”thorium reactors” — a very old idea that is now being dressed up in modern clothes and made to seem like a major scientific breakthrough, which it is not.
Thorium Reactors: Back to the Dream Factory by Gordon Edwards, Ph.D., President of CCNR, July 13, 2011 The Nuclear Dream Factory Every time a nuclear power reactor idea doesn’t work out, and ordinary people get down-hearted and even start to doubt the magnificence andbenificence of nuclear energy, the nuclear proponents rush back to their well-stocked dream factory to fetch another idea — one that is sufficiently unfamiliar and sufficiently untested that ordinary people have no idea whether it is good or bad, safe or dangerous, feasible or foolish, or whether the almost miraculous claims made about it are true or false.
Just a few years ago, nuclear proponents were pushing Generation 3 reactors – enormous plants that would generate huge amounts of electricity, yet be cheaper and faster to build than earlier models, as well as being safer and longer-lived.
Then Areva ran into a blizzard of problems trying to build one of these behemoths in Finland – the cost soaring by billions of dollars, the construction
time extended by years, and fundamental safety-related design problems
surfacing late in the game. Check and mate.
Undaunted, nuclear proponents quickly executed a 180-degree turn and are now promoting small reactors which can be mass- produced by the thousands and
sprinkled on the landscape like cinnamon on toast. Pebble-bed reactors, moltensalt reactors, thorium reactors, have been paraded before the public with as
many bells and whistles as the nuclear industry can muster, to distract people’s
gaze away fromthe construction fiascos, the litany of broken promises from the
past, the still-unsolved problems of nuclear waste and weapons proliferation, and
the horror that is Fukushima.
The following paragraphs are written to dispel some of the mystique surrounding
the idea of “thorium reactors” — a very old idea that is now being dressed up in
modern clothes and made to seem like a major scientific breakthrough, which it is
Thorium is not a nuclear fuel
The fundamental fact about thorium is that it is NOT a nuclear fuel, because
thorium is not a fissile material, meaning that it cannot sustain a nuclear fission
In fact the ONLY naturally occurring fissile material is uranium-235, and so — of
necessity –that is the material that fuels all of the first-generation reactorsin the
entire world. Thorium cannot replace uranium-235 in this regard. Not at all.
Thorium is a “fertile” material
But thorium-232, which is a naturally occurring radioactive material, is about
three times as abundant as uranium-238, which is also a naturally occurring
radioactive material. Neither of these materials can be useddirectly as a nuclear
fuel, because they are not “fissile” materials.However, both uranium-238 and thorium-232 are “f”fertile” materials, which means
that IF they are placed in the core of a nuclear reactor (one that is of necessity
fuelled by a fissile material), some fraction of thosefertile atoms will be
transmuted into man-made fissile atoms.
Some uranium-238 atoms get transmuted into plutonium-239 atoms, andsome
thorium-232 atoms get transmuted into uranium-233 atoms.
Both plutonium-239 and uranium-233 are fissile materials which are not naturallyoccurring. They are both usable as either fuel for nuclear reactors or as nuclear
explosive materials for bombs.
(The USA exploded an atomic bomb made from U-233 in 1955.)
Reprocessing of irradiated nuclear fuel
In general, to obtain quantities of plutonium-239 or uranium-233, it is necessary
to “reprocess” the irradiated material that started out as uranium-238 or thorium-
232. This means dissolving that irradiated material in acid and then chemically
separating out the fissile plutonium-239 or uranium-233, leaving behind the liquid
radioactive wastes which include fission products (broken pieces of split atoms,
including such things as iodine-131, cesium-137, strontium-90, etc.) and other
radioactive waste materials called “activation products” and “transuranic
Reprocessing is the dirtiest process in the entire nuclear fuel chain, because of
the gaseous radioactive releases, liquid radioactive discharges, and large
quantities of highly dangerous and easily dispersible radioactive liquids.
Reprocessing also poses great proliferation risks because it produces man-made
fissile materials which can be incorporated into nuclear weapons of various kinds
by anyone who acquires the separated fissile material.
