A Practical approach to reduce measurement uncertainty of Pu isotopic composition by high resolution spectrometry applied to product MOX powder

Hosoma, Takashi   ; Nakamura, Hironobu ; Mukai, Yasunobu ; Fujisaku, Sakae

For verification of MOX powder produced daily in a MOX conversion plant, it is expected to reduce uncertainty of NDA which enables bias defect verification and improves compatibility with plant operation. JAEA had studied conceptual design of such NDA in 2000 with DOE and there was a proposal to utilize analytical results of isotopic composition of the sources (plutonium nitrate) which were entirely verified by IAEA. The idea to determine weighing coefficients of the combination of the sources reproducing the peak ratios of measurable isotopes by HRGS was developed and confirmed using data obtained at PCDF and simulated HRGS data. It is possible to reduce uncertainty of HRGS to 1/2-1/3. For example, around 0.7% uncertainty of effective Pu ratio is realized, if HRGS achieves 2% uncertainty. It is sufficient to pick simply the latest four lots as the sources which were received to the facility at the time of measuring or verifying product MOX powder.