When a uranium atom splits, you’d think it would split in half.

U-235 splitting into two 117 - 118 nucleon atoms.

But it doesn’t. It splits lopsided: ~95 and ~140.

And it turns out, this is the main reason nuclear reactors work at all.

Why? 🧵 U-235 has 92 protons and 143 neutrons.

An even split would give 46 protons and 71 - 72 neutrons.

That would be palladium (Pd, with atomic number = 46)

But Pd is not stable when it has over 70 neutrons... it's stable at 60.

Why is it unstable at 70+?

Why did we choose liquid metal (sodium) as our reactor coolant?

Water-based reactors have way more operational history, so are we taking unnecessary risk?

No - it’s the inevitable next step in nuclear.

Here's why! 🧵
First we'll cover advantages of sodium.

Then we'll discuss the challenges.

At the end I'll explain why sodium is the inevitable endgame coolant for fission.

I asked someone high up in government,

“How would you reform nuclear regulation to maintain safety, while optimizing economics?”

They asked to remain anonymous, but here’s their take: 🧵 1) Fix radiation limits:

Currently, nuclear must not exceed 10 mrem / year in a release to the public.

This is 1% of the threshold known to have any measurable impact on human health.

Measurable impact here means a slightly observable impact in expected lifespan.

Henry J Kaiser was incredible.

He built highways, bridges, and The Hoover Dam.

But most impressively, he built 1,490 ships during WWII, 1/3 of the entire U.S. cargo fleet.

Here's how he reduced the time to build a ship from 8 months, to 4 days 🤯 (🧵)
Before Kaiser entered the industry, shipbuilding was a slow, meticulous craft, much like constructing a cathedral.

The process followed a traditional, step-by-step sequence that hadn’t changed much in decades:

What would it take to create the SpaceX of Nuclear, cutting costs by 10x?

For rockets, the answer was obvious: Make them re-usable.

What is the equivalent insight for reactors? 🧵 One possible answer: Factory mass manufacturing.

Let’s dive into exactly how this would lower costs, and by how much.

How much nuclear waste has the US ever created?

You may have heard it would fit on a football field...

But stacked how high? And stored how?

@whatisnuclear wrote a great post on this... 🧵(1/8) All the nuclear waste in the history of US Nuclear Power would fit in 8516 dry casks, shown above.

See below for a size comparison with the field goal posts.

This pile would be 135 m tall, about as tall as a 40 story building.

Excitement about the “nuclear renaissance” is high,

But we’ve been here before in 2007 and that renaissance failed.

What went wrong, and why will this time be different?

🧵(1/n) ➡️ The obvious answer is Fukushima, which hit in 2011.

This was a major setback, but the headwinds had already been mounting...

If you think the energy transition is going well, look at this:

Not only is clean energy barely even visible on a graph of energy use globally,

But oil and gas is still growing.

What’s going on here? (🧵) The grid (electricity) is only a small part of all energy used by humans:

Electricity: 25,000 TWh
All energy: 160,000 TWh

30% of the grid is clean, but that means only 6% of total energy is clean.

The rest (94%) is oil and gas.

An under-appreciated fact:

60-80% of nuclear's LCOE comes from paying off interest. That is insane.

Factory-made small reactors could solve this:

Instead of 1 large reactor that takes 7 yrs to build,
install 10 small reactors (2 per yr), minimizing debt.
👇🧵 One potential challenge: When you have 10-20 reactors on site to maintain, how do you prevent op-ex from getting too high?

This is an engineering challenge that can be resolved through design and automation.

For every ten likes, I’ll make this person increasingly realize how incredible nuclear power is Here they are, reading that nuclear is statistically just as safe as solar or wind

Unpopular view 👇

Solar + storage should NOT be used on the grid.

And yet, solar could still play the largest role in the energy transition.

How so?… 🧵 https://t.co/ihrsLF6oiItwitter.com/i/web/status/1…
➡️ Solar + storage is fundamentally weather-dependent.

As a result, as solar increases its share of the grid, its cost (capex) scales rapidly.

Meanwhile, for firm power (like nuclear, hydro, etc), capex scales only linearly with grid share.

Why does solar get more expensive?

The most important nuclear reactor that you've never heard of is….

The MARVEL reactor from @INL!

They received permission to start construction THIS WEEK.

Why should you care? ⬇️ MARVEL will likely be remembered as the start of the Second Atomic Age.

It’s been 70 years since the rise of the First Atomic Age. Back then, 52 reactors were built and tested at INL.

Unfortunately, few novel reactor designs have been explored since…

This is cool!

ORNL created an Augmented Reality tool so you can “see” radiation

Most ppl don't realize you’d see less radiation at a nuclear power plant than you would around a coal plant, or in some cases even your house How could that be?

Realistically, the radiation levels are normally harmless at all 3 places (in a nuclear plant, around a coal plant, and in your home).

So we’re talking about subtle differences in very low levels of radiation here...

BUT the logic is:

Investors have poured billions into fusion💥,

hoping to fund the ‘holy grail’ of energy.

I believe they’re funding an expensive science experiment that won’t play a role in our future grid (but will still be great for humanity).

Here’s why ⬇️ twitter.com/i/web/status/1… I’ll argue that fusion💥 (once it works) will offer no major advantages over what fission🪨 already offers (today),

and that fission🪨 will always be cheaper than fusion💥. twitter.com/i/web/status/1…

Radioactive metal was accidentally used in the construction of 1700 apartments in Taiwan in 1983. Nobody realized for 10 yrs.

Yet the 8,000 residents have reportedly had a LOWER cancer rate than others in the area.

How? Here's the controversial story of radiation hormesis 📖 👇 A familiar form of hormesis is: Exercise. 

A lack of exercise can be bad. A little exercise is better. Extreme exercise can harm you. 

Oxygen is another example; too little or too much call kill you. Hormesis describes any such response curve for a biological system.

For 40 years, nuclear power was expanding exponentially, ushering in a new era of clean & reliable power.

Then in 1989, it hit a wall.

What really happened? … 🧶 … Nuclear plants traditionally take 5–10 years to build.

This implies utilities stopped placing orders around 1980.

Why?

Millions of people mistakenly believe that Solar is now our cheapest option for powering the grid.

What's misleading them?

A sneaky metric known as LCOE. 🧶👇 Levelized Cost of Energy, or LCOE, is the total cost of a project, divided by the total energy that it produces in its lifetime.

If you build a field of low-cost solar panels that produce a lot of energy over their lifetime, it's a low LCOE and a great investment, right?

Experts can't seem to agree on the best way to decarbonize the grid.

Is the answer in renewables? Nuclear? Or do we need a new breakthrough technology?

Here's what you need to know 🧶👇 Where an expert lives can strongly influence their opinions on energy.

Climate & geology, politics, and raw material availability all come into play.

Arguments about energy can often feel like this: