What does "going critical" mean? If you shoot a neutron into some uranium ore, some atoms will split by fission, but you haven't made a nuclear reactor. Too many secondary neutrons leak out or get absorbed without splitting neighboring atoms. 1/n

The Engineering Test Reactor (ETR) was constructed in 1957 at the National Reactor Testing Station in Idaho. It was a 175 MWt reactor that absolutely hammered fuels and materials with high flux neutrons, fine-tuning the high-performance nuclear technology we use today www.youtube.com/watch?v=k_b3...

This Combustion Engineering facility in Chattanooga, TN fabricated 57 reactor pressure vessels for US reactors, plus more overseas, and lots of other heavy equipment. As the nuclear industry ramps back up in the US, I hope we see lots more facilities like this soon.

If you pull a vacuum on wood, then impregnate it with a monomer, and then irradiate it with gamma rays, you get a wood-plastic composite that is extremely tough while looking great. If it gets scuffed, you just buff it out, the finish goes all the way through. www.youtube.com/watch?v=k9sQ...

Industrial Applications of Nuclear Explosives (1958) That's one way to make a new harbor! www.youtube.com/watch?v=py9e...

Those new studies linking nuclear plant proximity to cancer use very weak scientific methods. No dose assessment, no control group. It's shameful that they passed peer review. Takedown here: www.breakthroughjournal.org/p/two-new-pa...

Visiting the Nuclear Ship Savannah in person is worth traveling to Baltimore for, especially since they recently opened up the reactor vessel. Saturday, February 21st. www.ans.org/news/2026-02... @americannuclear.bsky.social

This has to be the fastest way to add 10 GW of new nuclear capacity in the US (uprating existing reactors!) www.wsj.com/business/ene...?

ICYMI: @whatisnuclear.com digitized this 1967 film about the BONUS reactor, in Puerto Rico. Superheated steam from a boiling water reactor! whatisnuclear.com/news/2023-09...

Have you ever wondered if small nuclear reactors could possibly beat out the economies of scale from large reactors? Check out my latest report @theniaorg.bsky.social “Right-Sizing Reactors: Balancing trade-offs between economies of scale and volume” tinyurl.com/bdhz27wt

The classic mouse trap and ping pong ball demo, from Martin Marietta. Only problem is that the mouse traps flying around set off other mouse traps, dramatically increasing keff. They should have glued them to the bottom. (VHS quality because, well, it was on VHS)

I made a new 'microreactors' page. Benefits: 1. Novel power markets 2. Manufactured product 3. Within reach of VC 4. Fewer radionuclides Challenges: 1. Economies of scale 2. Tyranny of neutron diffusion 3. Shielding whatisnuclear.com/microreactor...

Presenting: A 1980s film describing uranium enrichment using gaseous diffusion. www.youtube.com/watch?v=U5gN...

🍿⚛️ Today we have: "Managing Radioactive Waste At the Nevada Test Site", a 1980 film from DOE, freshly scanned off of U-matic video cassette kindly provided to me by Prof. Ron Knief. www.youtube.com/watch?v=V1Jd...

Check out the state of nuclear fusion research as it stood in 1988 www.youtube.com/watch?v=Wuss...

It's not that advanced reactors aren't and can never be economical (that's crazy), but they haven't been economical so far (for very specific reasons) and have a steep hill to climb to achieve viability. As always, the only way to climb it is to build build build. www.youtube.com/watch?v=O2JL...

Those were the highlights. Here's the full 12-mins in documentary form www.youtube.com/watch?v=1LVq...

Nuclear waste transport cask testing... with Red Alert music

90s kids explain nuclear energy. youtu.be/6Cwkk2mMM64?...

Flash animations from the 2006 version of whatisnuclear dot com, made by yours truly. "This is what they stole from us" 😂

Neat site that explains the value of clean firm resources like nuclear, hydro, and geothermal in a highly decarbonized grid nathandiyer.github.io/clean-energy...

The Beetle, everyone's favorite actually-real mecha, inside and out. It was designed to do maintenance in the highly radioactive areas around nuclear-powered long-range bomber aircraft back in the nuclear-powered flight days.

I'm currently getting these historical nuclear films digitized. Standby! As far as I can tell, none of them exist online yet except the Accident Testing one, which shows the Sandia cask tests. I'm getting that one scanned with hopes that it'll be extra high quality for everyone's pleasure.

Yesterday, Russia announced that its new nuclear-powered cruise missile flew for 15 hours straight. The US had such a thing in development in the 1950s (see film), but it looks like the Russians have finally gotten one operational. www.youtube.com/watch?v=8qMu...

