The standardization of (237)Np was investigated. The certified massic activity for (237)Np was obtained by 4παβ liquid scintillation (LS) counting with correction for the (233)Pa daughter using the CIEMAT/NIST efficiency tracing method using a (3)H standard. Confirmatory measurements were also performed by high-resolution HPGe gamma-ray spectrometry, and by 4παβ(LS)-γ(NaI) anticoincidence counting. All results agree within the respective method's uncertainties. It was confirmed that the (237)Np/(233)Pa radioactive equilibrium is disturbed when making dilutions and/or removing aliquots.
Keywords: Anticoincidence counting; Efficiency tracing; Liquid scintillation (LS); Neptunium-237; Radioactivity; SRM.
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