# Cobalt-60

**Cobalt-60** (⁶⁰Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.27 years that decays by beta emission to nickel-60, emitting two high-energy gamma rays. Those gamma rays, at 1.17 and 1.33 MeV, make it the workhorse radiation source for sterilizing medical devices, irradiating food, and external-beam cancer radiotherapy, and it is the only source used in the commercial irradiators regulated by the [U.S. Nuclear Regulatory Commission](https://www.edgepedia.org/u-s-nuclear-regulatory-commission).<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup><sup> • </sup><sup>[2](https://www.nrc.gov/regulations-legislation/fact-sheets-brochures/backgrounder-on-commercial-irradiators)</sup>

| Key fact | Detail |
|---|---|
| Half-life | 5.27 years<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup> |
| Decay mode | β⁻ emission with 0.9992 branching to the 4⁺ level at 2505.8 keV in ⁶⁰Ni<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup> |
| Gamma emissions | 1173.2 keV and 1332.5 keV cascade to the ⁶⁰Ni ground state<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup> |
| Production | Neutron capture ⁵⁹Co(n,γ)⁶⁰Co in nuclear reactors, cross-section 18.7 barns<sup>[3](https://iaac-aeic.gc.ca/050/documents/p80124/146112E.pdf)</sup> |
| Global installed activity | About 500 MCi of cobalt-60 at about 200 facilities<sup>[4](https://nucleus.iaea.org/sites/diif/Pages/GammaRT.aspx)</sup> |
| Medical sterilization share | 40% of medical-industry sterilization modalities, versus 50% ethylene oxide gas and 10% e-beam<sup>[5](https://www.ncbi.nlm.nih.gov/books/NBK573888/)</sup> |
| Typical doses | Under 1 kGy to inhibit sprouting and kill insects; up to 10 kGy for pathogens in meat and fish; 25–50 kGy for medical device sterilization<sup>[4](https://nucleus.iaea.org/sites/diif/Pages/GammaRT.aspx)</sup> |
| Main producers | CANDU and RBMK power reactors; about 50% of global supply from Ontario CANDU reactors<sup>[6](https://www.nordion.com/cobalt-60/cobalt-60-supply/)</sup> |

## Nuclear properties

Cobalt-60 has a [nuclear spin and parity](https://www.edgepedia.org/nuclear-spin-and-parity) of 5⁺ and a half-life of 5.27 years. It decays by β⁻ emission, with 0.9992 branching, to the 4⁺ level at 2505.8 keV in nickel-60; a much less intense branch (0.0008) populates the 1332.5 keV level directly. From the 2505.8 keV level the familiar 4⁺ → 2⁺ → 0⁺ gamma cascade completes the decay to the ⁶⁰Ni ground state, producing the two gamma rays of 1173.2 keV and 1332.5 keV that carry almost the entire decay energy and appear at nearly 100% intensity per disintegration.<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup> The average beta energy is 95.8 keV, so most of the useful output is electromagnetic rather than particulate radiation.<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup>

The two gamma lines are so characteristic and intense that cobalt-60 serves as a calibration standard in gamma-ray spectroscopy, and the decay's angular properties have even been exploited for gamma-ray anisotropy thermometry at millikelvin temperatures, where the relative intensity of the lines depends on temperature.<sup>[1](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)</sup>

## Production

Cobalt-60 does not occur in nature in usable quantities. It is made by exposing targets of cobalt-59, the stable and naturally occurring form of the element, to neutron flux inside a nuclear reactor, where the ⁵⁹Co(n,γ)⁶⁰Co reaction converts the stable isotope into the radioactive one.<sup>[3](https://iaac-aeic.gc.ca/050/documents/p80124/146112E.pdf)</sup><sup> • </sup><sup>[7](https://www.edf.fr/en/the-edf-group/dedicated-sections/journalists/all-press-releases/edf-and-framatome-launch-a-feasibility-study-for-cobalt-60-production)</sup> Close to the core, where neutron flux is intense, production proceeds quickly enough that over the reactor's lifetime as much as a third of the cobalt present can be converted.<sup>[3](https://iaac-aeic.gc.ca/050/documents/p80124/146112E.pdf)</sup>

