Oak Ridge National Laboratory

 

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Oak Ridge facilities provide significant isotope production

OAK RIDGE, Tenn., April 24, 1997 — For most of the 40,000 nuclear medical procedures performed daily in the United States for diagnosis or therapy, chances are that the isotopes used originated at an Oak Ridge facility.

Research, processing, packaging and sales of enriched stable isotopes and radioactive isotopes (radioisotopes) all take place at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL), which includes the Isotope Enrichment Facility and the High Flux Isotope Reactor (HFIR).

"The Isotope Enrichment Facility supplies a significant portion of the world's enriched stable isotopes," said Emory Collins, senior technical advisor at ORNL .

After the enriched-stable isotopes are made radioactive - or irradiated - they have a variety of uses, including applications in medicine, research, education and industry.

"At least 50 percent of the isotope sales at Oak Ridge facilities are for medical applications," said Rocky Cline, isotope distribution manager. "The other 50 percent of sales are for industrial, education and research purposes."

Workers at the Isotope Enrichment Facility make stable isotopes of almost any element. At least 50 elements can be separated into 225 different stable isotopes.

Prices for stable isotopes range anywhere from 99 cents to $4,000 per milligram, depending on how rare they are and the difficulty in separating them, according to Scott Aaron, associate manager of the Isotope Enrichment Program.

Total sales volume in 1996 for both stable and radioactive isotopes was $12.5 million. Stable isotopes accounted for the majority of that total, or $7.3 million, Cline said.

The biggest sellers among stable isotopes in fiscal year 1996 were thallium-203, used in heart imaging, and strontium-88, used for cancer treatment. Thallium-203 generated $3 million in sales, and strontium-88 accounted for $1.4 million in sales.

For enriched stable isotopes to become radioisotopes, they must be irradiated in either an accelerator or a reactor.

"In an accelerator, the isotopes are bombarded with protons," Collins said. "In a reactor like we have, you bombard them with neutrons."

After irradiation, thallium-203 becomes thallium-204, and strontium-88 becomes strontium-89. Californium-252 and iridium-192 are the biggest sellers among radioisotopes. In fiscal year 1996, californium-252 accounted for almost $1.3 million in revenue, and iridium-192 generated $1.9 million.

Californium-252 is commonly used in cancer therapy, usually in ovarian and cervical cancers. Iridium-192 is sold mainly for industrial uses, such as radiography - which involves using gamma rays to inspect welds.

Californium-252 is processed in only one other place - Russia.

"Total market value of our entire enriched stable isotope inventory is around $380,000,000," Cline said. "But you've got to keep in mind that we can't sell all 225 of them. There are many of them that aren't used much right now because they have no known applications in medicine or industry.

"I know these fiscal year 1996 numbers sound very big; however, for any isotopes sold the money goes into a revolving fund," he said. "There is not enough revenue through production of commercial isotopes to support the production of isotopes for research, so Congress allocates funds to the overall program."

Although medical uses accounted for half the sales volume of isotopes and radioisotopes at ORNL, research efforts consume the largest quantity of the total volume.

"Only a small amount of the entire volume of radioisotopes is used for medical applications," Collins explained. "That little bit, though, catches a lot of the attention. That's understandable. Everyone's concerned about health-related issues."

Some radioisotopes can be bonded to certain compounds known as "carrier molecules" that take them to a specific part of the body for treatment or diagnostic purposes. They are often used as a bone-pain reliever in cancer treatments, specifically in the later stages of lung, breast and prostate cancers. These cancers often spread to other areas of the body, such as organs and bones.

Now, researchers believe tungsten/rhenium isotopes offer a more effective treatment.

Rhenium-188, though not yet approved by the Food and Drug Administration, has shown promising results in cancer treatments given in Europe and in clinical trials in the United States.

The ability to target specific areas to treat some cancer patients is a better alternative than surgery, because tumors often spread throughout the body, making it very difficult or impossible to surgically remove them, said Russ Knapp, Nuclear Medicine group leader in the Life Sciences Division at ORNL.

Knapp said he expects the HFIR facility to expand its irradiating capacity. HFIR has nine hydraulic tube irradiating positions, and plans are to add 48 more by mid-1997.

This addition could give ORNL a significant boost in its capacity to supply radioisotopes for medical purposes.

ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Research Corporation.