Organically bound tritium in freshwater ecosystems : long term trends in the environment of french nuclear power stations Françoise Siclet –EDF R&D National hydraulics and environment laboratory EMRAS II -WG7 – 24/28 January 2011
Radioecological survey in the environment of nuclear power plants 20 nuclear power plant sites with liquid and gaseous discharges of tritium along Atlantic coast along Gironde estuary along rivers : Rhone, Rhine, Loire, Vienne, Seine, Garonne, Moselle, Meuse tritium measurements (HTO and OBT) in aquatic and terrestrial environment Started in 1977 2 sites per year since 1992 Large data base that can be used to study evolution of background concentrations and influence of NPP discharges EMRAS II -WG7 – 24/28 January 2011
Location of studied sites 600 OBT measurements in fish, aquatic plants and sediments in freshwater ecosystems EMRAS II -WG7 – 24/28 January 2011
OBT in freshwater ecosystems around nuclear power plants (all samples from 1977 to 2009) p p p p p p 10000 10000 10000 10000 10000 10000 Bq / L eau combustion Bq / L eau combustion Bq / L eau combustion Bq / L eau combustion Bq/L eau combustion Bq/L eau combustion 1000 1000 1000 1000 1000 1000 100 100 100 100 100 100 10 10 10 10 10 10 1 1 1 1 1 1 poissons poissons poissons poissons poissons poissons vegetaux vegetaux vegetaux vegetaux vegetaux vegetaux bryophytes sediments bryophytes sediments sediments sediments sediments sediments MES MES MES MES MES MES Fish plants bryophytes sediments SPM EMRAS II -WG7 – 24/28 January 2011
OBT in sediments around nuclear power plants (all sampling sites) Rhône Rhin Loire Meuse Moselle Seine Garonne 1 000 000 100 000 OBT(Bq/L combustion water) 10 000 1 000 100 10 1 1980 1985 1990 1995 2000 2005 2010 OBT activities are decreasing in relation with decrease in fallout from atmospheric test 2 distinct groups : -Rhône and Rhine, exponential regression with half-life of 17 years -other rivers, exponential regression with half-life of 7 years No significant difference between station upstream and downstream NPP EMRAS II -WG7 – 24/28 January 2011
OBT in particulate matter upstream all NPP – comparison with downstream amont Creys aval Creys aval Bugey 100 000 amont Belleville aval Belleville suspended solids OBT (Bq/L combustion water) Rhône 1 000 10 000 suspended solids Loire 1 000 100 100 10 10 1 1 janv-99 juil-99 févr-00 août-00 mars-01 janv-01 juil-01 févr-02 août-02 mars-03 sept-03 avr-04 nov-04 OBT upstream significantly higher No difference between than downstream upstream and downstream Origin of tritium undetermined (could be linked to radioluminescent device industry ) EMRAS II -WG7 – 24/28 January 2011
Comparison with evolution of HTO in precipitations 1000 Berlin Thonon Irlande 100 HTO (Bq/L) 10 1 0,1 1957 1962 1967 1972 1977 1982 1987 1992 1997 2002 2007 Exponential decrease with a half-life of 6years Present level : 1 Bq/L in continental areas One order of magnitude lower than OBT in sediments of rivers other than Rhone and Rhine Taking into account radioactive decay, present level in sediments equivalent to level in precipitation 40 years ago, in agreement with the average residence time of organic matter in soils (Balesdent et al 1997) OBT in watershed (year n) = HTO in precipitation (year n –40). exp(- r . 40) EMRAS II -WG7 – 24/28 January 2011
OBT in fish around NPP (all sampling sites) Rhône Rhin Loire Meuse Moselle Seine Garonne 10 000 1 000 OBT (Bq/L combustion water) 100 10 1 1975 1980 1985 1990 1995 2000 2005 2010 OBT activities are decreasing in relation with decrease in fallout from atmospheric test Exponential regression with half-life of 6 years influence of NPP significant on rivers other than Rhône and Rhine : + 7 Bq/L (average) between upstream and downstream EMRAS II -WG7 – 24/28 January 2011
Calculation of the increases in river HTO activities resulting from power plant discharges- comparison to observed differences in fish OBT between upstream and downstream stations discharge added HTO OBT level concentration (Bq/L combustion Site Year fish species in river water) delta upstream- Bq/L downstream Dampierre 1992 anguille 7,8 1,5 St-Laurent 1993 anguille 4,3 9,4 Chinon 1994 anguille 3,0 -0,7 Cattenom 1997 anguille 27,9 10,61 Cattenom 1997 chevaine 27,9 16,38 Nogent 1997 brochet 11,5 14,8 Nogent 1997 chevaine 11,5 6,67 Belleville 2000 anguille 6,1 6,86 Belleville 2000 barbeau 6,1 6,25 Nogent 2000 anguille 32,5 12,98 Nogent 2000 chevaine 32,5 9,39 Dampierre 2001 barbeau 5,2 1,18 Golfech 2001 gardon 5,7 2,11 St-Laurent 2003 barbeau 2,2 1,24 Chinon 2003 anguille 3,2 0,5 Belleville 2004 chevaine 8,7 9,2 Chooz 2006 chevaine 17,0 5 Cattenom 2008 brême 41,4 31,17 Average OBT/HTO = 0,62 Good agreement with TRS 472 EMRAS II -WG7 – 24/28 January 2011 partition factor
Contribution of OBT in sediment to OBT in fish in upstream areas Calculation based on 2 term sources : - HTO in precipitation (year n) = HTO in surface waters(year n) - OBT in sediment (year n) • In rivers other than Rhone and Rhine, sediment OBT contributes to 13 % of fish OBT • In Rhone river, sediment OBT contributes to 1/10 000 of fish OBT EMRAS II -WG7 – 24/28 January 2011
Conclusions •In river catchments, where atmospheric test fallout is the main source of tritium, observed levels result from the exposure of aquatic organisms to two distinct tritium pools of different age : -tritiated water from rainfall (representing present fallout), -organic tritium from soils (formed over several decades) which supplies particulate matter to surface waters. . •in the Rhône and Rhine river basins, an additional source of organic tritium of very low bio-availability, probably originating from the luminous paint industry, is responsible for the spiking of sediment organic matter up to 100 to 100 000 Bq/L combustion water. •influence of NPP tritium discharges is detectable only in rivers, with low background OBT activities, i.e in other basins than the Rhône and Rhine. The observed increase in plant and fish OBT is lower than the discharge added HTO activity in water, which confirms the absence of bioaccumulation for tritium originating from HTO and the absence of highly bio-available tritiated organic molecules in NPP discharges See Gontier & Siclet, Radioprotection (submitted) EMRAS II -WG7 – 24/28 January 2011
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