Virtually all Low Specific Activity cobalt-60 for sterilization and radiation processing is produced by nuclear power utilities operating CANDU reactors or light water graphite-moderated RBMK reactors. About 50% of the global supply is produced in CANDU reactors in the province of Ontario, Canada; other producers include India, China, Russia, and Argentina.<sup>[6](https://www.nordion.com/cobalt-60/cobalt-60-supply/)</sup> Supply was under pressure from 2018 through 2023 due to challenges related to the Covid-19 pandemic.<sup>[6](https://www.nordion.com/cobalt-60/cobalt-60-supply/)</sup>

**Expansion into pressurized water reactors.** Because CANDU and RBMK designs historically dominated production, new capacity is being developed on other reactor platforms. Nordion acquired patents for cobalt-60 production in light water reactors from GE-Hitachi in 2019, and with Westinghouse developed technology for large-scale production in pressurized water reactors, which represent the majority of the world's roughly 400 nuclear reactors.<sup>[8](https://www.nordion.com/cobalt-60/investing-for-the-future/)</sup><sup> • </sup><sup>[9](https://www.nordion.com/nordion-acquires-technology-to-expand-future-global-cobalt-60-supply/)</sup> In January 2026, Westinghouse, Nordion, and [PSEG Nuclear](https://www.edgepedia.org/pseg-nuclear) announced key milestones establishing the first commercial-scale production of cobalt-60 in U.S. pressurized water reactors, using rodlets with nickel-plated cobalt-59 slugs inserted into Westinghouse fuel assemblies.<sup>[10](https://www.nordion.com/us-pwrs-launch/)</sup><sup> • </sup><sup>[11](https://westinghousenuclear.com/data-sheet-library/cobalt-60-production-in-us-pwrs/)</sup> In Europe, EDF and [Framatome](https://www.edgepedia.org/framatome) launched a feasibility study in 2025 to produce cobalt-60 for medical applications in a French PWR, with a first loading of demonstration capsules scheduled for 2026.<sup>[7](https://www.edf.fr/en/the-edf-group/dedicated-sections/journalists/all-press-releases/edf-and-framatome-launch-a-feasibility-study-for-cobalt-60-production)</sup> Research reactors also contribute specialized material: the [Advanced Test Reactor](https://www.edgepedia.org/advanced-test-reactor) at Idaho National Laboratory is the only U.S. source of the medical-grade cobalt-60 used in gamma knife therapy for brain tumors.<sup>[12](https://inl.gov/isotope-production/)</sup>

## Physical form and irradiation facilities

Industrial cobalt-60 sources generally comprise a number of solid metallic pellets or discs within a stainless steel source capsule, and the hazard is principally from external exposure unless the source suffers mechanical or heat damage.<sup>[13](https://nucleus.iaea.org/sites/connect/DSRSpublic/Documents/SSG-19_Nat-Strategy-Control-Orphan-Sources-p2011.pdf)</sup> In food irradiation facilities the radioactive material is contained in double-encapsulated stainless steel tubes called source pencils, placed in a rack that is immersed in an underground water chamber when not in use and raised when packaged product passes on a conveyor.<sup>[14](https://ccr.ucdavis.edu/food-irradiation/how-does-food-irradiation-work)</sup>

Two designs of U.S. commercial irradiator use radioactive sealed sources: underwater irradiators, where the sources remain in the pool at all times and product is lowered into the water in watertight containers, and wet-source-storage panoramic irradiators, where sources stored in water are raised into the air while product moves through the room behind thick concrete or steel shielding.<sup>[2](https://www.nrc.gov/regulations-legislation/fact-sheets-brochures/backgrounder-on-commercial-irradiators)</sup> All commercial irradiators regulated by the NRC use cobalt-60 as their source.<sup>[2](https://www.nrc.gov/regulations-legislation/fact-sheets-brochures/backgrounder-on-commercial-irradiators)</sup>

