This is the talk that I gave over lunchtime at the Clean Growth Leadership Network conference, held in London on September 6, 2022:
We’re all glad to be here and enjoying one another’s company as we talk about these important issues, but there’s no denying that we’re meeting under a shadow. All of us are seeing the news articles about what is happening across Europe. Factories shutting down. People unable to heat their homes. Small businesses closing up shop because the power bill arrives and it’s ten times bigger than anything they’ve ever seen before. We’re staring down the barrel of catastrophe and it’s only September! It’s still warm, but winter is coming and by every account it there will be days of reckoning ahead.
Britain has faced such energy crises before. Seven hundred years ago, this island was nearly deforested because the population survived by burning firewood. But a new energy source was found in the form of coal, and the forests had the space to return because coal was a simpler and more reliable way to heat homes and eventually, to run industry. The industrial revolution was born out of coal. We didn’t compete with other living creatures for coal. No animals dug for coal; no creatures ate coal. We were the only ones who wanted it, and although we had to tear up a non-trivial amount of land to get at that coal, beyond that, we were the only users of coal.
But the time has come to move beyond coal, and in Britain like most other places that has been largely done by turning to natural gas. The North Sea gave Britain a huge advantage with natural gas. Under those shallow waters, deep underground, were seemingly endless amounts of another material that no other creature on Earth depended on. Natural gas burned cleaner and was amenable to being piped around the countryside via a pipe network. It’s hard to burn coal to heat your home. You can do it but it’s dirty and messy and requires a lot of attendance to make it work. Natural gas isn’t like that. We can build systems that just automatically open up the valve when you need to admit the gas; we have furnaces that automatically light and burn the gas, and we have the ducting in our homes to heat each and every room. In almost every way, natural gas is an enormous improvement over coal for home heating.
Britain was some of the most fertile ground in the early days of nuclear energy. The British writer HG Wells had already been imagining for many decades a “world set free” by releasing the mysterious energies that bound together the atomic nucleus. Such ideas seemed to be exclusively the province of fiction and fantasy even though the work of Marie and Pierre Curie in France was showing that powerful “emanations” came from certain materials like uranium and thorium, and that the present understanding of physics simply could not explain how these radiations could exist! James Chadwick discovered the neutron in 1932, and its discovery was the key to the correct understanding of how matter itself is assembled. Once we knew there was a neutron, and once we knew that the neutrons and protons were held together by some mysterious “nuclear force” that overcame the mutual repulsion of the protons, it was only a matter of time before we would be able to harness this nuclear force, whatever it was.
HG Wells thought that we might speed up the decay of uranium and thorium and release nuclear energy that way. He wrote a utopian book in 1913 called “The World Set Free” around that idea. But alas, despite nearly a century of research, we have never figured out how to accelerate or decelerate the rate of radioactive decay even one iota. Which is a bit of a pity. The real answers to how the mysterious binding force of the atomic nucleus could be utilized were far more subtle. It turns out that light atomic nuclei can join together and be bound more tightly. And it also turns out that heavy atomic nuclei can decay and then also be bound more tightly. This is a bit of a surprise, the idea that both light and heavy nuclei are extremes of an overall effect. Who would have ever imagined that the universe was so constructed?
But perhaps the fertile imagination of HG Wells was the catalyst for a breakthrough in reality. The physicist Leo Szilard read Wells’ book “The World Set Free” in 1932, almost twenty years after its publication, and the next year conceived of the idea of a chain reaction based on Chadwick’s recently discovered neutrons. It happened very close to here, where Southampton Row passes Russell Square, just across from the British Museum. It was in September 1933, almost 89 years ago. Szilard stepped off the curb as the stoplight changed and suddenly in his mind he could see it. One reaction triggering two triggering four, and so on. In 1934 he even went so far as to take out a patent on the idea! But he assigned the patent to the Admiralty because he feared the ways that the idea of the chain reaction could be perverted into a weapon. At that moment Szilard could see the pattern, but he didn’t have the foggiest notion of what material could make it a reality. He wondered if beryllium might work, but we now know that it won’t. The next piece of the puzzle came about a few years later from the work of Enrico Fermi in Italy. Fermi noticed that his experiments with neutrons striking other materials had different results when he conducted them on a wooden table rather than on a marble table. This seemed utterly baffling to Fermi until he realized that the hydrogen in the wood was slowing down the neutrons in a way that the heavier materials in the marble table did not. We call this “slowing down” of neutrons “moderation” and it is central to the utilization of nuclear energy.
