The Z Machine at Sandia National Laboratories in New Mexico is one of the most powerful radiation sources in the world – and soon, it will emit 500 times more energy than it’s capable of now.
Researchers have revealed they are introducing tritium, a radioactive form of hydrogen, to the Z Machine’s fuel.
With a 50/50 mix of tritium and deuterium, they say the machine will be able to fire 80 times more neutrons as the fuel fuses with its massive electromagnetic field.
The Z Machine has long been used to provide crucial information for computer simulations that test the readiness of America’s nuclear stockpile without actually exploding weapons.
And, astrophysicists use it to recreate the conditions at stars and the cores of planets.
When it fires, the machine’s electromagnetic field crushes pre-warmed fuel, triggering fusion.
Some researchers hope that the pressures created by electricity and magnetism can achieve nuclear fusion for energy production.
With the addition of tritium, the Z Machine’s already neutron high upper limit will be pushed much farther, emitting 80 times the amount of neutrons.
And, it will produce far more energy than that from just deuterium, hydrogen’s other isotope and a relatively low-octane fuel, with 500 times the current energy production.
‘This thing about creating energy where none existed before – we don’t yet have a bonfire, but we’re squirting starter on the grill,’ said Mike Cuneo, a senior manager of Sandia’s Pulsed Power Accelerator Science and Technology group.
But, researchers are still in the early days of the process of adding tritium – it will be an estimated three years before the experiments approach a 50/50 mix.
So far, the team conducted a dry run in July to test containment hardware and instrumentation, and three weeks later, they ran the first tritium experiment using just a fraction of a percent in the fuel.
Only two other Department of Energy-supported sites use tritium – Lawrence Livermore National Laboratory and the Laboratory for Laser Energetics at the University of Rochester.
Tritium has potential to be an environmental hazard, and the researchers are taking serious precautions.
The molecule is extremely small and has a 12-year half-life, and they’re working to ensure this radioactive material doesn’t make its way into the million-gallon pools of water used to insulate the machine’s pulsed power components.
‘We’re going to crawl before we walk and run,’ said Cuneo.
‘We will gradually increase that fraction in contained experiments as we go. Tritium’s like sand at the beach, it gets into everything.
‘So for now, we can’t let it go anywhere. Laser facilities don’t have these pools.’
They also say tritium could bond to the metal walls of the Z Machine’s central area, posing a potential radioactive hazard where technicians enter to scrub it daily after it fires.
But, no tritium was released.
‘There was a high level of integration on facility containment and radiation protection, to do it right,’ said Brent Jones, facility integration lead.
‘The Sandia-California gas transfer group, with decades of experience dealing with tritium, developed a method of housing, delivering, and containing the material.
‘They built a device that could load a small but defined quantity of tritium; the neutron generator people filled the target with tritium; and the plutonium confinement folks contributed their shot expertise.’
The researchers are now working to determine if the isotope can be used safely in uncontained experiments.
There are nearly 100 Sandia personnel contributing to the effort, with funding from Sandia’s Laboratory Directed Research and Development program, and researchers from General Atomics, Los Alamos National Laboratory, the University of New Mexico, and Utah State University.
While confined tests are able to evaluate its compatibility with the machine’s materials and pressures, they don’t accurately measure the fusion outputs.
‘The use of contained tritium on Z is the first step on this journey,’ said Cuneo.
‘There is much more work to do. Similar to what is done at the laser [fusion] facilities, one idea [for an uncontained experiment] is to purge the tritium immediately after a shot so that it doesn’t stick to the walls of the Z chamber.
‘We need to be able to efficiently purge the center section back to a safe level before technicians enter to refurbish it.’
Once they do begin to conduct uncontained experiments, the researchers say this will first be done with very small levels of tritium.
Then, the will gradually increase the dose.
‘We hope to find that we will be able to safely handle 1-3 percent tritium in uncontained experiments,’ Cuneo said, ‘enough to advance Inertial Confinement Fusion applications, other weapons science applications and neutrons effects testing.’