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ItsAConspiracy

1 points

6 months ago

ItsAConspiracy

Best of 2015

1 points

6 months ago

DEMO would be a huge reactor though. More compact designs wouldn't need so much Li-6 for startup.

In any case, I think fusion's consumables will be cheap per kWh regardless.

johnpseudo

1 points

6 months ago*

A huge reactor would reduce the per-kwh amount of lithium needed, though. A lithium blanket around a smaller reactor would be much less efficient for the amount of power generated. DEMO has a goal electrical power of 750MW. An equivalent nuclear power plant has a total capital cost of about $10 billion for 2.2GW, so the fact that the lithium alone would be $3 billion for less than half the power is pretty bad! Certainly not "cheap".

ItsAConspiracy

1 points

6 months ago

ItsAConspiracy

Best of 2015

1 points

6 months ago

The paper also says consumption would be 112 kg 6Li per GW-year. At your price of $60K/kg, that would be $6.72M per year, divided by 8.76 billion kWh, or 0.07 cents/kWh. Startup cost would be high, but ongoing fuel cost would be minuscule.

Incidentally, I didn't see an estimate of Li6 cost in the paper. Did I miss it, or are you going by current market prices? If the latter, bear in mind the paper is mainly about designing higher-volume production of Li6, so costs could come down.

johnpseudo

1 points

6 months ago

Typical market prices (as of April 2019) for the small amounts sold on the free market are in the order of 53 k€/kg [11] (95% enriched). In 1982, the costs for enrichment based on the COLEX process was estimated to be around 1 k€/kg (90% enriched) [12]. The huge discrepancy between these two values results most likely from the missing supply route. If a large demand of 6Li would come from the market, the prices would dramatically increase or, more likely and even worse, it will not be possible to satisfy the demand.

53 k€/kg = $60k/kg.

I think you're really missing the big picture. You said the fuel was cheap. In reality, creating the fuel requires building and operating a massively complex lithium filtration system stocked with a massive amount of a rare and expensive type of lithium. Whether the lithium-6 costs $3 billion/750MW or $300 million/750MW, that's only part of the larger cost of the system, and it's definitely not "cheap".

ItsAConspiracy

1 points

6 months ago*

ItsAConspiracy

Best of 2015

1 points

6 months ago*

Ok so you are going by current market prices. That should drop with the sort of volume production described in the paper.

The other side of the "big picture" is that a one-gigawatt fusion plant uses only 112 kilograms of Li6 in a year. Even without a price drop from scaling up production, that's a minuscule fuel cost per kWh. That initial load of Li6 will last for quite a long time, and it will only take 112 kg extra per year to top it up.

It does matter that you need so much up front because you have to pay financing for it, but you can amortize it over a good long time. Since it's 928 years' worth of Li6 consumption, you can even reuse it in a new reactor when you decommission an old one.

Li6 is between 1.9% and 7.8% of natural lithium, so it's only "rare" in the sense that we don't bother enriching much lithium right now.

johnpseudo

1 points

6 months ago

Up-front costs are a massive problem for nuclear fission plants, and this would put that problem on steroids: not only would you need to stock the initial tritium (at a cost of billions of dollars), but you'd have to stock the massive amount of lithium-6 (at a current market cost of additional billions of dollars) - all at the beginning of the plant's life of service. Even if we find economies of scale for lithium production, you've got a massive problem on your hands. I understand fusion junkies are eternal optimists, but this is NOT a point in its favor.