Technical Aspects of the NIST Proficiency Tests for Source Manufacturer Accreditation
J.C. Cessna (NIST)
The NIST (National Institute of Standards and Technology) defines traceability as an "unbroken chain of measurements, each with stated uncertainties." The American National Standard ANSI N42.22-1995 "Traceability of Radioactive Sources to the National Institute of Standards and Technology (NIST) and Associated Instrument Quality Control" expands this definition to provide a framework in which associated sources can be provided with this same assurance of traceability. An important aspect of this standard is the definition of proficiency tests to be performed. Proficiency testing for radioactive source manufacturers is provided by the Measurement Assurance Program for the Nuclear Power Industry. This program is operated under a CRADA (Cooperative Research and Development Agreement) with the NEI (Nuclear Energy Institute) to provide research associates at NIST to administer the program. The program provides six distributions of blinded-activity sources per year to participants and allows participants to submit sources to NIST as well. Several sources were distributed recently and NIST maintains results submitted by participants. Results range from 10 percent to + 10 percent of the NIST value, with occasional outliers, generally due to calculation errors. ANSI N42.22 defines criteria for acceptance of proficiency testing results and NIST generates a Report of Traceability.