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DEPENDABLE POWER:
Most of the value of an electricity system lies in its capacity to sustainably supply dependable and CO2 emission free electric and thermal power. Nuclear power systems operate by transmuting nuclear fuel elements into reaction product elements where the average binding energy per nucleon in the reaction products is much larger than in the nuclear fuel elements. This change in average binding energy per nucleon becomes heat that is harvested by the coolant of a nuclear reactor.
Renewable energy may seem desirable but it lacks both dependability and thermal power capacity. In high latitiude countries, such as Canada and Russia, renewable electricity generation is both seasonal and intermittent and can provide at most only about 30% of the non-fossil energy required for fossil fuel displacement. The remaining 70% of the non-fossil energy required for fossil fuel displacement must come from dependable hydroelectric or nuclear power sources.
Dependable power sources are also required to black start and stabilize the public electricity grid.
With the exception of a few jurisdictions such as British Columbia, Quebec and Norway that have both both plentiful hydroelectric power and the geography required for seasonal hydraulic energy storage, most jurisdictions must rely on nuclear electricity generation for dependable non-fossil electric power.
The electric power output from a fleet of nuclear power stations is much more dependable than the electric power output from a fleet of renewable generators because:
a) Nuclear generators have a capacity factor of about 90% as compared to an average renewable generator capacity factor of about 30%;
and
b) The failure modes of nuclear generators are statistically independent whereas renewable generators have common mode failures.
Shutdown of one nuclear generator in a fleet of such generators does not diminish the electric power output of the other nuclear generators whereas all the solar panels in a fleet stop producing electricity at night and all the wind generators in a fleet stop producing electricity during low wind periods.
Natural gas fuelled generators have a potential common mode failure related to the available natural gas pipeline pressure, which is a big problem where electrically powered compressors are used maintain natural gas pipeline pressure. A sustained and widespread electricity grid failure can lead to loss of natural gas pipeline pressure. Absent fuel oil backup it becomes impossible to black start the electricity grid using natural gas fueled combustion turbine based electricity generation. Due to lack of voltage source power inverters and surge capacity at existing distributed wind and solar generators it is also impossible to restart the public electricity grid using only wind and solar electricity generation.
HEAT:
A large fraction of present fossil fuel energy consumption is for provision of heat. In urban markets it is much more economic to provide dependable nuclear district heat than to provide dependable heat powered by any form of non-fossil electricity generation.
NUCLEAR POWER SOURCES:
There are two methods of producing nuclear energy, fission of high atomic weight elements and fusion of low atomic weight elements. Both methods are explored in this web site section.
However, from a practical economic public power perspective nuclear energy released via fission of unstable fissile heavy isotopes, that are bred from abundant more stable fertile heavy isotopes, is the only dependable, sustainable and economic source of non-fossil power that can fully displace fossil fuels. A significant portion of the nuclear energy released must come from fast neutron induced fission to dispose of long lived nuclear waste and to sustain conversion of fertile isotopes into fissionable isotopes.
A 2013 overview of the various nuclear reactor technologies is contained in the text New Technologies Associated to the Construction of Nuclear Power Plants.
Public misconceptions about nuclear power are concisely addressed in a PragerU Video.
The status of civilian nuclear power in 2019 is summarized in Ensuring the Future of Nuclear Power.
The design of conventional light water cooled nuclear power reactors is summarized in the:
Nuclear Engineering Handbook
ADVANCED FISSION REACTOR DEVELOPMENT OVERVIEW:
A technical overview of current nuclear power issues is presented in the draft text: A Nuclear Green New Deal by Darryl Siemer. This text provides the perspective of a retired senior Idaho National Laboratory scientist on the future of nuclear power.
A March 2021 report titled: "Advanced" Isn't Always Better by Edwin Lyman raises a number of important issues which must be addressed by proponents of the various advanced reactor technologies. An important responding document is a Letter from Alex Cannara.
NUCLEAR FUEL SUSTAINABILITY:
Advances in Fast Neutron Reactor (FNR) technology have rendered obsolete past concerns about nuclear reactor safety and nuclear waste disposal. However, the present wasteful use of the limited supplies of the fissile isotopes U-235 and Pu-239 in unsustainable nuclear fuel cycles is an enormous concern. As fossil fuels are phased out the amount of available dependable power will be constrained by the available fissile isotope supplies. It will likely take at least a century to quadruple the fissile isotope inventory via fuel breeding.
A major problem today is that existing electricity markets reward nuclear reactor owners for low cost per kW output without taking into consideration long term fissile isotope supply sustainability. The existing water cooled nuclear reactor technology is not fuel sustainable and is rapidly depleting the natural fissile isotope resource.
LIQUID SODIUM COOLED REACTORS:
Another concern is squandering of limited public resources on development of new nuclear reactor types that are not fissile isotope sustainable. It is imperative to apply the limited public resouces to deployment of liquid sodium cooled Fast Neutron Reactors (FNRs), because only liquid sodium cooled FNRs provide a proven technology suitable for sustainably fully displacing fossil fuels.
