DOE/ET/51013—292
DE91 016969
PFC/RR-91-9
A COMPARISON of RADIOACTIVE WASTE
from FIRST GENERATION FUSION REACTORS
and FAST FISSION REACTORS with
ACTINIDE RECYCLING*
M. Koch and M.S. Kazimi
April 1991
Plasma Fusion Center
and
Department of Nuclear Engineering
Massachusetts Institute of Technology
Cambridge, MA 02139 U.S.A.
*This work was partially supported by EG&G Idaho, Inc.
and the U.S. Department of Energy under DOE Contract
No.
DE-AC02-78ET-51013 and DE-FG02-91ER-54110
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A Comparison of Radioactive Waste
from First Generation Fusion Reactors
and Fast Fission Reactors with
Actinide Recycling
by
M. Koch and M.S Kazimi
Abstract
Limitations of the fission fuel resources will presvtmably mandate the replace-
ment of thermal fission reactors by fast fission reactors that operate on a
self-
sufficient closed fuel cycle. This replacement might take place within the next
one hvmdred years, so the direct competitors of fusion reactors will be fission
reactors of the latter rather than the former type. Also, fast fission reactors,
in contrast to thermal fission reactors, have the potential for transmuting long-
lived actinides into short-Uved fission products. The associated reduction of the
long-term activation of radioactive waste due to actinides makes the comparison
of radioactive waste from feist fission reactors to that from fusion reactors more
rewarding than the comparison of radioactive waste from thermal fission reactors
to that from fusion reactors.
Radioactive waste from an experimental and a commercieil fast fission reactor
and an experimental and a commercial fusion reactor heis been characterized. The
fast fission reactors chosen for this study were the Experimental Breeder Reactor
II (EBR-II) and the Integral Fast Reactor {IFR). The fusion reactors chosen for
this study were the International Thermonuclear Experimental Reactor (ITER)
Eind a Reduced Activation Ferrite Helium Tokamak (RAFHT).
The four reactors considered operate on an idealized self-sufficient closed
fuel cycle, i.e. actinides and tritiimi are regarded as fuel emd recycled back
to the reactor. In the caise of the two fast fission reactors, actinide recycUng
is possible without detrimental effects to the neutronics, because at the very
high average neutron energies in these reactors, not only plutonitun, but also
most other actinides become fissionable, i.e. constitute fuel rather than poison.
Reedisticeilly, the radioactive waste from the two faist fission reactors will contain
some actinides and that from the two fusion reactors will contain some tritiiun.
However, since actual separation efficiencies are expected to be in the 99.9%
range, the radioactive waste wiU contain less than 0.1% of the actinides or the
tritivun. In contrast, thermal fission reactors do not operate on a self-svifficient
closed fuel cycle and hence their radioactive waste contains up to 100% of the
actinides.
The fast fission and the fusion reactors have been approximated as a set of
homogenized reactor components of simple cylindrical and/or hexagonal geom-
etry. Reactor components as radioactive waste were characterized by several
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pareuneters. These parEimeters describe the volume and activation of radioactive
waste and are pertinent to US regulatory standards.
Build-up and decay of radionuclides in reactor components were simulated
by the computer codes ORIGEN-IHOT fast fission reactors and ONEDANT and
REAC-IHoT fusion reactors. Auxihary computer codes were developed to convert
the output of those three computer codes into radioactive waste parameters. The
parameters were not normaUzed to the different power levels of the compeured
reactors, but rather evaluated for these reactors as built.
The comparison of radioactive waste parameters shows that radioactive waste
from the experimental fast fission reactor may be less haizardous than that from
the experimental fusion reactor. Inclusion of the actinides would reverse this
conclusion only in the long-term. Radioactive weiste from the commerciad fusion
reactor may Jilways be less hazardous th£in that from the commercial fast fission
reactor, irrespective of the inclusion or exclusion of the actinides. The fusion
waiste would even be far less heizardous, if advanced structviral materials, like
siUcon carbide or vanadiimi alloy, were employed.
Also,
radioactive waste from the experimental fast fission reactor may be less
hazardous than that from the commercial fast fission reactor. This is a direct
consequence of the utiUzation of highly ^^^ U enriched fuel in EBR-II resulting
in a lower activation than the utihzation of uraniimi-plutonivmi-minor-actinides
fuel in IFR. Radioactive WEiste from the commercial fusion reactor may be less
hazardous than that from the experimental fusion reactor. This is a direct con-
sequence of the utiUzation of standard materials (55316) in ITER resvdting in a
higher activation than the utiUzation of Reduced Activation Materials (RAF) in
RAFHT.
The generation of High Level Radioactive Waste (HLRW) is likely not
to be avoided even for
RAFHT.
The volimie of radioactive waste from the two fusion reactors is larger than
the volvune of radioactive wEiste from the two faist fission reactors. Material
selection in the fusion reactors plays a far more important role in controlUng the
activation of the radioactive waste than it does in the fast fission reactors. If
recycUng of fusion reactor structureil materials is fovmd feasible in the future, the
volume of radioactive waste from fusion reactors will be reduced.
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