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NIST History

Radiation Physics Building

Cobalt-60 Pool Source

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In 1965, on the newly built Gaithersburg, Maryland, campus of the National Bureau of Standards (NBS, now the National Institute of Standards and Technology, or NIST), a cobalt-60 “pool source” was installed in a special annex to Building 245 known as the F wing. For more than 50 years, the intense radioactivity of the source provided a national calibration facility for high-dose industrial radiation dosimetry, the measurement of radiation exposure. 

A man in a suit stands next to a large metal tank.
NIST acquired a 50,000-curie cobalt-60 source from the Atomic Energy Commission at Oak Ridge National Laboratory (ORNL). The cobalt-60 was contained in 12 stainless steel capsules, like the one Scott Smith (pictured) is examining. During transit from Oak Ridge to NIST’s Washington, D.C., laboratories, the capsules were placed in a 5-ton, water-cooled lead container (foreground). (Note water connections on top of the container.)
Credit: NIST

High-dose radiation sources come into play when sterilizing food and medical equipment, measuring the durability of electronic equipment in high-radiation environments such as outer space, and in measuring the biological effects of high doses of radiation. Multiple cobalt-60 sources are available for use at NIST, but the pool source, when it was installed, was one of the most intense, well-calibrated facilities in the U.S. 

Schematic of sample holder placement in pool source irradiator
Schematic of sample holder placement in pool source irradiator
Credit: NIST

Cobalt-60 has a half-life of 5.26 years; thus, the initially intense source decayed over 10 half-lives until it no longer provided a useful dose rate compared with the other sources available to the Dosimetry Group. It was decommissioned in 2018. 

A large metal ball is pulled out of a pit with an overhead pulley
The cobalt-60 source being removed from the pool in the F wing in 2018
Credit: NIST
Physics and Radiation
Created July 29, 2019, Updated August 18, 2025
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