Advanced Fuel Cycles and Breeders
“Any nuclear reactor-fuelling regime that requires reprocessing, or that uses
plutonium-239 or uranium-233 as a primary reactor fuel, is called an “advanced
fuel cycle”. These advanced fuel cycles are intimately related with the idea of a
“breeder” reactor — one which creates as much or more fissile material as a
byproduct than the amount of fissile material used to fuel the reactor.
So it is only in this context that thorium reactors make any sense at all — like
all breeder concepts, they are designed to extend the fuel supply
of nuclear reactors and thus prolong the nuclear age by centuries. The breeder concept is very attractive to those who envisage a virtually limitless
future for nuclear reactors, because the naturally occurring uranium-235 supply is
not going to outlast the oil supply. Without advanced fuel cycles, nuclear power
is doomed to be just a “flash in the pan”.
Thorium reactors are most enthusiastically promoted by those who see
“plutonium breeders” as the only other realistic alternative to bring about a longlived nuclear future. They think that thorium/uranium-233 is a better fate than
They do not see a nuclear phaseout as even remotely feasible or attractive.
“Molten Salt” reactors
Molten salt reactors are not a new idea, and they do not in any way require the
use of thorium — although historically the two concepts have often been linked.
The basic idea of using molten salt insteadof water (light or heavy water) as a
coolant has a number of distinctadvantages,chief of which is the ability to achieve
much highertemperatures(650 deg. C instead of 300 deg. C) than with
watercooled reactors,and at a much lower vapour pressure.
The higher temperature meansgreaterefficiency in converting the heat into
electricity, and the lowerpressure means less likelihood of an over-pressure
rupture of pipes,and less drastic consequences of such ruptures if and when they
Molten salt reactors were researched at Oak Ridge Tennessee throughout the
1960s, culminating in the Molten Salt Reactor Experiment (MSRE), producing 7.4
megawatts of heat but no electricity. It was an early prototype of a thorium
breeder reactor, using uranium and plutonium as fuels but not using the thorium
blanket which would have been used to “breed” uranium-233 to be recovered
through reprocessing — theultimate intention of the design.
This Oak Ridge work culminated in the period from 1970-76 in a design for a
Molten Salt Breeder Reactor (MSBR) using thorium as a “fertile material” to
breed “fissile” uranium-233, which would then be extracted using a reprocessing
Molten Salt Thorium reactors without reprocessing?
Although it is theoretically possible to imagine a molten-salt reactor design where
the thorium-produced uranium-233 is immediately used as a reactor fuel without
any actual reprocessing, such reactor designs are very inefficient in the”breeding” capacity andpose financial disincentives of a serious nature to any
would-be developer. No one has actually built such a reactor or has plans to build
such a reactor because it just isn’t worth it compared with those designs which
have a reprocessing facility.
Here’s what Wikipedia sayson this matter (it happens to be good info):
To exploit the molten salt reactor’s breeding potential to the fullest, the reactor must be co-located with a reprocessing facility. Nuclear reprocessing does not
occur in the U.S. because no commercial provider is willing to undertake it. The
regulatory risk and associated costs are very great because the regulatory
regime has varied dramatically in different administrations.UK, France,
Japan, Russia and India currently operate some form of fuel reprocessing.
Some U.S. Administration departments have feared that fuel reprocessing in any
form could pave the way to the plutonium economy with its associated
A similar argument led to the shutdown of the Integral Fast Reactor project in
1994.The proliferation risk for a thorium fuel cycle stems from the potential
separation of uranium-233, which might be used in nuclear weapons, though only
with considerable difficulty. Currently the Japanese are working on a 100-200
MWe molten salt thorium breeder reactor, using technologies similar to those
used at Oak Ridge, but the Japanese project seems to lack funding.
Thorium reactors do not eliminate problems
The bottom line is this. Thorium reactors still produce high-level radioactive
waste, they still pose problems and opportunities for the proliferation of nuclear
weapons, they still pose catastrophic accident scenarios as potential targets for
terrorist or military attack, for example.
Proponents of thorium reactors argue that all of these risks are somewhat
reduced in comparison with the conventional plutonium breeder concept.
Whether this is true or not, the fundamental problems associated with nuclear
power have by no meansbeen eliminated.
Gordon Edwards, Ph.D., President,
Canadian Coalition for Nuclear Responsibility http://www.ccnr.org/think_about_thorium.pdf