New Post (68) : On a lighter note
A Nation Of Sheep Will Beget A Government Of Wolves - Edward R. Murrow
On a lighter note…
One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors. – Plato
Charlie Brown
Wednesday, December 8, 2010
The Indian case for Thorium
New Post (67) : The Indian case for Thorium
Thorium is much more abundant in nature than uranium.
Thorium can also be used as a nuclear fuel through breeding to fissile uranium-233.
Thorium continues to be a tanatalising possibility for use in nuclear power reactors, though for many years India has been the only sponsor of major research efforts to use it.
Nature and sources of thorium
Thorium is a naturally-occurring, slightly radioactive metal. It is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium. Soil commonly contains an average of around 6 parts per million (ppm) of thorium.
The most common source of thorium is the rare earth phosphate mineral, monazite, which contains up to about 12% thorium phosphate, but 6-7% on average. Monazite is found in igneous and other rocks but the richest concentrations are in placer deposits, concentrated by wave and current action with other heavy minerals. World monazite resources are estimated to be about 12 million tonnes, two-thirds of which are in heavy mineral sands deposits on the south and east coasts of India. There are substantial deposits in several other countries
Thorium as a nuclear fuel
Thorium, as well as uranium, can be used as a nuclear fuel. Although not fissile itself, Th-232 will absorb slow neutrons to produce uranium-233 (U-233), which is fissile (and long-lived). The irradiated fuel can then be unloaded from the reactor, the U-233 separated from the thorium, and fed back into another reactor as part of a closed fuel cycle. Alternatively, U-233 can be bred from thorium in a blanket, the U-233 separated, and then fed into the core.
Over the last 40 years there has been interest in utilising thorium as a nuclear fuel since it is more abundant in the Earth's crust than uranium. Also, all of the mined thorium is potentially useable in a reactor, compared with the 0.7% of natural uranium in today's reactors, so some 40 times the amount of energy per unit mass might theoretically be available (without recourse to fast neutron reactors). But this relative advantage vanishes if fast neutron reactors are used for uranium.
India's plans for thorium cycle
With about six times more thorium than uranium, India has made utilization of thorium for large-scale energy production a major goal in its nuclear power programme, utilising a three-stage concept:
Pressurised heavy water reactors (PHWRs) fuelled by natural uranium, plus light water reactors, producing plutonium.
Fast breeder reactors (FBRs) using plutonium-based fuel to breed U-233 from thorium. The blanket around the core will have uranium as well as thorium, so that further plutonium (particularly Pu-239) is produced as well as the U-233.
Advanced heavy water reactors burn the U-233 and this plutonium with thorium, getting about 75% of their power from the thorium. The used fuel will then be reprocessed to recover fissile materials for recycling.
This Indian programme has moved from aiming to be sustained simply with thorium to one 'driven' with the addition of further fissile uranium and plutonium, to give greater efficiency.
In 2009, despite the relaxation of trade restrictions on uranium, India reaffirmed its intention to proceed with developing the thorium cycle.
((( Another option for the third stage, while continuing with the PHWR and FBR stages, is the use of subcritical accelerator driven systems. )))
Developing a thorium-based fuel cycle
Despite the thorium fuel cycle having a number of attractive features, development has always run into difficulties.
The main attractive features are: The possibility of utilising a very abundant resource which has hitherto been of so little interest that it has never been quantified properly. The production of power with few long-lived transuranic elements in the waste. Reduced radioactive wastes generally.
Much development work is still required before the thorium fuel cycle can be commercialised, and the effort required seems unlikely while (or where) abundant uranium is available. In this respect, recent international moves to bring India into the ambit of international trade might result in the country ceasing to persist with the thorium cycle, as it now has ready access to traded uranium and conventional reactor designs.
Nevertheless, the thorium fuel cycle, with its potential for breeding fuel without the need for fast neutron reactors, holds considerable potential in the long-term. It is a significant factor in the long-term sustainability of nuclear energy.
Charlie Brown
Thorium is much more abundant in nature than uranium.
Thorium can also be used as a nuclear fuel through breeding to fissile uranium-233.
Thorium continues to be a tanatalising possibility for use in nuclear power reactors, though for many years India has been the only sponsor of major research efforts to use it.
Nature and sources of thorium
Thorium is a naturally-occurring, slightly radioactive metal. It is found in small amounts in most rocks and soils, where it is about three times more abundant than uranium. Soil commonly contains an average of around 6 parts per million (ppm) of thorium.
