Radioactivity in produced water from Norwegian oil and gas installations – concentrations, bioavailability, and doses to marine biota

Large amount of produced water, containing elevated levels of radionuclides (mainly 226Ra and 228Ra), is discharged to the sea~in connection with oil and gas production on the Norwegian continental shelf. The main objective of this project has been to establish radiological safe discharge limits for radium associated with other components in produced water. We present a summary of the methodology developed and the overall results obtained. Our results show that presence of added chemicals like scale inhibitors in the produced water have a marked influence on the speciation of radium, i.e. formation of radium and barium sulphates when produced water is mixed with seawater. Radium's behaviour in the sea has been modelled using the DREAM model. Also, we have showed that the bioavailability of radium may be increased due to presence of scale inhibitors. Juvenile cod has been exposed to radium through food and from water. The uptake in different organs, i.e. skin, gills, liver, blood, and kidneys, show large variability, but is modest in all organs

Enhanced levels of

A numerical model has been applied to simulate the fate of 226Ra radionuclides in the ocean, generated from discharges of produced water in the Norwegian Sector of the North Sea. The model simulates the transport, dilution and the (possible) deposition on the sea floor of 226Ra. Figures are presented for the concentration levels and deposition rates of 226Ra in the ambient for various assumptions for the fate of the 226Ra in the ocean (as dissolved, as adsorbed to ambient organic particles that sink down on the sea floor, and as forming Ba(Ra)SO4 particles). Concentration levels and deposition rates are compared with natural levels and fluxes of 226Ra in the ocean and to the sediment, respectively. The added concentration levels/fluxes are found to be generally relatively small, compared to natural levels/fluxes. The reason for this is attributed to the presence of fairly high natural levels/fluxes of 226Ra