Pascal Bailly du Bois

Transfer of tritium released into the marine environment by French nuclear facilities bordering the English Channel.

Controlled amounts of liquid tritium are discharged as tritiated water (HTO) by the nuclear industry into the English Channel. Because the isotopic discrimination between 3H and H is small, organically bound tritium (OBT) and HTO should show the same T/H ratio under steady-state conditions. We report data collected from the environment in the English Channel. Tritium concentrations measured in seawater HTO, as well as in biota HTO and OBT, confirm that tritium transfers from HTO to OBT result in conservation of the T/H ratio (ca. 1 × 10(-16)). The kinetics of the turnover of tritium between seawater HTO, biota HTO, and OBT was investigated. HTO in two algae and a mollusk is shown to exchange rapidly with seawater HTO. However, the overall tritium turnover between HTO and the whole-organism OBT is a slow process with a tritium biological half-life on the order of months. Nonsteady-state conditions exist where there are sharp changes in seawater HTO. As a consequence, for kinetic reasons, the T/H ratio in OBT may deviate transiently from that observed in HTO of samples from the marine ecosystem. Dynamic modeling is thus more realistic for predicting tritium transfers to biota OBT under nonsteady-state conditions.

Reconstruction of the 236U input function for the Northeast Atlantic Ocean: Implications for 129I/236U and 236U/238U‐based tracer ages

A reconstruction of historical discharges of 236U into the Northeast Atlantic Ocean by nuclear installations is presented. The nuclear reprocessing facilities Sellafield (SF), Great Britain (GB) and La Hague (LH), France and potentially also the nuclear fuel processing installation Springfields (SP), GB represent the main contributors of 236U in the Northeast Atlantic Ocean. Because data on 236U releases is lacking, 236U discharges from SP and SF are estimated based on the U-isotopic systematics found in the discharges from LH. The resulting reconstruction of 236U releases indicates that, until 2013, a total of (95±32) kg of 236U was discharged from SF, SP, and LH. In a second step, the reconstructed 236U releases are combined with 129I data from literature and oceanic and atmospheric box models are used to derive the 129I/236U and 236U/238U input functions that, for example, can be used to calculate tracer ages of Atlantic Waters in the Arctic Ocean. Our conceptual results show that the combination of 129I/236U and 236U/238U generally allows the estimation of tracer ages over the past approximately 25 yr if contributions of 236U from global fallout are considered. Finally, as a proof of concept, the new method is applied to calculate tracer ages of Arctic Ocean surface samples (collected in 2011/12) and the results are in good agreement with literature data. We conclude that the combination of 129I/236U with 236U/238U in a dual tracer approach provides a sensitive tool for the calculation of tracer ages and ventilation rates in the North Atlantic region. This article is protected by copyright. All rights reserved.

Correction: A dual pathways transfer model to account for changes in the radioactive caesium level in demersal and pelagic fish after the Fukushima Daï-ichi nuclear power plant accident

[This corrects the article DOI: 10.1371/journal.pone.0172442.].

Modélisation hydrodynamique de la dispersion à court terme dans une mer macro tidale : validation par des mesures à haute résolution de radiotraceur solubles

DISPRO project aims to validate hydrodynamic models dispersion parameters by field data for the short-term (hours to week) and short distances (100 meters to 30 km). This project is based on a 2D instantaneous currents model with a mesh size of 110 m, coupled with high frequency field data collected in the release plume. At this step of the works, measurements confirm the reliability of the model during six hours following a release. This validation made possible developpement of models with known incertitude to simulate dispersion of dissolved substances in realistic conditions for normal or accidental situations in macrotidal seas.