I think if I was a horrible nuclear engineering professor I'd give a homework or exam problem using INL's Advanced Test Reactor fuel as an example. It's weird.

How weird? The core is comprised of 40 fuel elements, each of which is a 45-degree sector of a thick cylindrical tube of concentric fuel plates. Imagine sandwiching 0.020" of uranium metal between two sheets of 0.015" aluminum cladding and bending that into tubes ranging from 5" to 10" in diameter. Nest 20 or so of these tubes then cut the tubes lengthwise into 8 pie pieces. Now take 6 pie pieces and form a 3/4 circle. Take 4 more to make a half circle and connect that to the first 6 but curving the opposite direction. Do this three more times and connect the ends so you have a cloverleaf shape - that's your core.

You might ask, why the hell would anyone do that aside from the fact that it's the early 1960s and the AEC would let you? Well, if you draw this weird squiggly mess on a piece of paper, you notice that a grid of nine 5" diameter tubes can fit within the serpentine arrangement of fuel elements. You put experiments in those tubes, fire up the reactor and irradiate the bejeezus out of them.

There are no control rods - instead there are 16 control drums surrounding the core which rotate to expose some beryllium that reflects neutrons back into the core. Core croticality and power are controlled by controlling how many neutrons leak out of the core. Compare this with power reactors which use neutron absorbers instead. Another control scheme you see is separating fuel into moving and stationary elements and move the fuel into a more or less leaky configuration depending on whether you want more or less power.

Aluminum-clad plate fuel was common in the late-1950s/early-60s test reactors but typically it was arranged as flat plates in square fuel elements. This odd serpentine arrangement allows for different lobes of the core to be operated at different power levels which is convenient if you are running multiple simultaneous experiments that need different conditions.

This reactor uses 93% enriched fuel which is pretty spicy (commercial power reactor fuel is typically 5%, natural uranium is <1%). This is the sort of specialty facility you use if you're designing a new reactor and you need to see how parts behave inside a reactor core. There's only so much computer modeling can tell you, especially if you have limited experimental data (what do you think those computer models are based on...?)

Anyway, there's often a focus in college classes on modern power reactor fuel which is relatively simple and commercially relevant. Oddball reactors like the ATR work on the same fundamental principles but have unique characteristics that reflect their specialty role as test and research reactors. https://inl.gov/advanced-test-reactor/

The proceedings of the Bridges Math Art conference were published online a couple of days ago: https://archive.bridgesmathart.org/2026/

This is always a highlight of the year for me; but especially so this year, because they contain a paper that I co-wrote!

So I thought I would say a bit about it here, and over the next few days as I find time to add bits & pieces.

The title, and the topic of the paper, is Caltrops: https://archive.bridgesmathart.org/2026/bridges2026-165.html

But what, I hear you cry, is a caltrop‽

(1/?)

A phenomenon I've noticed recently is people trying to occupy some untenable middleground wrt to the use of systems sold as "AI" -- this is a position where people try to recognize the harms of this tech but also hold space for "responsible" or "ethical" use.

🧵>>

From the "Pivot to woodworking" department

#InfoSec #ShitPost #DevOps #Logs #VennDiagram

WaPo reports the Justice Department took the extraordinary step of seeking to force reporters for The Washington Post and the Wall Street Journal to testify before a federal grand jury — but withdrew the subpoenas earlier this month after they were challenged by the news organizations.

"The grand jury subpoena to Washington Post reporter Ellen Nakashima this spring was related to sensitive reporting about a national security matter, the person said. The Justice Department also issued subpoenas to appear before a grand jury to three Wall Street Journal journalists, who also reported on national security issues."

"The Washington Post was fighting the demand in federal court in the Eastern District of Virginia in sealed proceedings when the government rescinded Nakashima’s subpoena, according to the official familiar with the matter. The Justice Department also withdrew the Wall Street Journal subpoenas, which the news organization had challenged in the same federal court, according to the official, who spoke on the condition of anonymity to discuss proceedings that are not public. None of the journalists testified before the grand jury, the official said."

"The purpose and scope of the investigations that triggered the subpoenas are not clear, but the person familiar said they relate to national security matters. While the journalists are no longer scheduled to appear before a grand jury, the Justice Department’s action reflected a new front in the Trump administration’s aggressive tactics toward the media as it attempts to crack down on government leaks to the press and content that administration officials think is unfair to the president."

Just another prong in the administration's efforts to go after news organizations and harass and intimidate journalists for doing their jobs.

https://www.washingtonpost.com/national-security/2026/06/23/doj-issued-then-withdrew-subpoenas-force-post-wsj-reporters-testify/

My client is a caregiver to their mother, who has little access to short term memory. My client explains that the tv has just updated and reorganized its Home Screen. She knew how to access her shows on the old Home Screen. Now, every time she powers up the tv, she’s deluged with ads and trending slop and has to relearn how to use the device to find her shows, from scratch, as if starting over again for the first time. This is now a nightly half-hour ordeal. The update was mandatory. They were never given an option to keep the system she knew.

Chopping vegetables has worked the same way for fifty thousand years. Why do these assholes think they have the right to change how a tv works?

#MoveSlowAndFixThings