Mint Explainer: Fusion power — miracle or mirage?

These are just baby steps

Scientists at the US government’s Lawrence Livermore Laboratory in California injected two megajoules of energy through a laser into a very small fuel pellet. The process fused two hydrogen isotopes and generated three megajoules of energy — Essentially, a reactor produced more energy than was fed into it. The development, which comes after decades of research, has delighted scientists, but the days of abundant fusion energy are far. First, there was no net gain in energy in the experiment. To have a practical significance, the energy converted into the laser beams must be much less than the energy output from the fusion experiment. We are still nowhere close to that. The experiment only generated more energy than the laser energy fed into the pellet. There is a substantial energy loss while converting electricity to light. Also, the experiment only lasted fractions of a second, and can only be repeated once every few hours, limiting its practical utility.

Fusion fuel is scarce

The US scientists fused deuterium and tritium isotopes of hydrogen, the easiest of the four fuel combinations that can be used in fusion. Deuterium can be extracted from water, and is cheap and easily available. However, tritium does not occur naturally and is hard to produce. Canada’s nuclear reactors supply tritium to the world at the moment. Supplies will have to be ramped up exponentially to make fusion energy commercially viable.

Future reactors may be able to “breed” the tritium they need. The energy-charged neutrons generated in the experiment can break lithium into helium and tritium, if the reactor wall has a film of lithium. But there are hurdles along the way.

There will be tritium shortages to begin with, as the available supplies of lithium are likely to be eaten by the pilots in the run-up to scaling up fusion energy. And then, the tritium breeding by reactors will be just about sufficient to keep supplying fusion energy from a plant. Tritium leakages or plant closures for maintenance can drive tritium levels precariously low.

Fusion is prohibitively expensive

Fusion energy plants are capital-intensive. According to 2021 estimates by Paris-based engineering group Assystem, it could cost several times more than a fission reactor. Unless costs come down, with prices of essential components dropping, nuclear fusion plants may be uncompetitive compared to other sources of energy, it said.

Again, tritium is one of the most expensive materials in the world. There are alternatives, but they burn at much higher temperatures, making the process more complex.

Hence, it’s unlikely that fusion energy can emerge as a cheap and scalable alternative to fossil fuels in the near term. Renewables appear to be much a better alternative for rapidly developing economies like India and China.

Tritium is a nuclear weapons hazard

Nuclear weapons use tritium, without which the yield of a nuclear warhead drops significantly, making it much less powerful. A tritium-driven fusion-energy ecosystem will have the obvious danger of being abused by rogue states, damaging global nuclear disarmament initiatives.