The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

The HTRs can be used to provide high-temperature heat to chemical plants, refineries, steel
production, and other industrial applications—markets currently served by fossil fuels and
that are responsible for about 16% of the total greenhouse gas emissions of the U.S. The
largest high-temperature process heat market are refineries that consume about 7% of the
nation’s total energy demand—about equal to the total energy output of the nation’s existing
nuclear power plants.
The longer-term incentive for the HTR is its potential for liquid fuels production while
minimizing greenhouse gas releases. Liquid fuels can be produced from oil, natural gas,
oil sands, oil shale, coal, and biomass. However, the less the feedstock resembles gasoline
or diesel fuel, the more energy is required to convert the feedstock into gasoline and diesel
fuel. While the refining of light crude oil consumes ~15% of the crude oil in the refining
process, the energy consumed by a coal liquefaction plant exceeds the energy value of the
gasoline and diesel fuel that is produced. Because we are transitioning from light crude oil
to alternative feedstocks, the carbon dioxide emissions from the production of a gallon of
gasoline or diesel fuel are expected to rise over the next several decades.
If external energy sources are available for refineries, coal liquefaction plants, and biorefineries,
greenhouse gas emissions can be minimized. For biofuels, the availability of external
energy sources for biorefineries determines the contribution of biofuels. It has been estimated
that the U.S. could ultimately produce 1.3 billion tons of renewable biomass per year
without major impacts on food and fiber production. If burned, the energy output would
equal about 10 million barrels of diesel fuel per day. If converted to ethanol, the energy
value of the ethanol would be equivalent to 5 million barrels of diesel per day with most
of the remaining energy used in the biomass-to-fuels production process. If external heat
and/or hydrogen are available, the same biomass could produce about 12 million barrels of
diesel fuel per day. Biofuels have the potential to replace oil in the transport sector but only
if biorefineries have external energy sources. Because plants extract carbon dioxide from
the atmosphere, the use of biofuels does not increase greenhouse gas emissions to the atmosphere
provided that a low-carbon energy source provides the energy to the biorefinery.
Recent reviews (Forsberg 2008) have evaluated the use of nuclear energy for liquid fuels
production. Some applications can use lower temperature heat from LWRs but many applications
require high-temperature heat. The largest long-term market may be the production
of gasoline and diesel from biomass using high-temperature processing and hydrogen.
Biorefinery processes (Ondrey 2010) today convert only a fraction of the biomass to gasoline
and burn the remaining biomass to provide the heat and hydrogen for the biorefinery.
By replacing the biomass consumed in operating the biorefinery, an HTR could triple fuel
yields per ton of biomass.
teChnoloGy deSCription
There are various designs of HTRs but all use the same basic coated-particle fuel. The potentially
unique societal benefits (safety, safeguards and nonproliferation, fissile fuel burning,
and waste-form performance) of HTRs are associated with the characteristics of this
fuel. Potential disadvantages (such as higher fuel manufacturing costs) are also associated
with this fuel.
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