RESUMO
From a commercial supplier a solution containing 134Cs has been standardized at National Laboratory for Ionizing Radiation Metrology (LNMRI) for the first time using three Liquid scintillation based measurement. These measurement methods are 4πß-γ live-timed anticoincidence counting, 4πß-γ coincidence counting and 3H-standard efficiency tracing with the CNET methods. The results obtained by anticoincidence counting was adopted as reference value and its combined uncertainty was 0.38%. The agreement of this reference value with coincidence counting and CNET methods were 0.39% and 0.34% respectively and were in consistency with each uncertainty method. The weighted mean results coincidence counting and CNET methods are also in close agreement 0.03% with anticoincidence counting method and meets the requirement of primary and national standard. This standardization was made in order to reduce the uncertainty in 134Cs measurement in Brazil and also following a request made by Bureau International des Poids and Mesures for new submission to International Reference System. The LNMRI last submission was made in 1987. Therefore from a 134Cs master solution a NIST ampoules was prepared and LNMRI/IRD submitted it to the International Reference System, Bureau International of Poids and Measures (SIR/BIPM). In this paper will be analyzed the LNMRI measurement and performance each measurement methods and also take into account the reference value of KCDB, we determined also the 134Cs gamma emission probabilities of main energy.
RESUMO
In this work, a 68(Ge+Ga) solution has been standardized at the National Institute of Ionizing Radiation Metrology (LNMRI), in Brazil, in the frame of an international key comparison CCRI(II)-K2.Ge-68 piloted by National Institute of Standards and Technology (NIST/USA). The 4πß(LS)-γ(NaI(Tl)) anticoincidence method with live-time and extended dead-time was used and its result was validated by 4πß(LS)-γ(NaI(Tl)) coincidence counting and liquid scintillation counting using the Triple to Double Coincidence Ratio (TDCR) method. The deviations of the activity concentration values of coincidence and TDCR measurements from the anticoincidence result were 1.7% and 0.63%, respectively, which were within experimental evaluated uncertainties at ~95% level of confidence (coverage factor k = 2). The combined relative standard uncertainties were 0.65%, 0.70% and 0.53% for anticoincidence, coincidence and TDCR methods, respectively. These values are consistent with the results reported by Cessna at the ICRM2017 conference.
