Environmental Distribution and Long-term Dispersion of Reactor 14CO2 Around Two German Nuclear Power Plants

Abstract

Carbon-14 data on atmospheric CO2 as well as on plant material (tree leaves and wheat) from the vicinity of two German boiling water reactors (Philippsburg and Isar/Ohu) are reported. Atmospheric CO2 samples taken routinely with an integration time of one or two weeks 1.75 km downwind of the Philippsburg reactor (900 MW electrical power) show a maximum 14C excess concentration of delta 14C (excess) = 300 +/- 7%, corresponding to 12.7 mBq m-3 (STP air). The long-term average excess amounts to delta 14C (excess) = 47 +/- 3%, corresponding to 2.0 mBq m-3 (STP air). The concentrations observed with plant material at the same sampling site range between delta 14C (excess) = 0% and 120%, corresponding to 0 and 27 mBq (g carbon)-1. With the meteorological dispersion parameters actually measured at the nuclear power plants, the dispersion factors for the various sampling sites and for the individual periods of sampling were calculated on the basis of a one-dimensional Gaussian plume model. With the observed 14C excess concentrations and the dispersion factor, a "theoretical" (i.e. calculated) reactor 14C source strength is then determined. For the Philippsburg reactor, which is situated in the flat Rhine valley, the "theoretical" and the observed yearly mean 14C emissions compare rather well (within a factor of 2). A significant systematical deviation from the model was found in the concentration decrease with source distance: the decrease predicted between the 1.75-km and 3.25-km distances is steeper than actually observed. The 14C excess concentrations found in tree leaves around the Isar/Ohu reactor (907 MW electrical power) at 1-2 km distance fall into the same range as observed at Philippsburg. In the hilly terrain at this reactor site, the model calculations agree well with the observed values up to a distance of 1 km if the relative elevation of the sampling site is taken into account by introducing a "reduced stack height" in the model calculations. This method fails in predicting the concentrations at distances greater than 1 km from the source.

Spatial distribution of Δ<sup>14</sup>CO<sub>2</sub> across Eurasia: measurements from the TROICA-8 expedition

“…14 CO 2 values 50-300‰ over background have been measured within 2 km of two German BWR reactors (Levin et al, 1988) and plant material around the Ignalina, Lithuania RBMK reactor is elevated by up to 20 000‰, with typical values 250‰ above background (Magnusson et al, 2004). In order to screen for such local enrichments we used the HYSPLIT back-trajectory model (Draxler and Rolph, 2003), obtaining back-trajectories for each sampling location and time (Fig.…”

Measurement of the carbon 14 activity at natural level in air samples

“…Several publications discuss various aspects of 14 C production rate of nuclear installations [1,3]. In this study, we investigated chemical forms such as CO 2 and CH 4 .…”

Carbon-14 in Tree Rings in the Vicinity of Ignalina Nuclear Power Plant, Lithuania

“…A fraction of the generated 14 C is released continuously during normal operation of NPPs, mainly in two chemical forms; oxidized, i.e. carbon dioxide (CO 2 ), and reduced, which mostly is in the form of CH 4 (Levin et al, 1988). Because of the easy incorporation of 14 C in CO 2 form into global carbon cycle, rapid mobility, long 14 C half-life and particularly considerable inventory, these releases should be considered very carefully in estimating their local and global effect on the individual effective dose and collective dose commitments.…”