A once valuable nuclear tool now a liability for Univby Art Hughes, Minnesota Public Radio
A massive machine once used to study the building blocks of atoms has turned into a sizable liability for the University of Minnesota. The tandem particle accelerator has been mostly dormant for three decades. But its close proximity to the collapsed 35W bridge site has forced the university to decide whether to keep or dismantle the accelerator. Either way, the price tag will be big.
Minneapolis, Minn. — At the time it was built, the tandem accelerator was on a decidedly out-of-the-way plot of land--the river flats close to the Mississippi River.
"The river flats below the 35W bridge at that time was the university garbage dump," recalls U of M Physics professor John Broadhurst, "which meant we had the best-fed looking rats in the building you could see. They were about as big as a cat."
Broadhurst is one of the fathers of the accelerator.
In 1965 he took a year's sabbatical from the University of Birmingham in England to help design and build Minnesota's machine--one of only eight in the world. He moved to Minnesota permanently three years later to use the accelerator for his own nuclear research.
Broadhurst remembers increasing anti-nuclear sentiment at the time from radical groups such as the Weathermen influenced the decision about where the accelerator should reside.
"This was the time when anything with the word 'nuclear' was thought to be bad," Broadhurst said. "And so it was thought that this system, which is not capable of making dangerous products or anything, would be best put quietly where it didn't trouble people."
Such a quest was probably not easy. The Van de Graff tandem accelerator is anything but discreet. It's housed inside a nearly football field-sized room. The walls are four feet to six feet thick to contain any stray radiation.
The accelerator itself is roughly the size and shape of a small submarine. Inside, the submarine is filled largely with glass under high pressure. The accelerator uses high voltage to propel atomic particles at specified targets--mostly the nuclei of other atoms. Scientists would then study how the atomic particles reacted.
Broadhurst said the accelerator did "a lot of solid, good work on identifying the properties of nuclei, in a way that was important for the theorists at the time."
The university's accelerator was active for ten years starting in 1969. Then the benefits of particle accelerator research plateaued and funding dried up. It was last used briefly in 1992 to study the structure of a steel alloy.
The tandem accelerator building is a mere 50 feet from where the 35-W bridge fell. When the span collapsed last August, the building was not damaged.
Still, the university decided--for safety and liability reasons--to remove faculty and students working on other projects in the building.
University officials were then confronted with the question of whether it's worth keeping the building at all. University project manager Matt Stringfellow is overseeing the accelerator discussions. He said officials are considering three options: mothball the building and the accelerator, remove the accelerator and tear down the structure, or remodel the building for another purpose.
"We don't have firm decisions in place yet at the university. But we're pursuing additional information about demolishing the building," Stringfellow said. "And that would be what we have to do to decommission and remove the accelerator machine from the building prior to demolition of the building."
Stringfellow estimated the cost of tearing the building down at around $400,000. That doesn't include the work to dismantle the accelerator which could cost much more. Remodeling the structure could cost as much as $11 million.
Meanwhile, Professor Broadhurst doubts the building will survive.
"The building itself, parts of it has been used for other research and that's probably one of the biggest losses," Broadhurst said. "The building, because it's remotely located, and has radiation shielding--six foot thick concrete walls--could be used for what I call large and nasty research."
Broadhurst said he is already getting queries about parts from Yale University and the handful of other places that have similar accelerators still in operation. University officials meet again in July to map out the next stage for the building and accelerator.
- Morning Edition, 05/29/2008, 7:25 a.m.