## Applications

**Medical device sterilization.** The largest use is sterilization of single-use medical and dental products, including syringes, surgical gloves, artificial joints, and implants such as orthopedic devices and heart valves.<sup>[5](https://www.ncbi.nlm.nih.gov/books/NBK573888/)</sup> Gamma radiation from cobalt-60 accounts for 40% of the sterilization modalities used by the medical industry.<sup>[5](https://www.ncbi.nlm.nih.gov/books/NBK573888/)</sup> A typical validated process delivers a minimum dose of 25 kGy to achieve a sterility assurance level of 10⁻⁶, under the ISO 11137 standard for radiation sterilization.<sup>[15](https://www.accessdata.fda.gov/cdrh_docs/pdf20/K202665.pdf)</sup> Large industrial irradiators of more than 1 MCi are almost exclusively used for this purpose, delivering the required 25–50 kGy doses at high speed.<sup>[4](https://nucleus.iaea.org/sites/diif/Pages/GammaRT.aspx)</sup>

**Food irradiation.** Cobalt-60 is, at present, the radioisotope most extensively employed for gamma irradiation of food.<sup>[16](https://www.cfs.gov.hk/english/programme/programme_rafs/programme_rafs_ft_01_03_irfood.html)</sup> The FDA lists the purposes as preventing [foodborne illness](https://www.edgepedia.org/foodborne-illness) by eliminating organisms such as *Salmonella* and *E. coli*, preserving food by destroying spoilage organisms, controlling insects in imported tropical fruits, delaying sprouting and ripening, and sterilizing foods for storage without refrigeration.<sup>[17](https://www.fda.gov/food/buy-store-serve-safe-food/food-irradiation-what-you-need-know)</sup> Doses are relatively low: less than 1 kGy to inhibit sprouting, slow ripening, and kill insects in grains, fruits, and vegetables, and up to 10 kGy to destroy pathogens in meat and fish.<sup>[4](https://nucleus.iaea.org/sites/diif/Pages/GammaRT.aspx)</sup> The FDA has evaluated the safety of irradiated food for more than 30 years and found the process safe, and the WHO, CDC, and USDA have also endorsed it.<sup>[17](https://www.fda.gov/food/buy-store-serve-safe-food/food-irradiation-what-you-need-know)</sup>

**Radiotherapy.** Cobalt-60 has been the most widely used isotope for teletherapy, external-beam treatment of cancer, because it offers a good compromise between photon energy, half-life, specific activity, and means of production; cesium-137 teletherapy was discontinued during the 1980s.<sup>[18](https://dirac.iaea.org/Home/Equipment)</sup> In the Gamma Knife, used for stereotactic radiosurgery of the brain, about 200 sealed cobalt-60 sources are arranged in a circular array to focus many tiny beams on a defined point; about 200 such devices were installed worldwide in 2012.<sup>[19](https://www.iaea.org/sites/default/files/bull554dec2014.pdf)</sup> Cobalt units remain attractive where infrastructure is limited because of lower initial cost than equivalent linear accelerators and less dependency on power and working conditions.<sup>[20](https://videoserver1.iaea.org/media/HHW/Radiotherapy/ICARO%20proceedings/Posters%20-%20Electronic%20Posters%20ICARO/091P-Patil.pdf.pdf)</sup>

**Industrial radiography and other uses.** Cobalt-60 is one of the most common sealed sources in industrial radiography, used to inspect the internal structure of pipelines, welds, castings, and building materials for defects; its greater penetrating power suits it to extremely thick or heavy-walled steel.<sup>[21](https://www.nuclearsafety.gc.ca/eng/acts-and-regulations/regulatory-documents/published/html/regdoc2-5-5/index.cfm?pedisable=true)</sup> High-activity sources also support the Sterile Insect Technique, in which radiation-sterilized male pests are released area-wide to mate without producing offspring.<sup>[4](https://nucleus.iaea.org/sites/diif/Pages/GammaRT.aspx)</sup>

