavily

contaminated water need to be moved from turbine build-

ings and trenches so that workers could gain access

(Wakeford 2011).

The concentrations of 137Cs in seawater off the eastern

Japan coast prior to the nuclear accident were between 1

and 4 Bq m-3 (Nakanishi et al. 2011). Measurements of

radionuclides in seawater revealed significantly high levels

of concentrations towards the end of March 2011. Seawater

concentrations reached 68 MBq m-3 for 134Cs and 137Cs

and exceeded 100 MBq m-3 for 131I in early April 2011

(Bailly du Bois et al. 2012). These concentrations began to

fall as of 11 April 2011 and, at the end of April, had

reached a value close to 0.1 MBq m-3 for 137Cs (IRSN

2011). The concentrations measured in seawater before 30

March 2011 were primarily due to radioactive fallout from

the atmosphere and they varied from 2 to 27 kBq m-3 for137Cs and 3 to 57 kBq m-3 for 131I (IRSN 2011). The

radionuclide with short half-lives like 131I ceased to be

detectable after a few months and should not have any

large-scale and long-term impact. Others, like 137Cs will

persist in the marine environment for several years. Their

persistence in the water column is dependent on the

respective affinity of the radionuclides for the particles in

suspension in surface waters which are likely to settle and

carry the radionuclides to the sea bed. During the first

month of leakage, the ratio of 134Cs/137Cs uniformly

showed a value of unity. This makes the tracking of

Fukushima-derived radionuclides in the ocean quite

straightforward, since the only source of 134Cs, considering

its short half-life, in the North Pacific Ocean at this time

would be the FDNPS accident (Buesseler et al. 2012).

A 134Cs/137Cs activity ratio of unity is considerably

higher than what it was 25 years ago when a ratio of 0.54

was reported in Chernobyl fallout (Aarkrog 1988). In the

oceans, the behaviour of cesium is conservative and

about one per cent of it is attached to marine particles.

However, this small fraction at such a high concentration

levels as observed near the FDNPS will result in high

concentrations in sediments and biota in seawater and

will continue to remain so for at least 30–100 years due

to the long half-life of 137Cs (Bowen et al. 1980;

Buesseler et al. 1991). Considerable attention was given

to 131I leakages due to its relatively high activities and

tendency to accumulate in the human thyroid if ingested

via land-based food supply or if bio-concentrated by

seaweeds and consumed as part of the Japanese diet.

Coastal water concentrations of different radionuclides

were decreased by a factor of 1,000 in the month fol-

lowing the peak release. This is a consequence of ocean

mixing and reduction in the radioactive leakages into the

sea. According to Buesseler et al. (2012) direct radioac-

tive releases into the Pacific Ocean were dominated by

leakages from the FDNPS Unit 2 during April 1–6, 2011.

The radioactive leakages from the turbine building of the

FDNPS are considered as direct releases and radioactive

fallout from atmospheric emissions as indirect releases

into the Pacific Ocean in the present study.

The releases of different radionuclides into the Pacific

Ocean due to leakage of highly radioactive effluent from

the FDNPS are estimated in this study using a simple and

quick methodology (source reconstruction). The method-

ology utilizes the concentrations at a chosen location

measured at different times. Such quantitative estimates

of radionuclide releases into the environment are neces-

sary for assessing the short-term and local-scale as well as

long-term and large-scale radiological impact of the

nuclear accident. Few studies on the estimation of

radioactive leakages into the Pacific Ocean following the

nuclear accident at the FDNPS are reported in the liter-

ature. IRSN (2011), based on the concentrations measured

in the water pooled in the turbine hall of Unit-2, esti-

mated that about 2.3 PBq of 137Cs could have been leaked

into the sea. They also estimated that about 3.3 PBq of131I could have been leaked into the sea. According to

Bailly du Bois et al. (2012) about 22 PBq of 137Cs was

leaked into the Pacific Ocean in total at the end of the

major leakage on 8 April 2011. Tsumune et al. (2012)

used a regional ocean model to simulate 137Cs concen-

trations due to leakages into the sea off Fukushima and

found that a total amount of (3.5 ± 0.5) PBq of 137Cs was

leaked into the sea from 26 March 2011 to the end of

May 2011. The simulated temporal change in 137Cs

Environ Earth Sci

123

concentrations near Fukushima agreed well with obser-

vations in this case. Buesseler et al. (2012) based on a

simple trapezoidal integration of the nuclide vs. depth

profiles of concentrations estimated the inventory of 137Cs

in the sea as 2 PBq following the nuclear accident at the

FDNPS. TEPCO (2011) analyzed the accumulated waters

in the turbine buildings of Unit-2; which leaked into the

sea; and evaluated the concentrations of 131I (5.4 TBq

m-3), 134Cs (1.8 TBq m-3) and 137Cs (1.8 TBq m-3).

The diameter of the crack on the wall was reported as

3 cm; height of the outflow as 75 cm and the flying

distance of the outflow jet as 65 cm (TEPCO 2011).

Using jet flow dynamics, TEPCO (2011) had calculated

the total outflow volume for 5 days as 520 m3. The

product of this volume and the concentrations of the ra-

dionuclides in the pit yielded their leakages on an

empirical basis. The estimated leakages were 2.81 PBq

for 131I, 0.94 PBq for 134Cs and 0.94 PBq for 137Cs.

Later, TEPCO (2012) revised the radioactive leakage

estimates using an oceanic circulation and dispersion

model. The model was used to estimate the radioactive

leakages that reproduced the measured concentrations of

radionuclides in the sea. The estimated leakages were

11 PBq for 131I, 3.5 PBq for 134Cs and 3.6 PBq for 137Cs

(TEPCO 2012).

Most of these studies reported the leakage of 137Cs into

the Pacific Ocean from FDNPS following the accident.

Few studies reported the leakages of 131I and 137Cs. The

present study estimates the radioactive leakages of 7 ra-

dionuclides such as 131I, 134Cs, 136Cs, 137Cs, 99mTc, 140Ba

and 140La based on their measured concentrations using

an iteration technique of a two-dimensional advection–

dispersion model. Out of these radionuclides, 136Cs,99mTc, 140Ba and 140La are very short-lived ones. Their

radiological impact on the environment is trivial. How-

ever, knowledge on the estimates of their leakages during

a nuclear accident is useful for accounting for all the

radioactive releases from the damaged nuclear power

plants as well as for understanding the features of such

accidents.

