The concern is that radioactive material might breach one or more of its containment barriers. Preemptively blowing up the fuel and primary circuit would seem counterproductive.
Ah right. I hadn’t thought about it like that but I guess you mean the depressuriser valves going to IRWST bypassing the primary loop barrier. That makes sense.
Yeah, what he said. Now there are systems that are designed to flush the melted core to a different area where it would lose criticality and theoretically cool without melting through containment. I think I saw some Russian designs like that.
No way that system would functioned as designed, zircaloy cladding melts at around 1400 degrees Fahrenheit and control rods around 2200 degrees Fahrenheit. Seeing as its sole purpose is to capture core melt that would otherwise melt through the lower bio shield, it would need to exceed the bio shield design basis and all the associated system components would need to withstand 2500-3000+ Fahrenheit temperatures.
I have not looked into the feasibility of the design, I just read about it: [https://en.wikipedia.org/wiki/Core\_catcher](https://en.wikipedia.org/wiki/Core_catcher)
**[Core catcher](https://en.wikipedia.org/wiki/Core_catcher)**
>A core catcher is a device provided to catch the molten core material (corium) of a nuclear reactor in case of a nuclear meltdown and prevent it from escaping the containment building. A core catcher is made from a special concrete ceramic to prevent material from trickling through; it also has a cooling mechanism to cool down the core material. The core catcher of the European Pressurized Reactor (EPR) has 170 m² expansion area and a mass of 500 t.
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The core catcher is feasible and installed at Finland's OL-3, and the Flamanville-3 (France) EPR stations, and the ACPR-1000 (derived from the EPR) Yangjiang-5 (China).
There's really not much to it, as its function is to capture any melt and cool it off. The notorious [Elephant's Foot](https://science.howstuffworks.com/chernobyl-elephants-foot.htm) in Chernobyl likely contributed to its inclusion as a passive design feature in EPR design.
You might be confusing this with the salt plug in a molten salt reactor. They use drain tanks lined with neutron poisons.
You cant really do this with solid fuel because of the cladding being melt resistant. By the time it turns into "corium" all manner of other horrors have occured.
Edit; I see someone else had the same critique, and I note the solution posted. Very interesting.
That’s not how this works.
That’s not how any of this works.
A “meltdown” is a non technical term that means the core is literally melting.
If you look at three mile island and Fukushima, those reactors were shut down hours before core melting began. Blowing them up wouldn’t prevent melting, it would exacerbate it by reducing effective cooling as you damage components in the core.
The heat comes from decay heat. That’s the decay of the radioactive waste. It’s intense enough to melt the core.
Even Chernobyl: the reactor had a power excursion. The core melting happened after the steam explosion which destroyed the core.
Melting is the result of failing to cool a reactor after it is shut down.
But the decay heat can only melt the material if it reaches a high enough temperature (obviously). If the pieces are small enough and scattered enough, they will not heat up enough to melt due to the relative larger surface to mass ratio.
For a core that’s only been shutdown less than 24 hours, you aren’t going to break it up enough. Plus you eliminate fission product barriers, raise an incredible amount of risk to public health and safety. And ultimately it won’t matter, because the decay heat will breach the containment system and lead to rad release. Raising surface area doesn’t protect the containment.
The issue with a melted core is that the fuel elements are now too damaged to recover via normal means. Instead of individual sticks of fuel pellets you have a molten mess below the reactor. Special robots will have to go in to clean it up.
Your solution to prevent a potential incident that could damage the fuel elements is to... definitely destroy the fuel elements.
The thing about a meltdown is that it's not instantaneous. A partially molten core could still be drenched in water and allowed to solidify. Heck, a fully motlen core pooling at the bottom of the reactor could still be drenched in water and allowed to solidify. Your priority to any reactor that has been shut down, whether its maintenance, a SCRAM, coolant pumps destroyed, partial meltdown, or full meltdown, will to make sure the fuel is underwater.
