Precise and accurate determination of plutonium by controlled-potential coulometry and its uncertainty evaluation

Yamamoto, Masahiko   ; Ishibashi, Atsushi; Nagayama, Tetsuya; Surugaya, Naoki ; Kurosawa, Akira; Hiyama, Toshiaki

Precise analysis of plutonium is necessary for material control and safeguards in nuclear facility. Thus, controlled-potential coulometry, which yields absolute results and high precision, was applied for the determination of plutonium. The coulometry system and sample pretreatment procedures were optimized following ISO12183:2005. Plutonium sample prepared from NBL CRM-126 Pu metal was measured and agreed well with certified value. For spike preparation of isotope dilution mass spectrometry (IDMS), plutonium solution was prepared from MOX powder. Plutonium content was 15.5995 mgPu/g. The uncertainty was calculated by ISO/BIPM Guide to the Expression of Uncertainties in Measurements. The relative expanded uncertainty was 0.023% with confidence interval of 95%. The results were in good agreement with those obtained by IDMS. Thus the proposed coulometry method was successfully applied for the determination of plutonium at the highest level of precision and accuracy.