March 1999


ORNL’s calutrons wrap up historic half-century of isotopes

calutron
As a war-time technology, the calutrons are ending their run looking and working pretty much the same as they began.
One of ORNL’s last working links to the Manhattan Project may be finally retired. The calutrons, which made enriched uranium for the first atomic weapon and later produced stable isotopes for a world still discovering ways to use them, will likely not run again.

ORNL has received instructions from DOE to shut the devices down permanently. Up until about a year ago, the calutrons were producing stable isotopes after resuming operations in 1995 following a three-year shutdown.

Although the technology, and the machines themselves, are more than half a century old, obsolescence isn’t the reason they are being taken out of service. Little about the calutrons has changed since E. O. Lawrence designed them at the onset of World War II to parry a perceived Nazi thrust toward a nuclear weapon.

Economics is the main reason. With a fairly expensive upkeep and a well-stocked stable-isotope market supplied by cut-rate foreign sources, particularly Russian, the sales and resulting funding appropriations simply weren’t there to keep them going. Ironically, the end of the Cold War and the dissolution of the Soviet Union, the former “reliable enemy,” have been major factors in the calutrons’ demise—similar to the way the “world economy” has affected other older industries.

“Much of the current situation is tied to the reemergence of Russian calutron marketing,” says Jerry Klein of the ORNL Isotope Program. “The collapse of the Soviet Union’s central planning establishment enabled individual sites to go out and market their wares.” In cash-strapped Russia, some institutions are going after hard currency with newfound capitalistic flair.

“One of the closed cities, Sverdlovsk 45, has taken an aggressive stance in selling stable isotopes, in some instances undercutting our prices by 20 percent or more,” Klein says. “But overseas competition isn’t the only reason. One of our biggest sellers was thallium-203, used in heart scans, and one of our major customers has begun to recycle it, which has cut demand.”

The calutron shutdown does not put ORNL out of the stable isotopes business. The Isotope Program has enough inventory of most stable isotopes to last for years (another strike against the calutrons, actually) and the radioisotope business, which uses calutron-derived stable istopes for target material, is vigorous. ORNL’s market mix of stable isotopes and radioisotopes is about half and half, Klein says.

“We have plenty of inventories of the majority of stable isotopes for at least the next four or five years,” Klein says. “Headquarters’ plan is to initiate a study for producing research quantities of exotic isotopes when the need arises. These wouldn’t be commercial quantities, but if scientists need milligram quantities of rare isotopes, DOE would be able to produce them.

“There are about half a dozen technologies around that would enable them to do that—from small calutrons to AVLIS—although I can’t say whether they would work as well as existing calutrons.”

The calutrons’ staying power has been a testament
to their versatility and technically solid design.

Indeed, the calutrons’ staying power has been a testament to their versatility and technically solid design. After other ways were found to produce highly enriched uranium, the calutrons’ mission turned to stable isotope production. The machines, which are essentially mass spectrographs that use electromagnetic fields to separate elements according to their mass, can produce almost any isotope on demand.

At the end of the Persian Gulf conflict in 1992, weapons investigators found that Iraq was counting on calutron technology to produce material for its nuclear weapons program, which spurred renewed interest in ORNL’s machines. Iraq’s calutron development project was subsequently destroyed.

There are concerns in the scientific, commercial and defense communities about relying solely on foreign sources for stable isotopes, especially when the producer is unstable politically and economically. However, the large inventories and evolving technologies seem to allay those concerns somewhat.

Meanwhile, the calutrons have been placed in a “cold standby” status, which would allow for a restart, although prospects for that are very remote. Decisions are pending on whether and when to commence final dismantlement, which would involve draining oil that contains PCBs from their transformers and electromagnets.

Once the oil is drained and the internal insulation is exposed, they’ll quickly ruin, Klein says. “Then they will be gone forever.”

But Klein stresses that the calutron shutdown doesn’t mean the end of ORNL’s Isotope Program. ORNL will continue to distribute stable isotopes from its well-stocked inventory, Klein says.

“And with the High Flux Isotope Reactor, which is very unique for producing radioisotopes, ORNL is still big-time in the radioisotopes business.”—B.C.