Small nuclear reactors: tiny NuScale reactor gets safety approval

Post by wukerplank » Fri, Sep 04, 2020, 8:28 AM UTC

nix23 wrote: post #405

candiodari wrote: post #403

Earlier quoted context omitted.

> During normal operation, the primary is entirely contained within the primary containment, and circulates naturally, using the differential temperature and gravity. The steam system can is used to remove heat. If it's using gravity, what happens if this whole reactor gets tilted? What happens at 10 degrees? 45? 90? 180? Are there any critical angles where it would melt down? I'm curious how you would make such a de…

>what happens if this whole reactor gets tilted? What happens at 10 degrees? 45? 90? 180? Are there any critical angles where it would melt down? Ahh i see, a flat earth believer ;)

Post by tlear » Fri, Sep 04, 2020, 8:30 AM UTC

i_am_proteus wrote: post #356

jhallenworld wrote: post #52

Here is the NRC website about this reactor: https://www.nrc.gov/reactors/new-reactors/smr/nuscale.html Here is an interesting sub-report: https://www.nrc.gov/docs/ML2022/ML20224A525.pdf Information withheld for security reasons. One item concerns the "ultimate heat sink". What happens when the ultimate heat sink is lost? Well a design assumption is that it is not lost: https://www.nrc.gov/docs/ML2020/ML20205L410.pdf…

Nuclear engineer here. I've read through a good portion of the regulatory submission to the NRC and have a few takeaways that oppose some of the less-well-informed takes in this thread: - The reactor differs substantially from existing PWRs by encasing the primary in double containment, using natural circulation flow for both normal operation and emergency cooling. There are no pumps needed (or installed) to move coo…

Post by Gravityloss » Fri, Sep 04, 2020, 8:33 AM UTC

cameldrv wrote: post #297

_jal wrote: post #265

Earlier quoted context omitted.

It does, but it makes sense to explore fail-safe designs. Depending on a lack of incompetence in dangerous systems works until it doesn't. To the extent that these things can simply halt when incompetently managed, they should. If anyone disagrees, I'd like to know why they think the next hundred years are going to be so much freer of political shortsightedness and corruption than the last hundred.

Fukishima is a perfect example. Unit 1 had been retrofitted with an isolation condenser, which should have been able to prevent a meltdown even with no power, but it wasn't activated, for reasons that remain murky.

Post by Cthulhu_ » Fri, Sep 04, 2020, 8:44 AM UTC

dheera wrote: post #329

patmorgan23 wrote: post #313

Earlier quoted context omitted.

You'd still need a heat exchanger at some point, and you want a lot of surface area and thin walls for that.

Random thought experiment -- why not just drop it in the middle of a lifeless desert, forget about heat exchangers, and just let it slowly melt its way down through the crust of the earth? Assuming it went straight down and into the mantle, it would probably not impact the ecosystem.

Post by Cthulhu_ » Fri, Sep 04, 2020, 8:51 AM UTC

tgsovlerkhgsel wrote: post #163

phkahler wrote: post #144

Earlier quoted context omitted.

And so a pool of water is not enough because it will boil away. A continuous flow must be present that can not be interrupted.

Around 600-700 kWh per cubic meter depending on temperature. The reactor outputs around 200 MW thermal. So if you have one of them in an olympic size swimming pool 50x25x2 meters, 2500 m^3, it'd need ~8 hours to evaporate the whole pool at full output. If you assume decay heat as 1% of regular output ( https://en.wikipedia.org/wiki/Decay_heat ), you'd need to add (or have stored) ~3 m^3 of water per hour, or slightly…