Methodology

Advection–dispersion model

Realistic and credible environmental models that simu-

late the transfer and accumulation of radionuclides in

specific media are essential for predicting doses and risks

to human health and environmental quality from past,

present and future contamination (Whicker et al. 1999).

Many studies are available on modelling of both natural

and anthropogenic radioactivity transport in the

environment, dose and risk assessment (Yadigaroglu and

Munera 1987; Thiessen et al. 1999; Bobba et al. 2000;

IAEA 2001; Monte et al. 2009; Aksoy and Guney 2010;

Gonzalez-Fernandez et al. 2012; Yadav et al. 2012).

Environmental models can be classified into forward

models and inverse models depending on their purpose.

Forward modelling is used to estimate the concentrations

of pollutants in the environment based on flow and

dispersion parameters when the source parameters are

specified. Inverse modelling is used for parameter esti-

mation including the source strength, location and time

of origin from known concentrations observed at various

locations and instants of time. However, forward mod-

elling can also be used for parameter estimation provided

the modelling scheme includes the possible uncertainties

in the known parameters including those in the measured

concentrations. Such a study has been carried for the

source reconstruction in this work using a two-dimen-

sional advection–dispersion model as shown below

(IAEA 1985):

oC

ot¼ o

oxDx

oC

ox

� �þ o

oyDy

oC

oy

� �� Ux

oC

oxþ Uy

oC

oy

� �

� kC þ Q

ð1Þ

where C is the concentration of the radionuclide (Bq m-3),

x is the axis along the flow direction (m), y is the lateral

axis (m), Ux is the water flow velocity along the x-axis

(m s-1), Uy is the water flow velocity along the y-axis

(m s-1), Dx is the longitudinal hydrodynamic dispersion

coefficient (m2 s-1), Dy is the lateral hydrodynamic dis-

persion coefficient (m2 s-1), k is the radioactive decay

constant (s-1), Q is any source term (Bq m-3 s-1) and t is

the time elapsed after release (s).

Assuming a straight coastline, constant water flow

velocity along the coast (Uy = 0), constant water depth and

constant hydrodynamic dispersion coefficients, the solution

of the two-dimensional advection–dispersion model for an

instantaneous release of unit radioactivity (1 Bq) from a

vertical line source at x = 0 and y = ys for a semi-infinite

medium is given by (Schreiber 1978):

Ci x; y; tð Þ ¼ X x; tð Þ Y y; tð Þ=h ð2Þ

where x varies from -? to ?, y varies from 0 to ?, Ci is

the concentration of the radionuclide due to instantaneous

release (Bq m-3) and h is the average mixing depth in the

coastal sea (m). The definitions of X and Y are given below

(Schreiber 1978):

Xðx; tÞ ¼ 1ffiffiffiffiffiffiffiffiffiffiffiffi4pDxtp exp � ðx� UxtÞ2

4Dxt

!� kt

" #ð3Þ

Environ Earth Sci

123

Yðy; tÞ ¼ 1ffiffiffiffiffiffiffiffiffiffiffiffi4pDyt

p exp � ðy� ysÞ2

4Dyt

!" #þ exp � ðyþ ysÞ2

4Dyt

!" #( )

ð4Þ

where ys is the distance between discharge outfall and coast

(m).

The concentration of a radionuclide in seawater during

the release period due to continuous release, Cd (Bq m-3),

can be evaluated by integrating Eq. 2 with respect to time

as given below:

Cdðx; y; tÞ ¼ q

ZT

0

Ciðx; y; sÞds ð5Þ

where q is the constant release (leakage) rate of the

radionuclide for a specified release period (Bq s-1), T is the

release period (s) and Ci is the concentration due to

instantaneous release of unit radioactivity. Equation 5 can

be used to estimate the concentrations of radionuclides due

to continuous release during the release period.

The concentration of a radionuclide in seawater during

the post release period (after termination of the release)

can be evaluated by the convolution integral given

bedlow:

Cpðx; y; tÞ ¼ q

ZT

0

Ciðx; y; t þ sÞds ð6Þ

where Cp is the concentration during the post release period

(Bq m-3) and t is the post release period (s) whose origin is

at the end of the release period, T. The total time involved

is (T ? t).

The measured concentrations of radionuclides in sea-

water on a spatial and temporal scale are the basic data to

be used in the source reconstruction exercise. Equation 5

was used to calculate the concentrations of different ra-

dionuclides for a specified time within the release (leakage)

period at a chosen location, where measured concentrations

were available, assuming 1 Bq s-1 release of each radio-

nuclide due to leakage. The resulting concentrations of

each radionuclide at this distance were compared with the

measured concentrations at the same distance and the ratio

between them was used to scale up or scale down the

release (leakage) rates of the radionuclides. These calcu-

lations were repeated for many combinations of hydro-

logical parameters within the range of their reported values

pertaining to the study region for a radionuclide and the

average release rate of the radionuclide due to leakage was

derived. The total released quantity of a radionuclide due to

leakage is equal to the product of the release rate and the

period of release. The schematic of the methodology is

given in the flow chart.

Set release rate (q), Period of release (T), Number of parameter combinations (N)

Select the advection-dispersion model (ADM)

Select one set of hydrological parameters

Collect the data on measured concentration for a specified time within the release period at a chosen location

Simulate the ADM to calculate the concentration at the chosen location

Estimate the ratio, R, between measured concentration and estimated concentration

Scale up/down the assumed release rate, q, using the ratio, R (=qR)

Are all the N sets of input data used?

