Whatever you bring from outside is just to bootstrap it once you turn it on. (I imagine they are not collecting the tritium between runs, but it's something you are expected to do.)
There is another, unrelated issue that if we decide to scale (H + D) fusion power, for decades we will need more tritium than they can generate.
The only reason fission isn't more profitable is politics. Politics are making investment and research into fission needlessly costly.
It will cost at least a $billion to take apart and dispose of Indian Point, shut down recently because it was leaking radioactive stuff into the Hudson.
In Sweden, where I live, about half of our electricity is from nuclear. It's built and operated by a state owned entity called Vattenfall and while they currently have a politically appointed board that is against nuclear they operate (for profit) all of our nuclear reactors. The only reason we don't build more is because they've made it practically impossible (not illegal) to expand nuclear energy through various political motivated decisions. Sweden had a referendum on the continuation of nuclear energy after the Chernobyl accident, we did vote, though by a narrow margin to transition away from nuclear. However, this past winter we had huge supply issues and people ended up having to pay 4x for electricity due to the premature shutdown of nuclear (meanwhile we had to power up oil and gas burning to compensate). Right now, most people in Sweden are of the opinion that we should keep our nuclear reactors. I, together with several others would like to us to expand our energy production from nuclear to prevent a reliance on oil and gas.
Politics is how policy is determined. People have tried other ways. Sometimes they worked. For a while.
Diverting money from building out renewables (and transmission lines) to build nukes ensures, at minimum, another decade of increasing reliance on oil and gas, and then paying more for power than you would have for renewables.
Sweden cannot depend on solar alone, we have plenty of hydro in the northern parts of the country and wind doesn't work during winter. Wind also kills birds and insects, en masse.
People have an irrational fear towards nuclear. Fact is, very few people have died because of nuclear energy. If you compare deaths vs produced watts, nuclear is the single safest energy source by several orders of magnitudes.
Also, I don't know if that's a typo or a misunderstanding but we are not talking about nuclear weapons, i.e. nukes we are talking about thermonuclear energy production. These are two different things altogether.
Didn't know that fusion generators produced its own fuel! If it produces more than enough, then the excess tritium is considered radioactive waste?
The energy of the neutrons is transformed into heat by adsorbing them into some shielding walls. The materials for those walls will be chosen to minimize the quantity of radioactive waste that is produced by the extremely intense neutron irradiation, but it is impossible to avoid completely the production of radioactive waste.
So all the fusion generators planned for the near future will generate radioactive waste, but in significantly less quantities than fission reactors of the same power.
Because they produce an intense neutron flux, like the fission reactors, the fusion reactors can also be used for element transmutation by neutron capture, e.g. for producing tritium or for producing lightly-doped silicon crystals for the high-voltage electronic devices (by transmuting silicon into phosphorus).
However, such transmutation applications usually also need the use of a neutron moderator, to slow the neutrons down to whatever speed is optimal for producing the desired isotope, e.g. tritium. For tritium, heavy water can play both roles, of the neutron moderator and of the target containing the element to be transmuted.
Renewables do not incur such operating expenses. Put renewables and a fusion reactor on the grid, and fusion would never, ever win a bid.
"Fusion .. will generate ... less ... than fission"? The whole damn ten-thousand-ton reactor becomes radioactive waste in short order. Fortunately, none will be built, so it is only a theoretical problem.
Anyway, I imagine the people studying fusion have an answer to this, since it only requires normal centuries-old chemical knowledge.
I also do not believe fusion will ever be a competitive power source for stationary applications on Earth.
The people studying fusion are carefully restricting their attention to the immediate problems of getting it to work at all. E.g., ITER will have no lithium blanket.
They figure on building another whole reactor to be completed (initially guessed) 15 years later at (initially guessed) 4x cost to begin tackling practical difficulties of extracting useful thermal energy.
I don't know about fusion vs renewables, because renewables are better, but they need a lot of non-renewables to be manufactured. If a fusion reactor lasted 100 years, it would be a much better option than renewables.
It needs even bigger containment than a regular nuke because reactive molten lithium bursts into flame on contact with air. The oxidized product is an exploding cloud of vaporized radioactive drain cleaner. A thousand tons of lithium make a lot of drain cleaner.
And again, by that time all our power will be cheaply supplied by renewables with no disastrous failure modes, and maintained just by taking bits down and putting up new bits, in shirtsleeves when weather favors it.
That was one of the main questions the ITER was supposed to answer, wasn't it? AFAIK earlier designs were quite short-lived, but some small changes fixed it. We will know how long they last as soon as we don't have an ITER anymore.
What were these small changes that fixed it? Did they have anything to do with the cost going up by 3x?
Anyway, inducing radioactivity is not what would use it up. That just makes it super-expensive to do repairs. It would get used up through neutron bombardment weakening the crystal structure of the metals it is constructed of.