## Safety of irradiated materials

A recurring question is whether irradiation makes food or products radioactive. An IAEA compilation reports that scientists broadly agree that treating food with gamma rays emitted by cobalt-60 or cesium-137, with electrons under 10 MeV, or with X-rays under 5 MeV does not make it radioactive.<sup>[22](https://www-pub.iaea.org/MTCD/Publications/PDF/te_1287_prn.pdf)</sup> The reason is physical: gamma radiation from cobalt-60 does not elicit neutrons, the subatomic particles that can make substances radioactive, so meltdown and chain reactions cannot occur and irradiated foods and their packaging are not made radioactive.<sup>[23](https://ace.orst.edu/info/extoxnet/faqs/irradiat/howdone.htm)</sup> IAEA studies found that the increase in radiation background dose from consuming food irradiated to an average dose below 60 kGy with cobalt-60 gamma rays is insignificant and best characterized as zero.<sup>[16](https://www.cfs.gov.hk/english/programme/programme_rafs/programme_rafs_ft_01_03_irfood.html)</sup>

## Source security and end of life

Because a cobalt-60 teletherapy or irradiator source is highly radioactive, it falls among the risk-significant sources that regulators track closely. The NRC defines risk-significant sources as those in Category 1 and Category 2 of the IAEA Code of Conduct on the Safety and Security of Radioactive Sources, and cobalt-60 is among the isotopes used in such sources.<sup>[24](https://www.nrc.gov/regulations-legislation/fact-sheets-brochures/backgrounder-on-protection-and-security-of-radiation-sources)</sup> Disused sources that lose regulatory control can become orphan sources; exposure to an unshielded high-activity source can be lethal or cause severe radiation injury, and a damaged capsule can release material and contaminate the environment.<sup>[25](https://nucleus.iaea.org/sites/ns/code-of-conduct-radioactive-sources/Pages/disused-sources-guidance.aspx)</sup> Spent teletherapy sources are returned to the supplier or manufacturer, or disposed of safely and securely, and cobalt-60 sources need regular replacement by a licensed supplier because of decay.<sup>[19](https://www.iaea.org/sites/default/files/bull554dec2014.pdf)</sup> The metal-recycling industry is a particular concern, since significant mechanical or heat damage to a source in that setting can convert an external-exposure hazard into a contamination and internal-exposure hazard.<sup>[13](https://nucleus.iaea.org/sites/connect/DSRSpublic/Documents/SSG-19_Nat-Strategy-Control-Orphan-Sources-p2011.pdf)</sup>

Decay also ends useful service in laboratories. NIST acquired a 50,000-curie cobalt-60 pool source from the Atomic Energy Commission at [Oak Ridge National Laboratory](https://www.edgepedia.org/oak-ridge-national-laboratory), contained in 12 stainless steel capsules; with a half-life of 5.26 years as NIST states it, the initially intense source decayed over 10 half-lives until it no longer provided a useful dose rate, and it was decommissioned in 2018.<sup>[26](https://www.nist.gov/history/radiation-physics-building/facilities/cobalt-60-pool-source)</sup>

