Industrial Ecology and the Geoenvironment - Sustainable Practices in Geoenvironmental Engineering - page 133

kilogram). Initial radioactivity is by ission and activation products. This activity decays
rapidly after 100 years. Further activity appears to be contributed primarily by actinides
and actinide daughters. The horizontal line shown at a radioactivity level of 10 12 Bq repre-
sents the radioactivity for eight tonnes of natural uranium with daughters. The half-lives
of uranium 235 ( 235 U), 236 U, 238 U, and iodine 129 ( 129 I), which are 7.0 × 10 8 , 2.3 × 10 7 , 4.5 × 10 9 ,
and 1.6 × 10 7 years, respectively, tell one, for example, why disposal or safe containment of
the burned-up fuel rods is a special type of management problem for geoenvironmental
engineers. It is useful to note that if one establishes a reduction in radioactivity level to the
one matching natural uranium deposits (10 12 Bq level) as the required containment level of
security, this would require at least 100,000 years of “safe” containment isolation.
In addition to the problem of radioactivity, one needs to look at the heat generated by
the decay heat, which is the residual power or the heat generated in the fuel after cessa-
tion of operation (Figure 4.11) in relation to the time after cessation of operations. As can
be expected, the ission and activation products contribute to the heat in the canister in
the irst 100 plus years, after which time, the main contributor to the total heat is from
the actinides and actinide daughters. The discussion of containment of these radioactive
wastes can be found in Chapter 10.
4.8.3 Alternative Energy Sources and the Geoenvironment
The pursuit of alternative energy sources or means to produce energy without reliance on
nonrenewable fossil fuels such as coal and hydrocarbon resources has gained considerable
attention among those concerned with two principal issues: (1) generation of greenhouse
gases (GHG) from present fossil fuel energy-producing plants that have been faulted for
contributing directly to “global warming” and also from the means to procure the fossil
fuels themselves and (2) the need to conserve nonrenewable hydrocarbon resources, i.e.,
using renewable natural resources. The types of industries or efforts mounted to generate
energy for the consumer have earned the nickname of green energy sources , with the related
name of green energy production . The proper designation is alternative energy sources , with
the term alternative meaning alternative to coal and hydrocarbon resources (fossil fuels) . Some
of the alternative energy production-type industries are hydroelectric, solar, geothermal,
biomass, osmotic, wind, and ocean (tidal and waves). Strictly speaking, solar, geothermal,
ocean, and wind are nondepleting energy resources —meaning that they are always there , and
do not really undergo renewable processes over any speciied period.
The concerns in respect to the land compartment of the geoenvironment and in regard
to the sources of stressors from the use of these types of energy resources are not as severe
as with the nonrenewable resource types of energy production. In common with the other
types of energy production systems, the sources of geoenvironment stressors are from
construction of the production systems and also from the construction and delivery of
the harvested energy (transmission system). The various geoenvironment stressors are
thought to be mostly physical in nature.
4.9 Contaminating Discharges and Wastes
Table 4.2 gives a very short summary of many of the contaminating substances and
chemicals found in the geoenvironment as a result of deliberate discharges, spills, leaks,