Continental-scale enrichment of atmospheric 14CO2 from the nuclear power industry: potential impact on the estimation of fossil fuel-derived CO2

Abstract

Since aged carbon in fossil fuel contains no14C,14C/C ratios (∆14C) measured in at-mospheric CO2 can be used to estimate CO2 added by combustion and, potentially, provide verification of fossil CO2 emissions calculated using economic inventories. Sources of14C from nuclear power generation and spent fuel reprocessing can counteract dilution by fossil CO2. Therefore, these nuclear sources can bias observation-based estimates of fossil fuel-derived CO2if they are not correctly accounted for orincluded as a source of uncertainty. We estimate annual14C emissions from each nu-clear site in the world and conduct an Eulerian transport modeling study to investigatethe continental-scale, steady-state gradients of∆14C caused by nuclear activities and fossil fuel combustion. Over Europe, North America and East Asia, nuclear enrichmentmay offset 0–260 % of the fossil fuel dilution in∆14C, corresponding to potential biasesof 0 to−8 ppm in the CO2attributed to fossil fuel emissions, larger than the bias fromrespiration in some areas. Growth of14C emissions increased the potential nuclearbias over 1985–2005. The magnitude of this potential bias is largely independent of the choice of reference station in the context of Eulerian transport and inversion stud-ies, but could potentially be reduced by an appropriate choice of reference station inthe context of local-scale assessments.