21 March 2012

Breeder Reactors it is - But will it be 'Fast (Metal Cooled - Uranium) Breeders' OR 'Thermal (Molten Salt - Thorium) Breeders' ?

The Japanese Nuclear Crisis: Dr. James Mahaffey Responds
Dr James Mahaffey
'Atomic Awakenings' http://www.goodreads.com/book/show/6600498-atomic-awakening  outlines nuclear energy's discovery and applications throughout history. Mahaffey's brilliant and accessible book is essential to understanding the astounding phenomenon of nuclear power in an age where renewable energy and climate change have become the defining concerns of the twenty-first century.

This is the way it will be:  My purpose is not to sell nuclear power, because there is no longer a reason to sell it. Nuclear power, waiting quietly in its coma, has now become inevitable. That is, the ultimate need for nuclear power has finally caught up with its mad dash to develop. Whether you like it or not, the industrial world no longer has a choice. The age of burning coal and gasoline is over as atmospheric chemistry and general environmental pollution have approached states of crisis and hydrocarbons are becoming too expensive to burn. We need wind power, solar power, geothermal and hydro and anything else we can think of, but the base power must be constant running, high output nuclear stations. The real expansion of nuclear power is just awakening.....                              
Tom Blees is the author of Prescription for the Planet - The Painless Remedy for Our Energy & Environmental Crises. Tom is also the president of the Science Council for Global Initiatives  http://www.thesciencecouncil.com/

The Science Council for Global Initiatives is a growing international group of scientists, politicians, activists and other concerned men and women working together to articulate cohesive, efficient policies for solving the most serious problems ever faced by mankind. Resource wars, globe-girdling pollution, the threat of serious climate disruption; these challenges demand immediate international cooperation and inspiration on an unprecedented level. The world-class members of SCGI are creating the foundations for political and social structures that will enable us to meet the formidable challenges of the 21st century.


Two super-cool, undemonstrative, tell-it-as-it-is, professional communicators who know that energy from breeder reactors is sustainable - from the inexhaustible fuel sources of uranium and thorium, until the end of (Homo.s) time. And, within 2 or 3 decades, Breeder Reactors will be the main source of base-load energy for all of humankind.

But why do they only mention Fast Breeders, without even a nod or a wink towards Thermal Breeders which are so much more efficient and require only a fraction of the amount of fuel and therefore size of vessels, pumps, valves, etc..

But that's just a minor benefit of Thermal Breeders over Fast Breeders. There's a catalogue of other reasons why Fast Breeders should be second in the queue:

Liquid Metal Fast Breeder Reactors (LMFBRs), or any other acronym that fits, use highly reactive sodium as a coolant, exchanging heat with pressurised water. Sodium explodes on contact with water (and burns on contact with air) - so the system has a potent 'driver' to expel radiotoxic substances upwards and out into the environment.

Molten Salt Breeder Reactors (MSBRs) are thermal breeders, operating at atmospheric pressure, with both reactor and coolant salts of low chemical reactivity; there is no high pressure or chemically reactive ‘driver’ to expel radiotoxic substances into the environment. A reactor vessel leak or breach would result in the molten salt glug-glug-glugging down the side of the vessel into non-critically configured drain tanks, designed to remove decay heat.

LMFBRs operate at atmospheric pressure on the primary circuit side, but they do need large pressure vessels on the secondary side for steam generation - although nothing like the gigantic proportions of Light Water Reactor  (LWR) steam generators. Materials are competitively priced stainless steel, but plant and equipment is larger than equivalent MSBRs. Also, a separate and expensive, on-site fuel reprocessing plant is preferable to importing already processed fuel.

MSBRs also operate at atmospheric pressure, but the heat exchanger with the gas turbine fluid and coolant salt circuit (within the heat exchanger only) has to withstand high pressure. Also, the material to handle the molten fluoride salts is sophisticated Hastelloy N  which is expensive. However, because the plant is smaller and the fuel reprocessing 'built-in', it is likely that MSBRs come under the price of equivalent LMFBRs.

LMFBRs, at relatively low temperature, use steam turbine power, which might reach 38% efficiency of conversion of heat to electricity.

MSBRs use gas turbines at 48% efficiency - this means you get 25% more electricity for your (fuel cost) money.

Although both forms of breeders are roughly equivalent in respect of most other attributes, MSBRs have a substantial efficiency advantage over LMFBRs, when it comes to the development of a 'Hydrogen Economy'.

Hydrogen Economy
LMFBRs, because of their low-temperature operation, would have to produce electricity first, before that could be used to get to the temperatures required to produce hydrogen. A guesstimate might be 50% efficiency. 

MSBRs can output 750 °C process heat, which is capable of producing hydrogen directly and the efficiency is maximised.

The importance of a Hydrogen Economy cannot be overemphasised. See: 'Benefits of LFTRs.

Note:  LFTRs are the configuration of MSBR most suited to electricity generation. Other configurations of MSBRs may be better suited to 'burning' nuclear 'waste' and the plutonium stockpiles.

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