Since I have seen this article make the rounds a couple times now, I wanted to address how silly the arguments against this HEU fueled test reactor are. Here is a little thread about HEU fueled reactors and why these complaints are BS!🧵 1/11
reuters.com/world/us/us-ur… So first of all, what is HEU? Highly Enriched Uranium (HEU) is any uranium with more than 20% U-235, which is the naturally occurring fissile isotope. Natural uranium is 0.7% and typical reactor fuel is 3-5%, but some very small reactors use higher enrichment. 2/11

So I finally got around to reading this incredible book on NUCLEAR PUMPED LASERS and boy is it full of interesting stuff! The first 12 chapters are an updated English translation of a Russian book, while the final chapter is about work in the US. They did some wild stuff! 🧵1/13 The concept goes back to the invention of the laser. What if we could directly power a laser with the might of a nuclear reactor or explosion? This looked especially appealing when lasers were horrendously inefficient and thus the Nuclear Pumped Laser (NPL) was born! 2/13

Micro-reactors are quite the popular topic right now, so let's talk about how you make a REALLY micro-reactor using the best (thermal) nuclear fuel we know of, Americium! Specifically, the isotope Am-24m. 🧵1/ Americium was discovered in 1944 by Glenn Seaborg using a cyclotron, but is a pretty common transuranic (i.e. element after uranium) to encounter. It is a common isotope in spent nuclear fuel (~100g/ton), although most of it is Am-241 and Am-243. 2/

So there has been a big hubbub about the recent hydrogen production projects at places like the 9 Mile Nuclear plant. I get the concern over dirty hydrogen production as a form of greenwashing, but I also think the folks who are really worked up are missing something. 1/5 Say whatever you will about hydrogen as energy storage (I am not a big fan personally), but we already use a lot of hydrogen for critical industrial applications! ~90 MT per year, of which ~1/3 of that is fertilizer! Currently all of that is fossil derived hydrogen. 2/5

So fusion has been in the news quite a bit. Have y'all ever heard of the "only known way to get fusion power NOW" (paraphrasing Teller)? It is known as Peaceful Nuclear Explosion Reactor (PNER) or Project PACER! Set off thermonuclear bombs and make steam power! 🧵1/12 I had heard of the original idea many years ago, but never knew it was revisited until this past Friday. The original concept was to use 20-50 kT nuclear explosions every couple hours in a 100 m salt dome (made via nuke) to make >1 GWe via direct nuclear to steam heating! 2/12

Have you ever heard of a gas core reactor? No not a gas cooled reactor, but a reactor with a gas CORE! This is a concept dating back to the Manhattan Project to just let the core become gaseous (or maybe plasma) instead of solid or even liquid. 🧵1/16 The idea is quite old and is appealing since now the fuel has no damage limits, can be easily reprocessed online, and can run at truly stunning temperatures (thousands of degrees). You also don't have to convert UF6 back into U or UO2, which saves effort and energy. 2/16

Super quick thread on the NIF results since these got leaked early. I was under the impression the official announcement was on Tuesday, but I guess someone talked to the press early!🧵 1/17 ft.com/content/4b6f0f… So NIF is the largest, most energetic laser in the world. It was built to push a form of fusion called "inertial confinement fusion" (ICF) forward and help with the goal of stockpile stewardship (i.e. management of the nuclear arsenal). 2/17 lasers.llnl.gov

So when talking about recycling spent nuclear fuel (i.e. "waste"), we often like to focus on turning it back into more nuclear since that is an amazing trick! But there are also lots of useful isotopes to recover and if we recycle at scale it could really change things! 🧵 1/17 When atoms fissions, we get a broad range of isotopes with most of them massing either ~95 or ~137 amu, but there is a broad distribution and the exact make-up depends on isotope and neutron energy. 2/17 hyperphysics.phy-astr.gsu.edu/hbase/NucEne/f…

A term that is often tossed around in advanced nuclear propulsion circles that drives me nuts is "low radiation". It often isn't even right and NEVER means what people imagine it does (almost no shielding needed). Let's look at how many rads we actually get from reactions. 🧵1/11 Ionizing radiation in this case will be counted as gamma rays and neutrons, since the charged particles are easy to stop and typically very useful. Also we will ignore neutrinos since they aren't a health hazard. 2/11

A common question people like to ask when it comes to mobile nuclear (fission or fusion) applications is "how much will it weigh". I have some simple math and plots to help answer that! Keep in mind shield mass is almost everything for reactors! 🧵1/12 Now real shielding math is really complex and needs models. I was able to find (and fix the units on) a simple equation used for aircraft reactor studies though! It assumes H2O and DU shields that are all the way around the reactor (4pi) and 0.025 mR/hr on contact. 2/12

