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Title:
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Multirecycling of plutonium in advanced PWRs
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Author(s):
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Published by:
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Publication date:
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ECN
NUCLEAIR
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1998
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ECN report number:
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Document type:
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ECN-R--98-007
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Other
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Number of pages:
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Full text:
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85
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Download PDF
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Abstract:
The influence of the moderator-to-fuel ratio of MOX fueled PWRs on themoderator void coefficient, the fuel temperature coefficient, the moderator
temperature coefficient, the boron reactivity worth, the critical boron
concentration, the mean neutron generation time and the effective delayed
neutron fraction has been assessed. Increasing the moderator-to-fuel ratio to
values larger than three, gives a moderator void coefficient sufficiently
large to recycle the plutonium at least four times. Also the values of other
parameters like the boron reactivity worth, the fuel temperature coefficient,
the moderator temperature coefficient and the mean neutron generation time
improve with increasing moderator-to-fuel ratio. The effective delayed
neutron fraction is rather independent of the moderator-to-fuel ratio.
According to a point-kinetics model, a MOX fueled reactor with a
moderator-to-fuel ratio of four responds similarly to a moderator temperature
decrease as an UO2 fueled reactor with a moderator-to-fuel ratio of two.
This conclusion holds for both the instantaneous power increase and for the
deposited energy during a specific time interval. Scenario studies show that
four times recycling of plutonium in PWRs reduces the plutonium production
with a factor of three compared with a reference once-through scenario, but
that the americium and curium production triple. If the remaining plutonium
after four times recycling is disposed of, the reduction of the radiotoxicity
reaches only a factor of two. This factor increases to five at the maximum
when the plutonium is further recycled. Recycling of americium and curium is
needed to reduce the radiotoxicity of the spent fuel to lower values. In
general, the plutonium mass reduction increases and the minor actinides
production decreases with increasing moderator-to-fuel ratio of the MOX fuel.
Enlarging the moderator-to-fuel ratio can be achieved by increasing the rod
pitch or by reducing the fuel pin diameter. In both cases, the economic
penalty is about the same. 11 refs.
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