POWER March 2015 - 54

FUELS
(For a look at reactor designs under development,
see " THE BIG PICTURE: Advanced
Fission " in the November 2012 issue or at
powermag.com.)
Most of these advanced concepts are not
exactly new. Nuclear researchers have long
looked at liquid sodium as a reactor coolant,
because sodium has attractive characteristics,
including excellent heat transfer, a low melting
point, and a high boiling temperature.
Using sodium coolant could provide extended
fuel burnup. But sodium is inherently
dangerous, capable of burning or exploding
when exposed to water or air.
GE has put many years and millions of
dollars into its PRISM sodium-cooled, fast
neutron reactor design. TerraPower, a company
with financial backing from Microsoft
founder Bill Gates, is designing a sodiumcooled
" traveling wave reactor " using depleted
uranium (U-238 left after enrichment
has removed much of the fissionable U-235),
optimistically projecting commercialization
in " the late 2020s. "
There is also widespread work on developing
a fuel cycle based on the naturally
occurring element thorium. Bombarding
thorium with neutrons can transmute the
element into U-233, which does not occur
in nature and is fissile. The late nuclear
energy pioneer Alvin Weinberg long advocated
thorium reactors, because they cannot
melt down and do not produce plutonium,
used in weapons. The Atomic Energy Commission
experimented with thorium reactors
in the 1960s, but the technology lost out to
light-water reactors, as also occurred with
sodium-cooled reactors.
Thorium has its own set of inherent technical
and economic problems, among them
the need to reprocess the irradiated thorium
to get the U-233. A 2012 article in the Bulletin
of the Atomic Scientists claimed that a
thorium fuel cycle would be considerably
more expensive than the current uranium fuel
cycle and would " require too great an investment
and provide no clear payoff. "
Research into the thorium fuel cycle continues.
India has the most ambitious program.
India refused to sign the 1968 Nuclear NonProliferation
Treaty and exploded its own
atomic bomb in 1974, largely cutting itself
off from international assistance in developing
a nuclear power program. The country
has little indigenous uranium but lots of
thorium. That led India to explore a thorium
fuel cycle. The country is now getting international
assistance for conventional lightwater
reactors, but its interest in thorium has
not waned.
According to World Nuclear News, India
is building a 500-MW prototype thorium reactor,
expected to be in operation this year.
This step, said the publication, will " set
the scene for eventual full utilization of the
country's abundant thorium to fuel reactors.
Six more such 500-MWe fast reactors have
been announced for construction, four of
them by 2020. "
Less-ambitious thorium research and development
(R&D) efforts are under way in
Canada, China, Germany, Israel, Japan, Norway,
the UK, and the U.S. An article in The
Economist a year ago breathlessly touted the
thorium fuel cycle's advantages as if they
were newly discovered. U.S. interest is reportedly
at a very low level at the DOE. Sens.
Harry Reid (D-Nev.) and Orrin Hatch (RUtah)
have pushed to revive the government's
research into the liquid fluoride thorium reactor,
abandoned in the 1960s because it lacked
a military connection. Reid and Hatch have
repeatedly introduced legislation to revitalize
thorium R&D. Congress has shown no interest
so far. ■
-Kennedy Maize is a POWER
contributing editor.
The 2014 UDI Who's Who Directory covers more
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The directory provides:
* Nearly 8,100 plant management and support
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* Basic plant operating statistics for more than 1,500
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54
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POWER March 2015

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