Fossil Fuels at Peak
Nuclear Power No Solution to Peak Oil
- Part 11
by John Rawlins
John Rawlins has a B.S. in physics and a Ph.D. in nuclear physics. He retired in 1995 from the Westinghouse Hanford Co. at the Hanford site in Eastern Washington. Currently, he teaches physics and astronomy at Whatcom Community College.
This is the last segment in the series examining peak oil. See the sidebar for a list of previous articles.
Many developed and developing countries are now strongly considering adding nuclear power (or more nuclear power) to their electricity generating mix. For most, the motivation is to allow future retirement of fossil fuel electricity generation plants (mostly coal) in an attempt to reduce carbon dioxide emissions.
For some (notably Iran), the motivation is to replace electricity generation by oil, which is in decline in Iran. They may also be considering doing what several countries have done in recent decades, that is, use knowledge gained in the commercial nuclear electric generation sector to develop nuclear weapons.
With the recent rise in concern about greenhouse gas emissions, nuclear power seems a reasonable alternative (yes, even in Bellingham). Remember, however, unless we convert to electric transport, more nuclear power will not help the transport sector.
In 1976, my first quasi-commercial job was working for Westinghouse-Hanford Company as a reactor physicist to help start up the Fast Flux Test Facility (FFTF) located on the Hanford site in eastern Washington. The reactor was a 400 megawatt (thermal) sodium-fueled reactor used to test materials for the U.S. breeder reactor program. It did not produce electricity.
The core was mixed oxide fuel using plutonium from the U.S. weapons production program. Surrounding the core were nickel metal assemblies to reflect neutrons leaving the core back into the core. So the FFTF was not a breeder reactor, but it had prototypical breeder reactor neutron conditions in the core region and it was an excellent test vehicle for breeder components.
About the time we were starting up the reactor, President Carter was deciding to cancel the U.S. breeder program! His main reason for the decision was that the breeder fuel cycle, or plutonium fuel cycle, involved chemically separating a pure plutonium metal stream in the chemical re-processing plant. That pure plutonium would make an inviting target for theft for illicit purposes by individuals, small groups or even nations.
In essence, he was saying that humans are not highly enough evolved to manage a plutonium fuel cycle safely. Nevertheless, the 400 megawatt reactor I worked on operated very successfully for about a decade before shutting down. I drifted into technical group management after completion of the startup program and documentation.
During that management phase, I participated in a number of company initiatives to develop new business for the FFTF as well as for other parts of the Hanford site.
The most complex and interesting new business idea was an advanced fuel cycle paper study using breeder-like facilities to destroy other heavy elements (like curium and americium) produced in the breeder reactor and chemically separated in the plutonium fuel cycle.
These types of schemes implicitly require chemical re-processing and fuel re-fabrication involving highly radioactive species. The idea is to keep recycling these problematic heavy nuclei through the breeder reactor rather than trying to dispose of them in deep geologic formations.
In 1993, I was the technical organizer of an international meeting in Seattle that focused on innovative advanced reactor and fuel cycle designs. We invited scientists and engineers from all the countries in the world that had some kind of nuclear power operation, including Russia.
The meeting was a few years after the breakup of the former Soviet Union, and we were all struck with the desperate state these world-class Russian experts found themselves in. We had to pay for their plane tickets, their hotel costs, and their food costs everything in order to get them to the meeting.
We did have an agenda for them, however. The State Department wanted to offer U.S. help in consolidating all the nuclear materials and weapons scattered throughout the former Soviet states. We also wanted to explore using weapons grade uranium and plutonium from the former Soviet Union and from the U.S. as conventional thermal reactor fuel in a move to reduce the amount of that material in the world. That negotiating process created some very strange bedfellows indeed!
That meeting never left my mind in later months. My bottom line reasoning was that President Carter was right human civilizations have lives on the order of hundreds, rarely thousands, of years.
Those elements, particularly plutonium, have half-lives much longer than that and are potentially extremely dangerous in the wrong hands and most external hands would be wrong. Humans are indeed too immature to manage advanced fuel cycles, and in my judgment the risks are not worth the gains.
I shifted management jobs to form a new group of physicists to do waste disposal risk assessments and never returned to the fuel cycle and innovative reactor design studies.
End of Uranium Fuel
Uranium is essentially a finite resource, in the sense that weve mined the easy stuff, and like oil, the remainder comes at a higher and higher price, until someday it wont be worth further effort to mine it.
Some recent geologic/economic assessments concluded that simply continuing to operate todays number of reactors around the world will result in a peak in uranium production this century possibly within a few decades.
At best, another round of uranium-fueled thermal reactors would be but a stopgap move to delay the inevitable shutdown of nuclear fission power roughly around the end of this century.
A successful breeder reactor program would have the potential to continue with nuclear power for around a thousand years or more at todays level.
Other problems also plague the industry. Plant construction costs are high because of all the concrete involved, which in turn depends on oil supply. We can expect those construction costs to skyrocket in a post-peak-oil world.
The time to license and build a plant is 1015 years, and that translates to a very high financial risk as well.
Many Northwesterners might recall the WPPSS (pronounced woops, appropriately), Washington Public Power Supply System, fiasco. Construction started on five reactors at once in Washington state (1970s) but only one actually went into operation. The WPPSS construction program was a multibillion dollar financial failure, and most investors lost almost everything. I would no more invest in a new nuclear plant than I would leap from an airplane.
No country in the world has yet succeeded in actually disposing of any spent fuel or high-level nuclear waste. The U.S. spent-fuel-disposal program chose disposal criteria that I believe are inherently impossible to meet.
