Fukushima derived radionuclides in the ocean

Michio Aoyama Meteorological Research Institute, Japan

Talk Outline 1. Global cesium distribution and mass balance - pre Fukushima 2. Fukushima cesium - mass balance of 137Cs - surface transport and subduction to the ocean interior IAEA Scientific Forum 17-18 September 2013 Vienna, Austria

Decay corrected accumulative fallout of 137Cs

derived from atmospheric weapons tests as of 1970

Michio Aoyama, Katsumi Hirose and Yasuhito Igarashi, Re-

construction and updating our understanding on the global

weapons tests 137Cs fallout, Journal of Environmental

Monitoring, 8, 431-438, 2006.

In Northern Hemisphere

765±79 PBq 1970

In the North Pacific Ocean

290±30 PBq 1970

69±7 PBq 2011

Chernobyl accident 1986

85 PBq

A pathway of weapons tests derived 137Cs in the North Pacific Ocean,

tracer of sea water movement

Fig. S2 Possible pathway of 137Cs in the Pacific Ocean based on 3-D observations of 137Cs in 2000s (Aoyama et al., 2013)

We can expect that Fukushima

origin radiocaesium should go

same pathway

Pathways of Fukushima derived

radionuclides to the Ocean

• Atmospheric deposition

• Direct release

• Groundwater discharge

• River runoff

TEPCO Press release

137Cs : 1.8E+12 Bq/m3

Simulated atmospheric deposition of 137Cs (Bq m-2) (by Masingar II of MRI)

(Aoyama et al., in preparation)

4

Boiling Water Reactor Systems "Nuclear

Reactor Concepts" Workshop Manual,

U.S. NRC

3.6±0.7 PBq to the ocean (Tsumune et al., 2013)

14–17 PBq to the atmosphere

700 PBq was in the three core 140 PBq in stagnant water

(Nishihara et al.,, 2011) (Nishihara et al., 2011)

140 PBq in stagnant water

12 - 15 PBq to the ocean

137Cs mass balance

More than 99% of released radioaesium to the ocean

was transported offshore, then to the ocean interior

30 GBq day-1

Revised estimation

R/V Mirai

NYK AQUARIUS

凌風丸

R/V Hakuho Maru

NYK Heijin

Sampling locations during the period from

March 2011 to Oct. 2012

134Cs in surface water in April – June 2011

10 Bq m-3

Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013.

134Cs in surface water in July – Sept. 2011

10 Bq m-3

Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013.

10 Bq m-3

134Cs in surface water in Oct. – Dec. 2011

Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013. 10 Bq m-3

134Cs in surface water in Jan. – Mar. 2012

Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013.

(Aoyama et al., BG 10 3067-3078, 2013)

Apr-Jun

2011

Jul-Sep

2011

Oct-Dec

2011

Jan-Mar

2012

Surface speed of contaminated water ca. 7 km day-1

8

X

0 5 10 15 20 250

100

200

300

400

500

600

700

800

Vertical profiles of 134Cs

at 40N, 165E on 12 Oct. 2011 Stn KS1109-3101

and

at 39N, 165E on 11 June 2012 stn RF1205-4418

KS1109-3101

RF1205-4418

134Cs / Bq m-3

Dep

th /

m

Oxygen maximum

Sigma0=26.3

Station 3101 4418

Year 2011 2012

Month 10 6

Bq m-2

Bq m-2

134Cs

inventory2710+-210 2350+-190

0 - 200 m 2150 520

Deeper than

200 m520 1830

Oct. 2011

Over time, Cs moves east and subducted in the ocean interior

June 2012

Bq m-3

137Cs cross section along 165 ºE in June 2012

Start of travel into ocean interior N

Possible pathway of Fukushima derived

radionuclides in the North Pacific Ocean

Fig. S2 Possible pathway of 137Cs in the Pacific Ocean

We found start of travel of Fukushima derived

radioactivity in the ocean interior.

Summary of budget of 137Cs

for pre- and after the Fukushima accident

Main portion of Fukushima derived radioactivity

already subducted into the ocean interior and is

moving to southwest ward.