How Sure Can We Be of Nuclear Fusion?

How solid is the case for nuclear fusion? Most of us would say, in principle at least, that it is rock solid. Bloomberg has an article on the Trump administration and funding for nuclear fusion efforts, that is funding associated with the International Thermonuclear Experimental Reactor (ITER).

The article quotes a senior plasma physicist as stating,

The biggest obstacle to the world’s fusion-energy future is funding, Sauthoff says.

But is funding the only obstacle to an energy future dominated not by renewables but nuclear, in this case nuclear fusion? The case for nuclear fusion is really, if at all, critically evaluated with respect to principle, it seen as being a clean, abundant, cost effective, and proliferation resistant form of nuclear energy unlike nuclear fission based power generation.

One problem of nuclear fusion that I have known about is their potential for generating neutrons, which can be used to irradiate uranium for plutonium production. This, in addition to other problems rarely considered, were discussed in a fascinating analysis by Daniel Jassby, himself a retired nuclear fusion physicist, at the Bulletin of the Atomic Scientists.

He observes,

But unlike what happens in solar fusion—which uses ordinary hydrogen—Earth-bound fusion reactors that burn neutron-rich isotopes have byproducts that are anything but harmless: Energetic neutron streams comprise 80 percent of the fusion energy output of deuterium-tritium reactions and 35 percent of deuterium-deuterium reactions.

Now, an energy source consisting of 80 percent energetic neutron streams may be the perfect neutron source, but it’s truly bizarre that it would ever be hailed as the ideal electrical energy source. In fact, these neutron streams lead directly to four regrettable problems with nuclear energy: radiation damage to structures; radioactive waste; the need for biological shielding; and the potential for the production of weapons-grade plutonium 239—thus adding to the threat of nuclear weapons proliferation, not lessening it, as fusion proponents would have it.

There are other issues associated with nuclear fusion that it shares with nuclear fission, in addition to problems unique to fusion, according to Jassby

In addition, if fusion reactors are indeed feasible—as assumed here—they would share some of the other serious problems that plague fission reactors, including tritium release, daunting coolant demands, and high operating costs. There will also be additional drawbacks that are unique to fusion devices: the use of fuel (tritium) that is not found in nature and must be replenished by the reactor itself; and unavoidable on-site power drains that drastically reduce the electric power available for sale.

These analyses look at fusion on its own, but when we consider fusion relative to the strong case for renewables *and* the urgency of the ecological challenge posed by climate change it’s hard not to appreciate that renewable energy is where we must invest our hopes as well as our dollars.