Yes

No

Estimate the average release rate and standard deviation. Find out the total release by multiplying the average release rate by the period of release

Input data

Large number of sampling points in the near shore and

offshore regions of the Pacific Ocean were fixed by TEPCO

as shown in Fig. 1. Seawater samples were collected at

these sampling points regularly and analyses were carried

Fig. 1 Sampling points in the Pacific Ocean near Japan (TEPCO

2011). TEPCO sampling points are indicated by ‘T’ and MEXT

sampling points are indicated by ‘M’

Environ Earth Sci

123

out to evaluate the concentrations of several radionuclides

(TEPCO 2011). Figure 1 shows that Sampling Point T1 is

around the south discharge canal of FDNPS which is

approximately 330 m from the Unit-4 canal. Sampling

Point T2 is around the north discharge canal of FDNPS

which is approximately 30 m from the discharge canal of

Units-5 and 6. Sampling Point T3 is at the north discharge

canal of Fukushima Daini Nuclear Power Station, which is

approximately 10 km from the FDNPS in the downstream

direction. Sampling Point T4 is along the Iwasawa Sea-

coast in the downstream direction, which is about 16 km

from the FDNPS or about 7 km from the Daini Nuclear

Power Station at Fukushima. Sampling Point T5 is about

15 km offshore from the FDNPS. Sampling Point T6 is

about 15 km offshore from the Daini Nuclear Power Sta-

tion at Fukushima. Sampling Point T7 is about 15 km

offshore from the Iwasawa Beach. Sampling Point T8 is

about 15 km offshore from Hirono Town; Sampling Point

T9 is about 15 km offshore from Minami-Soma City and

Sampling Point T10 is about 15 km offshore from Uke-

dogawa River. The MEXT (Ministry of Education, Culture,

Sports, Science and Technology) samplings points are

indicated with M in this figure.

Measured concentrations of different radionuclides such

as 99mTc, 131I, 134Cs, 136Cs, 137Cs, 140Ba and 140La in

seawater are available at Sampling Point T1 to Sampling

Point T4 with a frequency of two times in a day since 20

March 2011 onwards. However, Sampling Points T3 and

T4 lie south of the FDNPS along the seacoast in the

downstream direction. For example, Figs. 2 and 3 depict

concentrations of 131I, 134Cs and 137Cs at Sampling Point

T3 (10 km south of the FDNPS in the downstream direc-

tion) and Sampling Point T4 (16 km south of the FDNPS in

the downstream direction), respectively. Two peaks are

visible for these radionuclides at both the sampling points

on 29 March 2011 and 7 April 2011. The peak concen-

trations of 131I vary between 3 and 3.8 MBq m-3 at both

the sampling points. The concentrations of 134Cs and 137Cs

are lower than those of 131I at least by a factor of 2.

Advection will not have any effects on these sampling

points at least during a period of few months as they lie at

the downstream of FDNPS. However, the anti-cyclonic

gyre in the Pacific Ocean may affect the concentration

distribution at these sampling points after few months. The

maximum possible effect of dispersion within a period of

14 days will be seen only within a radius of 5 km from the

discharge point [calculated based on the dispersion length

which is equal to (Dxt)1/2 where Dx = 20 m2 s-1 and

t = 14 days]. The magnitude of concentrations, their times

of occurrence and the locations of these sampling points

clearly indicate that these concentrations at T3 and T4 have

not resulted from the radioactive leakage from the FDNPS.

These data are included in Figs. 2 and 3 to show that there

were sources other than the radioactive leakages into the

Pacific Ocean (such as radioactive fallout from the

atmosphere).

It can be seen that the concentrations generated by the

indirect releases are significantly lower than those due to

the radioactive leakages. For example, the maximum

concentration of 131I measured at Sampling Point T3 and

Sampling Point T4 is about 3.8 MBq m-3, whereas it is

about 120 MBq m-3 at Sampling Point T1 and Sampling

Point T2. According to TEPCO (2011), the measured

concentrations of 131I and 137Cs at 10 km offshore were 1.6

and 0.32 MBq m-3, respectively, on 29 March 2011. The

same at 16 km offshore were 1.3 and 0.23 MBq m-3,

respectively. Such low concentrations in the offshore sea-

waters are not caused by radioactive leakages from the

FDNPS. They might have been caused by radioactive

0.01

0.1

1

10

23-Mar 28-Mar 2-Apr 7-Apr 12-Apr 17-Apr 22-Apr 27-Apr 2-May

Co

nce

ntr

atio

n (

MB

q m

-3)

I-131Cs-134Cs-137

Fig. 2 Concentrations of 131I, 134Cs and 137Cs at Sampling Point T3

[10 km south of FDNPS along the coast in downstream direction

(TEPCO 2011)]

0.01

0.1

1

10

23-Mar 28-Mar 2-Apr 7-Apr 12-Apr 17-Apr 22-Apr 27-Apr 2-May

Co

nce

ntr

atio

n (

MB

q m

-3)

I-131Cs-134Cs-137


[16 km south of FDNPS along the coast in downstream direction

(TEPCO 2011)]

Environ Earth Sci

123

fallout from the atmosphere. Stohl et al. (2012) and Morino

et al. (2011) estimated that the accumulated atmospheric137Cs deposition to the ocean peaks at 50 to 200 kBq m-2.

Hence, the measured concentrations of different radio-

nuclides at Sampling Point T1 (330 m) are used for the

estimation of radioactive leakages from the FDNPS. The

concentrations of these radionuclides at Sampling Point T2

(30 m) are used for the verification exercise. The concen-

tration data at Sampling Point T1 and Sampling Point T2

are presented in Figs. 4 and 5, respectively. TEPCO (2011)

and IRSN (2011) also used the concentration data at

Sampling Point T1 and Sampling Point T2 for estimating

the leakages of different radionuclides into the Pacific

Ocean.

According to TEPCO (2011) the outflow of radioactive

liquid effluent through a crack on the concrete wall of a pit

in the turbine building near the intake canal of Unit-2 was

observed at around 09:30 on 2 April 2011. The outflow was

sealed at around 17:38 on 6 April 2011. TEPCO has no

reasonable evidence to estimate when the outflow has

started. However, some conclusions on the beginning of

outflow can be drawn from the measured concentrations of

different radionuclides at Sampling Point T1 and Sampling

Point T2, which are available from 21 March 2011

onwards. Table 1 presents the concentrations of 131I, 134Cs

and 137Cs at Sampling Point T1 from 21 March 2011 to 29

March 2011. The concentration of 131I on 21 March 2011

was estimated as 5.07 MBq m-3. The concentrations of134Cs and 137Cs on this day were estimated as around

1.5 MBq m-3. The concentrations of 131I, 134Cs and 137Cs

on 23 March 2011 were measured as 5.9, 0.25 and

0.25 MBq m-3, respectively. Table 1 indicates that the


steadily increased from 24 March 2011 onwards. The


started decreasing after 6 April 2011 (Fig. 4). The con-

centrations at Sampling Point T2 also decreased after 6

April 2011 (Fig. 5). Following any discharge into seawater,

the concentration of a radionuclide at a sampling point

normally increases from background value to a higher and

constant value during the release period. The crack on the

wall of the turbine building at the FDNPS might have

occurred on 11 March 2011 due to the earthquake followed

by the Tsunami. The sequence of events at the FDNPS,

especially with respect to the cooling of the reactor cores,

indicate that highly contaminated water might have started

collecting in the turbine building from 12 March 2011

onwards. Large quantities of contaminated water might

have collected within a period of 10–12 days. All these

0.001

0.01

0.1

1

10

100

1000

18-Mar 23-Mar 28-Mar 2-Apr 7-Apr 12-Apr 17-Apr 22-Apr 27-Apr 2-May 7-May

Co

nce

ntr

atio

n (

MB

q m

-3)

