Nuclear fusion: it’s time for a reality check | Letters

I can’t help thinking Ed Miliband has not been accurately briefed when he says a government funding pledge means Britain is within “grasping distance” of “secure, clean, unlimited energy” from nuclear fusion (Ministers pledge record £410m to support UK nuclear fusion energy, 16 January).

Before we start talking about nuclear fusion via magnetic confinement as a commercially viable source of energy, five main challenges have to be met by the scientific community, each one of them a potential showstopper. We have to demonstrate:

1) That we can run a burning plasma for hours (if not in steady state) with Q=40 (Q being the ratio between power coming from the fusion reactions and power used to heat the plasma) without disruptions. If all goes well, at some point in the future, the ITER fusion project your article mentions will run a burning plasma with Q=10 for about 10 minutes.

2) That we can handle and exhaust the heat escaping from such a plasma and impinging on the first wall of the confining device.

3) That we can breed in the blanket of a power plant more tritium than we burn in the plasma. (Tritium is not readily available in nature and must be produced.)

4) That the materials used to build such a plant can withstand the neutron fluence coming from the burning plasma without losing their structural properties and without becoming excessively radioactive.

5) That a fusion reactor can be operated reliably and maintained by remote handling, minimising the downtime needed for maintenance.

These are massive scientific and technological challenges, the solution of which (despite progress being made) is not in the near future. The reward for finding a solution will be immense and therefore research must continue with humility and tenacity, but there is no room for overoptimistic or triumphalist statements, which can only undermine the credibility of the scientists and engineers working on the problem.
Luca Garzotti
Abingdon, Oxfordshire