Worldwide Open Proficiency Test: Determination of ... - Nucleus - IAEA

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Draft, page 14 Alpha Counts per channel 400 350 300 250 200 150 100 50 0 226 Ra 222 Rn 225 Ac 221 Fr 217 At 214 Po 3 4 5 6 7 8 Alpha Energy (MeV) Figure 9: Alpha-ray spectrum of Ra-226 separated from a moss soil sample (tracer: Ra-225 (beta emitter), through ingrowing At-217, short lived alpha emitting decay product)
3. PERFORMANCE CRITERIA Several rating systems have been developed for determining a laboratory’s performance and the meaning of the results of the different scoring systems are not always comparable. Among various statistics, z-scores and u-scores are most often used. The drawback of z-scores is that the uncertainty of the participant’s measurement result is not taken into account for the evaluation of performance. In the case of u-scores, the evaluation includes uncertainties of the participant measurements and the uncertainty of the assigned value. Laboratories performing well in classical proficiency testing (z-scores) will not necessarily exhibit the same level of performance when their analytical uncertainties are considered in the evaluation. The proficiency testing scoring system applied by the IAEA Terrestrial Environment Laboratory takes into consideration the trueness and the precision of the reported data and it includes in the evaluation both the total combined uncertainty associated with the target value of proficiency testing samples and the total uncertainty reported by the participating laboratories. According to the newly adopted approach, the reported results are evaluated against the acceptance criteria for accuracy and precision and assigned the status “acceptable” or “not acceptable” accordingly. A result must pass both criteria to be assigned the final status of “acceptable”. The advantage of this approach is that it checks the credibility of uncertainty statement given by the participating laboratories, and results are no longer compared against fixed criteria but participants establish their individual acceptance range on the basis of the uncertainties assigned to the values. Such an approach highlights not only methodological problems affecting the accuracy of the reported data but also identifies shortcomings in uncertainty estimation. In addition, three other statistical parameters namely: z-score, IAEA/Laboratory result ratio and relative bias are calculated as complementary information for the participating laboratories. 3.1.Relative bias The first stage in producing a score for a result Value reported (a single measurement of analyte concentration in a test material) is obtaining the estimate of the bias. To evaluate the bias of the reported results, the relative bias between the reported value and the target value is calculated and expressed as a percentage: 3.2. The z-score value Bias Valuereported − Valuetarget relative = × 100% (1) Value The z-score is calculated from the laboratory results, the target value and a standard deviation in accordance with the following equation: target Value Value − reported target z Score = (2) On the basis of the “fitness for purpose” principle, the target standard deviation (σ) is: σ 0.10 x Value target The laboratory performance is evaluated as satisfactory if | z Score | ≤ 2; questionable for 2
Page 1 and 2: IAEA Analytical Quality in Nuclear
Page 3 and 4: FOREWORD A reliable determination o
Page 5 and 6: 1. INTRODUCTION A reliable determin
Page 7 and 8: 2.1. Proficiency test objectives 2.
Page 9 and 10: To confirm the assigned target valu
Page 11 and 12: program achieving complete sample d
Page 13 and 14: 2.3.4.3. Determination of U-234, U-
Page 15: AlphaCounts per channel 2000 1500 1
Page 19 and 20: acceptable”, a further check is a
Page 21 and 22: TABLE 4. SUMMARY EVALUATION OF ALL
Page 23 and 24: Lab. code Number of reported Scored
Page 29 and 30: 4.2. General recommendations and le
Page 31 and 32: Difference S2-S4 (%) Difference S2-
Page 33 and 34: 4.4. Recommendations related to the
Page 35 and 36: [Bq/kg] 70 60 50 40 30 20 10 0 Ra-2
Page 37 and 38: Figure 22: Part of the Thorium radi
Page 39 and 40: 5. CONCLUSIONS The IAEA-CU-2009-03
Page 41 and 42: REFERENCES [1] DUEWER, D.L., A Robu
Page 43 and 44: APPENDIX I: PERFORMANCE EVALUATION
Page 45 and 46: Lab code Rep. Value Rep. Unc. Unc.
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[Bq/kg] 650 575 500 425 350 275 200
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[Bq/kg] 650 600 550 500 450 400 350
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[ B q /k g ] 70 60 50 40 30 20 10 L
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Lab code Rep. Value Rep. Unc. Unc.
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[Bq] 50 45 40 35 30 25 20 15 10 120
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[Bq/kg] 60 50 40 30 20 10 0 25 223
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[ B q /k g ] 60 50 40 30 20 10 0 72
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[Bq/kg] 15 13 11 9 7 5 3 1 74 131 2
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[Bq/kg] 45 41 37 33 29 25 21 17 13
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[Bq/kg ] 19 17 15 13 11 9 7 5 3 286
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[Bq/kg] 19 17 15 13 11 9 7 5 3 1 25
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[ B q /k g ] 5.5 5 4.5 4 3.5 3 2.5
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[ B q /k g ] 3.5 3.0 2.5 2.0 1.5 1.
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[Bq /kg ] 8.5 7.5 6.5 5.5 4.5 3.5 2
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[Bq/kg] 7.5 6.5 5.5 4.5 3.5 2.5 1.5
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[B q /k g ] 13 11 9 7 5 3 1 515 26
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[Bq /kg ] 11 9 7 5 3 1 219 250 233
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[Bq/kg] 13 11 9 7 5 3 1 273 5264 26
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APPENDIX II: LIST OF PARTICIPATING
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Dr. Victor Badulin Public Exposure
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Dr. David Lobb Department of Soil S
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Petr Rulik Monitoring Department Na
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Mr. Benoit Daniel Eichrom Europe Ru
Page 235 and 236:
Prof. Dr. Constantin Papastefanou A
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Mr. A.G. Hegde Health Physics Divis
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Mr. Mario Montalto Istituto Di Radi
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Mr. Samer J. Al-Kharouf Radiation P
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Ms. Snezana Dimovska Radioecology R
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Dr. Andrzej Komosa Department of Ra
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Ms. Ana-Maria Apostu Dept. of Life
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Mr. Peter Jovanovic Department of P
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Dr. Catalina Gasco Leonarte Ed. 3a
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Dra. Montserrat Llaurado Departamen
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Mr. Abdullah Dirican Turkish Atomic
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Dr. Paul Smedley Centre For Environ
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Mr. Kevin T. Claver Environmental A
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