world power demands, the use of nuclear power must continue to grow as
a safe, emission free, reliable, and economical source of energy. However,
at the rate waste is produced by the existing fleet of nuclear reactors
in the U.S., new repository capacity equal to the statutory capacity of
the yet-to-open Yucca Mountain would be needed about every 20 years. Therefore,
the ability to expand, or even maintain the nuclear power capacity in
the U.S. will be limited, unless either additional disposal capacity is
identified, or waste volume, proliferation risk, and toxicity dose are
on this motivation, methods to reduce nuclear waste volume and toxicity
have been proposed that involve a large fleet of systems using liquid
metal-cooled, fast breeder reactor technologies. However, the use of these
technologies has been questioned. Critics argue that significant amounts
of new waste and ample opportunities for plutonium diversion would be
created, that estimated deployment times are too long to be of any benefit,
and that estimated costs are prohibitive.
far preferable option for the destruction (transmutation) of waste from
reactors is based on the use of thermal Modular Helium Reactor systems
(MHRs). An essential feature of the MHR transmuter is the use of ceramic-coated
fuel particles that are strong and highly resistant to irradiation, thereby
allowing very extensive destruction levels ("deep burn") in one pass.
The ceramic coatings are also durable and impervious to moisture for long
periods of time, providing an attractive residual waste form. In addition,
the fixed moderator (graphite) and neutronically transparent coolant (helium)
provide inherent safety features for the destruction of nuclear waste
that cannot be replicated in any other design.
plutonium destruction tests and recent engineering developments in the
use of modular helium reactor technologies indicate that transmutation
of nuclear waste in these systems could be practical and economically
viable in the near term.
destruction would be performed rapidly without the need for multiple
reprocessing of large amounts of weapons-usable plutonium or other fissionable
materials, thus eliminating long-term proliferation risks associated
with repeated handling of plutonium, and limiting the generation of
MHR technology could be available for deployment in a short time, thus
making a positive contribution to the solution of waste treatment in
a timely manner. Credibility for this is strengthened by two considerations:
(1) utilities in the U.S. and abroad are considering MHR technologies
for the next generation of nuclear reactors, and (2) MHR technologies
are currently being developed in Russia for the destruction of weapons-grade
materials while generating electric power.
the Deep Burn Transmutation, MHR-based, the destruction of reactor waste
is logically carried through one burn-up cycle, achieving virtually complete
destruction of proliferation materials, and roughly 95% destruction of
all transuranic waste. While it would be possible to reduce the residual
waste inventory further through repeated processing and recycle in the
MHR system, there is little advantage in doing so since: (1) virtually
all proliferation materials would already be destroyed, and (2) more high
level secondary waste is produced with each additional reprocessing stage.
brief outline of the Deep Burn, MHR-based, Transmutation concept
transmutation of nuclear waste involves treating reactor spent fuel and
bombarding it with "customized" neutron radiation to fundamentally change
its characteristics and make it significantly easier to dispose of.
initial treatment of nuclear waste is the traditional and well proven
UREX (Uranium Extraction) process, extensively described in previous
documents, including the DOE-sponsored transmutation roadmap.
the MHR nuclear waste destruction concept, the thermally fissile component
of the nuclear waste (made into "driver" fuel) fissions and generates
the neutrons necessary to achieve the conversion of the thermally non-fissile
component into fissionable isotopes ("transmutation" fuel) and their
two fuels are fabricated with the same ceramic coated particle technology
already developed for commercial MHR systems, sized to favour immediate
fission (driver fuel), or absorption-followed-by-fission (transmutation
to some perceptions, in the right environment thermal neutrons are perfectly
capable of transmuting both major and minor actinides: Cross sections
and specific destruction rates are large.
of the nuclear waste destruction is done in MHR reactors (critical systems)
of very similar design to systems currently proposed for high efficiency
energy production (including "prismatic" and "pebble bed" variants).
This extensive transmutation is achieved using the principle that "fresh
fuel burns old fuel" in cores that are zoned with fuels of different
the neutron self-generating ability of the driver fuel is exhausted,
the transmutation fuel is extracted from the MHR critical system and
is irradiated in a second-stage MHR system without further reprocessing,
thereby avoiding the problems associated with the handling of volatile
actinides (Americium and Curium).
extra neutrons required to implement the second transmutation stage
(where 20% of the overall destruction is accomplished) could be generated
by an accelerator-driven spallation target housed in the center of MHR
subcritical cores. Alternatively, a large fraction of the necessary
neutrons could be obtained using 20% enriched uranium, thereby substantially
reducing the use of subcritical systems.
the final residual wasteform, ceramic-coated exhausted fuel is very
durable and remains impervious to moisture well beyond the life of metal
containers currently contemplated for spent fuel disposal.