Tc-99m

I-131

Cs-134Cs-136Cs-137Ba-140La-140

Fig. 4 Concentrations of different radionuclides at Sampling Point

T1 around 330 m south from the discharge canal of FDNPS Units 1-4

(TEPCO 2011)

0.001

0.01

0.1

1

10

100

1000


Co

nce

ntr

atio

n (

MB

q m

-3)

Tc-99mI-131Cs-134Cs-136Cs-137Ba-140La-140

Fig. 5 Concentrations of different radionuclides at Sampling Point

T2 around 30 m north from the discharge canal of FDNPS Units 5–6

(TEPCO 2011)

Table 1 Concentrations of radionuclides at Sampling Point T1

(330 m) on different dates (TEPCO 2011)

Date Time Concentration (MBq m-3)

131I 134Cs 137Cs

21 March 2011 14:30 5.07 1.49 1.48

22 March 2011 06:30 1.19 0.15 0.15

23 March 2011 08:50 5.9 0.25 0.25

24 March 2011 10:25 4.2 0.45 0.44

25 March 2011 08:30 50 7 7.2

26 March 2011 14:30 74 12 12

27 March 2011 08:30 11 1.9 1.9

29 March 2011 08:20 100 24 24

29 March 2011 1,355 130 31 32

Environ Earth Sci

123

observations point towards the inference that leakage of

highly contaminated water from the turbine building might

have started around 24 March 2011 and stopped around 6

April 2011 leading to 14 days of release. The concentration

levels at the discharge point were exceedingly high, with a

peak 137Cs concentration of 68 MBq m-3 on 6 April 2011

and the timing of peak release occured approximately one

month after the earthquake (Buesseler et al. 2012). Tsu-

mune et al. (2012) implied that the direct release was

during 26 March to 6 April 2011 leading to a total release

period of 12 days. Peaks of different radionuclides

observed on 6 April 2011 followed by lower concentrations

on further days indicate the possibility of stoppage of the

direct release on 6 April. According to Bailly du Bois et al.

(2012) the influence of leakages was particularly signifi-

cant from 26 March 2011 to 8 April 2011 in the vicinity of

the nuclear facilities and the drop in the concentrations

measured after 10 April 2011 showed that there were far

smaller leakages after this date.

The FDNPS is located on the coast of the island of

Honshu, more than 200 km north-east of Tokyo. The coast

runs north–south, facing the Pacific Ocean. The seabed

shelves off gently to a depth of 200 m, 50 km from the

coast and then drops suddenly to more than 5,000 m about

100 km offshore (IRSN 2011). In the coastal zone, the

currents are generated by the tides, wind and the general

Pacific Ocean circulation. In the short-term, the tidal effect

is predominant and it moves the masses of water with a

rapid alternating motion along the coast towards the north

and towards the south. The wind influences the circulation

of the surface waters. The Kuroshio and Oyashio are the

major ocean currents in the region, which are flowing

towards northeast (Fig. 6). Ocean currents off Japan would

lead to both southward transport of water along the coast

via the Oyashio current, and northward-driven diversions

due to surface wind shifts (Shimizu et al. 2001; Yasuda

2003). The general large-scale circulation is the result of

the interaction between the Kuroshio ocean current, which

comes from the south and runs along the coast of Japan,

and the Oyashio current, which comes from the north

(IRSN 2011). The coastal waters in the vicinity of the

FDNPS are situated in the zone where these two currents

interact, creating variable gyratory currents. The net flow

of seawater is towards the northeast direction as shown in

Fig. 6. The velocities of these currents (Ux) vary from 0.4

to 1.2 m s-1. The longitudinal dispersion coefficients (Dx)

are reported to be varying between 10 and 20 m2 s-1. The

lateral dispersion coefficients (Dy) vary between 1 and

2 m2 s-1. These hydrological data of the Pacific Ocean

reported by Yanagimoto and Taira (2003) and Stewart

(2006) are used in the model. Ranges of these hydrological

data are given in Table 2 with 5 values for each parameter.

The maximum number of parameter combinations in this

case is 125 (= 5 9 5 9 5). Hence, the number of param-

eter combinations, N, is taken as 125. Model computations

are carried out for 125 different combinations of Dx, Dy and

Ux to generate meaningful statistics. For making such

combinations, equal weightage has been given to all the

parameters. An average seawater mixing depth of 5 m is

used in the model (Inoue et al. 2012). Dispersion of the

soluble radionuclides will mainly take place in the mixed

layer. Therefore, two-dimensional advection–dispersion

models are adequate to track the transport of radionuclides

in this region.

Fig. 6 Major ocean currents in the Pacific Ocean near Japan

Table 2 Hydrological parameters used in the model

Dx (m2 s-1) Dy (m2 s-1) Ux (m s-1)

10.0 1.0 0.4

12.0 1.2 0.6

15.0 1.5 0.8

18.0 1.8 1.0

20.0 2.0 1.2

Total combinations of parameters (N) = 5 9 5 9 5 = 125

Table 3 Average leakage rate and total leakage of short-lived ra-

dionuclides from the FDNPS estimated based on their measured

concentrations at Sampling Point T1 (330 m) on 29 March 2011 at

14:10 h

Nuclide Half-life (y) Concentrationat SamplingPoint T1(MBq m-3)

Averageleakage rate(TBqday-1)

Total leakage(PBq)

99mTc 6.872 9 10-4 0.16 1.23 ± 0.26 0.02 ± 0.004136Cs 3.605 9 10-2 2.8 21.2 ± 4.62 0.29 ± 0.06140Ba 3.494 9 10-2 5 37.8 ± 8.24 0.53 ± 0.12140La 4.597 9 10-3 2.5 19.0 ± 4.12 0.27 ± 0.06

Environ Earth Sci

123

Results and discussion

Equation 5 is used to estimate the leakages of different

radionuclides into the Pacific Ocean from the damaged

FDNPS. The leakages of short-lived radionuclides such as99mTc, 136Cs, 140Ba and 140La are estimated using their

measured concentrations on 29 March 2011 at 14:10 h at

Sampling Point T1 (Table 3). Continuous and consistent

measurements are not available for these radionuclides on

other dates. The radioactive leakages of 131I, 134Cs and

137Cs are estimated using their measured concentrations at

Sampling Point T1 on several days as shown in Tables 4, 5,

6, respectively.

