A framework for including enhanced exposure to naturally occurring radioactive materials (NORM) in LCA

Abstract

Purpose Despite advances in the development of impact categories for ionising radiation, the focus on artificial radionuclides produced in the nuclear fuel cycle means that the potential impacts resulting from increased exposure to naturally occurring radioactive materials (NORM) are still only covered to a limited degree in life cycle assessment (LCA). Here, we present a potential framework for the inclusion of the exposure routes and impact pathways particular to NORM in LCA. Methods We assess the potential magnitude of enhanced NORM exposure, particularly in light of the potential use of NORM residues in building materials, and set out the potential exposure routes that may exist. We then assess the current state of the art, in terms of available fate, exposure and damage models, both within and outside of the LCA sphere. Finally, these exposure routes and modelling techniques are combined in order to lay out a potential framework for NORM assessment in LCA, both in terms of impact on humans and ecosystems. Results and discussion Increased exposure to NORM radionuclides can result either from their release to the environment or their proximity to humans as they reside in stockpiles, landfills or products. The exposure route via products is considered to be increasingly significant in light of current attempts to incorporate technologically enhanced NORMs (TENORM) including bauxite residue into building materials, by groups such as the ETN-MSCA REDMUD project. Impact assessment models for NORM exposure are therefore required to avoid potential burden shifting in the assessment of such TENORM products. Models describing the fate of environmental releases, the exhalation of radon from building products and the shielding effects on landfills/stockpiles are required to assess potential exposure. Subsequently, models relating exposure to radiation sources and the effective internal and external dose received by receptors are required. Finally, an assessment of the damage caused to the receptors is desirable. Conclusions A sufficient suite of currently existing and internationally recognised models exist that can, with varying degrees of modification, form the building blocks of a comprehensive NORM characterisation method for LCA. The challenge ahead lies in consolidating these models, from disparate fields, into a coherent and generally applicable method for the assessment of enhanced NORM exposure in LCA.

Impact assessment of enhanced exposure from Naturally Occurring Radioactive Materials (NORM) within LCA

“…LCIA characterisation models for enhanced exposure to NORM were developed according to the framework set out in Joyce et al (2016). This implementation is described in section 3 below, and is available as an Excel file in the online supplementary materials.…”

“…To validate and verify the new model developed from the Joyce et al (2016) framework, we need to display that the model (a) is useable, (b) represents the real world system with a sufficient level of accuracy and (c) matches current state of the art (Carson, 2002). We selected an approach, similar to the one described by Harder et al (2014) and Heimersson et al (2014) and performed impact method evaluation, sensitivity checks, and midpoint and endpoint indicator cross comparison.…”

“…Data for potassium emissions from residual landfill (specifically 'Redmud from bauxite digestion| treatment of, residual material landfill') are available in Ecoinvent (Doka, 2009), with 28.19% of emissions occurring in the short term, and the remainder (71.81%) in the long term. No data are available for uranium and thorium, therefore following the recommendation of Joyce et al (2016), we begin with the default assumption that in the long term 100% of the nuclides are emitted to the environment from landfill over the 60,000 year period, and that this release is linear, with 1/600 of the releases taking place over the first 100 years. The sensitivity of the model to this assumption is assessed.…”

“…There is an increasing interest towards the valorisation of this residue (European Commission, 2014MSCA-ETN REDMUD, 2015) with its incorporation into construction materials representing a potentially viable solution (Klauber et al, 2011). BR however has concentrations of 238 U and 232 Th greater than in the bauxite ore from which it is derived, and as such, its utilisation raises the issue of NORM exposure (Joyce et al, 2016).…”

“…As stated in the ILCD handbook (European Commission, 2011) extension of the number of radionuclides covered by ionising radiation life cycle impact assessment (LCIA) models for both human health and biota is a high priority task. Joyce et al (2016) have set out a framework for the inclusion of Naturally Occurring Radioactive Materials (NORM) exposure in the LCA framework. In this paper, we outline implementation of this framework and the validation of the LCIA models produced.…”