L. Pujol et Ja. Sanchez-cabeza, Determination of longitudinal dispersion coefficient and velocity of the Ebro river waters (Northeast Spain) using tritium as a radiotracer, J ENV RAD, 45(1), 1999, pp. 39-57
Tritium routinely released as low-activity liquid radioactive waste by the
Asco nuclear power plant (Tarragona, Spain) was used as a radiotracer to de
termine the longitudinal dispersion coefficient and velocity of the Ebro ri
ver waters (Northeast Spain). Several field experiments, in coordination wi
th the nuclear power plant, were carried out during 1991. After a tritium r
elease, water was sampled downstream at periodic intervals during several h
ours. Tritium was measured with a low-background liquid scintillation count
er and the time evolution of its concentration for different locations was
obtained. In order to determine the longitudinal dispersion coefficient and
the velocity of the Ebro river waters, experimental data were fitted using
an analytical, a box-type and a numerical model to solve the one-dimension
al advection-diffusion equation. The observed mixing length occurred about
50 channel widths downstream from the point source, shorter than values pre
dicted from some published expressions (100-300 channel widths). For the ri
ver water flows investigated, ranging from 178 to 915 m(3) s(-1), longitudi
nal dispersion coefficients ranged from 41 +/- 30 to 392 +/- 45 m(2) s(-1)
and mean velocities ranged from 0.563 +/- 0.011 to 1.278 +/- 0.019 ms(-1).
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