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UCRL-VG-137402 This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract W-7405-Eng-48. DOE Analytical Services Program 2014 Workshop
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Lawrence Livermore National Laboratory UCRL-VG-134702 2 There was a site At which three organizations decided to collect some samples for a radiological assessment And split them But the results didn’t come out quite as well as they had hoped...
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Lawrence Livermore National Laboratory UCRL-VG-134702 4 Split in the field between three organizations
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Lawrence Livermore National Laboratory UCRL-VG-134702 5 Key questions for 239+240 Pu: Is it above 2.5 pCi/g? i.e., above a derived-from-risk screening level? Is it above 0.01 pCi/g? i.e., is it above “fallout background”? More precisely, is it above a value being used to represent an upper limit for fallout background? How did the Pu reach the site?
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Lawrence Livermore National Laboratory UCRL-VG-134702 6 Total dissolution Chemical separation Alpha spectroscopy Lab A and B results were surprisingly different Lab A and C good agreement
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Lawrence Livermore National Laboratory UCRL-VG-134702 10 Data are obviously of different quality Organization A didn’t really understand why Noted that counting times were different Speculated about particulate nature of radionuclides in soil Noted that some Lab B QC showed large variation Organization A wrote a report, used uncertainty- weighted average of Lab A and B results
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Lawrence Livermore National Laboratory UCRL-VG-134702 11 Was not involved in any way in 1995 Reviewed data, released a draft report for public comment Used only Lab B results Counted number of samples above 0.01 pCi/g Reached a very different conclusion about how the Pu reached the site
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Lawrence Livermore National Laboratory UCRL-VG-134702 12 Based on Lab B results 13 of 19 above 0.01 pCi/g, ignoring uncertainty 6 of 19 above 0.01 pCi/g, considering uncertainty 13/19 = 68% = “throughout the site” = “air pathway” Based on Lab A results 6 of 19 above 0.01 pCi/g, ignoring uncertainty 6 of 19 above 0.01 pCi/g, considering uncertainty 5 of the 6 located consistent with “sludge pathway”
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Lawrence Livermore National Laboratory UCRL-VG-134702 16 In order to exceed 0.01 pCi/g (the so-called “background”) Lab A needed 20 to 30 net counts Lab B needed 2 to 4 net counts Is it valid to use Lab B results to make above/below background inferences? Not always Lab B results are much more variable at low levels Example: 0.0105 ± 0.0189 with MDC = 0.0438 was considered evidence of being above 0.01 pCi/g by Organization D
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Lawrence Livermore National Laboratory UCRL-VG-134702 17 Instructions to Lab A: MDC should be 0.005 pCi/g or less This is a surrogate for “good performance at low levels” Instructions to Lab B: “Tell us if it is above 2.5 pCi/g” This implies that large variability at low levels is acceptable
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Lawrence Livermore National Laboratory UCRL-VG-134702 18 Lab A 5 gram aliquot 24 hour counting time Lab B 0.5 gram aliquot 16 2/3 hours counting time This explains why the two labs have such different results on many samples, and why Lab B results are so variable Aliquot size is the more crucial of these
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Lawrence Livermore National Laboratory UCRL-VG-134702 19 From Pitard, F., 1993 as reproduced in Myers, J., 1997 Don MacQueen: Note, demonstrate concept visually here using bag of granola, with raisins as the ‘contaminant’ Don MacQueen: Note, demonstrate concept visually here using bag of granola, with raisins as the ‘contaminant’
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Lawrence Livermore National Laboratory UCRL-VG-134702 20 Lab B’s results do not measure small differences near “background” precisely, but this was not well understood Most especially, by Organization D! — Based on their draft report, Organization D did not attempt to understand DQOs, or differences between data sets Organization A did not understand well enough soon enough to effectively discuss D’s interpretation Organizations A, B, and C had little or no discussion of DQOs Organizations B and C did not raise the DQO issue when it would have helped Organization A’s 1995 report would have been better if they had understood the DQOs more thoroughly
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Lawrence Livermore National Laboratory UCRL-VG-134702 21 All of the labs met their clients’ requirements It is the client’s responsibility to understand and share DQOs But, Lab B could have helped Lab B was aware that comparisons with 0.01 pCi/g were of interest Lab B project manager did make comparisons with 0.01 pCi/g in the analytical report cover letter
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Lawrence Livermore National Laboratory UCRL-VG-134702 22 When splitting samples, clients should insist on the same data quality objectives. Organization A did not do this. If the DQOs are not the same, make sure everyone understands the limitations (and document them).
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Lawrence Livermore National Laboratory UCRL-VG-134702 24 Data users were not sufficiently aware of the 1995 data quality objectives Data users did not understand the limitations of Lab B’s 1995 results (limits that were specified by Organization B and met their needs) Misuse of Lab B’s results enabled Organization D to introduce a huge “red herring” into the site assessment process Because of failure to consider the data quality objectives
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Lawrence Livermore National Laboratory UCRL-VG-134702 25 The client’s responsibility does not end at the lab’s front door Good scientific interpretation of a number requires full knowledge of how the number was generated Coordinate, Cooperate, COMMUNICATE!
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