France and Japan will be vying in the Washington meeting on Saturday to be named the venue for ITER, which aims to be a test bed for what is being billed as the clean, safe, inexhaustible energy source of the future.
"We have the structure, scientific and technical environment to ensure that this scheme can start up with competence, expertise and solid safety guarantees," French Research Minister Claudie Haignere says.
Haignere will be pushing for the town of Cadarache in southern France.
"If our site is chosen, Japan will cover the costs that are needed," says Hidekazu Tanaka, a senior official at the Japanese Education, Culture, Sports, Science and Technology Ministry, promoting the northern Japanese village of Rokkasho-mura.
No more Chernobyls
At present, nuclear energy is derived from splitting atoms of radioactive material to unleash a controlled chain reaction whose by-product is heat.
But more than half a century of experience in fission has thrown up some serious problems, ranging from the nightmare of Chernobyl to the perils of transporting nuclear material and where and how to store dangerous long-term waste.
Nuclear fusion takes the opposite approach, seeking to emulate the Sun.
The solar crucible takes the nuclei of two atoms of deuterium, which is the heavy form of hydrogen, and fuses them together to form tritium (the other isotope of hydrogen) and in so doing releases huge amounts of energy.
There is a virtually limitless source of deuterium in the world, because it can be derived from water; as for tritium, it is not a natural element, but can be easily made by irradiating it with lithium at high pressure.
Theory to practice
That is the theory, and getting from there to a workable prototype plant of commercial size is what ITER is all about.
For all the allure of nuclear fusion as a boundless energy source, and the promise that, unlike nuclear fission, it offers no environmental headache, the technical hurdles remain immense.
Among the many problems are how to efficiently confine the plasma cloud in the magnetic field so that charged particles do not slip out, and the energy cost in pumping up the plasma to such high temperatures in comparison with the energy yield.
No one has achieved a long self-sustaining fusion event to date. The record, achieved by European scientists at a small experimental tokamak at Cadarache on 4 December is six and a half minutes, releasing a thousand megajoules of energy.
The cost of building and running ITER and constructing all the necessary infrastructure, such as roads and housing, is put at $10 billion over 30 years, of which three billion will trickle down into the local economy, according to the Cadarache campaign team.