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4th Generation Nuclear Power

There is about a million times more energy available in the nucleus, compared with the chemical energy of molecules exploited in fossil fuel burning. In today’s nuclear (fission) reactors neutrons cause a nucleus to fission, releasing energy as well as additional neutrons that sustain the reaction. The additional neutrons are ‘born’ with a great deal of energy and are called ‘fast’ neutrons. Further reactions are more likely if these neutrons are slowed by collisions with non-absorbing materials, thus becoming ‘thermal’ or slow neutrons.

by Dr. James Hansen (written Dec. 21, 2008;  revised Jan. 18, 2009)

Some discussion about nuclear power is needed. Fourth generation nuclear power has the potential to provide safe base-load electric power with negligible CO2 emissions.

All nuclear plants in the United States today are Light Water Reactors (LWRs), using ordinary water (as opposed to ‘heavy water’) to slow the neutrons and cool the reactor. Uranium is the fuel in all of these power plants. One basic problem with this approach is that more than 99% of the uranium fuel ends up ‘unburned’ (not fissioned). In addition to ‘throwing away’ most of the potential energy, the long-lived nuclear wastes (plutonium, americium, curium, etc.) require geologic isolation in repositories such as Yucca Mountain.

There are two compelling alternatives to address these issues, both of which will be needed in the future. The first is to build reactors that keep the neutrons ‘fast’ during the fission reactions. These fast reactors can completely burn the uranium. Moreover, they can burn existing long-lived nuclear waste, producing a small volume of waste with half-life of only sever decades, thus largely solving the nuclear waste problem.

The other compelling alternative is to use thorium as the fuel in thermal reactors. Thorium can be used in ways that practically eliminate buildup of long-lived nuclear waste.

The United States chose the LWR development path in the 1950s for civilian nuclear power because research and development had already been done by the Navy, and it thus presented the shortest time-to-market of reactor concepts then under consideration. Little emphasis was given to the issues of nuclear waste. The situation today is very different. If nuclear energy is to be used widely to replace coal, in the United States and/or the developing world, issues of waste, safety, and proliferation become paramount.

Nuclear power plants being built today, or in advanced stages of planning, in the United States, Europe, China and other places, are just improved LWRs. They have simplified operations and added safety features, but they are still fundamentally the same type, produce copious nuclear waste, and continue to be costly. It seems likely that they will only permit nuclear power to continue to play a role comparable to that which it plays now.

Both fast and thorium reactors were discussed at our 3 November workshop. The Integral Fast Reactor (IFR) concept was developed at the Argonne National Laboratory and it has been built and tested at the Idaho National Laboratory. IFR keeps neutrons “fast” by using liquid sodium metal as a coolant instead of water. It also makes fuel processing easier by using a metallic solid fuel form. IFR can burn existing nuclear waste, making electrical power in the process. All fuel reprocessing is done within the reactor facility (hence the name “integral”) and many enhanced safety features are included and have been tested, such as the ability to shutdown safely under even severe accident scenarios.

The Liquid-Fluoride Thorium Reactor (LFTR) is a thorium reactor concept that uses a chemically-stable fluoride salt for the medium in which nuclear reactions take place. This fuel form yields flexibility of operation and eliminates the need to fabricate fuel elements. This feature solves most concerns that have prevented thorium from being used in solidfueled reactors. The fluid fuel in LFTR is also easy to process and to separate useful fission products, both stable and radioactive. LFTR also has the potential to destroy existing nuclear waste, albeit with less efficiency than in a fast reactor such as IFR.

Both IFR and LFTR operate at low pressure and high temperatures, unlike today’s LWR’s. Operation at low pressures alleviates much of the accident risk with LWR. Higher temperatures enable more of the reactor heat to be converted to electricity (40% in IFR, 50% in LFTR vs 35% in LWR). Both IFR and LFTR have the potential to be air-cooled and to use waste heat for desalinating water.

Both IFR and LFTR are 100-300 times more fuel efficient than LWRs. In addition to solving the nuclear waste problem, they can operate for several centuries using only uranium and thorium that has already been mined. Thus they eliminate the criticism that mining for nuclear fuel will use fossil fuels and add to the greenhouse effect.