The highest leakage among the short-lived radionuclides

is observed for 140Ba (0.53 PBq) followed by 136Cs

(0.29 PBq) and 140La (0.27 PBq). The lowest leakage is

observed for 99mTc (0.02 PBq). These radionuclides are

extremely short lived and hence will not sustain in seawater

for more than few days. Their radiological impact on the

environment is trivial. However, knowledge on the

Table 4 Average leakage rate

and total leakage of 131I from

the FDNPS estimated based on

measured concentrations at

Sampling Point T1 (330 m)

Half-life of131I = 2.203 9 10-2 y

Date of

sampling

Time of

sampling

Leakage period

(h)

Concentration

(MBq m-3)

Leakage rate

(PBq day-1)

25 March 2011 08:30 46.1 50 0.38 ± 0.08

26 March 2011 08:20 69.9 30 0.23 ± 0.05

26 March 2011 14:20 76.1 74 0.56 ± 0.12

27 March 2011 08:30 94.1 11 0.08 ± 0.02

27 March 2011 13:50 99.4 11 0.08 ± 0.02

29 March 2011 08:20 142.0 10 0.75 ± 0.16

29 March 2011 13:55 148.0 130 0.98 ± 0.22

30 March 2011 08:20 166.0 32 0.24 ± 0.06

30 March 2011 13:55 172.0 180 1.38 ± 0.33

31 March 2011 08:40 190.0 74 0.57 ± 0.14

31 March 2011 14:00 196.0 87 0.67 ± 0.16

1 April 2011 08:20 214.0 71 0.54 ± 0.12

1 April 2011 14:00 220.0 38 0.29 ± 0.06

3 April 2011 08:40 262.0 29 0.21 ± 0.04

3 April 2011 13:50 268.0 25 0.18 ± 0.04

4 April 2011 09:20 287.0 11 0.08 ± 0.02

4 April 2011 14:20 292.0 41 0.30 ± 0.06

5 April 2011 08:55 311.0 16 0.12 ± 0.03

5 April 2011 14:10 316.0 11 0.08 ± 0.02

Average leakage rate 0.41 ± 0.35

Total leakage during 14 days (PBq) 5.68 ± 4.89


and total leakage of 134Cs from




Half-life of 134Cs = 2.06 y

Date of sampling Time of sampling Leakage period (h) Concentration (MBq m-3) Leakage rate

(PBq day-1)

26 March 2011 14:30 76.1 12.0 0.09 ± 0.02

29 March 2011 08:20 142.0 24.0 0.18 ± 0.04

29 March 2011 13:55 148.0 31.0 0.23 ± 0.05

30 March 2011 13:55 172.0 47.0 0.36 ± 0.08

31 March 2011 08:40 190.0 21.0 0.16 ± 0.04

31 March 2011 14:00 196.0 25.0 0.19 ± 0.05

1 April 2011 08:20 214.0 22.0 0.17 ± 0.04

1 April 2011 14:00 220.0 11.0 0.08 ± 0.02

3 April 2011 08:40 262.0 11.0 0.08 ± 0.02

3 April 2011 13:50 268.0 10.0 0.07 ± 0.01

4 April 2011 14:20 292.0 19.0 0.14 ± 0.03



Environ Earth Sci

123

estimates of their leakages during a nuclear accident is

useful for accounting for all the radioactive releases from

the damaged plants. The highest leakage among 131I, 134Cs

and 137Cs is observed for 131I (5.68 PBq) followed by 137Cs

(2.25 PBq) and 134Cs (2.24 PBq). Among these radionuc-

lides, concern of large-scale and long-term impacts exists

mainly for 137Cs and to a certain extent for 134Cs.

The concentrations of all the radionuclides at Sampling

Point T2 (30 m) are found to be lower than those at

Sampling Point T1 (330 m) for most of the sampling times.

The highest concentration of 131I at 330 m is

180 MBq m-3 (on 30 March 2011). The highest concen-

tration of 131I at 30 m is 120 MBq m-3 (1 April 2011). On

29 March 2011, the concentrations of 131I at 330 and 30 m

are 130 and 51 MBq m-3, respectively. The concentrations

of 134Cs and 137Cs are measured as 31 and 32 MBq m-3,

respectively, at 330 m on this day. The concentrations of

these radionuclides at 30 m are 12 MBq m-3 on this day.

This indicates that Sampling Point T1 (330 m) lies most

possibly in the plume centreline along the flow direction

(y = 0) and Sampling Point T2 (30 m) probably lies away

from the plume centre and flow direction. The estimated

average leakages are used to reproduce the measured

concentrations of different radionuclides at 30 m at dif-

ferent distances along the y axis using Eq. 5. For a distance

of y = 25 m, very good matching is observed between the

measured and estimated concentrations of different radio-

nuclides on 29 March 2011 as shown in Fig. 7. This good

agreement between the measured and estimated concen-

trations of different radionuclides provides certain confi-

dence in the estimated radioactive leakages.

Calculations show that about 11.28 PBq of radioactivity

leaked into the Pacific Ocean from the damaged FDNPS.

