nuclear fusion anyone?

[philehidiot]

It really doesn't. There is no risk of decay heat for a fusion reactor, so no requirement for external power should the reactor trip. The same can be said of more advanced fission designs but we're still waiting on walk-away safe reactors to get built, and they're safe because of thermal design, not because of inherent safety of the fuel/process.

With fusion reactors, the reaction is difficult to sustain so a failure leads to the reactor pretty much just stopping. There's no massive lump of fission products to meltdown without sufficient cooling, no graphite moderators to catch fire, no control rods to get stuck. Even in a deliberate, catastrophic containment breach you have a worst-case of a tritium leak, which is still of no substantial concern to health.

There is great incentive to develop fusion power reactors for the above reasons and more, it's not just a sideways step from fission in terms of safety, etc.

I think you misread my statement (or, more likely, I phrased it stupidly) - the comment on the fusion issue was the legacy and decomissioning of loads of low level waste.

But you have piqued my interest - it has been a while since I had chance to talk to someone who actively works in the field and the part about walk away reactors is something I hadn't heard of being close to ready. I'm assuming they use passive cooling circuits that work to remove enough heat without any mechanical input as long as the cooling circuit is intact? Gonna also guess this is a pressurised water based system to help with the whole negative temperature coefficient of reactivity? So active cooling fails, passive coolant continues to circulate by using the heat to move the fluid and the behaviour of the water as it heats up due to the failure of the active system leads to reduced interaction with neutrons and thus slowing of the reaction? How are they achieving this? With a load of Noctua heat sinks in the core working in reverse?

Another question - the big practical drawback of fission is that you can't quickly and easily ramp the output up and down to cope with quickly changing demand or the wind deciding to go up or down. So you can't use it to cover dips in output, surges in demand or balance the grid and rely on CCGTs. Would fusion be the same or could you quickly ramp the output up and down? Would it be worth using fusion to provide 110% of requirements and using the excess which would vary to do something silly like electrolyse water for hydrogen?

[watercooled]

Ah I see, but I think I mentioned about the decommissioning waste elsewhere. The waste from a fusion reactor is far smaller in volume and more short-lived compared to that from a fission reactor.

Walk-away safe is a term used to describe reactor designs which would be safe even even everyone just downed tools and left the site, no external power, no additional cooling supply, fire engines dumping water, etc. As far as I know we are still some way off having any built.

There are a few different ways to accomplish it but we're talking about passive safety of a shut-down reactor, i.e. dealing with decay heat. That part should be academic though as a reactor should automatically trip if it loses connection to the grid, etc. Even on current reactors, the SCRAM isn't the hard part with a loss of supply - on some types the control rods are held up with electromagnets so they naturally fall in the event of a supply loss, and with others, there's some sort of backup system to insert them rapidly anyway.

IIRC some of the designs are molten salt based rather than conventional PWR or whatever.

There are a few designs which are being marketed but stuff in that industry moves slowly, considering funding for first-of-kind builds, GDA processes or equivalent, public opposition to anything with 'nuclear' in the name, time to actually build it, etc.

I'm not really sure about how quickly output could be varied with fusion but the designs I'm aware of operate off a steady fuel supply to the core (hence their safety - removing the fuel supply causes almost immediate shutdown as the core will only contain a few seconds' worth of fuel at any given time, as I understand it). In theory I imagine you'd just vary the fuel supply accordingly (not quite that simple of course given how much of a balancing act the fusion reaction appears to be) but you'd still have some delay as with any large generator due to thermal mass of the generating equipment, etc.

[philehidiot]

Cheers. Interesting stuff. I heard about molten salt reactors - I think there's gonna be one in the thorium car, don't ya know!

Personally, I'd have the control rods propelled by a five-year-old with a laggy band round their fingers. Those kids are lethal.

Personally, I'd love to have a nuclear reactor in my back garden. I used to live right next to Ferrybridge power station and the thing is just amazing to behold.

[Galant]

Well, they've only gone and done it! (Sort of)

https://news.sky.com/story/nuclear-f...nergy-12767376

For the first time, a fusion reaction has been achieved that has put out more energy than it took in!

It's far from bring a reliable energy source (being very expensive and needing a large cool down period in between), but the theory has been proven. This could work:

"How long before we're using this process to create energy?
Inevitably, the question is asked as to how long the assembled scientists believe it will be before the process is "commercialised" - ie, creating energy that we can use.

Jennifer Granholm starts us off, saying: "It's going to take a while."

Dr Kim Budil goes further.

"There are very significant hurdles, not just in the science, but in the technology," she says.

"This is one igniting capsule, one time, and to realise commercial fusion energy you have to do many things."

Dr Budil is clearly here to inject a very healthy dose of realism into proceedings, for the benefit of the more giddy among us viewers.

"Probably decades. Not five decades, as we used to say. I think it's moving into the foreground, and with concerted effort and investment, a few decades of research on the underlying technologies could put us in a position to build a power plant.""

[jimbouk]

It'd be interesting to see the dependency tree of 'how to make a commercial fusion reactor' and see where all the different current projects are working towards. From a not very aware perspective this one seemed to be about the capsule allowing things to stay contained and increasing the pressure/temperature(?) Are other projects working on different ways to get to solve the same point on the tree or tackling different problems? I'm sure it's not that simple mind!

Still, I'm hopeful that they'll achieve this before society collapses.

[kalniel]

Energy that reached the fuel at least. It still cost several hundred times that energy to power the lasers. However, it's at least one step further along the (very long) process.

[Saracen999]

From what one (academic) scientist was saying, this latest achievement is a major hurdle, in that it's proof of concept that energy out > energy in. But, there's a whole series of technical challenges between proof of concept and commercial implementation. Many/most of the problems have been solved but need to be polished, made more efficient and made commercially viable. Which suggests it's doable, but it isn't going to be owering cities any time soon. He suggested 10 years absolute minimum, and when did anything on this scale ever happen in the absolute minimum time?

So, one hurdle of many, but a very important hurdle.

Interesting times, as the Chinese saying goes.

[ik9000]

Interesting and very needed news. We need a big push now. Cern have been playing with plasma containment in their toroidal thing so it's possible that will be another piece of the jigsaw in getting the process to scale up as I think their testing has been showing the heat containment should be possible. Whether the plasma and laser process can coexist I don't know, I thought they were two different approaches but hopefully society can resist the corrosive creep of ignorant stupidity that seems to be propagating for long enough to see these get built and into service

[[GSV]Trig]

Best time for them to be pushing this tbh, its been going on for years but all of this energy crisis gumpfh has made people take a bit more notice.

[badass]

I was mildly excited until I saw that this was a Tritium+Duterium fusion process. That's the one that's the easiest to achieve but useless. The problem is that there's enough fuel for research reactors but not enough for large scale energy production at any point in the future. The fuel used is created as a byproduct from nuclear fission reactors that are getting decommissioned.

However what they learn from this will certainly help for the holy grail of nuclear fusion - plain old hydrogen with a mass number of 1 fusion.

[ik9000]

Yes. This has been the problem with laser fusion for a long time: finding a demonstrable renewable source material that is abundant enough. I thought they'd demonstrated heavy hydrogen isotopes already though so I'm confused why the hype now if that's all they did this time (again).

[badass]

Yes. This has been the problem with laser fusion for a long time: finding a demonstrable renewable source material that is abundant enough. I thought they'd demonstrated heavy hydrogen isotopes already though so I'm confused why the hype now if that's all they did this time (again).

I'm guessing new funding round imminent ;-)

[Output]

My immediate thought upon seeing this news: