Thread by @energybants

TAISHAN, CHINA NUCLEAR EVENT THREAD

I'll update this with what we know and what we're learning.

First: this isn't a public health risk. Appears to be a fairly typical nuclear plant event caused by one or more fuel bundles leaking fission products into the core cooling water.

https://twitter.com/cnnbrk/status/1404292017589473281

Taishan, the plant in question, is one of several plants China built in partnership with foreign nations over the past few decades to get as much experience and tech transfer as possible.

Taishan: two EPRs, built with France. Big PWRs, 1660MW each.

Went into operation 2018-19

Taishan, like all pressurized water reactors (PWRs) and essentially all commercial nuclear plants ever, uses ceramic fuel.

Yes, a material sort of like your coffee mug, but with uranium.

This fuel type was chosen in the history of nuclear for its extreme resistance to heat.

The ceramic fuel comes in little pellets, which are stacked into long metal rods, with a tight fit to help heat transfer from the pellet to the rod to the water cooling the rods.

Fission takes place in the pellets, producing heat and lighter elements. Like noble gas Xenon.

The logic behind the use of ceramic fuel is that its extreme resistance to heat, and hardness, keeps most of these lighter elements trapped inside.

That means one extra layer of protection against these radioactive fission products escaping. Next layer is the metal fuel rod.

The problem with ceramics is that, as you may know with your coffee mug, they crack.

When the pellet is undergoing fission in the reactor, the buildup of fission products puts pressure on the pellet and it swells a bit, and little cracks start forming.

This is expected.

These cracks let some fission gases out into the inside of the fuel rod.

Then, if the fuel rods does its job, the gases are retained inside, not just the years in operation in the reactor, but for the five years spent cooling off in a pool and then in storage after that.

In the United States, these fuel rods used to crack and leak all the time, with an average of several dozen "leakers" per reactor over the life of the plant.

Then all the fuel manufacturers got together to institute extreme quality control to stamp it out.

They've succeeded.

WHAT ARE NOBLE GASES? ARE THEY DANGEROUS?

Helium, Neon, Argon, Krypton, Xenon, and Radon are the "noble" gases, so called because of their extremely low ability to combine with any other elements.

Xenon forms in fuel from uranium atoms breaking apart into smaller chunks.

This Xenon comes in a few flavors, including Xenon-131 and Xenon-133, so named for their atomic masses being 131 and 133. The difference is the number of neutron particles in them.

Compared to naturally occuring Xenon, these are radioactive.

Their ability to hurt us is limited.

Why is their ability to hurt us so limited?

Because they are noble gases, they can't really combine with anything in a way that keeps the radioactivity near us, like the issue was with iodine in the days after Chernobyl (iodine is a necessary nutrient taken into the thyroid).

The presence of Xenon in the water coolant indicates that at least one fuel rod is letting fission products into the cooling water passing through the core.

But in the hundreds of similar incidents in the USA, this hasn't led to harm to the public.

WHY HASN'T THE PLANT SHUT DOWN?

Leaking fuel rods are a maintenance headache, not a risk to public safety.

Eliminating leaking rods in the USA was a big effort but worth it for making refueling outages faster, easier, and cheaper.

Our incredible 94% uptime is one reward.

We can detect even the tiniest amounts of radioactive substances. And because all nuclear plant events have to be reported no matter how minor, this means lots of reports.

Leaking fuel rods are extremely well understood in part because of all these reports.

This means that shutting down after fuel rod leaks have been detected are a matter of how important the electricity is for the grid at that time, how close to a refueling outage the plant is, how extreme or paranoid the nation's regulator is, and so on.

As long as Taishan monitors the level of fission products in the cooling water, and there isn't a sudden increase indicating lots more leakers, they'll probably stay online.

Here's a story from a decade ago about a similar incident, just for reference:

marketwatch.com/story/chinas-d…

What Three Mile Island demonstrated is that even a full core meltdown in a pressurized water reactor needn't expose the public to any health threat from these same fission products.

What Chernobyl demonstrated is that you really do gotta avoid the milk for a few weeks if your entire reactor blows up, but it wasn't even enough to shut down the power plant, which kept operating nuclear reactors for 14 years until bought off by the EU to close in year 2000.

What this incident is teaching us is that when you have nuclear reactors plus bad industry communications plus CNN you get lots of clicks but only on links, not on Geiger counters.

For those commenting on the plant's location, yes, near cities is where electricity is needed.

Now, if there's xenon there is bound to be a bit of iodine too. But as the xenon is so excited to get out there and see the world, it serves as a helpful early warning signal that there might be fuel rod cracks.

They'll clean it up next refueling outage.

https://twitter.com/energybants/status/1404484217824845825

How do they know which radioactive isotopes are floating around?

Because radioactive particles decompose in predictable ways, we can tell based on the energy level of particles or gamma rays coming into detectors which atoms are out there breaking down.

Apologies if this thread causes people to have a boring day after an exciting start.

If you need an emergency to get you going, how about Texas running out of power again today?

https://twitter.com/ERCOT_ISO/status/1404493708012265479

COVID, CHINA, AND NUCLEAR

The frenzy here around what seems to be a common situation, fuel rod leakers, seems to be related to COVID and possible origins from...leaks.

Viruses are wildly more dangerous than nuclear accidents because they multiply.

Fukushima did not multiply.

To the contrary, not only did the meltdowns at Fukushima not lead to some chain reaction of meltdowns elsewhere, they actually led to adding backup generators to nuclear plants all over the world, such that even the same triggering event won't cause such an event in the future.

Viruses are so much harder to detect than nuclear particles. In fact nuclear particles are pretty much the easiest thing in nature to detect, as even a few atoms near a sensor can provide massive information about what/where/when.

Which can also lead to sensational headlines.

One of the underappreciated things that makes nuclear energy so safe is that even countries that have beefs with each other cooperate to an unusual extent on plant safety and improving operations.

Because an incident anywhere is an incident everywhere. Nuclear stories go viral.

Will Taishan, having touched the zeitgeist and set off CNN, lead to a call for a global fuel industry No Leakers campaign?

Maybe. We know it's possible to manufacture, install, and operate fuel such that it doesn't happen. It's just hard!

China's fuel operations will mature.

From @OperadorNuclear, the many different ways these fuel rod leaks tend to pop up, which also gives a sense of the total commitment to perfection (or as near as we can get to it in this fallen world) required to achieve No Leakers goal in the USA:

Essentially everything presumed in this thread yesterday has been confirmed to my satisfaction. Thanks all for the kind feedback.

Will follow up with details when available.