The Obama campaign, properly in my opinion, opposed the Yucca Mountain nuclear repository. Indeed, there is a far more effective way to use the $25 billion collected from utilities over the past 40 years to deal with waste disposal. This fund should be used to develop fast reactors that eat nuclear waste and thorium reactors to prevent the creation of new long-lived nuclear waste. By law the federal government must take responsibility for existing spent nuclear fuel, so inaction is not an option. Accelerated development of fast and thorium reactors will allow the US to fulfill its obligations to dispose of the nuclear waste, and open up a source of carbon-free energy that can last centuries, even millennia.

The common presumption that 4th generation nuclear power will not be ready until 2030 is based on assumption of ‘business-as-usual”. Given high priority, this technology could be ready for deployment in the 2015-2020 time frame, thus contributing to the phase-out of coal plants. Even if the United States finds that it can satisfy its electrical energy needs via efficiency and renewable energies, 4th generation nuclear power is probably essential for China and India to achieve clear skies with carbon-free power.

Implications

All of the slack in the schedule for averting climate disasters has been used up. The time has past for ‘goals’, half-measures, greenwashing, and compromises with special interests.

We have already overshot the safe level of greenhouse gases. Things are just beginning to crumble – Arctic ice is melting, methane is bubbling from permafrost, mountain glaciers are disappearing. We must move onto a different course within the next year or two to avoid committing the planet to accelerating climate changes out of our control.

Geophysical boundary constraints are crystal clear: coal emissions must be phased out and emissions from unconventional fossil fuels (tar shale, tar sands, e.g.) must be prohibited.

Priorities for solving the climate and energy problems, while stimulating the economy are steps to: (1) improve energy efficiency, (2) develop and deploy renewable energies, (3) modernize and expand a ‘smart’ electric grid, (4) develop 4th generation nuclear power, (5) develop carbon capture and sequestration capability.

Prompt development of safe 4th generation nuclear power is needed to allow energy options for countries such as China and India, and for countries in the West in the likely event that energy efficiency and renewable energies cannot satisfy all energy requirements.

Deployment of 4th generation nuclear power can be hastened via cooperation with China, India and other countries. It is essential that hardened ‘environmentalists’ not be allowed to delay the R&D on 4th generation nuclear power. Thus it is desirable to avoid appointing to key energy positions persons with a history of opposition to nuclear power development. Of
course, deployment of nuclear power is a local option, and some countries or regions may prefer to rely entirely on other energy sources, but opponents of nuclear power should not be allowed to deny that option to everyone.

Coal is the dirtiest fuel. Coal burning has released and spread around the world more than 100 times more radioactive material than all the nuclear power plants in the world. Mercury released in coal burning contaminates the world ocean as well as our rivers, lakes and soil. Air pollution from coal burning kills more than 100,000 people per year. If such consequences were occurring from nuclear power, nuclear plants would all be closed. Mining of coal, especially mountaintop removal, causes additional environmental damage and human suffering. It is time for all the coal plants to be closed, indeed, averting climate disasters demands that all coal plants be phased out. Coal is best left in the ground.

Nevertheless, R&D for carbon capture and sequestration (CCS) deserves strong support. It is needed to provide the full range of options in energy choices, for countries that insist on exploiting their coal resources. Moreover, CCS has another potentially more important role to play: it could be used at power plants that burn biofuels, such as agricultural wastes. This sort of ‘geoengineering’, which draws excess CO2 out of the air and puts it back in the ground where it came from, may be needed to get atmospheric CO2 back to a safe level.

Transition to the post-fossil-fuel era with clean atmosphere and ocean, requires a carbon tax. That tax will cause unconventional fossil fuels to be left in the ground, as well as much coal and some oil and gas that resides in remote regions. The public will accept such a tax if the funds are returned entirely to the public, no funds going to Washington and other capitols for politicians and lobbyists to determine its fate. Tax and 100 percent dividend is not sufficient by itself – many other actions are needed – but it is necessary. No time remains for a transition via ineffectual half measures.

Frank communication with the public is essential. At present, all around the world, governments are guilty of greenwash, an implausible approach of goals and half-measures that will barely slow the growth of CO2. The world, not just the United States, needs an open honest discussion of what is needed. It is a tremendous burden to place on the President elect, who seems to be the only potential candidate. The only chance seems to be if he
understands the truth – the whole truth.

Young people realize that they, their children, and the unborn will bear the consequences of our actions or inactions. They do not blame their parents, who legitimately ‘did not know’ what they were starting. Young people have recently worked hard to influence the democratic process. Now they expect the system to take appropriate actions. If that does not happen, surely they will begin to raise their voices louder.

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