But Fermi and others had to flee their homes in Europe for Britain and America due to Nazi persecutions of Jews. And so working groups were dispersed even as new working groups were brought together under difficult circumstances. The next piece of the puzzle came from Germany itself. An exceptional chemist there named Otto Hahn had already been instrumental in the discovery of the element protactinium, and in 1938 his group had been bombarding uranium with Fermi’s slowed-down (moderated) neutrons, trying to find a different way to make that newly-discovered element protactinium. But instead he kept finding a material that seemed almost exactly like barium. Now this simply shouldn’t be. Barium is about half the size of uranium. Hahn thought he had made a mistake, but he hadn’t. It really was barium. Hahn had split the atomic nucleus, but it was his research partner Lise Meitner, a Jewish physicist who had fled Germany for Copenhagen, who had correctly identified what Hahn had actually done. She could scarcely believe that an atomic nucleus could split, but she had the intellectual courage to put this seemingly impossible conclusion forward to Otto Hahn.
This was probably the worst possible time and place for such a discovery to have been made. Within a few months, Hitler’s armies invaded Czechoslovakia and only a few months later, Britain and France declared war on Germany. Szilard had emigrated to America in the fall of 1938 and was working with a research team at Columbia University when he learned of Hahn and Meitner’s discovery of fission in uranium. He had also learned that the son-in-law of the famous Marie Curie had discovered that Chadwick’s neutrons were emitted from the fission reaction. Now he knew that a neutron could cause a fission, and that the fission event itself would release more neutrons. All of the pieces seemed to be in place for what he had imagined years earlier: the self-sustaining chain reaction. But no one believed him, not even the brilliant Enrico Fermi. So Szilard begged, borrowed, and stole what he needed to pull together what we might call today a “proof of concept” experiment. The experiment worked; not well enough to sustain the chain reaction, but he saw enough multiplication of neutrons to see that the central idea was essentially correct.
Szilard and his team suspected that there was something else going on as well. Chadwick’s discovery of the neutron had given scientists the correct framework at long last to understand the structure of the atomic nucleus, and just a few years later in 1935 a determined Canadian physicist discovered that uranium actually had two different natural forms. Both of these had 92 positively-charged protons, but they had different numbers of Chadwick’s neutrons. One of them had three less neutrons than the other, but that fact didn’t seem terribly important at the time because this lighter form of uranium only constituted less than one percent of the content of natural uranium.
Szilard was beginning to suspect that this lighter form of uranium, which we know today as uranium-235, had very very different properties in the chain reaction than its far more abundant and heavier sibling. His further experiments proved it. It was uranium-235 that was fissioning, not uranium-238. Uranium-238 seemed “dull”, in other words, it seemed to have no propensity to fission at all. This was a huge revelation. Only a tiny fraction of a sample of uranium would be susceptible to fission; the vast majority of the uranium was utterly inert. The prospect of nuclear energy or nuclear weapons from unmodified uranium seemed rather unlikely.
Szilard knew from Fermi’s work that hydrogen would slow neutrons down, so he thought to use normal water but it didn’t work too well. He came to realize that the normal “light” hydrogen in the water was absorbing more of the neutrons. So he tried graphite and it worked much better. The carbon in the graphite had very little propensity to absorb neutrons, and more of them could promote the chain reaction. Szilard was becoming more and more concerned about the potential of a chain reaction in uranium to be used as a weapon. He also knew that some of the richest supplies of uranium in Europe were in Czechoslovakia, and were now under the control of Hitler. But he also knew that the Belgians had been recovering uranium from their colony in the Congo, and so he drafted a letter to President Roosevelt, alerting him that uranium could be used to make power and to make bombs. Szilard was savvy enough to know that no one at that level of power would care what he thought, so he wrote the letter as if it came from his famous friend Albert Einstein and asked Einstein to deliver it to the US president. The letter marked the beginning of an effort to develop the process of nuclear fission into a weapon.