## References

1. [4.3 Cobalt-60, Journal of Research of NIST](https://nvlpubs.nist.gov/nistpubs/jres/088/3/V88-3.pdf)
2. [Backgrounder on Commercial Irradiators, U.S. Nuclear Regulatory Commission](https://www.nrc.gov/regulations-legislation/fact-sheets-brochures/backgrounder-on-commercial-irradiators)
3. [Technical Document, Impact Assessment Agency of Canada](https://iaac-aeic.gc.ca/050/documents/p80124/146112E.pdf)
4. [Gamma Facilities, International Atomic Energy Agency](https://nucleus.iaea.org/sites/diif/Pages/GammaRT.aspx)
5. [Radioactive Sources and Alternative Technologies in Sterilization, NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK573888/)
6. [Cobalt-60 Supply, Nordion](https://www.nordion.com/cobalt-60/cobalt-60-supply/)
7. [EDF and Framatome launch a feasibility study for cobalt 60 production, Groupe EDF](https://www.edf.fr/en/the-edf-group/dedicated-sections/journalists/all-press-releases/edf-and-framatome-launch-a-feasibility-study-for-cobalt-60-production)
8. [Cobalt-60: Investing for the Future, Nordion](https://www.nordion.com/cobalt-60/investing-for-the-future/)
9. [Nordion Acquires Technology to Expand Future Global Cobalt-60 Supply, Nordion](https://www.nordion.com/nordion-acquires-technology-to-expand-future-global-cobalt-60-supply/)
10. [Nordion, Westinghouse, and PSEG Reach Key Milestones to Launch First-Ever Production of Cobalt-60 in U.S. Pressurized Water Reactors, Nordion](https://www.nordion.com/us-pwrs-launch/)
11. [Cobalt-60 Production in U.S. PWRs, Westinghouse Nuclear](https://westinghousenuclear.com/data-sheet-library/cobalt-60-production-in-us-pwrs/)
12. [Isotope Production, Idaho National Laboratory](https://inl.gov/isotope-production/)
13. [SSG-19: National Strategy for Control of Orphan Sources, IAEA](https://nucleus.iaea.org/sites/connect/DSRSpublic/Documents/SSG-19_Nat-Strategy-Control-Orphan-Sources-p2011.pdf)
14. [How does Food Irradiation work?, Center for Consumer Research, UC Davis](https://ccr.ucdavis.edu/food-irradiation/how-does-food-irradiation-work)
15. [FDA 510(k) K202665, Sterilization by Cobalt 60 irradiation](https://www.accessdata.fda.gov/cdrh_docs/pdf20/K202665.pdf)
16. [Safety of Irradiated Food, Centre for Food Safety, Hong Kong](https://www.cfs.gov.hk/english/programme/programme_rafs/programme_rafs_ft_01_03_irfood.html)
17. [Food Irradiation: What You Need to Know, U.S. Food and Drug Administration](https://www.fda.gov/food/buy-store-serve-safe-food/food-irradiation-what-you-need-know)
18. [Division for Human Health: DIRAC, IAEA](https://dirac.iaea.org/Home/Equipment)
19. [Reducing Risks from Sealed Radioactive Sources in Medicine, IAEA Bulletin 55-4](https://www.iaea.org/sites/default/files/bull554dec2014.pdf)
20. [ICARO poster: Cobalt-60 teletherapy equipment, IAEA](https://videoserver1.iaea.org/media/HHW/Radiotherapy/ICARO%20proceedings/Posters%20-%20Electronic%20Posters%20ICARO/091P-Patil.pdf.pdf)
21. [REGDOC-2.5.5, Design of Industrial Radiography Installations, Canadian Nuclear Safety Commission](https://www.nuclearsafety.gc.ca/eng/acts-and-regulations/regulatory-documents/published/html/regdoc2-5-5/index.cfm?pedisable=true)
22. [IAEA-TECDOC-1287: Natural and Induced Radioactivity in Food](https://www-pub.iaea.org/MTCD/Publications/PDF/te_1287_prn.pdf)
23. [EXTOXNET: How Is Food Irradiation Done?](https://ace.orst.edu/info/extoxnet/faqs/irradiat/howdone.htm)
24. [Backgrounder on Protection and Security of Radiation Sources, U.S. NRC](https://www.nrc.gov/regulations-legislation/fact-sheets-brochures/backgrounder-on-protection-and-security-of-radiation-sources)
25. [Guidance on the Management of Disused Radioactive Sources, IAEA](https://nucleus.iaea.org/sites/ns/code-of-conduct-radioactive-sources/Pages/disused-sources-guidance.aspx)
26. [Cobalt-60 Pool Source, NIST](https://www.nist.gov/history/radiation-physics-building/facilities/cobalt-60-pool-source)

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*Topic: Encyclopedia › Physical world and mathematics › Physics › Particles and nuclei › Nuclear physics › Applied nuclear and radiation science › Isotope applications and radiometric dating › Industrial and engineering isotope applications*

*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Sep 30, 2026; Oct 15, 2026 · Last review: Oct 15, 2026*

*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*

License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license