Dec 20 2016

New Radiation Resistant Metals

radiation-alloysThis is a bit of a wonky technical post, but that is actually a point I want to make. Often I find that the scientific advances that have the most potential get the least coverage, while interesting but incremental advances, or one-off findings, are given broad coverage with sensational headlines. This is an unfortunate artifact of how scientific news is communicated. First, a company’s or institution’s press office will determine if the new study or finding is press-worthy, and if so they will compose a press release. Then journalists and news outlets will decide if it is worth publishing, which usually means – can they spin it as a major breakthrough, creating or solving some “mystery”, a potential cure for some disease, or tie it to some science-fiction technology.

Meanwhile, real advances that are not “sexy” get overlooked. So when I saw this item I thought, this is likely to be one of those advances with huge potential but very little press coverage.

Researchers have figured out how to make metal alloys that are far more resistant to radiation damage than existing alloys. The key is mixing three or more different metals in equal proportions. They compared nickel to nickel-iron, nickel-cobalt-iron, and nickel-cobalt-iron-manganese-chromium. The alloys with three or more metals were 100 times more resistant to radiation damage than the pure nickel.

When metals are exposed to a lot of radiation at high temperature, they tend to swell. This can affect structures around them, but also causes them to become less dense, which can reduce their shielding efficacy. Further, the metals accumulate structural damage over time, limiting their lifespan.

When radiation hits a metal atom it can kick it out of the crystal structure. The atom can travel relatively far within the crystal, leaving behind a small hole that does not move as fast or far. This can result in a large number of holes coalescing into a larger cavity, which weakens the integrity of the metal.

The alloys, however, contain atoms of different sizes mixed together. This has the result of slowing the movement of atoms that get kicked out by the radiation, so they stay closer to their holes and are more likely to combine again with the hole, healing the structure and preventing the formation of cavities (as you can see in the picture above).

The obvious application of this knowledge is in nuclear reactors. The radioactive fuel needs to be stored in canisters, and the effectiveness and lifespan of those canisters is important to the safety of the reactors.

Another potential use could be in structures in space, which may be exposed to high levels of radiation (not as high as a nuclear reactor, but persistent over decades). The lifespan of the shielding of satellites, spacecraft, space stations, and even Moon or Mars bases could benefit from such alloys.

Other researchers are working on nanostructured alloys to have the same property – defect restoration producing radiation tolerance. The idea here is to structure the alloy to contain nanopores that essentially have the same effect as the alloys. The advantage of the alloys is that they are easier and cheaper to manufacture (at least for now).

There is also research looking at metal foams, which can be much more effective at absorbing different types of radiation for the same weight. This would be essential for radiation shielding in spacecraft where weight is a critical limiting factor. In fact, one of the technological limitations in getting people to Mars is shielding the crew compartment for the many months journey, including time they would spend on Mars. Improved radiation shielding could be critical to the feasibility of such missions.

As an aside, when reporting on this news item the Daily Caller claimed:

Nuclear power, even accounting for high-profile nuclear accidents, is already statistically the safest way of generating electricity. Coal power kills 280,000 people for every trillion kilowatt hours it produces. Rooftop solar kills 440 for the same amount of electricity. Nuclear energy only kills 90, by this measure, including deaths from disasters.

The link goes to an interesting Forbes article, which is worth a read itself. Nuclear has the best safety record partly because it generates so much electricity for the amount of infrastructure. As safe as, say, wind power is, you need a lot of wind turbines to create the same amount of electricity as nuclear, and the occasional turbine worker falling off to their death is enough to exceed total deaths from nuclear power.

The coal numbers are also interesting. World wide coal deaths are 10 times that of the US, which the article attributes to the clean air act, which they claim is the piece of legislation that has saved more lives than any other. This emphasizes the point that the health care costs alone of coal burning and other fossil fuel burning make it cost effective to switch to cleaner forms of energy, and should be considered in any comparison.

Where does the death toll from solar come from?

The large quantity of materials required for unconventional systems implies huge industrial efforts in mining, refining, fabricating, and constructing the collectors, storage systems and all related apparatus. Every form of industrial activity has an associated risk, which can be found through accident statistics compiled by national organizations. When all the multiplications and additions are done, we find that the risk from unconventional energy systems can be substantial.

This is another reason to give nuclear power a serious consideration when trying to figure out how we are going to shift our energy infrastructure (in time) to minimal CO2 emissions. This also brings us back to the current study – improved radiation shielding could make nuclear power even safer.


I am often reminded of the following quote:

“Amateurs talk about tactics, but professionals study logistics.”
– Gen. Robert H. Barrow, USMC (Commandant of the Marine Corps) noted in 1980

This stuck with me because of the realization that what seems interesting, exciting, and important to the lay person may not be the truly most important aspect of something. Experts may tend to focus on aspects of their field that seem boring, but are critically important. No one talks about the logistics of a major battle, but that is often where real victory or failure lies.

The same is true in many fields, including much of technology. In general it’s my sense is that material science is greatly important, but gets relatively little attention. Making a new metal alloy is just about as boring a news item as you can imagine, but these are the kinds of advances that have the real potential to be game-changers.

11 responses so far