What if it hadn’t been 1939? What if the world hadn’t been at war? Would Szilard have labored so hard to demonstrate the chain reaction? Would he have been searching for a material that made it possible? Very likely he would not have been doing these things. Very likely he would not have pursued this work with such vigor. Unfortunately, we humans happened to discover nuclear fission in uranium at the worst of all possible times, a time when we so feared that it might be perverted into a weapon that we immediately set out to pervert it into a weapon. And we became precisely what we feared.
At first all the efforts to produce nuclear weapons centered on the enrichment of uranium, taking that tiny fraction of uranium that was fissile and increasing its potency until it could be fashioned into an explosive. The vast majority of the uranium, however, would simply be discarded. But that view began to change when a young American chemist named Glenn Seaborg began teaching at Berkeley in 1939. His position afforded him access to an incredible new machine that they had built there under the guidance of the Nobel laureate Ernest Lawrence. This machine, called a cyclotron, could produce more neutrons that any other source, and with them Seaborg and his partners bombarded many elements, including uranium. What they found would have incredible consequences. They already knew that uranium-235 would fission, but the vast bulk of uranium seemed inert and very likely worthless. Under the neutron beam of Lawrence’s machine, Seaborg found that common uranium, uranium-238, could be transformed into a new element, and that that material, just like uranium-235, was susceptible to the fission reaction. The material came to be known as plutonium.
Plutonium changed the objectives of nations for the simple reason that it was a different element than uranium, and thus, could be separated from uranium by chemical means. By contrast, the two isotopes of uranium were utterly and completely chemically identical. There was no way to separate them chemically. Any effort to separate them would have to exploit tiny mass differences that would be very difficult. But not plutonium. It was a different element entirely from uranium and chemical differences permitted an effective separation.
If only you had some. Berkeley’s cyclotron could only make micrograms of plutonium, nowhere near enough for a reactor or a weapon. But by this point Szilard had convinced his friend Enrico Fermi that the chain reaction was possible, and with military support, Fermi built the first true nuclear reactor in December of 1942. It used uranium metal and graphite to slow down neutrons. The uranium metal and graphite were arranged in a large pile, and thus is was called Chicago Pile number one. Its operation confirmed that the chain reaction in uranium was real and could be perpetuated almost indefinitely, so long as the reactor continued to be resupplied with fresh fuel. There was no doubt after Chicago Pile number one that nuclear reactors could be built.
Whether or not they could be cooled was another question. In order to make plutonium, these “piles” would need to be much larger and operate at much higher powers. Within two years, Fermi’s group had grown from their first pile with a power level of a fraction of a watt, to a graphite pile with a power of two million watts, to an even larger water-cooled graphite pile with a power of five hundred million watts. This was what it took to make enough plutonium for a weapon.
Despite all this power, there was not one speck of electricity. These piles sacrificed all of the thermal power they produced to their water coolant. Their only goal was to make plutonium, not to make electricity. And they were all in the United States. The Manhattan Project partners of Canada, the UK, and the US, had decided that for safety and security from enemy attack, that all of the piles and uranium enrichment facilities would be in the United States during the war. It was a decision that they came to regret.
Meanwhile, brilliant Glenn Seaborg continued to add to his list of accomplishments with the Berkeley cyclotron. He turned its beam on thorium and created a new isotope of uranium called uranium-233. Like plutonium and uranium-235, uranium-233 was also fissile. So now Seaborg had figured out how to turn all of uranium and all of thorium into nuclear energy in a fission reactor. The discovery had a profound effect on him. He was the first of all our species to realize that nuclear fuels had the potential to sustain our industrial civilization for thousands, even hundreds of thousands of years into the future, provided that we used them efficiently. In the midst of the most destructive war ever fought, a war fought largely over access to energy in various forms, young Glenn Seaborg realized that there was nothing to fight over. That all nations might be energy independent forever provided that they would utilize his discoveries.
