2006 Int. Congress on Advanced Nuclear Power Plants(ICAPP'06)
開催地
和文:
英文:
Reno,Nevada,USA
アブストラクト
A new reactor burnup strategy CANDLE (Constant Axial shape of Neutron flux,
nuclide densities and power shape During Life of Energy producing reactor) was proposed, where
shapes of neutron flux, nuclide densities and power density distributions remain constant but
move upward (or downward) along its core axis.
This burnup strategy can derive many merits, especially from safety point of view. The change
of excess reactivity along burnup is theoretically zero, and the core characteristics, such as power
feedback coefficients and power peaking factor, are not changed along burnup.
Application of this burnup strategy to neutron rich fast reactors makes excellent
performances. Only natural or depleted uranium is required for the replacing fuels. About 40 % of
natural or depleted uranium undergoes fission without the conventional reprocessing and
enrichment.
If the LWR produced energy of X Joules, the CANDLE reactor can produce about 50X Joules
from the depleted uranium left at the enrichment facility for the LWR fuel. If we can say LWRs
have produced energy sufficient for full 20 years, we can produce the energy for 1000 years by
using the CANDLE reactors with depleted uranium. We need not mine any uranium ore, and do
not need reprocessing facility. The burnup of spent fuel becomes 10 times. Therefore, the spent
fuel amount per produced energy is also reduced to one-tenth.
The equilibrium core contains a lot of instable materials such as higher actinides and fission
products, the enough amounts of which can not be obtained easily. The construction of the initial
core is a difficult problem. However, by using enriched uranium substituted for actinides in the
equilibrium core, we can construct the initial core whose power profile is similar to the
equilibrium one and will reach the equilibrium state without any big change during transient.
At present we do not have any material standing for such a high burnup. However, the
CANDLE burnup can be realized by employing simple reprocessing, which separates actinides
and fission products and replaces the cladding by new one.
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