The performance evaluation of mass spectrometer in NMCC

Uranium and plutonium isotopic composition and concentration in samples taken for Safeguards purpose are sent to the Nuclear Material Control Center (NMCC) to be measured by Thermal Ionization Mass Spectrometry (TIMS) and Isotopic Dilution Mass Spectrometry (IDMS) after separation of elements with Ion Exchange Separation Method. As the Mass Spectrometers are primary important instruments in the NMCC, their Quality Control (QC) is indispensable. From the view points of external quality control, we are participating in the Safeguards Measurement Evaluation Program (SMEP) held by the New Brunswick Laboratory (NBL) of DOE in USA to assure our accuracy and precision in measurements are under control. Recently a new laboratory started its operation in the NMCC with some new Mass Spectrometers, which required finding the overall performance of the TIMS and IDMS in the NMCC. In the paper we will present measurement and evaluation results of uranium and plutonium isotopic standards (NBLCRM137, U020, U500, IRMM072, etc.) in the four Mass Spectrometers to investigate effect of measurement factors such as within days, between days, between instruments as one of internal QC expecting these results would contribute to further improvement of measurements in the NMCC. (author)