Environmental Engineering FOURTH EDITION

334 ENVIRONMENTAL ENGINEERING

Vertical dispersion

and

lateral winds

Water supply well

Human consumption

Irrigation on food chain

Leachate crops

_*_

Aquifer L.

Confining strata

Figure 16-6. Potential movement of radioactive materials from waste storage and
"disposal" areas to the accessible environment.

food in several Eastern and Northern European countries. Close to the Chernobyl plant,
enough radioactive material was deposited fmm the air to produce an external, or
immersion, dose; this sort of external dose is sometimes referred to as groundshine.
Water transport occurs whenever radionuclides in surface or subsurface soil, or
on vegetation surfaces, erode or leach into a watercourse, as well as when airborne
radionuclides fall out on surface waters. Leaching into waterways, and transport of
radionuclides in groundwater, can take enough time so that shorter half-life nuclides
may have decayed to negligible levels before entering the human food chain. These
processes remain problematical for long half-life nuclides, however. Chapters 6 and 11
address water transport considerations that are somewhat applicable to the problems
associated with radioactive waste.
Radionuclides also move from deposition or contamination of ground surfaces into
the human food chain. Plant uptake mechanisms cannot distinguish between radioac-
tive and stable isotopes of the same element, and will take up radioactive isotopes of
stable nutrient elements. Animals eating the plants will absorb radioisotopes in the
same way. For example, a cow eating a plant contaminated with Sr-90 will metabolize
the radionuclide into her milk, and thus pass it along in the food chain.

RADIOACTIVE WASTE MANAGEMENT

The objective of the environmental engineer is to prevent the introduction of radioactive
materials into the biosphere, and particularly into the environment accessible to human
activity, for the effective lifetime (about 20 half-lives) of these materials. Control of