NIST offers calibration services on the radioactivity of over 50 radionuclides. Calibrations are provided to meet the requirements of industry, research, environmental monitoring, and the life sciences. Radioactivity calibration services are available for alpha- and beta-particle-emitting solid sources, beta-particle solutions, and gamma-ray solutions.

In order to offer such a broad range of services, NIST must place stringent limitations on the physical and chemical form and activity range of sources that can be accepted. To ensure that these specifications are understood, it is essential that there be good communication between the technical user and the technical contact at NIST. When planning to have a source calibrated, the user should discuss the following points with the NIST contact:

A. Type of calibration: More than one type of calibration is often available for a given source. A cobalt-60 source, for example, may be calibrated in terms of total activity or gamma-ray-emission rate. (Inquiries regarding the calibration of radioactive sources for exposure rate should be directed to the Dosimetry Group. See Service ID Numbers 47010C to 47040S.) The required uncertainty in the calibration should also be discussed.

B. General packaging and shipping requirements: Two general requirements apply to all sources submitted for calibration: (1) all shipments must conform to applicable Nuclear Regulatory Commission (NRC) and Department of Transportation (DOT) packaging and transport; and (2) source descriptions, including approximate activity, must be provided in advance. The NIST Gaithersburg Radiation Safety Division (GRSD) must approve the receipt of radioactive material, and sources may be refused if the necessary information is not available. Copies of regulations may be obtained from Operations Division, Office of Hazardous Materials, Department of Transportation, Washington, DC 20950. Postal regulations prohibit the mailing of radioactive materials that require a caution label under DOT regulations.

All sources arriving at NIST are checked by the GRSD for radiation level and source integrity. Sources should be shipped to the attention of the technical contact at NIST.

Do not ship sources to the mailing address. Contact the technical staff for the required shipping address.

C. Reports of Calibration: A Report of Calibration is sent upon completion of a radioactivity calibration service. If the user has particular requirements for documentation of the calibration, these should be discussed with the technical contact at NIST before the services are performed.

D. Sample Preparation, Packaging, and Shipping: All samples submitted for calibration must be chemically and physically stable. The chemical form of solutions suggested for gamma-ray emitters are described below. A special lot of borosilicate-glass ampoules must be used for gamma-ray emitters. Empty ampoules are provided for this purpose. The volume of material in the ampoule should be (5.0 ± 0.2) mL.

E. Possession of licensed materials: In submitting a source for calibration that will be returned, it is necessary for the submitter to certify that he is duly authorized to possess the source under license by the applicable authority. In the case of individuals residing in a State that has entered into agreement with the Nuclear Regulatory Commission, State regulations are applicable to all sources. In the case of other individuals, NRC regulations are applicable.

Calibration of Beta-Particle-Emitting Solid Sources (Activity)

Alpha- and beta-particle-emitting solid-metal sources may be calibrated using the National Institute of Standards and Technology (NIST) 2π proportional counters. The calibration is in terms of alpha- or beta-particle-emission rate into 2π steradians (43030C). Alpha-particle-counting rates can be converted to activity upon request. Beta-particle-counting rates can sometimes be converted to activity for an increased fee and will result in an uncertified value (43040C). Mixed-alpha-emitting sources may be calibrated using the 2π proportional counter and the percentage per radionuclide is determined using a solid-state detector (43050C). There should be no more than 4 primary radionuclides present, each radionuclide must contribute at least 20 % of the total activity and the energies of the detected alpha particles must be sufficiently separated in the spectrum to enable accurate fitting. 

Sources must be electrically conductive. 

These services are not intended to identify unknown sources or determine impurities.

Backscattering corrections for a variety of source-mount materials are discussed in NCRP Report 58 (Section 3.7) and in NBS SP 250-5, Alpha-Particle Calibrations. Specifications for these calibration services are given in Table 3.

Table 3. Specifications for Measurements Using the 2 π α/β Proportional Counters and Passive Implanted Planar Silicon (PIPS) Detector