Out of this, 131I constitutes 50.3 %; 134Cs 20 %; 137Cs

20 %; 140Ba 4.6 %; 136Cs 2.6 %; 140La 2.3 % and 99mTc

0.2 % of the total radioactive leakage. This is apart from

the radioactive fallout from the atmosphere into seawater,

which is considered as a major portion of the atmospheric

emissions between 12 March and 23 March 2011 (Bailly

du Bois et al. 2012). Most of the radioactive emission in the

atmosphere, in the case of Fukushima nuclear accident,

was deposited into the Pacific Ocean. Most of the radio-

active releases from the Chernobyl nuclear accident were

airborne. About 20, 10, 13 and 6 % of reactor inventories

for 131I, 134Cs, 137Cs and 140Ba were released into the

atmosphere for the Chernobyl accident, respectively (Val-

kovic 2000). It is, in general, observed that there is no

linear relationship between the fission yields and airborne

releases. For example, the fission yield of 131I is 2.88 %,

whereas the fission yield of 137Cs is 6.14 %. However, the

atmospheric emission of 131I is about 7 % more than that of137Cs in the case of Chernobyl nuclear accident (Valkovic

2000). This is because the atmospheric emissions of ra-

dionuclides depend on chemical properties of radionuc-

lides: highly volatile 131I is preferentially emitted into the

atmosphere.


and total leakage of 137Cs from




Half-life of 137Cs = 30.2 y

Date of sampling Time of sampling Leakage period (h) Concentration (MBq m-3) Leakage rate

(PBq day-1)

26 March 2011 14:30 76.1 12.0 0.09 ± 0.02

29 March 2011 08:20 142.0 24.0 0.18 ± 0.04

29 March 2011 13:55 148.0 32.0 0.24 ± 0.05

30 March 2011 13:55 172.0 47.0 0.36 ± 0.08

31 March 2011 08:40 190.0 21.0 0.16 ± 0.04

31 March 2011 14:00 196.0 25.0 0.19 ± 0.05

1 April 2011 08:20 214.0 22.0 0.17 ± 0.04

1 April 2011 14:00 220.0 11.0 0.08 ± 0.02

3 April 2011 08:40 262.0 11.0 0.08 ± 0.02

3 April 2011 13:50 268.0 10.0 0.07 ± 0.01

4 April 2011 14:20 292.0 19.0 0.14 ± 0.03



0.01

0.1

1

10

100

Tc-99m I-131 Cs-134 Cs-136 Cs-137 Ba-140 La-140

Co

nce

ntr

atio

n (

MB

q m

-3)

MeasuredEstimated

Fig. 7 Comparison of measured and estimated concentrations of

radionuclides at Sampling Point T2 (30 m) on 29 March 2011 at

14:10

Environ Earth Sci

123

Many times 137Cs fluxes give a good estimate of other

radionuclides released due to nuclear accidents. Tables 5

and 6 show that the 134Cs/137Cs activity ratio in the leakage

is about 1. Such a ratio indicates recent nuclear accidents as

this ratio decreases with time due to the short half-life of134Cs (Aarkrog 1988). The 134Cs/137Cs activity ratio in the

measured concentrations at 30 m and 330 m was about 1 as

shown in Fig. 8. In the present study, the 131I/134Cs activity

ratio in radioactive leakage was about 2.5. Figure 8 also

depicts the 131I/134Cs ratio in the measured concentrations

at 30 m (Sampling Point T2) and 330 m (Sampling Point

T1). At 30 m, 131I/134Cs ratio increased from 1.5 to 8.6 and

then fell to 0.32. At 330 m, 131I/134Cs ratio increased from

3.4 to 24 and fell to 0.18. The activity ratio of 131I/134Cs at

30 m on 24 March 2011 was about 8.6 and reduced to 3.8

on 31 March 2011 after about 8 days indicating the

radioactive decay of 131I. The activity ratio of 131I/134Cs at

330 m on 24 March 2011 was about 7.9 and reduced to 3.9

after 8 days (neglecting the high ratios on 25 and 26 March

2011). The 131I/137Cs ratio is a useful tool for determining

whether 137Cs concentrations in the ocean result from

radioactive leakage into the ocean or radioactive fallout

from the atmosphere (Tsumune et al. 2012). If this ratio in

the seawater follows the radioactive decay of 131I with

time, then the source is derived from direct releases such as

radioactive leakages; otherwise, the source is derived from

indirect releases such as radioactive fallout from the

atmosphere. This is because of the preferential deposition

of 131I and 134Cs (or 137Cs) due to their particle sizes during

emission. The fact that the 131I/134Cs ratios at both these

distances before 24 March do not follow the radioactive

decay of 131I indicates that radioactive leakages into the

Pacific Ocean had approximately commenced from 24

March 2011. Bailly du Bois et al. (2012) showed that a

major portion of the atmospheric emissions occurred

between 12 March and 23 March 2011. The 131I/134Cs

activity ratios in soil were found to be varying between 50

and 61 (Tagami et al. 2011). According to Chino et al.

(2011), the 131I/134Cs activity ratios in the atmosphere

varied larger than those in soil.

Figure 9 presents the concentrations of 131I, 134Cs and137Cs at Sampling Point T1 (330 m) during the post release

period, i.e. from 6 April 2011 onwards. The concentration

data are fitted into exponential equations. The correlation

coefficient of the fitting is about 0.94. The overall depletion

rates of 131I, 134Cs and 137Cs in seawater work out to be

0.01, 0.0069 and 0.007 h-1, respectively. The radioactive

decay constants of 131I, 134Cs and 137Cs are 3.592 9 10-3,

3.84 9 10-5 and 2.62 9 10-6 h-1, respectively. If the

radioactive decay rates are removed from the overall

depletion rates of these nuclides in seawater, their envi-

ronmental depletion rates work out to be 6.41 9 10-3,

6.86 9 10-3 and 6.99 9 10-3 h-1, respectively. These

depletion rates are almost constant, indicating the influence

of advection and dispersion over any other nuclide-

dependent removal such as sorption by suspended sediment

particles. The average environmental depletion rate of

these radionuclides in seawater works out to be about

6.75 9 10-3 h-1, which corresponds to an environmental

half-life of 148.15 h (6.2 days) for the leakages of these

radionuclides. Bailly du Bois et al. (2012) estimated the

environmental half-life of 137Cs in seawater as 7 days for

its leakage.

A comparison of measured and estimated time history of131I concentrations at Sampling Point T2 is depicted in

Fig. 10. The oscillations of measured concentrations as

observed in Fig. 10 indicate that the release is not constant

and there exists influence of local oscillatory forcing

0.01

0.1

1

10

100


Rat

io

I-131/Cs-134 at 30 mCs-134/Cs-137 at 30 mI-131/Cs-134 at 330 mCs-134/Cs-137 at 330 m

Fig. 8 Ratios of 131I/134Cs and 134Cs/137Cs in seawater at Sampling

Point T1 (330 m) and Sampling Point T2 (30 m)

y = 2.9114e-0.0069x

R2 = 0.8818

y = 3.0555e-0.007x

R2 = 0.8863

y = 4.2503e-0.0105x

R2 = 0.8937

0.01

0.1

1

10

0 48 96 144 192 240 288 336 384 432 480 528 576 624

Time (hr)

Co

nce

ntr

atio

n (

MB

q m

-3)

Cs-134Cs-137I-131Expon. (Cs-134)Expon. (Cs-137)Expon. (I-131)

Cs-134

Cs-137

I-131


(330 m) after termination of release where 0 h corresponds to 14:10 h

on 6 April 2011

Environ Earth Sci

123

functions such as tides on concentrations as Sampling Point

T2 is very close to the coast. Tides will cause temporal

changes in the current field dominated by the Kuroshio

Current. The present study is based on an analytical model

which cannot account for non-constant release rate or the

influence of oscillatory forcing functions such as tides.

