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The object of this web page is to convey to non-scientific persons the vital role of Trans-Uranics (TRU) and Fast Neutron Reactors (FNRs) to the future existence of mankind.
Today nuclear energy is mainly obtained via fission of the rare uranium isotope U-235. However, the economic supply of that isotope is limited and reasonable projections indicate that the rare uranium isotope U-235 will become very expensive during the coming decades. However, vast amounts of clean, dependable and sustainable energy are potentially available from the abundant uranium isotope U-238. Large reserves of U-238 are in storage in the forms of used nuclear reactor fuel and tailings from uranium U-235 enrichment plants. However, TRU and FNRs are needed to access the energy contained in U-238.
Trans-Uranics (TRU) are atoms with atomic numbers (number of protons per atom) greater than 92, the number of protons in a uranium atom. The TRU elements are: Neptunium, Plutonium, Americium, Curium, Berkelium, Californium, Einsteinium, Fermium, etc. TRU does not naturally occur on Earth today because all the TRU atom isotopes have half lives that are much shorter than the age of planet Earth. The only way that TRU atoms occur on Earth today is via synthesis using either a particle accelerator or a nuclear reactor. For this reason TRU are sometimes referred to as man made elements.
Mankind needs FNRs to provide dependable and sustainable nuclear power to displace fossil fuels. In a fuel sustainable FNR TRU acts as a quasi-catalyst that enables use of the abundant uranium isotope U-238 as fuel for production of dependable and sustainable nuclear power. The power output of a FNR is proportional to the size of the FNR's TRU inventory. Due to the large stocks of depleted uranium (almost 100% U-238) the potential cumulative energy output from FNRs has almost no practical upper limit.
Today one of the main problems with exploitation of this source of nearly unlimited energy is lack of public awareness about it. The TRU necessary to access this energy is routinely being wasted by parties who lack a basic understanding of fast neutron nuclear physics.
The most common TRU isotope is Pu-239, which if isolated can potentially be used to make implosion type nuclear weapons. However, from the perspective of FNRs the TRU elements and their isotopes act as a group, without separation or isolation. It is neither necessary nor desirable to separate them. Keeping TRU atomic isotopes as a group makes them unsuitable for use in nuclear weapons and aids in their disposal.
Since the dawn of nuclear electric power the fossil fuel industry has viewed the prospect of dependable and sustainable nuclear power as an existential threat and has falsely convinced both the public and governments that:
a) TRU is a proliferation danger;
b) TRU is an unsolvable pollution problem;
c) TRU should be buried in deep geological repositories;
d) TRU should not be permitted to displace fossil fuels.
However, the reality is that TRU can readily be disposed of using Fast Neutron Reactors (FNRs) and that mankind needs a large TRU inventory in FNRs to enable displacement of fossil fuels.
The only solution to the CO2 driven climate change on planet Earth is to leave fossil fuels in the ground and to produce clean (non-fossil) power by other methods.
The solution for supply of clean dependable power is nuclear power. However, the water cooled nuclear power reactors that are in wide use today are not fuel sustainable. Further, due to now obvious climate change, most major countries have new nuclear reactors either planned or under construction. A problem today is ensuring future economic supply of fuel for all these new nuclear reactors. Most existing nuclear power reactors are fueled by the rare uranium isotope U-235 for which there is only a limited economic supply which will likely be depleted within a few decades.
Fortunately there is an alternative nuclear fuel cycle that is sustainable.
FAST NEUTRON REACTORS (FNRs):
As early as the 1960s the concept of using fuel breeding Fast Neutron Reactors (FNRs) to produce sustainable nuclear power was well known. During the 1980s and early 1990s such FNRs became an experimental reality. Some power FNRs have operated for over 30 years. The concept is to fission Pu-239 with fast neutrons and to use the resulting excess fission neutrons to both fission other TRU atoms and to breed abundant fertile U-238 into more fissile Pu-239. The original concept was to extract the bred Pu-239 from the U-238 using a chemical process known as PUREX, which process was originally perfected for making plutonium based nuclear bombs.
