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 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
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.
A pathway of weapons tests derived 137Cs in the North Pacific Ocean, tracer of sea water movement We can expect that Fukushima origin radiocaesium should go same pathway Fig. S2 Possible pathway of 137Cs in the Pacific Ocean based on 3-D observations of 137Cs in 2000s (Aoyama et al., 2013)
Pathways of Fukushima derived radionuclides to the Ocean • Atmospheric deposition • Direct release • Groundwater discharge • River runoff Simulated atmospheric deposition of
137Cs (Bq m-2) (by Masingar II of MRI) (Aoyama et al., in preparation) 137Cs : 1.8E+12 Bq/m3 TEPCO Press release 4
137Cs mass balance 14–17 PBq to the atmosphere 12 - 15 PBq to the ocean 140 PBq in stagnant water 3.6±0.7 PBq to the ocean Boiling Water Reactor Systems "Nuclear (Tsumune et al., 2013) Reactor Concepts" Workshop Manual, U.S. NRC 700 PBq was in the three core 140 PBq in stagnant water (Nishihara et al.,, 2011) (Nishihara et al., 2011)
30 GBq day-1 Revised estimation More than 99% of released radioaesium to the ocean was transported offshore, then to the ocean interior
Sampling locations during the period from March 2011 to Oct. 2012 NYK AQUARIUS R/V Mirai R/V Hakuho Maru NYK Heijin 凌風丸
134 134 Cs in surface water in July – Sept. 2011 Cs in surface water in April – June 2011 X Apr-Jun Jul-Sep 2011 2011 134Cs in surface water in Oct. – Dec. 2011 134Cs in surface water in Jan. – Mar. 2012 Surface speed of contaminated water ca. 7 km day-1 10 Bq m-3 10 Bq m-3 Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013. Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013. Oct-Dec Jan-Mar 2011 2012 8 (Aoyama et al., BG 10 3067-3078, 2013) 10 Bq m-3 Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013. 10 Bq m-3 Aoyama, M. et al., Biogeosciences, 10, 3067-3078, 2013.
Vertical profiles of 134Cs at 40N, 165E on 12 Oct. 2011 Stn KS1109-3101 Over time, Cs moves an easd t and subducted in the ocean interior at 39N, 165E on 11 June 2012 stn RF1205-4418 134Cs / Bq m-3 0 5 10 15 20 25 0 Oct. 2011 100 200 Station 3101 4418 Year 2011 2012 m 300 Oxygen maximum
June 2012 Month 10 6 h / Sigma0=26.3 400 pte Bq m-2 Bq m-2 D 500 134Cs 2710+-210 2350+-190 inventory 600 KS1109-3101 700 RF1205-4418 0 - 200 m 2150 520 800 Deeper than 520 1830 200 m
137Cs cross section along 165 ºE in June 2012 Start of travel into ocean interior N Bq m-3
Possible pathway of Fukushima derived radionuclides in the North Pacific Ocean We found start of travel of Fukushima derived radioactivity in the ocean interior. Fig. S2 Possible pathway of 137Cs in the Pacific Ocean
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.