The spent fuel continues to accumulate and resides in cooling ponds at the various 100 or so reactor sites around the U.S. I do not expect to see any spent fuel go into the Yucca Mountain repository (in Nevada) during my lifetime, even if I should live another 30 years.
The current fleet of reactors will begin shutting down around 2020 and will be largely gone by 2050. At present, nuclear power is responsible for nearly 20 percent of the countrys electricity production (more like 10 percent in the Pacific Northwest). A new generation of nuclear reactors appears to have little future in the existing U.S. political and economic situation. In any case, it cannot help mitigate a near-term peak in oil supply.
Final Conclusions of Peak Oil Series
The peaking of all fossil fuels this century will result in dramatic changes in how people in today's industrialized societies conduct their lives. First, a near-term decline in world oil production will force us to re-think our entire economic and physical infrastructure. Natural gas will peak shortly after that and will cause even more dislocation. Using coal as an oil/gas substitute would only worsen our global warming situation, and in any case coal may also peak within two to three decades.
No combination of alternatives appears to be able to replace more than about 10 percent of our present transport energy in a sustainable manner. The only potentially workable adaptation appears to be re-localization of everything we do including massive reduction in energy use, local energy generation, local food production, local building materials and local fabrication of all essential commodities.
Portland has recently adopted a re-localization plan that addresses the most critical anticipated impacts of peak oil and gas. The city is poised to begin the huge, decades-long process of rearranging the entire city infrastructure. Several other U.S. cities are developing their own plans The sooner we in Whatcom County take similar steps, the more likely we are to have any chance of a vibrant, or at least livable, future. §
Nuclear Power Primer
by John Rawlins
In a nuclear power plant, fission reactions involving only the nuclei of atoms are responsible for energy release. The energy released per reaction is on the order of a million times that released in chemical reactions (e.g. coal burning). When a nucleus fissions, it splits into two smaller fragments. These fragments, or fission products, are nearly equal to half the original mass. Two or three neutrons are also emitted.
The sum of the masses of these fragments is less than the original mass. The missing mass (about 0.1 percent of the original mass) has been converted into energy according to Einsteins equation: energy release = (change in mass) X (speed of light)2.
The word fissile means that the nucleus fissions (splits) readily when neutrons in the reactor strike the nucleus. Todays nuclear power plants use only a handful of elements that have fissile nuclei. Those fissile nuclei are: Uranium-235, Plutonium-239 and, in the thorium fuel cycle, Uranium-233.
The nucleus of an atom contains protons and neutrons. Every uranium nucleus contains 92 protons. Uranium-235 (U-235) has 143 neutrons (92 +143=235). Uranium-238 (U-238) has 146 neutrons (92+146=238). These differing versions of uranium are called isotopes.
These elements are radioactive. Only uranium and thorium are still present in Earths crust. Uranium, as found in nature, consists of 99.3 percent U-238 and 0.7 percent U-235. Only the U-235 atoms are fissile.
The Earth is 4.6 billion years old. The half-life of U-238 is about 4.5 billion years. So about half the original U-238 is still in the earths crust. The half-life of U-235 is about 700 million years. About 1/64 of the original U-235 is still in the crust.
Fission Process in Thermal Reactors
Neutrons produced by fission are highly energetic, or fast. The art of reactor design is to use the excess neutrons produced to create a chain reaction of fissions, without losing control of the reaction that is, a sustained chain reaction with constant power output.
In all operating reactors in the U.S., as well as in most of the world, the fuel coolant is water. Water is composed of hydrogen and oxygen atoms.
When a fast neutron born in the fission process collides with a hydrogen atom (a proton with an electron), the neutron will, on average, lose half its energy in the scattering reaction with the proton.
After a number of such scattering events, a neutron will have its energy reduced to a very small percentage of its original energy. It then gets the title thermal neutron.
These thermal (slow) neutrons have a very high probability of causing fission in U-235 nuclei quite a bit higher probability than for fast neutrons. Reactor physicists therefore refer to todays commercial reactors as thermal reactors. Thermal reactors require enriching the uranium fissile fuel content up to 35 percent U-235.
During operation, much of the U-235 breaks up (fissions) and eventually there is not enough fissile fuel left. The operators must remove some spent fuel and replace it with fresh fuel.
Another important reaction that occurs in thermal reactors is absorption of a neutron by Uranium-238. This produces Uranium-239 which decays rapidly to Plutonium-239 (Pu-239). Pu-239 has a half-life of about 24,000 years plenty long enough to use as a fissile fuel.
Some countries chemically reprocess their spent fuel and recycle this co-produced plutonium into fresh fuel, called mixed-oxide fuel, a mixture of uranium and plutonium oxides. The U.S. does not currently do this, but the U.S. Department of Energy episodically considers the option.
History of Nuclear Power
Back in the 1950s the U.S. had somewhat less than a centurys worth of uranium commercially available to mine, assuming we built over 100 thermal reactors.
The initial vision was that phase I of nuclear power would consist of thermal reactors operating on uranium fuel. We then would chemically reprocess that fuel to extract the plutonium to start up phase II of nuclear power, breeder reactors, based on plutonium fuel.
The breeder reactor core has plutonium oxide mixed with U-238 oxide for fuel, and surrounding the core region is a region of pure U-238 oxide (left over from all the phase I uranium enrichment).
Neutrons leaking out of the core region would create some more plutonium in the blanket region, as well as in the core region, so that gradually the U-238 eventually gets converted to plutonium.
Plutonium fueled breeder reactors use a liquid metal instead of water for coolant. The neutrons do not slow down appreciably, and the breeder reactor is a fast (neutron) reactor. The nearly universal choice of coolant for breeders has been liquid sodium (a metal). With good design, the reactor can produce more plutonium than it consumes hence the term breeder.