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December 24, 2022
Fusion Breakthrough at LLNL and its implcations
Writing about web page https://www.llnl.gov/news/national-ignition-facility-achieves-fusion-ignition
On December 5th, Lawrence Livermore National Laboratory (LLNL) announced the first ever net energy gain from laser-powered inertial fusion. This campaign reported that from 2.05 MJ of input energy, 3.15 MJ was reported as the output. This is a world-first for controlled fusion and marks a critical achievement in demostrating the possibility of fusion power.
So what are the implications for magnetic tokamak confinement and the broader fusion community?
While it can be argued that inertial confinement fusion differs considerably from magnetic confinement fusion, both require considerable energy input and both require the fusion triple product and hence fulfil the Lawson Critierion for a sufficient amount of time to achieve ignition of the plasma. In the case of magnetic confinement it is the toroidal plasma, for inertial confinement, it is the plasma induced by the vapourization of the fuel pellet by the lasers. The fact that positive energy has been demonstrated by at least one method of fusion is an important demonstration about that positive energy is possible using current techniques.
While this is important, it is critical to know the reliable positive energy is only one of the earliest critieria that need to be met. For fusion power to be practical, the energy has to be tranferred into a useful form. A practical reactor of any type must be capable of fusion pulses on a regular basis and to withstand the conditions caused by the heat and radiation by the fusing plasma. This leads to aspects of fusion reactor design whereby reactor components such as the cryogenics plant, diagnostics and gyrotrons to name a few require power and effectively reduce the net power generated from the fusion reactor such that the actual energy released/energy input is << 1
The result of this will be that a considerable period of fusion development when the next major development will be when gross energy input = energy output. That is, a fusion reactor which gives no net energy to the Grid but does not take energy out of the Grid unlike every single fusion experiment to date. This will demonstrate the fusion power has a level of maturity in that it can support its own reactions which will be the next signficiant milestone.
To summarise, while care must be taken to not overstate the importance of the LLNL result it does show that fusion power is well on its way from transitioning from a physics problem to an engineering problem. That isn't to say there will not any surprises on the physics front on the race to practical fusion but this is another piece of good news alongside the latest JET result. We await with bated breath for ITER's first plasma in 2026.