Environmental Engineering Reference
In-Depth Information
6.7
SUMMARY
More than 400 nuclear power plants are currently operating in the world, supplying about 17% of
the global electricity demand of more than 2E(15) kWh per year. While complicated, the technology
is well-developed, and the power plants operate relatively reliably.
Most of the current power plants use a reactor of the pressurized water type (PWR) in which
the fuel is uranium enriched to 3-4% uranium-235; the pressurized light water serves both as the
coolant and the moderator, and cadmium or boron control rods serve to control the power output or to
shut down the reactor. The boiling water reactors (BWR) use the same fuel and control rods, but the
coolant/moderator is in two phases: liquid water and steam. In some BWR the moderator is graphite.
Another type of reactor is used in the CANDU power plants, where the fuel is natural or slightly
enriched uranium, the coolant/moderator is heavy water, and the control rods are similar to the other
reactors. Breeder reactors have been primarily used to produce weapons-grade plutonium. They use
natural uranium and a coolant/moderator that usually is liquid sodium. Most of the breeder reactors
have been phased out since sufficient plutonium for weapons production has been stockpiled, and
there is no immediate scarcity of natural uranium.
Further advances in developing novel nuclear power plants are possible that will increase their
thermal efficiency, use less expensive fuels, such as natural uranium and thorium, and, foremost,
ensure their absolute safety.
Despite persisting concerns about nuclear power plant safety, only one acknowledged serious
accident occurred—that at Chernobyl in 1986—involving 28 mortalities and a yet unknown number
of latent morbidities. The Three Mile Island accident in 1979 is not known to have caused excess
mortality or morbidity. The Tokaimura accident in 1999 was not associated directly with power
plants, but with reprocessing spent fuel.
Nevertheless, the future of nuclear power plants is very much uncertain. In part the uncertainty
stems from the public's perception that nuclear power plants are inherently unsafe, notwithstanding
the contrary records and statistics. The other factor is economics. Although governments directly or
indirectly subsidized nuclear power plants by funding research, development, and the infrastructure
upon which the plants were founded, the production cost of electricity in existing plants is either
equal to or greater than that in fossil-fueled plants. New plants may become more expensive
than existing ones because of the increased capital investment needed for added safety features.
Production costs may also increase because a larger number of technical personnel will be required
to ensure safe operation of the new plant and also because of the imbedded cost of safe disposal of
spent fuel and decommissioning the plant after reaching retirement.
Realistically, the only conditions under which nuclear power plants will increase their share
of global electricity supply are as follows: (a) fossil fuels will become scarce and/or expensive;
(b) international or national policies to prevent the threat of global warming will militate against
electricity production by fossil-fueled power plants; (c) renewable energies cannot satisfy the
increasing electricity demand; (d) national policies of governments that wish to be independent
of foreign fossil fuel supplies; (e) national policies of governments that wish to develop nuclear
weapons, the ingredients of which (i.e., plutonium) come from reprocessed spent fuel of power
plants.
In any case, if nuclear power plants are to increase their share of electricity supply, the risk
of radiation accidents must be brought to near zero, and the problem of long-term disposal of
radioactive waste must be solved.
