Refining versus Enrichment, clarification by Gordon Edwards
(1) Canada has a long history of REFINING uranium at Port Hope.But Canada has never ENRICHED uranium.
In fact the Port Hope refinery was built around 1930 as a RADIUM refinery — to process the radioactive ores from Great Bear Lake in the NWT in order to extract the highly valuable radioactive heavy metal RADIUM, which was then selling for about $70,000 a gram. (A decade earlier, in the early 1920’s, it was selling for $100,000 per gram).
By 1940 the radium market had dried up because (1) the horrors or radium poisoning had become evident and people now regarded radium as too dangerous to handle; and (2) the outbreak of war.
In 1941 Canada was approached by both the British and the Americans to supply them with uranium, which they needed to build atomic bombs. Since radium is a radioactive byproduct of uranium, produced by the disintegration of uranium atoms, it was clear that the huge piles of refinery residues that had been dumped in the Port Hope harbour and piled here and there around the town must be rich in uranium too. Moreover the Port Hope refinery was the only facility in North America for refining radioactive materials such as uranium.
So the Canadian Government secretly bought up shares in the company and turned it into a “crown corporation” — Eldorado Nuclear. The PH refinery started sending refined uranium to the US and UK, extracted from the leftover radium residues. Eldorado also tried to re-open its mine at Port Radium on Great Bear Lake, but this proved to be a very difficult undertaking.
Then the US Government discovered that large stocks of uranium-rich radium concentrates were stored in a warehouse on Long Island (by the Belgian company Union Miniere which had extracted this material from their huge radium mine in the Belgian Congo)- for safekeeping during the ravages of World War II. The US Gov’t then sent this Congolese uranium to Port Hope Ontario to be refined, which greatly speeded up the supply of uranium for the bomb project.
The US Manhattan Project built three secret cities for the bomb project.
One was at Oak Ridge Tennessee, where they built the uranium enrichment facilities for the Hiroshima Bomb — which was a simple “gun-type” assembly using two subcritical masses of highly enriched uranium. All that is needed for such a device is that one of the masses is fired (like a projectile) into the other one (which functions as a target). When the two subcritical masses collide they form a supercritical mass and an enormous nuclear explosion results. This design is so simple that it never had to be tested — it was simply used on the city of Hiroshima without any prior testing.
Another city was built at Hanford in Washington State, where the first graphite-moderated plutonium production reactors were built along with the first reprocessing canyons to extract plutonium from the irradiated uranium fuel elements. These reactors used natural (unenriched) uranium as fuel, and as the U-235 atoms fissioned inside the reactor, a large neutron flux was created. Some of the neutrons impinged on U-238 atoms, turning them into Plutonium-239 atoms. By “lightly irradiating” the fuel, a very high percentage of Plutonium-239 (with relatively little of the higher plutonium isotopes) could be obtained. This stuff is called “weapons-grade” plutonium.
The third city was built at Los Alamos in New Mexico, where the design of the implosion mechanism for the first plutonium bomb was designed, built, and finally tested in the “Trinity” explosion at Alamogordo. For technical reasons, the simple “gun-type” assembly cannot be used when plutonium is used as the nuclear explosive material. Instead, an “implosion” type mechanism is required, whereby a spherical ball of plutonium is COMPRESSED by symmetrically-placed plastic explosives. When the ball of plutonium is compressed to a certain diameter it becomes a critical mass, and if it continues to compress it becomes “supercritical”. To get the biggest blast, you want to trigger the chain reaction at the moment of maximum superciticality, if it is possible to do so. Los Alamos had relatively little to do with the enriched uranium option; its main efforts were spent on the plutonium bomb.
So what is the difference between “refining” uranium and “enriching” uranium?
Refining is a purely chemical process. It changes the chemical form of the uranium and eliminates chemical impurities. At the uranium mill — generally built close to the mine — the ore is crushed and the uranium is separated out using solvents, then dried into a bright yellow powder called “yellowcake” which is primarily U3O8. (Three atoms of uranium combined with eight atoms of oxygen.) When the yellowcake arrives at the refinery, the U3O8 is converted into UO3 (uranium trioxide) and then further
transformed into UO2 (uranium dioxide) for use as reactor fuel for CANDU reactors, or into UF6 (uranium hexafluoride) for export to an enrichment plant in some other country.
Throughout the refinery processes, the isotopic composition of the uranium is unchanged. It is all natural uranium, consisting of 99.3 percent U-238 and 0.7 percent U-235. Chemically, the two isotopes of uranium are virtually identical; so any chemical change that affects one affects the other in exactly the same way and to exactly the same degree. There is no “enrichment” taking place.
But at the enrichment plant, the isotopic composition is changed by increasing the percentage of U-235 from its “natural” level of 0.7 percent to a “slightly enriched” state of 1-2 percent, or to a “low-enriched” state of 3-20 percent, or to a “high-enriched” state of 20-100 percent. These three degrees of enriched uranium are referred to as SEU, LEU, or HEU. Only HEU can be
used to make an atomic bomb.