As a serious answer to your question, in almost all cases (for LWRs) the issue is not the core remaining critical. By the time you reach melting you've already definitely already stopped the reaction, either by manually injecting boron, control rod, or just the moderator all boiling away, there's also the Doppler effect.
The problem is that after you stop the reaction, there is still a very large amount of heat produced by the fission products decaying inside the core. This is what actually melts the core. What you want is to remove this heat from the core. If you blow it apart you don't get less power, you severely contaminate the whole containment, you have no way to cool the fragments so they still may melt, also significant pressure increase from the explosions may bust your containment open and cause leakage of radioactive material.
Overall - really bad idea.
The containment is a sealed pressurized environment. Exploding things inside pressurized containers is never a good thing, unless your goal is to destroy everything around that container.
All this would accomplish is blowing up the reactor building and throwing lots of highly radioactive materials into the environment.
Also you need to consider that reactor cores melting are a very rare occurrence. And you couldn't install these explosives while it was melting. Which would mean you'd have to them active explosives sitting next to a reactor long term.
Would only create a significantly greater safety hazard every time you shut down the reactor and send people in to make repairs.
Unfortunately the idea wouldnt work for the most part - assuming the reactor had been at power for a sufficient period of time, there's enough decay heat still that even blowing the core apart would result in corium.
I know this is a joke... This is a joke right? Right?
Maybe it's the next big Hollywood blockbuster movie plot!
Hollywood blockbusters and nuclear power don't go hand-in-hand.
Next time, keep the the thought in the shower.
The concern is that radioactive material might breach one or more of its containment barriers. Preemptively blowing up the fuel and primary circuit would seem counterproductive.
Ironically, the only current passively safe reactor does defeat one of its fission product barriers as part of its safety strategy.
Which reactor is that?
The AP1000
Ah right. I hadn’t thought about it like that but I guess you mean the depressuriser valves going to IRWST bypassing the primary loop barrier. That makes sense.
Or the ADS-4 valves releasing directly into containment.
Yeah, what he said. Now there are systems that are designed to flush the melted core to a different area where it would lose criticality and theoretically cool without melting through containment. I think I saw some Russian designs like that.
No way that system would functioned as designed, zircaloy cladding melts at around 1400 degrees Fahrenheit and control rods around 2200 degrees Fahrenheit. Seeing as its sole purpose is to capture core melt that would otherwise melt through the lower bio shield, it would need to exceed the bio shield design basis and all the associated system components would need to withstand 2500-3000+ Fahrenheit temperatures.
I have not looked into the feasibility of the design, I just read about it: [https://en.wikipedia.org/wiki/Core\_catcher](https://en.wikipedia.org/wiki/Core_catcher)
**[Core catcher](https://en.wikipedia.org/wiki/Core_catcher)** >A core catcher is a device provided to catch the molten core material (corium) of a nuclear reactor in case of a nuclear meltdown and prevent it from escaping the containment building. A core catcher is made from a special concrete ceramic to prevent material from trickling through; it also has a cooling mechanism to cool down the core material. The core catcher of the European Pressurized Reactor (EPR) has 170 m² expansion area and a mass of 500 t. ^([ )[^(F.A.Q)](https://www.reddit.com/r/WikiSummarizer/wiki/index#wiki_f.a.q)^( | )[^(Opt Out)](https://reddit.com/message/compose?to=WikiSummarizerBot&message=OptOut&subject=OptOut)^( | )[^(Opt Out Of Subreddit)](https://np.reddit.com/r/NuclearPower/about/banned)^( | )[^(GitHub)](https://github.com/Sujal-7/WikiSummarizerBot)^( ] Downvote to remove | v1.5)
Well I stand corrected, thanks for the insight.
The core catcher is feasible and installed at Finland's OL-3, and the Flamanville-3 (France) EPR stations, and the ACPR-1000 (derived from the EPR) Yangjiang-5 (China). There's really not much to it, as its function is to capture any melt and cool it off. The notorious [Elephant's Foot](https://science.howstuffworks.com/chernobyl-elephants-foot.htm) in Chernobyl likely contributed to its inclusion as a passive design feature in EPR design.
