1. Standpoint of the French Institute for Radioprotection and Nuclear Safety (IRSN) on the impact of radioactive releases from the Fukushima-Daiichi nuclear accident on the marine environment Bruxelles, EU meeting, 03 Oct 2011 (http://www.irsn.fr/EN/news/Pages/201103_seism-in-japan.aspx) Paper sumitted to JER “Estimation of marine source-term following Fukushima Dai-ichi accident” by Bailly du Bois et al.

2. Bruxelles, EU meeting, 16 May 2011 2/4 IRSN estimation of the source-term of releases into seawater 137 Cs quantities were estimated on the basis of sample measurements in a 50 x 100 km area around the plant (issues: depth, mixing layer, atmospheric fallout, rain water washout, …) Exponential decay back extrapolated to April 8 -> 22E+15 Bq (depth of mixing layer ?) Total until July 18 -> 27E+15 Bq

3. Bruxelles, EU meeting, 16 May 2011 3/4 IRSN estimation of the rate of seawater renewal Exponential decay t 1/2 = 6.9 d Dilution by clean water through marine currents (remarkably constant) Convergence of Kuroshio and Oyashio  Seasonal changes in the ocean circulation ?  Return of contaminated water back in the area ? If no more releases occur and dilution remains constant, back to prior situation is expected in Nov 2011

4. Bruxelles, EU meeting, 16 May 2011 IRSN/Ifremer dispersion modelling (based on IRSN estimated source-term) Short distance matching calculations/measurements less than 1 km off the facility

5. Bruxelles, EU meeting, 16 May 2011 IRSN/Ifremer dispersion modeling (based on IRSN estimated source-term) Mid distance (color-scale changed by a factor 10) Long distance dispersion is not yet validated by measurements as of July 1 st, calculated values are below actual DL (5 Bq.L -1, but DLs below 0.001 Bq.L -1 are routinely achieved in radioecology)

6. Bruxelles, EU meeting, 16 May 2011 6/4 Inventory of main 137 Cs releases in the oceans SourcePBq (1E+15Bq) Fallout from nuclear weapon tests704* Nuclear fuel reprocessing 1951 - 2010 BNFL Sellafield41.21 Areva-NC La Hague1.04 Tchernobyl accident16* Solid waste dumping41.4 (beta + gamma) Fukushima accident Direct liquid release27 Atmospheric fallout0.076 (80 km radius circle) * Aarkrog, 2003. Input of anthropogenic radionuclides into the World Ocean. Deep Sea Research Part II: Topical Studies in Oceanography Volume 50, Issues 17-21, Pages 2597-2606

7. Bruxelles, EU meeting, 16 May 2011 Measurements in sediments average [ 137 Cs] until Aug 30 Cs, I, Te, Sr, Pu, Ba The map is a draft document with over- estimated values along the shore (this biais will be fixed) As regards Kd’s, amounts of 137 Cs in sediments are relatively low 137 Cs seems to increase with time (kinetics of transfer to particles and deposition) but is expected to level off in the forthcoming months. Because of remobilisation processes, sediments will behave as a secondary sources of contamination (postponed, remote and diffuse)

8. Bruxelles, EU meeting, 16 May 2011 FURTHER WORK PLANNED BY IRSN WITH COLLABORATIONS to compare the results of dispersion modeling by IRSN/Ifremer, Sirocco and Japan Atomic Energy Agency to estimate the transfers of radionuclides from seawater to biota by modeling in collaboration with Collecte Localisation Satellite (CLS)  radionuclides bioaccumulation in the different marine trophic levels will be dynamically predicted on the basis of dispersion modeling outcomes  maps of radioactive quality index to support monitoring survey for commercial fish species fish survey in the Pacific (IRSN and IFREMER) post-doc IRSN fellowship 8/4