Recommended values of 239Pu, 240Pu and 239+240Pu concentrations in reference material IAEA-315 (Marine sediment) estimated by thermal ionisation mass spectrometry, inductively coupled plasma-mass spectrometry and alpha spectrometry

The recommended concentrations of Pu-239, Pu-240 and Pu239+240 in reference material IAEA-315 (marine sediment) were estimated by three analytical methods: isotope dilution thermal ionisation mass spectrometry (TIMS), isotope dilution inductively coupled plasma-mass spectrometry (ICP-MS) and alpha spectrometry. The determination of Pu-239 and Pu-240 (Pu239+240 by alpha spectrometry) was carried out with samples from randomly selected bottles using each method. Plutonium-238 was also measured by alpha spectrometry. A plutonium-242 reference material was used as a spike for the quantitative analysis. The influence of Pu-242 in the samples was therefore calculated; however, this contribution was less than the range of uncertainty and did not influence the final results. The obtained data were statistically analysed using variance component analysis and paired comparison. The combined standard uncertainties from method/measurement, bottle and sub-sample were in the order of 3 to 6%. The main contributions to the uncertainty were from the material heterogeneity and from systematic differences between methods. Based on this study with twenty-seven analyses using 10-14 g sample mass, concentrations of (38 +/- 3) Bq kg(-1), (28 +/- 3) Bq kg(-1) and (66 +/- 4) Bq kg(-1) are proposed as recommended values for Pu-239, Pu-240 and Pu239+240, respectively, and (9.5 +/- 0.4) Bq kg(-1) for Pu-238 as an information value in reference material IAEA-315. In mass concentration units, these amount to (16.4 +/- 1.2) ng kg(-1), (3.3 +/- 0.4) ng kg(-1) and (0.015 +/- 0.003) ng kg(-1) for Pu-239, Pu-240 and Pu-238, respectively. The certified reference materials NIST 4350B and NIST 4354 were also analysed by TIMS for quality assurance of the method used in this study.