One of the people who was also profoundly affected by Seaborg’s discovery was another young Manhattan Project scientist named Alvin Weinberg. Weinberg had worked on the design of the plutonium-producing piles in the United States. Now he was obsessed with the potential of nuclear fuel, particularly thorium, to sustain human civilization essentially forever. He convinced his colleagues to work with him on a design for a thorium reactor, but when his wartime leadership learned of his efforts they squashed the effort and ordered him to stop.
The world was first introduced to the powers that bound the atomic nucleus when President Harry Truman announced that a nuclear weapon had been used to attack Japan on August 6, 1945. It was, perhaps, the worst rollout of a technology in the history of technology. One day, the world at large knew nothing of these things. The next day it seemed as though a piece of the sun had been torn from the sky and hurled at the enemies of the West.
But after the war ended decisions were made that made the situation far worse. The United States abandoned its wartime development allies Canada and the UK, cutting off all their access to plutonium, uranium enrichment, and nuclear technology. Without uranium enrichment yet with abundant uranium supplies, Canada developed nuclear reactors that used heavy water as a coolant and could produce electrical power. The UK decided that they wanted nuclear weapons and similarly cut off, they developed reactors that operated at high pressure and were cooled by gas, but could produce electrical power and plutonium simultaneously.
The US continued to build up its nuclear arsenal but did not worry about generating electricity, so it came as a national humiliation when they discovered in 1949 that the Soviet Union had detonated their first nuclear weapon in great secrecy. The attempt to keep nuclear weapons technology exclusively in the hands of the US had failed. Their response was to build a much larger weapon based around hydrogen fusion instead of just around uranium or plutonium fission. This “second Manhattan Project” turned out to be more massive than the first, and its product much more destructive.
For many years scientists had wondered what powered the sun. They knew that the sun was mostly hydrogen and helium, so they knew it wasn’t uranium fission or any such process releasing all that energy. During the 1930s the theory of nuclear fusion began to develop, and with it, a realization that it held the potential for nuclear weapons a thousand times more powerful than those based on fission alone. They called this weapon “the Super” and to build it the United States vastly increased their number of nuclear piles. They used both graphite and heavy water to make plutonium. They enriched more uranium than ever. And they began to produce a special radioactive form of hydrogen called tritium in their nuclear reactors by bombarding lithium with neutrons. Ironically, Szilard had just been reading about neutron reactions with lithium when he conceived of the chain reaction in 1933. Now it was the focus of intense national effort.
Two isotopes of hydrogen, deuterium and tritium, were the easiest path to a fusion bomb. Deuterium is natural but very rare, much more rare in normal hydrogen than uranium-235 is in natural uranium. Tritium is entirely manmade, produced in a nuclear reactor when lithium-6 is bombarded by neutrons. Deuterium and tritium together, in the intense conditions that can be created in the detonation of a fission bomb, will then fuse together and release vastly more energy through the fusion reaction.
Just as fission was conclusively demonstrated in 1942 with the Chicago Pile, fusion was conclusively demonstrated in 1952, just ten years later, when the United States detonated their first hydrogen bomb in the Marshall Islands of the Pacific. Two years later they detonated a far more powerful and practical hydrogen bomb. To put these weapons into perspective, they were roughly a thousand times more powerful than the fission bombs that dropped on Japan. They could literally destroy whole cities. The power of fusion was on display for the whole world to see.
But the technological lead of the United States was short-lived. Within a year the Soviet Union had detonated their own hydrogen bomb, and in less than ten years, they had detonated the most powerful weapon the world has ever seen. Britain was scarcely behind. Thanks to the plutonium produced in their gas-cooled piles in the north of England, they detonated their first fission bomb in 1952, just a month before the American hydrogen bomb, and their first fusion bomb in 1958. The French detonated their first fission bomb in 1960 and their first fusion bomb in 1968; China was not far behind.
