Viewing a single comment thread. View all comments

Nescio224 t1_j19jovd wrote

Reply to comment by [deleted] in How do fusion scientists expect to produce enough Tritium to sustain D-T fusion (see text)? by DanTheTerrible

>The reason people consider fusion to be a "holy grail" energy source is because it is capable of creating its own fuel.

Fission reactors can create more fuel than they consume as well. They are called breeder reactors. However the fuel for fission reactors is already so cheap that most commercial operators are not interested making it even more efficient. So what if fusion reactors can create their own fuel (which remains to be proven)? It doesn't matter if the reactors themselves are too expensive. Fusion is considered a "holy grail" because commercial large scale fusion is not yet real. When it becomes real, it will stop being a "holy grail", because there is almost no advantage to nuclear.

3

mystlurker t1_j19sve9 wrote

Isn’t part of the holy grail aspect of fusion that it lets you have a nuclear power source that has much lower radioactivity concerns than fission, making it easier to deal with both from a safety perspective but also a public acceptance perspective?

All the futurology stuff around fusion I saw always talked about how it was an unlimited CLEAN energy source. Nuclear power stopped growing partly due to insane costs and partly due to waning public acceptance after multiple disasters. It a fusion reactor exploded there may be major loss of life but it wouldn’t make the surrounding environment toxic for long periods, or at least that’s the idea.

Obviously if you need lithium it’s clearly not truly unlimited, but the idea of something you could scale out much faster than solar/wind is rather appealing.

10

Nescio224 t1_j1a3d5k wrote

>much lower radioactivity concerns than fission, making it easier to deal with both from a safety perspective but also a public acceptance perspective?

The amount of "radioactive waste"(=radioactive resources) would be comparable to a breeder reactor. Newer reactor designs are much safer than old ones. If you eliminate the most common risks in the design, you can easily reduce the chance of a meltdown to practially zero. The development cycle for nuclear power is much slower than for other technologies, because of their high lifetimes and low numbers. Imagine if we stopped developing cars after the first 4 designs, with the biggest charge being a few hundred cars, because they were too unsafe. That's where we are with nuclear. If you can drop the mean time between meltdown incidents from every 10 years to every 1000 years worldwide, then that does matter. People want to make you believe this technology is inherently unsafe and the designs can't be improved. That is completely false.

>All the futurology stuff around fusion

Most of the futurology stuff is made by people who have no clue what they are talking about.

> It a fusion reactor exploded there may be major loss of life but it wouldn’t make the surrounding environment toxic for long periods, or at least that’s the idea.

This study concludes that the relocation of people after the Fukushima nulcear accident was not justified on the grounds of radiological health benefit. Also that "long period" is "only" about 100 years. Nuclear has still the lowest death rate of all alternatives.

>Obviously if you need lithium it’s clearly not truly unlimited

Lithium is abount 10 times more abundant than Uranium, so supply is not an issue.

> but the idea of something you could scale out much faster than solar/wind is rather appealing.

Why are you assuming that you can build fusion reactors faster than fission reactors or solar/wind? There are no commercial fusion reactor yet and all existing designs are very early prototypes. The data to make that conclusion doesn't exist yet. Not to mention that fusion is at least 20 years away (as always) and we need a solution now.

8

mystlurker t1_j1a4avk wrote

You are misinterpreting my post, I’m not saying I necessarily agree or support various aspects of this, just explaining why there is this mythical aspect to fusion.

Facts about fission haven’t done well to change public perception. And public perception has an outsized impact on government policy.

Fusion theoretically offers the upsides of fission without the downsides and it theoretically offers better scaling than existing renewables. But as you said this is all theory. But that is what makes it the holy grail, in theory it has major upsides but it’s far off from production. Dismissing the human element here is to dismiss a large part of what defines the allure of fusion.

5

[deleted] t1_j19y0sh wrote

[removed]

1

RobusEtCeleritas t1_j1ah5rr wrote

There will be activation of reactor components, of course. But that will not result in nearly the amount of radioactivity per unit mass as the fission products in spent fission fuel.

1

atomfullerene t1_j19qxu4 wrote

Don't breeders produce fissile materials that could be used in weapons? I thought proliferation concerns were the main thing keeping them from being more widely adopted.

3

Nescio224 t1_j19ufka wrote

Yes, but that depends on the specific breeder design. Besides, if someone really wants nuclear weapons, there are a thousand different paths. Just look at north korea. The wikipedia article on breeder reactors states the reason why there is not more interest in breeder in the first paragraph: >Breeders were at first found attractive because they made more complete use of uranium fuel than light water reactors, but interest declined after the 1960s as more uranium reserves were found,[2] and new methods of uranium enrichment reduced fuel costs.

Breeders could extract 100 times more energy from the same fuel rod than an LWR can, but even at 1% efficiency LWR's are efficient enough that fuel cost is not an issue. That's just how OP the energy density of the fuel is.

9

RobusEtCeleritas t1_j1agwgi wrote

If you can breed fuel for a reactor, you can inherently breed fuel for a weapon too. Any spent fission fuel can in theory be reprocessed, and have material diverted for weapons purposes.

But that's why organizations like the IAEA closely monitor fuel cycles for proliferation concerns.

2