There were several practical implementation problems with the original concept.
a) There was public fear about use of plutonium and nuclear weapon proliferation;
b) As long as natural uranium is cheap and readily available the process is too complex and too expensive as compared to simple fission of U-235;
c) The PUREX process works only on plutonium, meaning that other TRU elements became difficult to manage nuclear waste;
d) The robotics necessary to automate the FNR fuel reprocessing and fabrication did not exist at the time;
e) Originally climate change was not perceived by the funding governments as a pressing issue;
f) People with the necessary technical expertise in fast neutron physics were retiring.
Due to unsubstantiated and irrational public fear about nuclear energy, for the three decades 1990 to 2020 there was little world wide nuclear power reactor construction and there were only about 400 major power reactors operating. If those would be the only continuing drain on the U-235 resource there would not be a U-235 availability problem this century. However, about 2020 voters and politicians in many countries were finally convinced that CO2 emissions are a serious problem and that nuclear power reactors provide dependable clean power (without CO2 emissions).
Today most major countries have plans to build additional nuclear power reactor capacity to mitigate climate change. Within two decades the number of operating nuclear power reactors is expected to double and that number will probably double again during the subsequent two decades. In short, the economic U-235 resource on planet Earth will likely be seriously depleted within as little as 40 years.
At that time, unless another dependable clean energy supply technology has been fully developed and deployed, planet Earth will likely revert to use of fossil fuels and soon thereafter the consequent rise in lower atmospheric temperature will cause a mass extinction of large land animals.
NEW ENERGY SUPPLY TECHNOLOGY:
The used fuel from present nuclear power reactors contains TRU, fission products and U-238. With suitable fuel reprocessing, the TRU can be concentrated and the fission products, which have relatively short half lives, can be discarded. The concentrated TRU acts as a quasi-catalyst which enables U-238 to be used to fuel Fast Neutron Reactors (FNRs) for millennia. However, while the cumulative energy output from a FNR is only limited by the supply of abundant U-238, the sustained FNR power output is limited by the FNR's TRU inventory.
To understand FNRs and efficient TRU production we must return to the 1960s.
After WWII Canada developed a nuclear power reactor technology known as CANDU (CANadian Deuterium Uranium). This technology uses heavy water for both cooling and neutron moderation. Heavy water is similar to ordinary light water except that the hydrogen atoms are replaced by deuterium atoms. Instead of the single proton nucleus of hydrogen a deuterium atom nucleus has both a proton and a neutron. Ordinary water contains a small fraction of heavy water. Heavy water can be separated from ordinary water by suitable cascade contact, distillation and electrolysis processes. However, these processes are expensive. Hence in CANDU nuclear power plants (NPPs) extraordinary measures are taken to prevent heavy water leakage and to recover any heavy water that does leak.
The heavy water provides three important benefits.
a) It allows the use of natural uranium fuel. Other reactor types rely on fuel enrichment which is inefficient and expensive and if required would make Canada dependent on foreign fuel enrichment plants. Right now Russia dominates the nuclear fuel enrichment market.
b) CANDU reactors maximize the TRU production at over 4 grams / kg of natural uranium as compared to about 1 gram / kg for Light Water Reactors (LWRs).
c) CANDU reactors produce tritium, which is needed for future nuclear fusion, which in principle could be used to increase the rate of TRU production.
The TRU is widely dispersed in used reactor fuel. However, the TRU can be redistributed to make both FNR core fuel and FNR blanket fuel.
The tritium is embedded in the heavy water but can be selectively extracted.
We now move forward to about 2010. Questions were being asked about whether nuclear power could be used to prevent further climate change. However, it soon became obvious that within a few decades a shortage of U-235 would prevent continued use of existing water cooled power reactor technology for long term climate change mitigation.
Circa 2010 Peter Ottensmeyer (or one of his students) came up with an insightful idea that would potentially change everything.
The PUREX concept was to selectively extract plutonium from everything else in used nuclear reactor fuel, because that is the process used to make a nuclear bomb. However, for a power reactor the objective should instead be to selectively remove most of the uranium from used reactor fuel and then to selectively extract fission products from the residue using a high temperature molten salt electrolytic process known as pyroprocessing.
The trick to making this new process economic is to first concentrate the TRU by selectively removing uranium oxide using a simple physical process involving aqueous crystal manipulation. That process can be done automatically in bulk using a recrystallization cascade.