Thus the two controllable techniques for releasing the energies of the atomic nucleus had both been theorized, realized, and weaponized in a frightening short period of time. Is it any wonder that the world came to fear these powers? Fission weapons were fearful enough, but limited in their reach. But when fission was hybridized with fusion, weapons with the power to destroy all of human civilization were now within the reach of several countries with the list seeming to grow. The fear was only enhanced with the dawn of the Space Age, and the realization that these weapons could be hurled on rockets from the other side of the globe with only a few minutes of potential warning and no means whatsoever to stop them in flight. All that could be done was to build enormous arsenals of these terror weapons in the hope that these would deter an attack. But the world had to learn to live on the knife’s edge of terror.
It is little wonder that people felt powerless against these terrifying forces and sought something…anything…they could do to fight back against the path to apocalypse and madness that seemed to lie before them. Unfortunately, some of the steps that were taken, no matter how well-intentioned, bore bitter fruits that haunt us to this day.
One of these was the campaign against nuclear testing. Most Western countries tested their nuclear weapons in the islands of the Pacific, seemingly far far away from their homelands. But careful instruments could pick up the faint radioactive traces of these tests, and the realization began to dawn that these faint traces would eventually spread anywhere and everywhere across the globe. Scientists urged a ban on tests of these nuclear weapons, particularly the giant super-powerful fusion weapon tests initiated at ground level that created the most radioactive fallout. One of the arguments that began to be deployed against nuclear testing was that no matter how vanishing small the levels of radiation that one experienced, there would be some correspondingly minuscule increase in the potential to later develop cancer. With this framework, some scientists believed that they could make a case to stop testing nuclear weapons. Because if you applied a tiny probability against an enormous cohort of people, you could compute some number of people that would develop a deadly cancer and die from it.
The problem was that this approach ignored the reality that human beings are exposed to sources of radiation all around them. They have radioactive carbon and potassium in their bodies. They inhale radioactive radon gas from the natural decay of uranium in the soils they live on. But the sun is the largest and most dangerous source of radiation. Indeed, if you were to lie exposed in the sun for twelve hours it is very likely that it would kill you. But some of the scientists who wished to see an end to nuclear weapons testing, for entirely honorable and understandable reasons, began to resort to a methodology that was at best, incomplete, and more likely, downright deceptive.
It had to do with the conviction that the artificial radioisotopes that had been produced through nuclear weapons testing posed a unique threat to the human race that was somehow distinct from the natural radioisotopes we encounter in our everyday life. Natural sources of radiation outnumbered artificial sources by a thousand-to-one, but the campaign of fear was effective. The public clamored for an end to nuclear weapons testing based largely around a campaign of fear around the radiation to which they might be exposed. The strategy accomplished its goal, but the derivative was bitter.
In a situation strangely analogous to some of the situations we faced today, some scientists felt like concepts and principles that were filled with ambiguity, like the levels of damage that a cell felt from low levels of radiation, had to be filled with certainty and clarity in order to support a larger ethical proposition, namely the suspension of nuclear weapons testing. But over time this certainty and clarity would be undermined by additional biological data, and a fuller understanding of the ability of the cell to repair radiation damage, while the larger societal principle that any radiation was potentially deadly persisted in the body politic for many many decades to come.
Another growing concern, also associated with small radiation exposures to large populations, had to do with wastes generated from these national nuclear weapons efforts. Haste makes waste, as the saying goes, and few places was this more true than in the national efforts to produce plutonium, where enormous reactors were built to create the material, while other giant chemical processing facilities attempted to tease the tiny amount of plutonium created from the much much larger amounts of uranium and fission products. At some of these sites contamination became wide spread and persistent, easily traceable due to the ease at which radionuclides can be detected even at trace amounts by technological means. When plutonium traces were found across the countryside in Sellafield, not from any nuclear accident but from the normal operation of the great uranium-graphite piles there, is it any wonder that the public began to question the ethics of continuing such a operation?
Even as a tremendously pro-nuclear engineer, I can imagine myself in those dark years from 1945 to 1965, at the height of the fever to produce plutonium across the world for weapons, asking myself, why on earth are we doing this? To what end are we trying to accomplish something? Isn’t the goal of this whole thing destruction and death, prefaced by contamination and a grotesque misallocation of resources? Where is the hope for the future of humanity in continuing along this path?
