The Life Cycle Of Nuclear Fission Fuel: From Stars To Burn-Up

November 14, 2024 by Maya Posch 47 Comments

Outdone only by nuclear fusion, the process of nuclear fission releases enormous amounts of energy. The ‘spicy rocks’ that are at the core of both natural and artificial fission reactors are generally composed of uranium-235 (U-235) along with other isotopes that may or may not play a role in the fission process. A very long time ago when the Earth was still very young, the ratio of fissile U-235 to fertile U-238 was sufficiently high that nuclear fission would spontaneously commence, as happened at what is now the Oklo region of Gabon.

Although natural decay of U-235 means that this is unlikely to happen again, we humans have learned to take uranium ore and start a controlled fission process in reactors, beginning in the 1940s. This can be done using natural uranium ore, or with enriched (i.e. higher U-235 levels) uranium. In a standard light-water reactor (LWR) a few percent of U-235 is used up this way, after which fission products, mostly minor actinides, begin to inhibit the fission process, and fresh fuel is inserted.

This spent fuel can then have these contaminants removed to create fresh fuel through reprocessing, but this is only one of the ways we have to extract most of the energy from uranium, thorium, and other actinides like plutonium. Although actinides like uranium and thorium are among the most abundant elements in the Earth’s crust and oceans, there are good reasons to not simply dig up fresh ore to refuel reactors with.

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Mining And Refining: Uranium And Plutonium

April 24, 2024 by Dan Maloney 40 Comments

When I was a kid we used to go to a place we just called “The Book Barn.” It was pretty descriptive, as it was just a barn filled with old books. It smelled pretty much like you’d expect a barn filled with old books to smell, and it was a fantastic place to browse — all of the charm of an old library with none of the organization. On one visit I found a stack of old magazines, including a couple of Popular Mechanics from the late 1940s. The cover art always looked like pulp science fiction, with a pipe-smoking father coming home from work to his suburban home in a flying car.

But the issue that caught my eye had a cover showing a couple of rugged men in a Jeep, bouncing around the desert with a Geiger counter. “Build your own uranium detector,” the caption implored, suggesting that the next gold rush was underway and that anyone could get in on the action. The world was a much more optimistic place back then, looking forward as it was to a nuclear-powered future with electricity “too cheap to meter.” The fact that sudden death in an expanding ball of radioactive plasma was potentially the other side of that coin never seemed to matter that much; one tends to abstract away realities that are too big to comprehend.

Things are more complicated now, but uranium remains important. Not only is it needed to build new nuclear weapons and maintain the existing stockpile, it’s also an important part of the mix of non-fossil-fuel electricity options we’re going to need going forward. And getting it out of the ground and turned into useful materials, including its radioactive offspring plutonium, is anything but easy.

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New Drug Has Potential As Dirty Bomb Antidote

May 25, 2023 by Dan Maloney 39 Comments

It perhaps goes without saying that one nuclear bomb can really ruin your day. The same is true for non-nuclear dirty bombs, which just use conventional explosives to disperse radioactive material over a wide area. Either way, the debris scattered by any type of radiation weapon has the potential to result in thousands or perhaps millions of injuries, for which modern medicine offers little in the way of relief.

HOPO 14-1, aka 3,4,3-Li(1,2-HOPO). The four hydroxypyridinone groups do the work of coordinating radioactive ions and making them soluble so they can be eliminated in urine.

But maybe not for long. A Phase 1 clinical trial is currently underway to see if an oral drug is able to scour radioactive elements from the human body. The investigational compound is called HOPO 14-1, a chelating agent that has a high affinity for metals in the actinide series, which includes plutonium, uranium, thorium, and ~~cerium~~ curium. Chelating agents, which are molecules that contain a multitude of electron donor sites, are able to bind to positively charged metal ions and make the soluble in aqueous solutions. Chelators are important in food and pharmaceutical processing — read the ingredients list on just about anything from a can of soda to a bottle of shampoo and you’re likely to see EDTA, or ethylenediaminetetraacetic acid, which binds to any metal ions that make it into the product, particularly iron ions that come from the stainless steel plumbing used in processing equipment.

The compound under evaluation, HOPO 14-1, is a powerful chelator of metal ions. Its structure is inspired by natural chelators produced by bacteria and fungi, called siderophores, which help the microorganisms accumulate iron. Its mechanism of action is to sequester the radioactive ions and make them soluble enough to be passed out of the body in the urine, rather than to have the radioactive elements carried around the body and incorporated into the bones and other tissues where they can cause radiation damage for years.

HOPO 14-1 has a number of potential benefits over the current frontline chelator for plutonium and uranium toxicity, DTPA or diethylenetriaminepentaacetic acid. Where DTPA needs to be injected intravenously to be effective, HOPO 14-1 can be made into a pill, making stockpiling and administering the drug easier. If, of course, it passes Phase 1 safety trials and survives later trials to determine efficacy.

Nuke Your Own Uranium Glass Castings In The Microwave

April 26, 2023 by Dan Maloney 20 Comments

Fair warning: if you’re going to try to mold uranium glass in a microwave kiln, you might want to not later use the oven for preparing food. Just a thought.