In the resulting FNR power reactor technology the TRU is self replicating. Thus, the door is open for powering future generations for millennia using FNRs, where the fuel is the abundant uranium isotope U-238 and there are almost no long lived nuclear waste products.
However, while the energy available from a FNR is proportional to the available amount of the abundant isotope U-238 the FNR power output is limited by the FNR's TRU inventory. In a suitably designed FNR this TRU inventory will gradually grow over time.
The CANDU reactors that Canada presently has produce about 4X as much TRU per unit of natural uranium consumed as do the Light Water Reactors (LWRs) presently used in the USA and many other countries. This issue has three important implications.
1) All new thermal neutron power reactors should be CANDU rather than LWR. This is a major political issue, especially in the USA;
2) The US nuclear regulatory environment must change because presently CANDU reactors cannot be licensed in the USA;
3) In the future, when the USA recognizes the consequences of its lack of TRU, the USA may have predatory designs on Canada's stocks of used CANDU fuel and/or TRU concentrates.
A difficulty is that, largely due to use of heavy water, CANDU reactors are more expensive to build and maintain than LWRs. If the world proceeds today with new LWR construction to mitigate climate change the economic benefit period will be short and after that, due to a severe TRU shortage, there will not be sufficient dependable power to support even a reduced world population. People will revert to use of fossil fuels and there will be a consequent global extinction of large animals.
If instead the world proceeds today with CANDU reactor construction the capital and operating costs are significantly higher than for LWRs but the benefits are that the grace period until U-235 is depleted is twice as long and when that grace period is over there should be sufficient TRU to produce enough sustainable nuclear power to support a reduced world population for millennia.
However, getting people today to make a rational decision to spend more money on new nuclear reactors now to enable future life for their descendants is not easy.
There are lesser industrial funding challenges which include TRU concentration, converting TRU concentrates into FNR fuel and then later reprocessing the FNR fuel. These processes involve working with highly radioactive substances and must be fully automated. Getting these automated processes working smoothly on a large scale together with a prototype power FNR will probably cost about $5 billion.
In Canada the Trudeau government is presently committing $30 billion to an oil pipeline expansion but has refused to spend even one dollar on TRU recovery. The federal government regards nuclear power as a provincial responsibility and the provincial governments, in order to comply with near term federal government CO2 emission reduction requirements, want to follow the least expensive and fastest route to near term CO2 emission reduction, which is water cooled SMRs.
The reality of today's ill considered government decisions is that when the economic U-235 resource is depleted, due to lack of TRU, the dependable power requirements of the human population of planet Earth will far exceed the dependable power supply capacity. At times of low renewable power production circumpolar populations will freeze in the dark and equatorial populations will die of heat stroke.
Unfortunately, at every turn there is irrational and uninformed opposition to sensible nuclear and climate change mitigation policy.
Building wind turbines may temporarily satisfy uneducated voters, but fast neutron reactors and their TRU based fuel systems are what is necessary to provide sustainable and dependable clean power.
The commercial issue that must be immediately addressed is TRU concentration. However, even its large scale demonstration requires a few million dollars that the Canadian government is presently unwilling to spend.
1) Natural uranium is 0.7 % U-235, 99.3 % U-238.
2) The energy potentially available from the U-238 content of natural uranium is about 100X the energy that can be obtained by fissioning the U-235 content of natural uranium.
3) Per kg of natural uranium consumed, fission of U-235 in a CANDU reactor yields about 2X as much energy as does fission of enriched U-235 in a LWR.
4) The power available from U-238 via an FNR is proportional to the FNR's TRU inventory.
5) Use of both heavy water and zirconium fuel tubes enables a CANDU reactor to produce 4X as much TRU per kg of natural uranium consumed as does a LWR.
6) Failure to optimize TRU production now is a disaster for our descendants because that failure will reduce the future TRU inventory and hence our descendants' access to economic nuclear power from U-238. They will be forced to at least partially rely on fission of U-235, which due to scarcity will be extremely expensive.
7) The future high cost of U-235 will motivate our descendants to use CANDU reactors due to the higher CANDU reactor efficiency at energy recovery from both natural uranium and used LWR fuel.
These facts need to be presented to both utility decision makers and to rational voters.
This web page last updated September 18, 2023
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