Plan around decay
Co-60 has a half-life of 5.27 years and loses about 0.3 percent of its activity each week. Ask for the activity you need on the day you start using it.
- 1 year87.7%
- 5 years51.8%
- 10 years26.9%
- 20 years7.2%
Sealed gamma reference sources
Feasibility review
Cobalt-60 for research
Two gamma rays in cascade, at 1173 and 1332 keV: a standard for high-energy calibration and coincidence work.
- Half-life
- 5.27 years
- Main gamma
- 1332.5 keV
- Decay
- Beta minus to Ni-60
- Exempt quantity
- 1 µCi
Co-60 at a glanceIAEA evaluated data
Research applications
Where Co-60 does the work.
Figures are simulated examples of each measurement.
Radiation detection
High-energy detector calibration1, 2
Its 1173 and 1332 keV lines are recommended standards for calibrating gamma-ray spectrometers at high energy.
More: High-energy detector calibration
Both lines are emitted in nearly every decay, with evaluated emission probabilities, which makes Co-60 one of the IAEA's recommended nuclides for energy and efficiency calibration.
Detector physics
Germanium detector acceptance3
Germanium detector resolution is measured on the 1332 keV line of Co-60.
More: Germanium detector acceptance
Resolution is quoted as the full width at half maximum of this peak, and the width at tenth maximum shows how far the peak departs from a pure Gaussian.
When the GERDA experiment characterized its 30 germanium detectors, resolution at this line averaged 1.72 keV. Co-60 measurements also gave each detector's active volume.
Nuclear physics
Gamma-gamma angular correlation4, 5
The two gamma rays of one decay are more often emitted along a common axis, a classic test of nuclear spins.
More: Gamma-gamma angular correlation
Two detectors count the 1173 and 1332 keV gamma rays in coincidence while one moves around the source. The rate follows W(θ) = 1 + cos²θ/8 + cos⁴θ/24, the pattern predicted for a 4 → 2 → 0 cascade.
Amato and colleagues measured it with two sodium iodide detectors and a 5 kBq source: the coincidence rate rose with the angle between the detectors, close to the prediction.
Radionuclide metrology
Activity by the sum-peak method6, 7
Close to a detector, both gamma rays of one decay can add into a 2506 keV sum peak, which gives source activity without a calibrated reference.
More: Activity by the sum-peak method
The sum peak, the two single peaks and the total count give the activity directly, with no need to know the detection efficiencies.
Kim and colleagues calibrated Co-60 sources this way with a germanium detector, correcting for angular correlation and pulse pile-up.
Scintillator research
Fast timing with prompt coincidences1, 8
Its two gamma rays leave each decay about a picosecond apart, so Co-60 measures the time resolution of fast detectors.
More: Fast timing with prompt coincidences
The 1332 keV level of nickel-60 has a half-life of 0.735 ps. The spread of time differences recorded by two detectors is then their combined time resolution.
Van Loef and colleagues measured 385 ps between a cerium-doped lanthanum bromide crystal and barium fluoride with Co-60 gamma rays.
Radionuclide metrology
Calibrator constancy checks9
A long-lived sealed source measured each day shows whether a radioactivity calibrator still reads the same.
More: Calibrator constancy checks
The IAEA recommends measuring a long-lived check source in a fixed geometry before each day's use. It names caesium-137 as a good option and lists Co-60 among the alternatives.
A Co-60 check source loses about 12 percent of its activity each year, so readings are compared with the decay-corrected value.
Forms
Co-60 forms researchers ask for
Every source is confirmed with its manufacturer before you order.
Point or disk source
Sealed, encapsulated Co-60
Detector checks, calibration and coincidence work
Feasibility reviewCalibrator reference source
Sealed vial geometry
Calibrator constancy checks
Feasibility review
Activity, certificate and lead time are set with the manufacturer at quote.
Before you order
Plan for decay and licensing.
Licensing
Exempt quantityNeeds a license1 µCi
A single Co-60 source at or below 1 µCi is an exempt quantity under 10 CFR 30.71, Schedule B. Above that, your institution needs a license that covers it.
- Combining exempt sources to exceed the limit is not covered.
- Agreement States apply equivalent rules. Your RSO reviews the exact source before you order.
Start a request
Request a feasibility review for Co-60.
No license file needed to ask. A scientist reads every request and replies with the next step.
- Name the measurementCalibration, timing or coincidence work sets the source form and activity.
- Give a reference dateState the activity you need on the day you start using it.
- Plan the next sourceActivity halves about every 5.3 years.
