Civil Engineering Reference
In-Depth Information
assured and inferred). “Reasonably assured” means that these uranium resources
can be mined, “inferred” means that additional investigations are required until the
uranium ores can be mined. At the same time IAEA and OECD/NEA prognosti-
cated additional speculative 7.77 million tons of uranium ores and further 4.2
million tons in the Chattanooga Shales in USA [
3
,
4
].
1.2 Uranium Consumption
A present LWR with a power capacity of 1 GW(e) consumes about 171 tons of
natural uranium (availability factor of 93 %) per year. This means, that e.g. about
370 GW(e) presently in operation (assumed all nuclear power reactors would be
LWRs) will consume over 80 years about 5 million tons of natural uranium.
Correspondingly a future 480 GW(e) nuclear power capacity (assumed all nuclear
power reactors would be LWRs) would consume in 180 years about 15 million tons
of natural uranium. Heavy Water Reactors or Light Water Reactors with plutonium
recycling would have by a factor of 1.55 lesser natural uranium consumption and
would extend the above time period correspondingly [
5
].
The fission neutrons originating from the fission process are moderated or
slowed down by the collision with atoms of a moderator or coolant, e.g. light or
heavy water, in the cores of LWRs and HWRs to so-called thermal energy of
0.025 eV. This corresponds to neutron velocities of 2,200 m/s. In liquid metal
cooled Breeder Reactors the fission neutrons originating from the fission process
are slowed down only to 0.2 MeV as the moderator or the coolant (sodium, lead or
lead-bismuth) is of medium or high atomic mass. In this range of neutron energies
of 0.2 MeV and higher the nuclear reactions for breeding of Pu-239 from U-238 are
favorable. This newly generated Pu-239 can be utilized as artificial fissionable
nuclear fuel in e.g. LWRs or FBRs.
Fast Breeder Reactors are started initially with uranium/plutonium fuel in their
core and uranium fuel in their blankets. They consume per GW(e) and year only
1.7 tons of U-238 (either natural uranium or depleted uranium from uranium
enrichment plants). The technical feasibility of sodium cooled Fast Breeder Reac-
tors has been proven already in the USA, Russia, UK, France, India and Japan
during the past decades. Fast Breeder Reactors require a closed fuel cycle with
spent fuel reprocessing and fuel refabrication [
5
,
6
].
This by a factor of about 100 lower fuel consumption (1.7 tons per year and GW
(e) for Fast Breeder Reactors compared to 171 tons per year and GW(e) for Light
Water Reactors) of fast Breeders would extend the above given time periods
accordingly. As the nuclear breeding is also possible for the Th-232/U-233 nuclear
fuel cycle, the available resources of natural uranium and thorium and the applica-
tion of Fast Breeder Reactors would prolong the above discussed 180 years to many
thousand years [
5
].
