Final report of the SIM⁶⁰Co air-kerma comparison SIM.RI(I)-K1

Abstract

Transfer chambers were used to compare the standards for 60Co air kerma maintained by seven laboratories. Six of the laboratories are members of the Sistema Interamericano de Metrología (SIM) regional metrology organization while the seventh is the International Atomic Energy Agency (IAEA) laboratory in Vienna. The National Research Council (NRC) acted as the pilot laboratory for the comparison. Because of the participation of laboratories holding primary standards, the comparison results could be linked to the key comparison reference value maintained by the Bureau International des Poids et Mesures (BIPM). The results for all laboratories were within the expanded uncertainty (two standard deviations) of the reference value. The estimated relative standard uncertainty of the comparison between any pair of laboratories ranged from 0.5% to 1.0%. The largest discrepancy between any two laboratories was 1.0%.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Photon absorbed dose standards

“…Since 2005 the key comparison was updated by new PTB and LNHB intercomparisons and the most recent results can be obtained from the BIPM key comparison website (http://kcdb.bipm.org/). Through the NRC as part of the key comparison group, the results of absorbed dose to water measurements performed within the Sistema Interamericano de Metrologia (SIM) regional metrology organization (SIM.RI(I)-K4) and the International Atomic Energy Agency (IAEA) were linked to the key comparison [77]. Among the labs participating in the key comparison group the average difference between the lab and BIPM amounts to 0.2% (1 SD 0.2%) and the largest difference 0.39%, showing that absorbed dose calibrations for 60 Co can be disseminated with a consistency of well below 0.5%.…”

Comparisons of the standards for air kerma of the GUM and the BIPM for60Co and137Cs gamma radiation

“…These data are presented graphically in Figure 3 where the black square indicates a result that dates prior to 1998 although the ARPANSA has made a comparison quite recently. The results of three published regional metrology organization (RMO) comparisons are also included [17,18,19]. It is of interest to note that the previous result of the GUM participation in the EUROMET comparison was prior to the update of their primary standard, using Monte Carlo corrections for the wall effects in particular.…”

“…The degree of equivalence between two laboratories i and j, one participant in BIPM.RI(I)-K1 and one in RMO.RI(I)-K1, or both participant in an RMO.RI(I)-K1, is given by a pair of terms both expressed in mGy/Gy: D ij = D i -D j and U ij , its expanded uncertainty (k = 2). The approximation for U ij is given in the relevant RMO.RI(I)-K1 Final Report [17,18,19].…”

Comparison of the standards for air kerma of the BEV and the BIPM for137Cs gamma radiation

“…Note that although the black squares indicate results that date prior to 1999, the BEV, VSL and the NRC have made comparisons more recently. The results of a recently published SIM comparison [13] and for the 2005 comparison with the ITN (Portugal) [14] are also presented.…”