The lab's giant laser misses key deadline
Original post made by Tim Hunt on Feb 7, 2013
Although the lab team has made significant progress, achieving ignition so more energy is produced from the nuclear reaction than it takes to generate it remains a daunting challenge; one that the late Edward Teller thought would be solved back in the 1960s. It remains elusive to this day.
The failure to achieve the ignition milestone resulted in a report to Congress that outlined both the progress and the next steps to keep moving ahead with a facility the size of three football fields that cost taxpayers $3.5 billion. That's 3 ½ times the original cost that was sold to Congress when it approved moving ahead with the giant laser facility as part of the nuclear weapons labs' (Lawrence Livermore, Los Alamos in New Mexico and Sandia in New Mexico) facilities requirement to assure that the nation's nuclear deterrent was still viable without testing nuclear warheads underground. There have been no tests since 1992.
Jeff Wisoff, one of the leaders of the laser program (his formal title is Principal Deputy Principal Associate Directoryou can ask him for a translation into English), explained that trying to do big science on a schedule with deadlines is challenging at best. In addition to the huge cost increase, the original construction required significant engineering advances to build and align 192 laser beams at a target the size of a pencil eraser. Retired lab director George Miller earned the top job by taking over the troubled laser program and guiding it through the construction to completion.
The facility is performing to or exceeding the design specifications so the engineering crew did its job well. For example, the gigabars of pressure applied to the target have increased from 25 in September 2010 to 100. The goal is 350 so they still have a large gap to close. The NIF team is much closer on implosion velocities where NIF has reached 300 kilometers per second against a goal of 350.
Wisoff believes the scientists and engineers have determined two key areas that need to be addressed to move toward ignition. The target is a sphere, but when the x-rays resulting from the laser beams start hitting it, it has become diamond-shaped. The first engineering challenge will be to make the changes necessary to maintain the spherical shape while the target is compressed.
The second issue is the mixture of hot and cold fuels. The engineering solution for this will be addressed after the sphere question. Wisoff cautions that the researchers do not know what else might loom behind these issues. Both may be resolved and other currently hidden challenges could pop up.
"The codes we use always have uncertainty to them. We will engineer our way to ignition, based upon codes, results based upon the diagnostics and then changes. It is an iterative process," Wisoff said.
While the team has aggressively pursued the ignition break-even that has not happened, it also conducted more than 200 experiments to answer questions about the functionality of the nuclear weapons stockpile. The revised plan that the National Nuclear Security Administration submitted to Congress calls for moving ahead with ignition experiments as well as those necessary for the nuclear stockpile and for basic science. It also leaves open the answer to the question of whether ignition will ever be achieved at NIF.
Some in Congress are likely to question why ignition was not achieveda fair questionbut one that should be viewed in light of 50-plus years of history. American taxpayers have invested $3.5 billion in the facility and about $300 million per year in operating money since the facility opened in 2009. For perspective, the lab's annual operating budget is about $1.7 billion.
When NIF opened, the lab program leaders were optimistic they could demonstrate ignition and then start engineering a commercial power. Those dreams of unlimited and cheap electricity remain just that dreams, despite a facility that has performed to specifications or better.
Incidentally, Wisoff is a retired astronaut who flew into space four times. He said that the commute to the International Space Station was remarkable, but the engineering challenges faced at NIF are daunting compared to those he faced in space.
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