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

November 14, 2024 by Maya Posch 48 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.

Continue reading “The Life Cycle Of Nuclear Fission Fuel: From Stars To Burn-Up” →

Is Your Tape Dispenser Radioactive?

March 11, 2022 by Al Williams 26 Comments

Do you have anything radioactive in your house? Most people will say no, but they are probably wrong. A host of things ranging from glow-in-the dark timepieces to smoke detectors have some amount of radioactivity. But as [Wheeler Scientific] points out, so do some old Scotch tape dispensers. You can watch the video, below.

The dispenser in question is the C-15 which was very common around offices, military bases, and homes for years. They were made up until the 1980s. You have to wonder why a tape dispenser would be radioactive, and [Wheeler] has the explanation.

When you pull tape from the dispenser, you don’t want the dispenser to slide around the desk, so it needs to be heavy. But no one wants to have a giant dispenser nor do you want to pay for one made from a dense metal. So the plastic dispenser contains a ballast to make it heavier. In the case of the C-15 that ballast is thorium-containing monazite sand. A vintage counter shows the radioactivity which isn’t much, of course, but still way less than the ordinary sand used in newer models. You can also see in the video that the material is paramagnetic.

Monazite used to be a primary source of lanthanides but getting rid of the thorium led to alternate sources in the 1960s although it is still used as an ore for thorium. We know some lenses are radioactive. If you want to search your home for radioactivity and you don’t have a Geiger counter, you don’t need much to build one.

Continue reading “Is Your Tape Dispenser Radioactive?” →

The Long History Of Fast Reactors And The Promise Of A Closed Fuel Cycle

October 8, 2019 by Maya Posch 86 Comments

The discovery of nuclear fission in the 1930s brought with it first the threat of nuclear annihilation by nuclear weapons in the 1940s, followed by the promise of clean, plentiful power in the 1950s courtesy of nuclear power plants. These would replace other types of thermal plants with one that would produce no exhaust gases, no fly ash and require only occasional refueling using uranium and other fissile fuels that can be found practically everywhere.

The equipment with which nuclear fission was experimentally proven in 1938.

As nuclear reactors popped up ever faster during the 1950s and 1960s, the worry about running out of uranium fuel became ever more present, which led to increased R&D in so-called fast reactors, which in the fast-breeder reactor (FBR) configuration can use uranium fuel significantly more efficiently by using fast neutrons to change (‘breed’) ²³⁸U into ²³⁹Pu, which can then be mixed with uranium fuel to create (MOX) fuel for slow-neutron reactors, allowing not 1% but up to 60% of the energy in uranium to be used in a once-through cycle.

The boom in uranium supplies discovered during the 1970s mostly put a stop to these R&D efforts, with some nations like France still going through its Rapsodie, Phénix and SuperPhénix designs until recently finally canceling the Generation IV ASTRID demonstrator design after years of trying to get the project off the ground.

This is not the end of fast reactors, however. In this article we’ll look at how these marvels of engineering work and the various fast reactor types in use and under development by nations like Russia, China and India.

Continue reading “The Long History Of Fast Reactors And The Promise Of A Closed Fuel Cycle” →