Granted, uranium glass isn’t as dangerous as it might sound. Especially considering its creepy green glow, which almost seems to be somehow self-powered. The uranium glass used by [gigabecquerel] for this project is only about 1% U₃O₈, and isn’t really that radioactive. But radioactive or not, melting glass inside a microwave can be problematic, and appropriate precautions should be taken. This would include making the raw material for the project, called frit, which was accomplished by smacking a few bits of uranium glass with a hammer. We’d recommend a respirator and some good ventilation for this step.

The powdered uranium glass then goes into a graphite-coated plaster mold, which was made from a silicone mold, which in turn came from a 3D print. The charged mold then goes into a microwave kiln, which is essentially an insulating chamber that contains a silicon carbide crucible inside a standard microwave oven. Although it seems like [gigabecquerel] used a commercially available kiln, we recently saw a DIY metal-melting microwave forge that would probably do the trick.

The actual casting process is pretty simple — it’s really just ten minutes in the microwave on high until the frit gets hot enough to liquefy and flow into the mold. The results were pretty good; the glass medallion picked up the detail in the mold, but also the crack that developed in the plaster. [gigabecquerel] thinks that a mold milled from solid graphite would work better, but he doesn’t have the facilities for that. If anyone tries this out, we’d love to hear about it.

The Intricacies Of Creating Fuel For Nuclear Reactors

January 10, 2023 by Maya Posch 51 Comments

All nuclear fission power reactors run on fuel containing uranium and other isotopes, but fueling a nuclear reactor is a lot more complicated than driving up to them with a dump truck filled with uranium ore and filling ‘er up. Although nuclear fission is simple enough that it can occur without human intervention as happened for example at the Oklo natural fission reactors, within a commercial reactor the goal is to create a nuclear chain reaction that targets a high burn-up (fission rate), with an as constant as possible release of energy.

Each different fission reactor design makes a number of assumptions about the fuel rods that are inserted into it. These assumptions can be about the enrichment ratio of the fissile isotopes like U-235, the density of individual fuel pellets, the spacing between the fuel rods containing these pellets, the configuration of said fuel rods along with any control, moderator and other elements. and so on.

Today’s light water reactors, heavy water reactors, fast neutron reactors, high temperature reactors and kin all have their own fuel preferences as a result, with high-assay low-enriched (HALEU) fuel being the new hot thing for new reactor designs. Let’s take a look at what goes into these fuel recipes.

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Roll The Radioactive Dice For Truly Random D&D Play

November 2, 2022 by Dan Maloney 22 Comments

When you have a bunch of people gathered around a table for a “Dungeons & Dragons” session, you have to expect that things are not always going to go smoothly. After all, people who willingly create and immerse themselves in an alternate reality where one bad roll of the dice can lead to the virtual death of a character they’ve spent months or years with can be traumatic. And with that trauma comes the search for the guilty — it’s the dice! It’s always the dice!

Eliminating that excuse, or at least making it statistically implausible, is the idea behind this radioactively random dice roller. It comes to us from [Science Shack] and uses radioactive decay to generate truly random numbers, as opposed to the pseudorandom number generators baked into most microcontrollers. The design is based on [AlphaPhoenix]’s muon-powered RNG, but with a significant twist: rather than depending on background radiation, [Science Shack] brought the power of uranium to the party.

They obtained a sample of autunite, a weird-looking phosphate mineral that contains a decent amount of uranium, perfect for stimulating the Geiger counter built into the dice roller. Autunite also has the advantage of looking very cool under UV light, taking on a ghostly “fuel rod glow,” in the [Homer Simpson] sense. The decay-powered RNG at the heart of this build is used to simulate throws of every standard D&D die, from a D4 to a D100. The laser-cut hardboard case holds all the controls and displays, and also has some strategically placed openings to gaze upon its glowing guts.

We really like the design, but we have to quibble with the handling of the uranium ore; true, the specific activity of autunite is probably pretty low, but it seems like at least some gloves would have been in order.

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Optimizing The Mining Of Uranium From Coal Ash And Seawater

August 23, 2022 by Maya Posch 55 Comments

Of all the elements that make up the Earth’s crust, uranium is reasonably abundant, coming in at 49th place, ahead of elements such as tin, tungsten and silver. Ever since humankind began to exploit uranium for its fissile properties in energy production, this abundance has also translated into widespread availability for mining. As of 2019, Kazakhstan, Canada and Australia formed the world’s main producers, accounting for about 68% of output.

Considering the enormous energy density of uranium when used as fuel in a nuclear fission reactor, the demand for uranium is relatively low, especially combined with the long (two years on average) refueling cycles of commercial reactors. The effect is that even with the very inefficient once-through fuel cycle – which only uses a fraction of the uranium fuel’s potential energy – uranium market prices have remained relatively low and stable even amidst geopolitical crises.

Despite this, the gradual rise in uranium market prices ($10/lb in 2003, $49/lb in 2022), as well as the rapid construction of new reactors is driving new exploration. Here recent innovations may make uranium fuel even more accessible to all nations, by unlocking the billions of tons of uranium found in plain seawater as well as the many tons of fly ash produced by coal plants every single day.

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