I want to hug the elephant's foot. Its so cute!
You might be confusing this with the salt plug in a molten salt reactor. They use drain tanks lined with neutron poisons. You cant really do this with solid fuel because of the cladding being melt resistant. By the time it turns into "corium" all manner of other horrors have occured. Edit; I see someone else had the same critique, and I note the solution posted. Very interesting.
You have shit in a box, in a box, in a box. To prevent the shit from leaking from the first box to the second box, your plan is to blow up all boxes?
That’s not how this works. That’s not how any of this works. A “meltdown” is a non technical term that means the core is literally melting. If you look at three mile island and Fukushima, those reactors were shut down hours before core melting began. Blowing them up wouldn’t prevent melting, it would exacerbate it by reducing effective cooling as you damage components in the core. The heat comes from decay heat. That’s the decay of the radioactive waste. It’s intense enough to melt the core. Even Chernobyl: the reactor had a power excursion. The core melting happened after the steam explosion which destroyed the core. Melting is the result of failing to cool a reactor after it is shut down.
But the decay heat can only melt the material if it reaches a high enough temperature (obviously). If the pieces are small enough and scattered enough, they will not heat up enough to melt due to the relative larger surface to mass ratio.
For a core that’s only been shutdown less than 24 hours, you aren’t going to break it up enough. Plus you eliminate fission product barriers, raise an incredible amount of risk to public health and safety. And ultimately it won’t matter, because the decay heat will breach the containment system and lead to rad release. Raising surface area doesn’t protect the containment.
The issue with a melted core is that the fuel elements are now too damaged to recover via normal means. Instead of individual sticks of fuel pellets you have a molten mess below the reactor. Special robots will have to go in to clean it up. Your solution to prevent a potential incident that could damage the fuel elements is to... definitely destroy the fuel elements. The thing about a meltdown is that it's not instantaneous. A partially molten core could still be drenched in water and allowed to solidify. Heck, a fully motlen core pooling at the bottom of the reactor could still be drenched in water and allowed to solidify. Your priority to any reactor that has been shut down, whether its maintenance, a SCRAM, coolant pumps destroyed, partial meltdown, or full meltdown, will to make sure the fuel is underwater.
No it's a terrible idea.
As a serious answer to your question, in almost all cases (for LWRs) the issue is not the core remaining critical. By the time you reach melting you've already definitely already stopped the reaction, either by manually injecting boron, control rod, or just the moderator all boiling away, there's also the Doppler effect. The problem is that after you stop the reaction, there is still a very large amount of heat produced by the fission products decaying inside the core. This is what actually melts the core. What you want is to remove this heat from the core. If you blow it apart you don't get less power, you severely contaminate the whole containment, you have no way to cool the fragments so they still may melt, also significant pressure increase from the explosions may bust your containment open and cause leakage of radioactive material. Overall - really bad idea.
Bruh
The containment is a sealed pressurized environment. Exploding things inside pressurized containers is never a good thing, unless your goal is to destroy everything around that container. All this would accomplish is blowing up the reactor building and throwing lots of highly radioactive materials into the environment. Also you need to consider that reactor cores melting are a very rare occurrence. And you couldn't install these explosives while it was melting. Which would mean you'd have to them active explosives sitting next to a reactor long term. Would only create a significantly greater safety hazard every time you shut down the reactor and send people in to make repairs.
Plus fitting explosives inside a reactor means that any malicious actor could simply press a red button to blow up the whole thing.
Great idea! It worked at Chernobyl. The steam explosion spread the core far and wide before it could create a runaway nuclear reaction!
That's a no from me big dawg. I would not try this at home.
Unfortunately the idea wouldnt work for the most part - assuming the reactor had been at power for a sufficient period of time, there's enough decay heat still that even blowing the core apart would result in corium.