After listening to @Dr_Keefer explain the isotope producing benefits of CANDUs yet again, I went looking for some more numbers on it and found this excellent page from OPG! 1/7 opg.com/innovating-for… Looks like CANDUs sterilize about 20% of the worlds single use medical devices via Co-60 production. That is pretty impressive, especially considering the plans to expand this production! 2/7

Many of you know that I absolutely *HATE* the idea of mining the Moon for He3. I even wrote a paper about why it is dumb for energy! Let's also explore why lunar He3 is silly for the current uses, namely neutron detection (although it has other uses). 1/12
space.nss.org/wp-content/upl… He3 is a really good gas for neutron detection, since it gobbles up thermal neutrons and is very safe compared to the typical alternative (BF3). There are other options out there, but around 2001 those were the top 2 technologies. 2/12

So I have an update to this thread on aircraft nuclear propulsion. There seem to have been some later studies and even fuel testing done and for civilian applications! Big thanks to the people that pointed me towards this stuff! 1/

https://twitter.com/GBruhaug/status/1576666195196989441?s=20&t=TZHf6ancJNQFrAmB_0cQaQ

There were studies on extremely large cargo aircraft using nuclear power as well as nuclear powered hovercraft for rapid cargo transit! These beasts would have hauled hundreds to thousands of tons across the oceans very quickly! 2/

Have you ever wondered about nuclear aircraft propulsion? Boy do I have the thread for you! I spent valuable time reading papers that are not relevant to my thesis, because sometimes I like to procrastinate by doing more work. Enjoy! 🧵1/23 In the US we started looking into nuclear propulsion for aircraft as early as 1948. The USAF wanted nuclear powered nuclear armed bombers to fly deterrent patrols of the USSR. Using nuclear energy they could stay aloft for days, weeks or potentially months! 2/23

I wasted an hour today answer a question I had about cost per watt for various sources across the EM spectrum. These are all sources you can actually beam power with (so light bulbs don't count). 1/2 Broadly speaking the higher the frequency, the more expensive per watt. THz and soft x-rays stand out as being extra expensive though. These are both in the range that is very hard to make at high powers, although there may be FELs that generate cheaper beams. 2/2

So last year I made a thread about my least favorite reactor, the tokamak fusion/fission hybrid. Today I want to tell you about my favorite oddball reactor that competes with that terrible design, the accelerator driven subcritical reactor (ADSR)! 🧵1/20 This concept probably will never make any economic sense, but it does have some interesting engineering/physics characteristics! The idea is also very old, with the first references coming from Lawerence himself in the 50s. 2/

So a certain space/tech person commented some misunderstandings about fusion fuel cycles recently and I figured I would make a thread outlining the *actual* reality of the 4 fusion fuels being considered (DT, DD, DHe3, and pB1) and clear the air. 🧵1/23 So we will start with DT, the "easiest" fusion fuel mix to get net energy from and BY FAR the most likely fusion fuel to be used in any reactors of any kind in our lifetime. This fuel mix is deuterium (H-2, heavy hydrogen) and tritium (H-3, radioactive heavy hydrogen). 2/23

So you may have heard of the banana equivalent dose, the idea that you get about 0.1 uSv by eating a banana. This is due to the naturally occurring K-40 and C-14 present and is in no way harmful! You would have to eat at least 35 million bananas at once to get sick. 🧵1/9 You may have... other problems if you try that! Now other things also can give you dose due to the variety of natural radionuclides in them. Let's start with seawater since radioactive water has been an off and on topic. 2/9

Since the myth of limited nuclear fuel supply is back in the zeitgeist due to some popular YT videos, I figured I would finally dive into the true insanity of nuclear fission fuel resources. Let's see just how long we can burn rocks! 🧵 1/23 So first and foremost, fission power is the process of splitting heavy atoms like uranium (but also neptunium, americium, and more) in a chain reaction. We get ~200 MeV from this reaction, which is a LOT! Millions of times more than chemical reactions. 2/23

So in keeping with my on and off posts about limits of energy systems, let's talk about FUSION! The power of the future (and always will be) as the joke goes...
🧵1/16 (actual fusion shot picture BTW, thanks LLE!) So there are three fusion fuel cycles worth talking about here on Earth. Deuterium-Tritium (DT), Deuterium-Deuterium (DD) and the mythical proton-Boron11 (pB11). DT is DRAMATICALLY easier than the other two, so we will start there.
2/16

So I have seen a lot of talk about a horrible proposal for everyone to just embrace intermittent power to “save the climate” and that this is somehow “just”. Let me tell you a personal story about just how infuriatingly bad and privileged this idea is. 🧵1/10 I grew up in Montana, a beautiful and sparsely populated state known for its great sights and harsh weather. It can get so nasty I was worried about snow during my summer wedding.. This nasty weather also results in very shitty electrical service. 2/10