One who showed the way forward through these times was a true successor to the utopianism of HG Wells, and that was the young biologist and physicist I had previously mentioned, Alvin Weinberg. Although wartime pressures had forced Weinberg to temporarily abandon his effort to develop the thorium reactor, he had carefully moved from opportunity to opportunity and became the head of one of the national nuclear laboratories in the United States, Oak Ridge National Laboratory in Tennessee. From that leadership position, Weinberg was at last able to pursue the future of nuclear power guided by principles of sustainability, safety, and minimization of waste generation.
Weinberg did not invent the reactor of the future, but it was gestated, so to speak, under his guidance and control. That reactor was the molten-salt reactor, a reactor of the future, a reactor design seemingly torn from the 21st century but brought into being in the 1950s. It is a reactor design to which we still find ourselves striving toward almost seventy years after its creation, for I and others strongly believe that this reactor holds the keys to our energy future.
At a time when the nations of the earth were striving to create plutonium for weapons, Weinberg and his Oak Ridge engineers were imagining a reactor that did not create plutonium. At a time when nuclear reactors used only a tiny, tiny fraction of the energy content of their fuel, leaving the rest as waste, Weinberg’s engineers were working to create a reactor that pushed fuel efficiency almost to the theoretical limit. And most significantly, at a time when reactor safety was not afforded the priority that it deserved, the molten-salt reactor offered options for safety that are still greater than just about every other option today.
But unfortunately, all of this was done at a time when there was no internet, no email, and extremely limited means for new ideas to be disseminated, especially in the field of nuclear engineering where the heavy hand of government classification made it nearly impossible for engineers and scientists to spread ideas worldwide if their governments decided not to allow them. Weinberg and his team were able to build one of their reactors and show that it worked almost exactly as they had predicted, but their success ironically brought about their own downfall, for there were government elements that did not want to see such success brought to light.
In the US in particular, the nuclear weapons enterprise in the late 1960s, now glutted by 25 years of plutonium production, was beginning to transition hundreds of thousands of nuclear-trained personnel from plutonium production for weapons to civilian power generation. It was a very bad time for a nuclear pioneer with the stature that Weinberg possessed to be saying that there was a better, safer, cleaner way to make nuclear energy, a way that severed the connection with weapons, and a way that enshrined safety and thrift as paramount in the design.
So they killed it and silenced Weinberg. In the US over a hundred large power-generating reactors were built from 1965 to 1995, the largest nuclear fleet in the world, and none of them were of the molten-salt reactor design. They all used uranium and they used it very inefficiently, extracting only about one half of one percent of the energy content of that fuel that was originally present, and letting all the rest go to waste. They searched for a home or a strategy for all that waste and finding none, it continues to accumulate to this day at the places where it was created. A very similar situation exists in Canada, Germany, and Korea. This “first-generation” of nuclear energy thus did not end up being the technology that might have “set the world free” and HG Wells could have imagined, but has in this decade truly come to its final conclusion. In the US two large reactors of the usual type are being built in Georgia. It is generally accepted there that these two will be the very last of their kind, and that no more large reactors of that type will ever be built again. Two more reactors of this exact same type were attempted to be built in South Carolina and bankrupted the utility that tried to build them while sending some of their executives to prison for fraud. These are additional reasons why the prospect for future large nuclear power plants of the conventional type in the US is essentially zero.
But of course things are different in the UK. Because they were cut off from easy access to some of the technologies of the Manhattan Project, and facing far more limited material constraints in the postwar period, the UK charted a different nuclear course than the US or France. They almost completely integrated their pursuit of plutonium for nuclear weapons and their desire for nuclear electricity, and built reactors capable of doing both almost from the outset. To accomplish this they differed from the US by using gas for cooling and graphite for neutron moderation. They built a whole fleet of first-generation reactors called MAGNOX and a second generation of reactors beyond it called AGR. Most of the nuclear plants in the UK were of these type. It wasn’t until the 1990s that the UK built a pressurized-water reactor for civilian power, the Sizewell B plant, and now their new reactors under construction at Hinkley Point C and Sizewell C are some of the largest pressurized water reactors on earth.
