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The National Standard of the Radionuclides Activity Unit in Poland

The National Standard of the Radionuclides Activity Unit in Poland. R. Broda, A. Chyliński, T. Radoszewski, K. Małetka, T. Terlikowska-Droździel Radioisotope Centre POLATOM, Świerk, Poland.

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The National Standard of the Radionuclides Activity Unit in Poland

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  1. The National Standard of the Radionuclides Activity Unit in Poland R. Broda, A. Chyliński, T. Radoszewski, K. Małetka, T. Terlikowska-Droździel Radioisotope Centre POLATOM, Świerk, Poland

  2. The President of the Central Office of Measures established the National Standard of the Radionuclides Activity Unit in Poland in 1999 The standard is applied and kept in the Radioisotope Centre POLATOM in Świerk

  3. The National Standard consists of: • Measurements systems:triple - double coincidences (TDCR)  4(LS)- coincidences and anticoincidences X- coincidences • Absolute measurements methods:triple to double coincidences ratio (TDCR)  4(LS)(X,eA)- coincidences and anticoincidences, tracer, multi-parameterX- coincidences • Measured sources: sources in liquid scintillator point sources

  4. 1. Triple - double coincidences TDCR system • The triple to double coincidences ratio (TDCR) method • For standardisation of the-emitters (e.g. 3H, 14C, 63Ni) and EC-emitters (e.g. 55Fe, 54Mn) • Pulses are registered in channels:AB, BC, AC, ABC (denoted T),AB+BC+AC (denoted D) • The detection efficiency is changed by the PMT defocalisation and a set of counting points is obtained A PMT S PMT PMT B C S - the liquid scintillator source

  5. The counting efficiency () is calculated using the theoretical model of the LS-detector • Activity (Ao) isdeterminedby solving the system of equations at each counting point: NAB = AoAB(A, B)NBC = AoBC(B, C)NAC = AoAC(A, C)NT = AoT(A, B, C) • Parameter is calculated:K = NT/ND = T/D Ao D 55Fe K • The fitting of the theoretical function D(K) to the set of counting points is checked

  6. 2.4p(LS)-g coincidences and anticoincidences system PMT • For standardisation of the -, -, (X,eA)- emitters and radionuclides with a complex decay • Counting rates registered: LS-channel (1-2 coincidence) NLS -channel (1+2 sum) N - coincidence NC - anticoincidence NAC • Window in the -channel is selected, detection efficiency LSis changed by the HT in the LS-channel NaI   1 2 g g PMT S PMT 2 1 NaI PMT S - the liquid scintillator source

  7. The activity (Ao) is determined by linear extrapolation in coincidence (C): Ao = 561,8  1,2 kBq/g NLSNNC if Ao 1-LS LS 1-LS LS where 0 0 152 Eu in anticoincidence (AC): NCN if LS = (1-LS)/LS NLSNN -NAC Ao N - NACN Various linear extrapolationwith three different windows(I, II and III) in the -channel where LS =

  8. 3.X-g coincidences system • For standardisation of the EC-emitters (where X are followed by  of a very similar energy) e.g. 125I • Counting rates registered: 1-channel N1 2-channel N2 1-2 coincidence NC • Activity of the 125I source is calculated: g g 2 1 PMT NaI P NaI PMT NC 2 NC 2 ( ) ( ) Ao = 0,997 N1 + N2 + 2 NC - the point source (P) on the Mylard foil

  9. Uncertainty of measurements %Counting statistic 0,1 - 0,2Detector draft 0,1 - 0,4Detector system parameters 0,1Weighing of the solution 0,1 - 0,2Nuclear data 0,01 - 0,3Theoretical model of the method 0,2 - 0,8Overall expanded uncertainty (k=2)  2,0 % • The overall uncertainty can be reduced by simultaneous measurements in the TDCR and 4(LS)- system

  10. Application of the National Standard (E) An example of transfer of the radionuclides activity unit: calibration of the HPGe detector NAoi (E) = E [keV] 60 109 57 113 65 203 85 137 54 60 241 Cd Co Zn Am Hg Sr Cs Co Mn Co Sn

  11. Many types the secondary standards (e.g. solutions, solid sources, multi-gamma) of nearly 50 radionuclides are produced in the RC POLATOM: 3H, 14C, 22Na, 24Na, 32P, 35S, 42K, 45Ca, 46Sc, 51Cr, 54Mn, 55Fe, 57Co, 58Co, 59Fe, 60Co, 63Ni, 64Cu, 65Zn, 75Se, 76As, 82Br, 85Sr, 86Rb, 90Sr+90Y, 99Mo, 109Cd, 110mAg, 113Sn, 124Sb, 125I, 131I, 133Ba, 134Cs, 137Cs, 144Ce+144Pr, 152Eu, 169Yb, 170Tm, 192Ir, 198Au, 203Hg, 204Tl, 241Am • International measurements traceability of the National Standard is based on participation in 27 intercomparisons (organised by BIPM, ICRM, EUROMET, other)

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