St Lucie Nuclear Reactor Unit 1 manually shutdown, 3 control rods drop into core

high_na_euv

Why they dropped?

Abh1Works

this is really interesting

AndrewKemendo

It’s great that nuclear power safety events are so well managed that nearly 100% of events go completely unnoticed by the public. Unironically this is the kind of headline I’m expecting in 2040 about one or more major AGI systems running an electrical grid, factory or similar.

ImOssir

I wonder why so much repetition in the article. Do they have word limit to hit? I wish it have provided some reasons on this

ck2

for "reasons" that they carefully left out? Florida should be added to title, it's not like the European shutdowns for overheating

fwipsy

https://www.nuclear-power.com/nuclear-power/reactor-physics/... Can someone check my understanding: Control rods are suspended above the reactor as a sort of a "deadman's switch" - if a loss of power occurs, they will drop into the reactor core to limit reactivity. As a result, sometimes control rods will drop into the reactor accidentally. In these cases, the automatic system may withdraw other rods in order to maintain power output. However, this may overshoot the target power output or create a localized, dangerous "hot spot" elsewhere in the reactor core. In order to avoid this, in this case, the operators chose to insert other control rods instead of trying to stabilize the reactor under load.

verytrivial

This "dropping" activity is not defined well in the context. Was it e.g. a controlled but uncommanded insertion? Or did something or some three things slip, snap, or something else? Can the rods be retrieved using BAU procedures, or is reactor in an annoying state now? The details divulged seems to have been driven by event reporting regulations, not any specific news gathering or investigation, right?

aeonik

This happened in 2024 too. This link (second one down, first event is missing control rods in Texas...) has almost the exact same wording as the article. https://www.nrc.gov/reading-rm/doc-collections/event-status/... I found the root cause of the older issue on LinkedIn of all places. https://www.linkedin.com/posts/robert-meyer-8672ab4a_st-luci... Root cause of 2024 was apparently a procedural issue combined with electrical failure of the control rod grippers.

julienchastang

I actually thought they were talking about the island in the Caribbean since Florida is not mentioned in the article. Anyway, in case you did not know, the reactor in question is in Florida: https://en.wikipedia.org/wiki/St._Lucie_Nuclear_Power_Plant

CoryOndrejka

Dropped rods are an incident but one that occurs because of pressurized water reactors being very default safe. Controls rods are one way the criticality of a reactor is controlled and US reactors (in general) will go sub critical if even one rod is fully inserted into the core. You will likely have heard of a reactor scram (which goes back to the safety control rod ax man) where in an emergency, all the rods are dropped back into the core, greatly reducing its criticality. In some cases, an interruption of electrical power will cause a rod (or three) to drop accidentally. This is a "dropped rod" incident and will force a reactor shut down because it is now sub critical. Lots of knock on effects -- sub critical, let heat in the primary loop, less steam and electricity generated in the secondary loop, etc -- but generally a non event that you practice for. There's no reason this would lead to a radiological event or more significant casualty.

asmodeuslucifer

At least they didn't make 300 square km uninhabitable. https://www.pref.fukushima.lg.jp/site/portal/kyoten-kuiki.ht... "Current Status: While "Difficult-to-Return Zones" still exist, decontamination and lifting of orders have reduced the designated area down to approximately 2.2% of the prefecture's total land area."

bcjdjsndon

3.6 rods? Not great but not terrible either

iambateman

If you've never seen the Smarter Every Day series on nuclear reactors[0], it's must-watch. It completely reshaped how I think about reactors. Tremendous respect for the people who work on those plants. [0] https://www.youtube.com/watch?v=v0afQ6w3Bjw&t=4007s

paulnpace

I liked it better in the olden days when the paper would print the location of the story at the beginning of the first paragraph.

LastTrain

Florida. RIP 5Ys.

jmward01

A challenge with news like this is there isn't an easy risk reference to put it into perspective. People only think of Chernobyl, Fukushima, 3-mile island, etc etc. We don't have something personal to relate it to to help us determine 'NBD, why is this a story?' or 'Wow! That was close!'. In everyday life I generally use driving to help me determine how risky something is. Driving is something most people do somewhat regularly and that we recognize as risky so we put controls on like training, regulations, special services, etc etc. Anything more risky than driving makes me really take notice. Anything less and I don't shrug it off, but I also don't get too worried. I appreciate the factual nature of this story but I think an important aspect of journalism is giving people relatable references that allow them to better understand the information presented. It would be helpful if a story like this gave that context because without it it is hard to understand if this is 'Wow! What a close one!' or 'I guess this is a little interesting?'.

codyswann

I live about four miles from the plant. I have not grown a second head... yet.

ck2

better article * https://lakelandgazette.info/news/2026/08/16/st-lucie-nuclea... archive because the website is overwhelmed and down most of day: * What Happened: At 9:47 a.m. EDT, Unit 1 was operating at 100% power when three control rods (part of the Control Element Assemblies) fell into the core due to an equipment/control fault. * Operator Action: Under standard safety protocols, dropping multiple control rods alters the reactor’s core dynamics. Plant operators with Florida Power & Light (FPL) executed a manual reactor trip (scram) to safely halt the fission reaction. * Current Status: The trip was uncomplicated, and all safety systems responded normally. Operators stabilized the reactor in Mode 3 (Hot Standby), with decay heat safely being removed via steam discharge to the main condenser. Unit 2 was completely unaffected and continued running normally. The Nuclear Regulatory Commission (NRC) Resident Inspector was notified via standard 4-hour non-emergency reporting procedures. * Why Control Rods Matter Control rods absorb neutrons inside a reactor. Inserting them slows or stops the nuclear chain reaction. While a single dropped rod can often be managed by reducing turbine output, multiple dropped rods require an immediate shutdown to prevent uneven power distribution and localized overheating in the fuel assemblies. Gravity-assisted dropping is a fail-safe mechanism designed into commercial pressurized water reactors so that if power to the drive mechanisms is lost or faulted, the rods default to falling safely into the core.

imnotr0b0t

I have mixed feelings. It seems like nothing serious happened, no one was hurt, and all the systems worked, but on the other hand, this is still an emergency. Why did those rods fall in the first place?

scythe

Apparently people surf at the beach near this reactor. I never went there when I lived in Florida, but my dad told me about it.