Decay data
Co-60 decay data
Decay schemeCo-60 to Ni-60
- Half-life
- 1,925.28 days ± 0.14
- Decay mode
- Beta minus (100%)
- Daughter
- Ni-60
- Decay energy (Q)
- 2822.81 keV
| Radiation | Energy (keV) | Per 100 decays |
|---|---|---|
| Beta | 317.9 max, 95.8 mean | 99.9 |
| Beta | 1492 max, 625.9 mean | 0.12 |
| Gamma | 1173.23 | 99.8 |
| Gamma | 1332.49 | 100 |
Source: IAEA LiveChart of Nuclides, ENSDF evaluation by E. BROWNE and J. K. TULI (literature cutoff 31 December 2012), retrieved 25 September 2026 [1]. Reference values; a manufacturer's certificate states the activity of a specific source.
Questions, answered
Co-60 questions
How long does a Co-60 source last?
Its activity halves every 1925.28 days, about 5.27 years, so about 88 percent remains after one year. How long a source stays useful depends on the lowest activity your measurement can use.
Can we buy Co-60 without a radioactive materials license?
For very small sources, possibly. A single Co-60 source at or below 1 microcurie is an exempt quantity under 10 CFR 30.71, and a distributor licensed under 10 CFR 32.18 can supply it to users without a license. Larger sources need a license that covers them. Your RSO decides how your institution handles each case.
What activity should we ask for?
State the activity you need at a reference date close to first use, and the instrument or measurement it serves. We confirm a matching source and certificate with the manufacturer before you order.
Does the certificate state the activity on delivery?
It states the activity at the manufacturer's reference date. We convert it to your delivery or first-use date on the quote, and the chart at the top of this page shows how the activity falls.
Can you supply high-activity Co-60 sources?
No. We handle research and check-source quantities only, not irradiator or other high-activity sources.
Can a decayed source be returned?
Some manufacturers take back their own sealed sources. A return is a separate shipment with its own RSO and shipping review, so ask us before the source reaches the end of its use.
More isotopes
Related isotopes
Sources
References
- IAEA Nuclear Data Section. LiveChart of Nuclides, Co-60 decay data (ENSDF evaluation). Retrieved 25 September 2026. www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html
- International Atomic Energy Agency. X-ray and Gamma-ray Standards for Detector Calibration. IAEA-TECDOC-619. Vienna: IAEA; 1991. www-pub.iaea.org/MTCD/Publications/PDF/te_619_web.pdf
- GERDA Collaboration, Agostini M, Bakalyarov AM, et al. Characterization of 30 76Ge enriched Broad Energy Ge detectors for GERDA Phase II. Eur Phys J C. 2019;79(11):978. doi.org/10.1140/epjc/s10052-019-7353-8
- Hamilton DR. On directional correlation of successive quanta. Phys Rev. 1940;58(2):122-131. doi.org/10.1103/PhysRev.58.122
- Amato EC, Anelli A, Barbieri M, et al. Measurement of the angular correlation between the two gamma rays emitted in the radioactive decays of a 60Co source with two NaI(Tl) scintillators. Eur J Phys. 2022;43(5):055802. doi.org/10.1088/1361-6404/ac78a3
- Araújo MTF, Poledna R, da Silva RL, et al. Absolute standardization of 22Na, 65Zn and 60Co by sum-peak method and critical analysis of instrumentation. J Phys Conf Ser. 2018;1044:012006. doi.org/10.1088/1742-6596/1044/1/012006
- Kim IJ, Park CS, Choi HD. Absolute calibration of 60Co by using sum-peak method and an HPGe detector. Appl Radiat Isot. 2003;58(2):227-233. doi.org/10.1016/S0969-8043(02)00295-6
- van Loef EVD, Dorenbos P, van Eijk CWE, Krämer K, Güdel HU. High-energy-resolution scintillator: Ce3+ activated LaBr3. Appl Phys Lett. 2001;79(10):1573-1575. doi.org/10.1063/1.1385342
- International Atomic Energy Agency. Quality Assurance for Radioactivity Measurement in Nuclear Medicine. Technical Reports Series No. 454. Vienna: IAEA; 2006. www-pub.iaea.org/MTCD/Publications/PDF/TRS454_web.pdf
- U.S. Nuclear Regulatory Commission. 10 CFR 30.71, Schedule B (exempt quantities). eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.71
- U.S. Nuclear Regulatory Commission. 10 CFR 30.18, Exempt quantities. eCFR, current as of 23 September 2026. www.ecfr.gov/current/title-10/section-30.18
Technical review by ConductScience, 25 September 2026. Next review 25 September 2027.
Need Co-60 for a specific instrument or measurement?
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