The most common source of thorium is the rare earth phosphate mineral, monazite, which contains up to about 12% thorium phosphate, but 6-7% on average. Monazite is found in igneous and other rocks but the richest concentrations are in placer deposits, concentrated by wave and current action with other heavy minerals. World monazite resources are estimated to be about 12 million tonnes, two-thirds of which are in heavy mineral sands deposits on the south and east coasts of India. There are substantial deposits in several other countries
Thorium as a nuclear fuel
Thorium, as well as uranium, can be used as a nuclear fuel. Although not fissile itself, Th-232 will absorb slow neutrons to produce uranium-233 (U-233), which is fissile (and long-lived). The irradiated fuel can then be unloaded from the reactor, the U-233 separated from the thorium, and fed back into another reactor as part of a closed fuel cycle. Alternatively, U-233 can be bred from thorium in a blanket, the U-233 separated, and then fed into the core.
Over the last 40 years there has been interest in utilising thorium as a nuclear fuel since it is more abundant in the Earth's crust than uranium. Also, all of the mined thorium is potentially useable in a reactor, compared with the 0.7% of natural uranium in today's reactors, so some 40 times the amount of energy per unit mass might theoretically be available (without recourse to fast neutron reactors). But this relative advantage vanishes if fast neutron reactors are used for uranium.
India's plans for thorium cycle
With about six times more thorium than uranium, India has made utilization of thorium for large-scale energy production a major goal in its nuclear power programme, utilising a three-stage concept:
Pressurised heavy water reactors (PHWRs) fuelled by natural uranium, plus light water reactors, producing plutonium.
Fast breeder reactors (FBRs) using plutonium-based fuel to breed U-233 from thorium. The blanket around the core will have uranium as well as thorium, so that further plutonium (particularly Pu-239) is produced as well as the U-233.
Advanced heavy water reactors burn the U-233 and this plutonium with thorium, getting about 75% of their power from the thorium. The used fuel will then be reprocessed to recover fissile materials for recycling.
This Indian programme has moved from aiming to be sustained simply with thorium to one 'driven' with the addition of further fissile uranium and plutonium, to give greater efficiency.
In 2009, despite the relaxation of trade restrictions on uranium, India reaffirmed its intention to proceed with developing the thorium cycle.
((( Another option for the third stage, while continuing with the PHWR and FBR stages, is the use of subcritical accelerator driven systems. )))
Developing a thorium-based fuel cycle
Despite the thorium fuel cycle having a number of attractive features, development has always run into difficulties.
The main attractive features are: The possibility of utilising a very abundant resource which has hitherto been of so little interest that it has never been quantified properly. The production of power with few long-lived transuranic elements in the waste. Reduced radioactive wastes generally.
Much development work is still required before the thorium fuel cycle can be commercialised, and the effort required seems unlikely while (or where) abundant uranium is available. In this respect, recent international moves to bring India into the ambit of international trade might result in the country ceasing to persist with the thorium cycle, as it now has ready access to traded uranium and conventional reactor designs.
Nevertheless, the thorium fuel cycle, with its potential for breeding fuel without the need for fast neutron reactors, holds considerable potential in the long-term. It is a significant factor in the long-term sustainability of nuclear energy.
Charlie Brown
Why Wikileaks leaks
New Post (66) : Why Wikileaks leaks
Wikileaks is no hero as some are trying to make them out to be.
Post the shock of 9.11 the enormous pressure on the US government to co-ordinate the workings of it’s various agencies responsible for national security led to information being placed indiscriminately on a wider digital net…accessible by “all and sundry” in the security community.
The leak was inevitable.
Wikileaks is---"shamelessly making capital from a traumatized nation’s response to a huge tragedy".
...like stabbing a mourner in the back !
Every freedom, journalistic and other, has to be worked within civilized boundaries.
In by book, Wikileaks has disgraced “journalism”.
I have nothing but unconcealed contempt for this brand of Wikijournalism.
In due course the real motivation between Wikileaks LEAKS will be revealed.
I hope !
Charlie Brown
Wikileaks is no hero as some are trying to make them out to be.
Post the shock of 9.11 the enormous pressure on the US government to co-ordinate the workings of it’s various agencies responsible for national security led to information being placed indiscriminately on a wider digital net…accessible by “all and sundry” in the security community.
The leak was inevitable.
Wikileaks is---"shamelessly making capital from a traumatized nation’s response to a huge tragedy".
...like stabbing a mourner in the back !
Every freedom, journalistic and other, has to be worked within civilized boundaries.
In by book, Wikileaks has disgraced “journalism”.
I have nothing but unconcealed contempt for this brand of Wikijournalism.
In due course the real motivation between Wikileaks LEAKS will be revealed.
I hope !
Charlie Brown
Subscribe to:
Posts (Atom)