Waste of Naturally Occurring Radioactive Materials (NORM) poses a challenge to operators and authorities alike.
The paper reviews legislation and practices regarding NORM waste management in the North Sea countries, with emphasis on the potential environmental impacts. The paper gives an overview of mechanisms causing NORM in the oil and gas industry, the various disposal methods, the legal regime, and the fate and effects in the external environment. Examples of current and future NORM waste challenges are given.
NORM in produced water mainly consists of Ra-226 and Ra-228, which has been dissolved from the geological materials of the reservoir. Parts of the dissolved Ra precipitate as RaSO4 in the process equipment onboard the installation (mainly in the separation systems), associated with precipitation of BaSO4 and SrSO4. If discharged to the sea, the vast majority of the dissolved Ra precipitates as RaSO4 or adsorbs to fine-grained particles and particulate organic matter. When assessing the fate and effects of NORM in the external environment, it is therefore essential to analyse both the fine-grained sediment transport pathways and the uptake mechanisms of marine life.
The strong particle-association of Ra must be taken into account when evaluating the possible environmental impacts of solid NORM waste disposal (from maintenance of equipment, decommissioning of installations, etc.). Re-injection of NORM back to the geological reservoir can be seen as an optimal way of disposing NORM waste, but the approach taken by different countries varies, depending on how the London Convention and the OSPAR Radioactive Substances Strategy are interpreted and implemented.
It is concluded that the NORM waste issue is not in all cases handled optimally with respect to health, safety and environmental impacts, partly because of the constellation of international conventions and national practices which is applied with significant variation from country to country.