However, within these uncertainties, the study provides

gross estimates of the leakages of different radionuclides

into the Pacific Ocean. The increase of concentrations

during the release period as well as the peak concentrations

are well depicted by the model as shown in Fig. 10.

A comparison is carried out between the presently

estimated radioactive leakages of 131I, 134Cs and 137Cs into

the Pacific Ocean from the damaged FDNPS and those

reported by different agencies (Table 7). Only three esti-

mates such as IRSN (2011); TEPCO (2011 and 2012) are

available for 131I leakages so far. Since TEPCO revised the

leakage estimates in 2012, their estimates reported in 2011

may be discarded for all the radionuclides. The 131I leakage

estimated in the present study is about two times lower than

that of TEPCO (2012). It is about 1.7 times higher than that

of IRSN (2011). The leakage of 134Cs estimated in the

present study is about 1.6 times lower than that of TEPCO

(2012). The leakage of 137Cs varies from 2 PBq (Buesseler

et al. 2012) to 22 PBq (Bailly du Bois et al. 2012), and the

highest reported leakage is about 11 times higher than the

lowest reported value. According to Estournel et al. (2012),

the source term estimated by Bailly du Bois et al. (2012),

based on an analysis of observations, is much higher.

Estournel et al. (2012) explained in detail how such a high

leakage is obtained by Bailly du Bois et al. (2012). If the

estimation of Bailly du Bois et al. (2012) is excluded, the

highest leakage (4.3 PBq) is about 2.2 times higher than

the lowest value (2 PBq). Variation by such a factor can be

regarded as acceptable considering the non-constant leak-

age rates, uncertainties in measurements and data and

usage of different modelling methods. The leakages of137Cs estimated by IRSN (2011); Buesseler et al. (2012)

and the present study match fairly well.

Conclusions

Leakage estimates of different radionuclides into the

Pacific Ocean from a concrete pit containing highly

radioactive effluent in the turbine building of the damaged

FDNPS are derived using a two-dimensional advection–

dispersion model. It is estimated that about 11.28 PBq of

0.001

0.01

0.1

1

10

100

1000

0 100 200 300 400 500 600 700 800 900 1000

Time (hr)

Co

nce

ntr

atio

n (

MB

q m

-3)

MeasuredModelled

Fig. 10 Comparison of measured and estimated concentrations of131I at Sampling Point T2 (30 m)

Table 7 Leakages of 131I, 134Cs and 137Cs into the Pacific Ocean from the FDNPS estimated by different agencies

Agency Estimated release

(PBq)

Remarks

131I 134Cs 137Cs

IRSN (2011) 3.3 – 2.3 Based on concentrations measured in the water pooled in the turbine hall of Unit-2. (Main leakage

period: 25 March–11 April 2011)

Bailly du Bois

et al. (2012)

– – 22 Based on measurements performed by TEPCO. (Main leakage period: 26 March–8 April 2011)

Tsumune et al.

(2012)

– – 3.5 Using a regional ocean model. (Main leakage period: 26 March–6 April 2011)

Buesseler et al.

(2012)

– – 2 Based on simple trapezoidal integration of the nuclide concentrations vs. depth profiles in the ocean.

(Main leakage period: 1 April–6 April 2011)

Estournel et al.

(2012)

– – 4.3 Based on numerical model simulation and comparison with observed concentrations in the vicinity

of the two outlets of the nuclear power plants. (Main leakage period: 25 March–8 April 2011)

TEPCO (2011) 2.81 0.94 0.94 Based on discharge concentrations and leak jet dynamics (Main leakage period: 2 April–6 April

2011)

TEPCO (2011) 11 3.5 3.6 Based on iteration of an oceanic circulation and dispersion model

Present study 5.68 2.24 2.25 Based on iteration of two-dimensional advection–dispersion model. (Leakage period: 24 March–6

April 2011)

Environ Earth Sci

123

radioactivity was leaked into the Pacific Ocean from the

damaged FDNPS. Out of this, 131I constitutes 50.3 %;134Cs 20 %; 137Cs 20 %; 140Ba 4.6 %; 136Cs 2.6 %; 140La

2.3 % and 99mTc 0.2 % of the total leakage. The environ-

mental half-life of 131I, 134Cs and 137Cs in seawater with

respect to the leakage is estimated as 6.2 days. The esti-

mated leakages of different radionuclides vary between

0.02 PBq (99mTc) and 5.68 PBq (131I). The leakages of134Cs and 137Cs are estimated as 2.24 and 2.25 PBq,

respectively. The study shows that advection–dispersion

modelling coupled with measurements is highly useful to

extract early information on the quantity and extent of

radioactive releases into the environment during nuclear

accidents.

Acknowledgments Authors express sincere thanks to TEPCO,

MEXT and NISA for making available large amounts of data per-

taining to the FDNPS nuclear accident in the public domain ever since

the occurrence of the accident. Thanks are also due to Dr. D. N.

Sharma; Director; Health, Safety and Environment Group; Bhabha

Atomic Research Centre for his keen interest in the study.

References

Aarkrog A (1988) The radiological impact of the Chernobyl debris

compared with that from nuclear weapons fallout. J Environ

Radioact 6:151–162

Aksoy AO, Guney MS (2010) Experimental determination of three-

dimensional dispersivities in homogeneous porous medium.

