Quantitative assessment of dissolved radiotracers in the English Channel: Sources, average impact of la Hague reprocessing plant and conservative behaviour (1983, 1986, 1988, 1994)

Abstract

Knowledge of long-term movements of water-masses in the English Channel has been substantially improved using hydrodynamic modelling coupled with radio-tracers studies ; nevertheless, the precision of results so obtained is still largely dependent on measurement precision.New tools are now available to make more accurate determinations of radio-tracer distribution : -Repositioning of station locations at the same tide reference-time, giving a homogeneous spatial data set, coupled with the possibility of interpolating and quantifying the amounts of dissolved radioactivity flowing through the English Channel ;-The first measurements of tritium ( 3 H) in seawater on a large scale in the English Channel demonstrate that this fully conservative radionuclide is a clearly identifiable marker of industrial releases ;-Recent campaigns carried out during the FluxManche II CCE (1994) programme show the general distribution of dissolved radionuclides 137 Cs, 134 Cs, 60 Co, 125 Sb, 106 Ru and 3 H in the English Channel and the Irish Sea ;-The re-utilisation of data from previous campaigns (1983, 1986 and 1988) provides indications, at any given location in the English Channel, about the average dilution and distribution of releases derived from the La Hague reprocessing plant.Excesses and losses of radionuclides are now quantified with respect to known source-terms ; estimates of losses are provided for non-conservative radionuclides, while an excess of 137 Cs was observed in the English Channel during the period 1983 -1994. This excess which has the same order of magnitude as the quantities released from La Hague plant in the English Channel, could be explained by about 1% of Sellafield reprocessing plant releases entering the Channel.These results confirm and give a more detailed picture of the previously known distribution of water masses in the English Channel. They lead to clear information about transit times and dilution at this scale, and provide directly comparable data for the validation of hydrodynamic models.

Tritium along the French coast of the English Channel

“…At the same period, in the English Channel, in the region of the Penly site, the concentrations measured within the scope of the Penly radioecological zero point were comprised between 1.5 and 3.9 Bq.l and reached 6 Bq.l -1 along the coast of the eastern English Channel [6]. It can therefore be noted over the last 20 years that the tritium concentration in waters entering the English Channel has slowly decreased, and that the tritium concentration of the English Channel waters has slowly increased.…”

Metals in marine environment (mollusc Patella sp., fish Labrus bergylta, crustacean Cancer pagurus, beach sand) in a nuclear area, the North Cotentin (France)

“…1, as well as nuclear sites in the Cotentin peninsula. The southernmost site in Barneville is considered as the reference site: It was located in the southern point of an anti-cyclonic gyre and is slightly affected by pollutants that might be released by the nuclear industries, the discharges of which tend to disperse the northeastwards Guéguéniat et al 1988;Bailly du Bois and Guéguéniat 1999). Dielette site is close to the nuclear power plant at Flamanville.…”

“…This chemical measurement campaign was intended to acquire reliable data for validating the models used by the NCRG to estimate concentrations of chemical substances in the environment from discharges data provided by nuclear facilities (AREVA NC, ANDRA, French Navy) and also aims to answer the societal questions about occurrence and concentrations. Although the impact of radioactive effluents released by the nuclear industry on radioactivity levels in seawater and marine species has been studied (Masson et al 1983;Germain and Miramand 1984;Bailly du Bois and Guéguéniat 1999;Germain et al 2000;Fievet et al 2006), there have been few studies of the impact of the released chemicals (Miramand and Bentley 1992). However, the quantities of chemicals that can be released by nuclear plants within regulation limits remain high.…”

A Review of the Radionuclide, Cobalt-60, as a Fine-Sediment Tracer

“…Discharges of 60 Co can be detected in close proximity to its release point in samples of seawater [61,64], in surface sediments or from shallow sediment cores [62,63]. Some researchers have exploited these licenced releases and used the signature of 60 Co as a tracer or geochemical marker to elucidate varying environmental processes [61,62,64,65].…”