Here's what neutron chain reaction dynamics kinda look like. The green bar is control rod position and the trace shows reactor power, starting at 1. After each control adjustment, there is a 'prompt jump' followed by a longer exponential tail from delayed neutrons.

Man! I was at a workshop in my home state of Michigan on Thursday and we were brainstorming ideas to bring more nuclear power industry to the state. I mentioned that the Upper Peninsula has pretty good geology for a long-term nuclear waste repository (reducing environment, precambrian rock)....

Can't reply on the post for some reason... but after 3 years of shutdown it does not take that much cooling to keep the spent fuel cooled. Something like a garden hose of water going in should suffice. I'm not super worried about it.

Taking a Geiger counter on a flight with the sound on is a great way to get some serious side-eye from your neighbors, maybe leading to a good discussion about dose rate

It's a true miracle of nature that water is both a good neutron moderator and reactor coolant. Its ability to moderate and cool at the same time is quite underappreciated in today's pro-nuclear circles.

The first Boiling Water Reactor experiments (BORAX) www.youtube.com/watch?v=oLlK...

Pretty neat model of a PWR from the 1965 Boy Scouts Atomic Energy merit badge book. Honestly, building this would help kids understand quite a bit about a reactor.

Looking into the core of BORAX-5, which pushed the limits of what a BWR could do: nuclear superheat and natural circulation. The superheat region is in the center. BWRs today are not so bold as to superheat steam. Have materials improved enough to try again? Probably!

We need Nuclear Reactor Consumer Labels! whatisnuclear.com/news/2025-08...

Getting these 45 historical nuclear films from 1955-83 dug up and digitized has been one of the coolest and most rewarding things I've done with What is Nuclear. Thanks to you all for your interest and support in this project! There are only ~100 left to get. whatisnuclear.com/museum/

For all you Anki users out there (free spaced repetition learning app), I made a deck for memorizing the US Nuclear Power Plants. Planning to expand it more later but it's starting out with just the operational commercial units. ENJOY! github.com/whatisnuclea...

Observation: the actions that get more investors to buy into your nuclear company are currently the opposite of those needed to develop an economical, operable, maintainable, and safe nuclear plant. Anyone have ideas about how to bring these back into alignment?

CNA in Singapore produced a nuclear power documentary called "The Nuclear Option" that you can watch online. They visited many key places and talked to lots of people. It came together super well! www.youtube.com/playlist?lis...

Beryllium triflute that fit between the pins in the PPA. Who's working on beryllium triflutes today?!

Here's Preliminary Pile Assembly-19, where rotating control drums were first mocked up in a critical facility around 1951. Note the six smaller hexagon outlines on each corner of the central hex, each of which represents a control drum.

We debate this endlessly within the pro-nuclear world, but I really don't think it's super complicated. There's plenty of room to promote either without throwing the other under the bus.

New safety minute about the WTR fuel failure whatisnuclear.com/safety-minut...

Here's the Neutronics Scoping Tool, which allows you to dial in a certain core height, radius, enrichment, and power rating and see if it will go critical and how long it will run. Then, it estimates the fuel LCOE, average discharge burnup, and a whole lot more. www.youtube.com/watch?v=GQzD...

Big Rock Point in Northern Michigan was the prettiest nuclear plant. It's crazy that one little 71 MWe plant like this can make enough electricity to power a whole county in peak fudgie season.

The Rickover memo in the form of a Dunning-Kruger curve whatisnuclear.com/news/2025-06...

Natural uranium is mostly U-238, with a 4.5 billion yr half-life. A kg of it kicks out 12M alpha particles per second with 4 MeV of energy each, generating 8 microwatts of ionizing radiation. It's not super hazardous, and you can hold it in the palm of your hand with a glove.

After much effort, I'm happy to finally present the Universal Reactor Memorandum of Understanding (MOU). This MOU is hereby issued between all current and future reactor companies and all current and future power customers. Congrats to all.

I just won a chunk of graphite from the world's first man-made nuclear reactor (CP-1) in a raffle from at the #ANSAnnual conference. I've desperately wanted one of these for decades, and entered at the last minute, thanks to a serendipitous seating at the lunch table. I'm so lucky and grateful!

Statement on firing of NRC Commissioner Hanson: www.ans.org/news/2025-06...

BREAKING: Nuclear Regulatory Commissioner Chris Hanson has been fired by President Trump. The NRC is one of the most independent agencies in the Federal Government. Statement from Hanson.

Who's all coming to #ANSAnnual in Chicago?