A Short Case for Recycling Used Nuclear Fuel
Tom Dolan 631-495-2947 tom@virginia-recycles-snf.com
https://virginia-recycles-snf.com/
https://wastetoenergynow.org
Nuclear energy is absolutely necessary to attain air pollution and carbon goals stated throughout the world. However, although the rest of the world is moving strongly into nuclear power, the United States has lagged over the last 40 years in nuclear energy development. To move this along, it will take leadership and education to the public. In this respect, nuclear advocacy has been conspicuously silent. This has been interpreted by the public that the anti-nuclear forces are right and that we should eliminate anything nuclear. This is the exact opposite of the truth, but perception is truth to each individual.
The biggest complaint in the anti-nuclear community is the inability of the nuclear industry to deal with used nuclear fuel. While it is clearly being handled safely, it is also clear that no long-term solution has emerged. This is (or should be) embarrassing to the professional nuclear community. The simplest part of the fuel cycle is the “back end” and our community has allowed political rhetoric to overshadow logical solutions to the problem. The existing nuclear community is being dominated by the long-standing ideas developed in the early days of the industry. The idea of throwing away a resource when only 5% of it has been used is completely against the modern-day idea of preserving the earth’s assets through recycling. So, part of the problem is getting the nuclear industry to reevaluate their thinking through the eyes of the 21st century.
Recycling is being conducted in France, and has been conducted since the beginning of their nuclear energy program. France supplies about 75% (down from 80%) of their electricity from nuclear power. In addition, the UK, Russia, China, Japan and India have programs to recycle their used nuclear fuel. So, what happened to the United States where nuclear power was born? One issue is the stated fear that recycling will unleash plutonium that may end up being used to make a bomb. However, except for a demonstration project to illustrate that it was possible, no country has taken this route. Not even North Korea. If any country wants plutonium suitable for a bomb, they simply design a reactor for this purpose and leave the fuel in for far less time than commercial reactors do. The reason is that plutonium is way too contaminated by higher isotopes of plutonium which make it difficult to produce a bomb. It is simply better to start from scratch as North Korea did. So, the issue of proliferation of plutonium from commercial used nuclear fuel, while an issue of concern, is not a major problem. Another issue is the massive misinformation left unanswered in the public’s eye regarding nuclear power. Eisenhower and Kennedy were outspoken on the benefits of nuclear power. Since Johnson, however, the issue has either been ignored or criticized by our leaders. Strong leadership would greatly help advance the cause, but there are enough grass-roots efforts in play that nuclear energy is slowly becoming “cool” again.
There are two different types of recycling for used nuclear fuel: aqueous (chemical) and non-aqueous (electro-chemical) pyroprocessing. Aqueous recycling is the method being used in the world today and involves dissolving all the fuel rod materials in a strong nitric acid bath and using chemistry to separate the different parts. Pyroprocessing uses molten salt as the solvent and electroplating as the separation method. Pyroprocessing has been around for almost 60 years, but only in the experimental prototype stage. Each has advantages and disadvantages like everything else, but either should be considered superior to discarding used nuclear fuel. I also find that the public does not accept “waste” burial, but loves the idea of recycling and the fact that there is a tremendous amount of energy left to produce carbon and pollution-free power.
Separation of used nuclear fuel means, basically, separating four distinct chemical groups in the fuel rods. The vast majority of the material is uranium. New fuel is about 96% uranium-238 and about 4% uranium-235. These are different isotopes of uranium and uranium-235 is the material that fissions and produces energy. When the used fuel is removed, the four basic categories of material remaining in the fuel material are:
Uranium – 95% of uranium entering the reactor never changes. Only about 1% of it is uranium -235.
Plutonium – about 1% of the used nuclear fuel. Plutonium is actually bonus energy. Some of the
uranium-238 transforms into plutonium-239 which can also fission and produce energy. When the reactor fuel is removed, there is some left that has not fissioned yet, but could be used for energy in the future.
Minor Actinides – less than 1% are higher isotopes of elements heavier than plutonium. Together with plutonium, these are called transuranics, or “TRU” because they are heavier than uranium.
Fission Products – This is what is left after a nucleus fissions – two atoms per fission. They emit heat and radiation, but they remain inside the fuel material. This comprises 3% of the material in used nuclear fuel, but is the major reason used nuclear fuel must be handled carefully and shielded from people.
While either recycling method would be preferable to burial, the method used mainly depends on which kind of reactor the fuel is to be recycled into. These fall into two main categories, although there are several types in each group. With only a handful of exceptions, our current reactors in the US and around the world use water to slow down the fission neutrons to lower energies where they are more likely to cause more fissions in the neutron chain reaction. Some advance reactors (and there is a long history of these) are fast neutron reactors in which the neutrons are not slowed down. The group of nuclear reactions that fast neutrons cause is quite different than those that slow neutrons cause. Fast neutrons actually extract energy from and change plutonium and the higher transuranics far, far more effectively than do slow neutrons. From a used nuclear fuel toxicity perspective one could view a water-cooled reactor with recycling as a trash compactor, while a fast reactor takes the role of incinerator.
Using water-cooled reactors to recycle used fuel, as France currently does, means that mixed oxide (MOX) fuel, a mixture of uranium oxide and plutonium oxide, is the resulting recycled fuel form. The U.S. does not do this. To recycle the plutonium in used fuel, the French use an aqueous chemical process involving large volumes of concentrated nitric acid in very large, expensive piping systems. They separate plutonium to re-mix with uranium oxide to make MOX. Each recycle reactor is only partly fueled with MOX, the rest being the usual uranium oxide. The drawback with this system is that the same material can be economically recycled only once or possibly twice. Further recycled fuel material contains increasing fractions of plutonium isotopes that (1) make obtaining and controlling a chain reaction more difficult, and (2) presents severe worker radiation protection challenges during fuel fabrication.
So the regular commercial water-cooled reactors in use today can only reduce the waste volume somewhat, but do not eliminate enough of it to be considered a solution to the used fuel disposition problem, nor do they extract much more than 1% of the nuclear energy stored in the original uranium.
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