Because of the unique way that the UK made nuclear power, they have one of the world’s largest inventories of separated plutonium. In other countries like the US in particular, the vast majority of the plutonium that their reactors have produced is still in the intact spent nuclear fuel. But in the UK because of some of the peculiarities of the MAGNOX design, the reactor fuel had to be chemically processed and the plutonium has been separated. And depending on who you might ask that plutonium is either a terrible threat or a tremendous opportunity. I prefer to see it as the latter. Although it may have been created in a Cold War atmosphere of terror, throwing it away as is presently planned only compounds the problem. Plutonium-239 has a half-life of 26,000 years. We try to bury it away for hundreds of thousands of years or we can try to do something much more productive and eliminate it permanently, efficiently and effectively.
In an analogy to the Ring in Tolkien’s Lord of the Rings trilogy, one does not simply throw away plutonium. It must be destroyed in the same place it was created, namely in the heart of a nuclear reactor. And not just any nuclear reactor, but in a molten-salt reactor. Now we reach the moment of opportunity. Even as we potentially destroy plutonium in this reactor, we can choose what we want to create. And there are two potential directions we can take. They are not exclusive to one another, we can actually pursue both at the same time. In one scenario we can destroy plutonium in an MSR to create uranium-233 from thorium, as Seaborg and Weinberg could foresee. In another scenario, we destroy plutonium to create tritium for fusion reactors.
Thorium reactors need uranium-233 to start most efficiently. Thereafter they can run on only thorium. In an analogous manner, fusion reactors need tritium to start up. After that they are meant to create sufficient tritium to sustain themselves for future operation. But regardless of whether we choose to pursue thorium or fusion or both, we need startup fuel, and we can and should use the UK inventory of plutonium to create those startup fuels.
But if we continue on today’s path we’ll simply throw it away, at great cost and at great waste, and accomplish exactly nothing. All of the titanic resources that this nation marshalled together to make that material will have been utterly in vain if we do so, and we will be no closer to a sustainable energy future. Our children and their children will lament our wastefulness and shortsightedness. But if we are wise, and choose to destroy plutonium effectively in the right kinds of molten-salt reactors, we can bequeath a legacy of starter fuels to our children and grandchildren that will heat their homes and power their cities and industries for thousands of years into the future. I know which path I prefer taking!
A particular kind of molten-salt reactor is required for these missions, one based on lithium-fluoride salt. You probably won’t be too surprised to hear that this is the kind of reactor that I’m working on today! What may surprise you, however, is to learn how many other industries stand to benefit from this approach.
I had previously mentioned how tritium is needed to start fusion reactors, and you may remember that I said that tritium is generated when neutrons strike an isotope of lithium. So in these lithium-fluoride reactors the lithium composition can be altered to favor the production of tritium, if desired, even as plutonium is consumed. In another version, which I personally favor, these lithium-fluoride reactors can instead produce uranium-233 from thorium as plutonium is consumed. The two isotopes of lithium can be used almost like a dimmer switch in a room to transition from one mission to another. If one desires the thorium approach, use lithium that is very nearly pure lithium-7. If one desires the fusion approach, use lithium that has more of the lithium-6 isotope in it. Gradations between the two may also represent feasible design outcomes.
With uranium-233 or tritium as starter fuels, thorium and fusion reactors can be built that will have a very sustainable, long-term fuel supply. They will not rely on uranium mining or enrichment like today’s reactors will. They will use far more earth-abundant resources. They have the potential to tread very lightly on the earth, and to come much closer to HG Wells’ utopian vision of a “world set free” by the energies of atomic nucleus. They will also largely utilize resources that other creatures on earth do not use, and thus have a potential environmental footprint that is very tiny compared to fossil fuels or to wind and solar energy.
And we will have solved the energy crisis permanently.
All of this is unlocked by the fundamental properties of thorium. We can make it happen. May we have the wisdom to do so.