So How is it done? Well, not easily! The earliest types of enrichment plants were called “gaseous diffusion” plants. These plants are huge – they are in fact the largest industrial structures on the face of the Earth.
Each enrichment plant of this type requires as much energy as a large city.
First we need to turn the uranium into a gas; and that’s why they make UF6 (uranium hexafluoride, also called “hex”). When slightly heated, UF6 turns into a very heavy, highly corrosive, chemically reactive, radioactive gas. This gas is drifted down miles of corridors and passed through thousands of very fine membranes which allow the smaller U-235 atoms to pass through a bit more easily than the larger U-238 atoms. So, bit by bit, miniscule improvements are made in the concentration of U-235 in comparison with U-238. But this process must berepeated tens of thousands of times before a really sizable increase in U-235 concentration is obtained.
Other technologies using ultracentrifuges or caulutrons can also be utilized to enrich uranium, but all these technologies require thousands of stages, lots of energy input, and at the end of the day it’s still a slow slow process.
And, by the way, they all require UF6 as an input….
(2) Canadian Material in Nuclear Weapons?
Until 1965, Canada signed military contracts to supply uranium to the US and (to a much lesser degree) to the UK. To the best of my knowledge, the last shipments of uranium in fulfillment of these military contracts were in 1972.
Canada also sold plutonium to the US military during the late 1950s and early 1960s, from the Chalk River nuclear reactors (mainly from the NRU). We also gave Britain its first plutonium, produced by the NRX reactor at Chalk River and extracted by means of a pilot reprocessing plant at Chalk River (built and operated by British scientists with Canadian assistance).
After 1965, Canada never SOLD uranium or plutonium under military CONTRACTS. However, that does not mean that Canadian uranium did not continue to find its way into bombs.
At the enrichment plant, all the uranium from different sources is blended together and there is no way of putting a “flag” on each little atom saying it’s from Canada or Australia or Colorado or South Africa. So lots of uranium is enriched into reactor fuel, and for every pound of fuel (LEU) that goes out the front door, ten pounds of depleted uranium (DU) goes out the back door.
And there it lies: acres and acres of DU from all these suppliers. The US military simply helps itself to the DU for (1) making plutonium triggers for its nuclear warheads; (2) making DU components for the third stage of the fission-fusion-fission bombs; or (3) more recently, for DU munitions etc.
Canada’s attitude is that there is NO Canadian uranium being used for military purposes, because at any given moment, the US can show Canada a sufficient quantity of DU lying out there in the fields to account for ALL the
uranium that Canada ever sent to the US for civilian enrichment. So while SOME Canadian uranium is inevitably ending up in bombs, there is an “equivalent amount” of uranium that is not ending up in bombs.
This is called the “principle of fungibility”. The term comes from the world of finance. If you deposit $10 in your bank account, you cannot later go to the bank and insist on seeing the exact ten-dollar bill that you deposited.
Instead the bank will give you another ten-dollar bill, every bit as good as the original ten-dollar bill that you deposited. It is wholly equivalent. It is fungible — i.e. exchangeable by its equivalent.
I, however, do not believe that this principle justifies an immoral situation. If for example the bank is investing in a brutally repressive regime, like the apartheid regime in South Africa for example, you are perfectly entitled to say indignantly that you do not want your money to be used for such a foul purpose. This justifiable indignation cannot be assuaged by the bank
manager saying, “Oh no! You misunderstand! We are not using YOUR money for such a foul purpose. Come to the vault and I will show you —
YOUR money is perfectly safe, right here in the vault.”
Of course the problem with this piece of sophistry is that the bank manager can say exactly the same thing to all of his customers, and thereby argue that NOBODY’s money is being used for this purpose, which is patently FALSE.
In a similar fashion, we have all these uranium mines in many different countries, all producing uranium EXCLUSIVELY for peaceful purposes.
NONE of them have any military contracts. Yet the military is making use of this material on a regular basis, while assuring ALL of the
suppliers that it is not THEIR uranium that is being so used.
Last year, at a workshop on uranium mining held in Nunavut, a man from the CNSC (Canadian Nuclear Safety Commission) raised this principle of fungability to explain why Canada had “clean hands” with regard to the
military use of uranium. I asked him privately, “Would you be happy if a country like Iran were enriching Canadian uranium, and using the depleted uranium for bombs, and meanwhile assuring you with the principle of fungibility that it was not CANADIAN uranium that was involved in this weapons program?”
He answered that he would not be happy with such a situation. “So what’s the difference?” I asked. “Are Canada’s ethical positions to be defended on the basis of double standards, or hypocrisy, not to mention downright self-deception?”
It was a rhetorical question.