Five further major benefits of liquid sodium cooled FNRs are:
1)Sodium is chemically long term high temperature compatible with other base metals (Fe, Ni, Cr, U, Pu, Mo) used for economic FNR fabrication;
2) The sodium cooled FNR fuel cycle can be configured to reduce long lived nuclear waste production more than 1000 fold as compared to existing water moderated reactors.
3) The use of sealed fuel tubes that permit almost all of the fuel reprocessing radio chemistry to be carried out at a shared remote facility instead of at each reactor site.
4) Potential for up to 800 degree C operation using fuel tubes fabricated from molybdenum depleted in Mo-95.
5) Potential for fuel extension using dedicated fuel tubes containing a mixture of ThCl4, KCl and LiCl where the Li is Li-7 and the Cl is Cl-37.
A major issue with liquid sodium cooled reactors is ensuring that the primary sodium never contacts air or water and that any secondary sodium fires remain small and inconsequential.
MOLTEN SALT COOLED REACTORS:
Another class of potentially fuel sustainable nuclear reactors is molten salt cooled reactors fuelled by thorium, which is naturally about 4X more abundant than is uranium. Thorium fuelled reactors operating with a with sustainable fuel cycle require continuous chemical processing of their blanket fuel to selectively remove protactinium. This selective protactinium removal is enabled by dissolving thorium in a molten salt coolant that can be continuously circulated for both chemical processing and heat removal.
The molten salt reactors can be further divided into chloride salt cooled fast neutron reactors with fuel tubes to maintain the core fuel geometry and fluoride salt cooled thermal neutron reactors that use a rigid moderator to maintain the core fuel geometry and hence can operate safely without fuel tubes.
Molten salt reactors superficially seem simple but they have numerous practical implementation problems primarily related to their higher temperature of operation, complex corrosion issues, moderator degradation and the sophisticated chemistry that that must implemented at each reactor site. The fluoride salt cooled reactors also have a safe power limitation related to the required minimum liquid fuel residency time inside the moderator assembly.
ADVANCED REACTOR DEPLOYMENT:
As of 2020 there are over 100 reactor-years of liquid sodium cooled nuclear reactor operating experience in several countries. The Russians have had a large size liquid sodium cooled power reactor program for many years. Their top of the line unit with significant operating history is the BN-800.The Chinese with Russian assistance have two liquid sodium cooled power reactors under construction with scheduled completion in 2023. There are no scientific or engineering constraints to almost immediate large scale deployment of liquid sodium cooled reactors operating with sustainable fuel cycles to meet the challenge of climate change.
By comparison there are only about 2 years (17,000 running hours) of fluoride salt cooled laboratory size reactor operating experience in North America and there is no operating experience with chloride salt cooled reactors. There are many unresolved material and radio chemistry issues with molten salt cooled reactors. The Chinese have had a large team of engineers working on molten salt reactor issues for over a decade. In spite of best intentions there is almost no possibility that molten salt cooled reactors operating with a sustainable fuel cycle can be scaled up and deployed sufficiently quickly to significantly impact climate change in the next few decades.
A major problem with reactor development in the USA is internal politics. The US Democratic party is unwilling to face the reality that in 1994, at a time when the USA led the world in liquid sodium cooled fast neutron reactor technology, then president Bill Clinton cancelled the entire multi-billion dollar program in favor of cheaper fossil fuels. The US Republican party has long been dominated by fossil fuel interests. Both parties have embraced a rigid nuclear regulatory regime that is focused on obsolete light water cooled reactors. The result is that the China, and Russia and India are now dominating the world nuclear power industry and in North America US companies are doing limited new reactor type demonstration in Canada due to Canada's more flexible nuclear regulatory regime. Unlike the new Chinese and Russian sodium cooled power reactors, no new present US power reactor technology is capable of sustained displacement of fossil fuels.
FUSION:
Other than via renewable energy, fusion based electricity generation is difficult and expensive to realize on Earth. For fundamental thermodynamic efficiency reasons, as long as low cost fission fuels are available, the cost per kWhe of Earth based fusion energy production will always remain much higher than the cost per kWhe of Earth based fission energy production. The fundamental difficulty is that over half of the electricity generated by a fusion reactor must be used to sustain the fusion reaction.
A possible avenue of future nuclear fusion fuel cost mitigation is mining He-3 from the surface of the moon. In theory it is possible to breed H-3 and hence He-3 in fusion reactors but sustaining the required controlled fusion reactions on Earth is extremely difficult. The problems include a low plasma density, a small fusion reaction cross section and large ongoing plasma energy loses via energetic neutron emission. The fusion reactor size required for a self sustaining fusion chain reaction with a reasonable net electric power output is believed to be too large for economic construction.
FOCUS OF THIS WEB SITE:
This web site section primarily focuses on liquid sodium cooled Fast Neutron Reactors (FNRs) fueled by U-238 bred into Pu-239/Pu-240 because this technology in combination with renewable energy generation provides the only viable way of sustainably and completely displacing fossil fuels during the next few decades while avoiding production of long lived nuclear waste. At some future date this technology will likely be supplemented by breeding Th-232 into U-233.
It is the intent of this author to eventually produce web pages addressing all of the above mentioned topics.
This web page last updated April 13, 2021.
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