Radionuclide Metrology Techniques Session

1. Radionuclide Metrology Techniques Session Posters

2. P-007 A MODIFIED METHOD FOR THE CHARACTERISATION AND ACTIVITY DETERMINATION OF LARGE AREA SOURCESA.Švec(a), H.Janßen(b), L.Pernická(a), R.Klein(b)(a) Slovak Institute of Metrology(b) PTB • Absorption, auto-absorption and backscattering in large area source active layers cause known difficulties in their activity determination through direct measurements. • Discovered a correlation between the efficiency and a “characteristic source parameter” related to the absorption in air. • “characteristic parameter” is derived from a set of measurements in equidistant source positions from a large area detector. • After calibrations with certified and homogeneous standard sources, the instrument and the method enable the determination of efficiency values corrected for absorption and auto-absorption. • The procedure works equally well for alpha and beta sources.

3. P-049 Response calculation for standard ionization chambers in APMP using EGS4 Monte Carlo codeYasushi Sato(a) , Akira Yunoki(a) , Yoshio Hino(a) , Takahiro Yamada(b)(a) NMIJ, Japan, (b) JRA, Japan • Comparisons aimed at improving the calibration factors of ionization chambers used as secondary standards within the APMP region (51Cr, 57Co, 60Co, 137Cs and 139Ce). • The calibration factors for IG11 chambers showed good agreement in high energy region (from 51Cr to 60Co). • Calibration factor ratios vary significantly in the low energy region (from 57Co to 51Cr) for the same IG11 chamber types. • To explain such tendencies, Monte Carlo calculations using the EGS4 code were employed (down to 1 keV photon energy). • Monte Carlo calculations do not yet explain fully the differences in reported calibration factors, but showed the degree of effect was due wall thickness of well, sample holder material and counting gas.

4. P-057 Random-summing correction and pile-up rejection in the sum-peak methodM. Capogni, A. Ceccatelli, P. De Felice, A. FazioENEA-INMRI • Standardization of 125I by Sum Peak Counting with 2 well–type NaI(Tl) detectors. • Measurement of Single and Coincident Event peak count rates (AI and AII), using 5 different pulse recording systems. • Random summing effects with respect to the use of pile-up rejection and live time correction circuits are investigated. • Activity concentration was calculated and reported as function of the AII count rate, and extrapolated toAII=0 yielding a value of activity concentration corrected for random-summing and dead-time losses. • Theoretical model, based on Poisson statistics, was proposed to explain the experimental data. The rate of pile-up losses and dead-time losses for both energy regions I and II and for the spectrometric and SCA systems were estimated. • Good agreement between the simulated and experimental data was observed.

5. P-064 Standardisation of 54Mn and 65Zn using software coincidence counting systemMiroslav Havelka*, Pavel Auerbach, Jana SochorováCMI • 4p (PC) - g coincidence efficiency extrapolation with the beta efficiency variation made • - by computer discrimination • - by source self-absorption • For 65Zn standardisation, discusses a procedure for optimal g - ray energy window setting based on beta and coincident beta spectral analysis. • Shows the benefits of SCC approach … easily adjust coincidence counting parameters • Comparison with classical coincidence measurements.

6. P-104 Standardisation of 241Am solutionM.Koskinas, E. Silva, I. Yamazaki, M. DiasIPEN-CNEN/SP • The standardization of 241Am by the Laboratório de Metrologia Nuclear (LMN) at the IPEN, in São Paulo • The activity measurement was carried out in a 4 (PC)- coincidence system. The 4 proportional counter used for alpha detection has a 0.1 mm thick Al window in the outside wall in order to minimize g -ray attenuation. • Extrapolation technique was employed to determine the activity of the solution. The efficiency was changed by two different methods: addition of external absorbers and electronic threshold of alpha spectrum. • The events were registered using a Time to Amplitude Converter (TAC) associated with a Multichannel Analyser. • Discussion of uncertainties.

7. P-108 Standardization of 152Eu and 154Eu by 4pβ-4pg coincidence method and 4p(β+g) integral countingT. Yamada a, Y. Nakamura a, Y. Kawada a, Y. Sato b and Y. Hino ba JRA, Japan, b NMIJ, Japan • 4pβ-4pg configuration : • (4pb) : two 20mm2 * 1mm plastic scintillation sheets, sandwiched around source. Source assembly inserted in : • (4pg) : NaI(Tl) well detector. • 4pβ-4pg coincidence counting : (3 different gamma gates). 152Eu : 154Eu impurity (0.85%) 154Eu : 152Eu (9%) and 155Eu(3%) impurities. (Plan to repeat with a “pure” solution) • 4p(β+g) sum counting : Inefficiency variation by EGS4 simulation and threshold variation • Good agreement between methods.

8. P-111 Standardisation of 99mTcM. SahagiaIFIN-HH, Romania • 4pPC-g coincidence method (three measurement variants) • Coincidences between (119.5 – 142.6) keV conversion electrons and KX-rays • Coincidences between 2.13 keV conversion electrons and 140.5 keV g –rays (in two variants) • Corrections • Compton Background of K X-ray peak • Sensitivity of P.C. to 140.5 keV g rays • Efficiency Extrapolations • General coincidence equations were written, with specific forms, for the three measurement variants • Comparison with the ionization chamber calibration