Guest essay by Eric Worrall
A new ITER Nuclear Fusion timetable has been agreed, which slips the first scheduled Deuterium / Tritium burn to 2035 – 8 years after the original scheduled date. But an exciting and unexpected US breakthrough has just breathed new life into one of the oldest approaches to achieving controlled nuclear fusion.
New schedule agreed for Iter fusion project
An updated schedule for the Iter fusion project has been approved by the Iter Council, which represents the countries taking part in the project. Under the new schedule, first plasma is now slated for 2025 and the start of deuterium-tritium operation is set for 2035.
A two-day meeting of the Iter Council at the Iter headquarters at Saint-Paul-lez-Durance in France unanimously approved the project’s baseline – its overall schedule and cost. The project is to build the world’s biggest tokamak fusion reactor at Cadarache in southern France. It should be large enough and hot enough to reach ‘ignition’ and maintain a stable heat-generating plasma for minutes.
“The overall project schedule was approved by all Iter members, and the overall project cost was approved ad referendum, meaning that it will now fall to each member to seek approval of project costs through respective governmental budget processes,” the Iter Organization said in a statement yesterday.
The Council concluded that project construction and manufacturing have sustained a rapid pace for the past 18 months, “providing tangible evidence of full adherence to commitments”. The successful completion of all 19 project milestones for 2016, on time and on budget, is “a positive indicator of the collective capacity of the Iter Organization and the Domestic Agencies to continue to deliver on the updated schedule”, it said.
The year 2035, with the possibility of further schedule slippages, seems an awfully long time to wait to know whether large scale nuclear fusion is viable.
Thankfully there are other possible approaches which don’t involve vast UN administered bureaucracies.
Breakthrough in Z-pinch implosion stability opens new path to fusion
Researchers have demonstrated improved control over and understanding of implosions in a Z-pinch, a particular type of magneto-inertial device that relies on the Lorentz force to compress plasma to fusion-relevant densities and temperatures. The breakthrough was enabled by unforeseen and entirely unexpected physics.
Recently, however, researchers using the Z Machine at Sandia National Laboratories have demonstrated improved control over and understanding of implosions in a Z-pinch, a particular type of magneto-inertial device that relies on the Lorentz force to compress plasma to fusion-relevant densities and temperatures. The breakthrough was enabled by unforeseen and entirely unexpected physics.
According to existing theory, however, the imposed magnetic field should not have significantly impacted the growth of the instabilities that normally shred the liner and prevent high levels of compression during the implosion. But, while fusion plasmas are subject to various forms of instability, referred to as modes, not all these instabilities are detrimental. The pre-magnetized system demonstrated unprecedented implosion stability due to the unpredicted growth of helical modes, rather than the usual azimuthally-correlated modes that are most damaging to implosion integrity. The dominant helical modes replaced and grew more slowly than the so-called “sausage” modes found in most Z-pinches, allowing the plasma to be compressed to the thermonuclear fusion-producing temperature of 30 million degrees and one billion times atmospheric pressure. The origin of the helical modes themselves, however, remained a mystery.
Z-pinch is one of the oldest experimental approaches to controlled fusion, because it is so simple. Z-pinch is essentially a giant electrical transformer, but instead of a secondary coil, the fusion plasma forms the secondary. Triggering a pulse of current through the transformer primary induces an enormous current in the plasma, which in turn generates an extremely intense magnetic field, squeezing the plasma (hopefully) to nuclear fusion temperatures.
The downside of Z-pinch is the force tends to be applied like squeezing a sausage – all the goodness squirts out the ends of the Z-pinch. But the researchers at Sandia National Laboratories claim to have found a way to fix this problem.
Obviously we’ve all been here before, nuclear fusion research is littered with exciting breakthroughs which never fulfil their early promise. But given the long wait until ITER is finally switched on, there is plenty of opportunity for clever attempts to research exotic approaches to nuclear fusion to leapfrog the multi-decadal UN project.