Comparisons of the standards for air kerma of the GUM and the BIPM for 60Co and 137Cs gamma radiation

Direct comparisons of the standards for air kerma of the Glowny Urzad Miar (GUM, Poland) and of the Bureau International des Poids et Mesures (BIPM) were carried out in the Co-60 and Cs-137 radiation beams of the BIPM in 2006. The results, expressed as ratios of the GUM and the BIPM standards for air kerma, are 1.0023 with a combined standard uncertainty of 2.4 x 10(-3) in Co-60, and 0.9995 with a combined standard uncertainty of 2.9 x 10(-3) in Cs-137. The result in Co-60 agrees with the direct comparison carried out in 1996 when the new correction factors adopted by the GUM and the BIPM in 2007 and 2009 are applied for the present comparison.