Environ Earth Sci 60:383–393

Bailly du Bois P et al (2012) Estimation of marine source-term

following Fukushima Daiichi accident. J Environ Radioact

114:2–9

Bobba AG, Singh VP, Bengtsson L (2000) Application of environ-

mental models to different hydrological systems. Ecol Model

125:15–49

Bowen VT et al (1980) Fallout radionuclides in the Pacific Ocean:

Vertical and horizontal distributions, largely from GEOSECS

stations. Earth Planet Sci Lett 49:411–434

Buesseler KO, Livingston HD, Casso SA (1991) Mixing between oxic

and anoxic waters of the Black Sea as traced by Chernobyl

cesium isotopes. Deep-Sea Res 38:S725–S745

Buesseler KO et al (2012) Fukushima-derived radionuclides in the

ocean and biota off Japan. PNAS 109:5984–5988

Chino M et al (2011) Preliminary estimation of release amount of 131I

and 137Cs accidentally discharged from the Fukushima Daiichi

nuclear power plant into the atmosphere. J Nucl Sci Technol

48:1129–1134

Estournel C et al (2012) Assessment of the amount of cesium-137

released into the Pacific Ocean after the Fukushima accident and

analysis of its dispersion in Japanese coastal waters. J Geophys

Res 117:C11014. doi:10.1029/2012JC007933

Gonzalez-Fernandez D, Garrido-Perez MC, Casas-Ruiz M, Barbero

L, Nebot-Sanz E (2012) Radiological risk assessment of

naturally occurring radioactive materials in marine sediments

and its application in industrialized coastal areas: Bay of

Algeciras, Spain. Environ Earth Sci 66:1175–1181

IAEA (1985) Hydrological Dispersion of Radioactive Material in

Relation to Nuclear Power Plant Siting. Safety Guide Seires

50-SG-S6. International Atomic Energy Agency, Vienna

IAEA (2001) Generic Models for use in assessing the Impact of

Discharges of Radioactive Substances to the Environment.

Safety Reports Series No 19. International Atomic Energy

Agency, Vienna

IAEA (2011) Web Site: http://www.iaea.org/newscenter/news.

Vienna: International Atomic Energy Agency

Inoue M et al (2012) Low levels of 134Cs and 137Cs in surface

seawaters around the Japanese Archipelago after the Fukushima

Daiichi Nuclear Power Plant accident in 2011. Geochem J

46:311–320

IRSN (2011) Impact on the Marine Environment of Radioactive

Releases following the Nuclear Accident at Fukushima Daiichi.

Information Note dated 13 May 2011. France: Institute for

Radiological Protection and Nuclear Safety

MEXT (2011) Web Site: http://www.mext.go.jp/en/contents. Ministry

of Education, Culture, Sports, Science and Technology, Japan

Monte L, Perianez R, Boyer P, Smith JT, Brittain JE (2009) The

role of physical processes controlling the behaviour of radio-

nuclide contaminants in the aquatic environment: a review of

state-of-the-art modelling approaches. J Environ Radioact

100:779–784

Morino Y, Ohara T, Nishizawa M (2011) Atmospheric behavior,

deposition, and budget of radioactive materials from the

Fukushima Daiichi nuclear power plant in March 2011. Geophys

Res Lett 38:L00G11. doi:10.1029/2011GL048689

Nakanishi T et al (2011) Vertical distributions of 99Tc and 99Tc/137Cs

activity ratio in the coastal water off Aomori, Japan. J Environ

Radioact 102:774–779

NISA (2011) Web Site: http://www.nisa.meti.go.jp/english/files.

Nuclear and Industrial Safety Agency, Japan

Schreiber DL (1978) Liquid Pathway Generic Study—Impacts of

Accidental Radioactive Releases to the Hydrosphere from Float-

ing and Land-Based Nuclear Power Plants. Rep No NUREG-0440.

Washington: US Nuclear Regulatory Commission

Shimizu Y, Yasuda I, Ito S (2001) Distribution and circulation of the

coastal Oyashio intrusion. J Phys Oceanogr 31:1561–1578

Stewart RH (2006) Introduction to Physical Oceanography. Texas

A&M University

Stohl A et al (2012) Xenon-133 and caesium-137 releases into the

atmosphere from the Fukushima Daiichi nuclear power plant:

determination of the source term, atmospheric dispersion, and

deposition. Atmos Chem Phys 12:2313–2343

Tagami K et al (2011) Specific activity and activity ratios of

radionuclides in soil collected about 20 km from the Fukushima

Daiichi Nuclear Power Plant: Radionuclide release to the south

and southwest. Sci Total Environ 409:4885–4888

TEPCO (2011) Web Site: http://www.tepco.co.jp/en/press/corp-com/

release. Tokyo Electrical Power Company, Japan

TEPCO (2012) Web Site: http://www.tepco.co.jp/en/press/

corp-com/release. Tokyo Electrical Power Company, Japan

Thiessen KM, Thorne MC, Maul PR, Prohl G, Wheater HS (1999)

Modelling radionuclide distribution and transport in the envi-

ronment. Environ Pollut 100:151–177

Tsumune D et al (2012) Distribution of oceanic 137Cs from the

Fukushima Daiichi Nuclear Power Plant simulated numerically

by a regional ocean model. J Environ Radioact 111:100–108

Valkovic V (2000) Radioactivity in the environment. Elsevier,

Amsterdam

Wakeford R (2011) And now, Fukushima. Editorial. J Radiol Prot

31:167–176

Whicker FW, Shaw G, Voigt G, Holm E (1999) Radioactive

contamination: state of the science and its application to

predictive models. Environ Pollut 100:133–149

Yadav RR, Jaiswal DK, Yadav HK, Gulrana (2012) Three-dimen-

sional temporally dependent dispersion through porous media:

analytical solution. Environ Earth Sci 65:849–859

Environ Earth Sci

123

http://dx.doi.org/10.1029/2012JC007933

http://www.iaea.org/newscenter/news

http://www.mext.go.jp/en/contents

http://dx.doi.org/10.1029/2011GL048689

http://www.nisa.meti.go.jp/english/files

http://www.tepco.co.jp/en/press/corp-com/release




Yadigaroglu G, Munera HA (1987) Transport of pollutants: summary

review of physical and dispersion models. Nucl Technol

77:125–149

Yanagimoto D, Taira K (2003) Current measurements of the Japan

Sea proper water and the intermediate water by ALACE floats.

J Oceanogr 59:359–368

Yasuda I (2003) Hydrographic structure and variability in the

Kuroshio-Oyahio transition area. J Oceanogr 59:389–402

Yasunari TJ et al (2011) Cesium-137 deposition and contamination of

Japanese soils due to the Fukushima nuclear accident. Proc Natl

Acad Sci USA 108:19447–19448

Environ Earth Sci

123

estimation of radioactive leakages into the pacific ocean due to fukushima nuclear accident

Documents