30 years of reactor characterization on the NBSR

The NIST nuclear reactor irradiation facilities used for neutron activation analysis have been well characterized for absolute neutron flux measurements, variations within each irradiation facility, neutron energy measurements of each facility, and temperature and pressure measurements. This has been accomplished with various sample materials and under a range of conditions including biological samples inside of sealed quartz ampoules, and for radiation damage measurements on the polyethylene rabbits used for all pneumatic tube irradiations. As a result of all these measurements, initiated in 1969 and still continuing, the NBSR irradiation facilities have become the most highly characterized NAA irradiation facilities in the world. This paper describes the methods and techniques developed and used for characterization of the NBSR irradiation facilities.