Ni-63 is of considerable interest and importance in radionuclidic metrology as well as for radiation protection surveillance around nuclear facilities.
Generally, 63Ni has great utility as a low-energy β - calibration standard because of the favorable combination of long half-life (T = 100 a) and β - endpoint energy. Primary standardizations of 63Ni have been actively pursued by national radionuclidic metrology laboratories for over 40 years. As a medium-energy [Eb(max) = (66.945 ± 0.004) keV; Eb(ave) = 17.43 keV] pure-beta emitter, it is often used as a test case for evaluating measurement proficiency in international comparisons. In addition, assays of 63Ni are often performed because 63Ni is a principal neutron-activation product of nickel, found at nuclear-power reactors and their environments. It is also one of the radioactive and chemically corrosive contaminants in high-level liquid-waste at nuclear fuel storage and reprocessing facilities. A new primary radioactivity standardization of 63Ni was performed. This standardization was used to support SRM 4226D which is presently out of stock. The standardization links all previous 63Ni standardizations that have been performed over the past 42 years (1968; 1984; 1995; 2006) adding another point for the determination of the half-life by radioactive decay. The primary standardization of 63Ni was performed by CIEMAT/NIST 3H-standard efficiency tracing (CNET) and the value confirmed by the triple-to-double-coincidence ratio (TDCR) method. The certified massic activity of the new issue of 63Ni is wholly consistent with the decay corrected certified activity in SRM 4226C (issued in 1995), SRM 4226B (issued in 1984) and SRM 4226 (issued in 1969) using the previously derived half-life value of (101.1 ± 1.4) and hence confirming the extant value. The present agreement with the previous issues are +0.6 %, +0.9 % and +0.5 %, respectively.
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