INTRODUCTION

The Protocol to the Treaty contains a provision (Part I, paragraph 11) that thenetwork of radionuclide monitoring stations is supported by laboratories that arecertified by the Technical Secretariat to carry out, when required, additionalanalyses of samples from the particulate and noble gas stations.The purposes ofanalysis at the laboratory are:

Analysis of Network QA/QC and Level 5 samples at Certified Radionuclide Laboratories

Dongmei Han, Mika Nikkinen, J. S. Elisabeth Wieslander, Abdelhakim Gheddou, Herwig StangelPreparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) Organization, Vienna International Centre, P.O. Box 1200, A-1400 Vienna, Austria

Samplecategory

Numberof samples

Number of Analysis results

QA/QC 436 436

Level 5 27a) 54b)

Totals 463 490

QA/QC and Level 5 samples sent to laboratories in 2008-2010

a) 8 consecutive Level 5 samples were from JPP37 in May 2010b) Level 5 samples are split and sent to two laboratories

QA/QC Result Comparisons according to Be-7 metrics

Anthropogenic Radionuclide Identification for Level 5 SamplesLaboratory confirmation of CTBT relevant radionuclides in level 5 samples depends on the following factors:

• the radionuclide’s half-life in question; • the decay time between sample collection and laboratory measurement which is mainly the transportation time from station to laboratory; • the activity of the radionuclide in the sample.

Nuclide ID Cs-137 Co-604) Eu-155 Zr-95 Nb-95 Rb-86 I-1313) Na-241)2) Tc-99m2)3)

Laboratory Confirmation of radionuclides for 19 (38 splits) normal Level 5 samples

(a) To corroborate the results of the routine analysis of a sample fromanInternational Monitoring System station, in particular to confirm thepresence of fission products and/or activation products;

(b) To provide more accurate and precise measurements;(c) To clarify the presence or absence of fission products and/or activation

products in the case of a suspect or irregular analytical result fromaparticular station.

The Provisional Technical Secretariat (PTS) routinely requests the RadionuclideStation Operators to send samples to Certified Radionuclide Laboratories basedon quality assurance and quality control programme (QA/QC) of theradionuclide monitoring network or if a sample is considered to containmultipleCTBT relevant radionuclides (categorized as Level 5 sample) based on dataanalysis.

QA/QC samples are randomly selected from station samples thathave beenreviewed and categorized. It is usually one sample per quarter from eachcertified station. All selected QA/QC samples meet the minimum requirementsof IMS radionuclide station specifications.

All Level 5 samples from certified stations are split and sent to two independentcertified laboratoriesfor measurementandanalysis. This is donein accordance

Station SRID Lab u-Test DA% Conclusions/Actions

Single observation of disagreement result

RN54 54200804060611 ATL03 3.13 -12.23

Deviation is acceptable. Isolated case for the station. No further sample sent from the station due to defective detectorcooler since June 2008. New X-cooler was installed in December 2010. Station QA/QC sample resumed in 2011.Result for one QA/QC sample in 2011 was in good agreement.

RN66 66200907010511 NZL12 3.51 35.02

Experiment for RASA filter handing at laboratory: NZL12 tested removing the scrim before compressing the filter.The compressedfilter had a nice shape,but some Be-7 remainedon the scrim as verified by gamma-ray

u-test DA (%) Number of

resultsInterpretation of theresult comparison

u <1<±15 % 294 In agreement (67.4%)

≥±15% 1 *Probably agreement (29.6%)1 ≤ u < 3

<± 15 % 96

≥±15% 32

u ≥ 3<±15 % 1

Not in agreement (3.0%)≥±15% 12

* Unreasonable uncertainty reported by laboratory

QA/QC Result Comparisons according to Be-7 metrics

Interpretation of Result Comparisons and Actions Taken or Planned

Nuclide ID

Half-life

Cs-137

30.07y

Co-60

5.27y

Eu-155

4.76y

Zr-95

64.02d

Nb-95

34.98d

Rb-86

18.63d

I-131

8.02d

Na-24

14.96h

Tc-99m

6.01h

Frequency of NID

Identified by IDC24 10 2 2 2 2 16 10 10

Frequency of NID

confirmed by Labs22 2 0 2 2 0 7 0 0

1) Na-24 is an activation product from nuclear explosions and listed as a CTBT relevant nuclide. It also originates fromcosmic-ray interactions (spallation) in the atmosphere and is therefore frequently detected.2) For Na-24 and Tc-99m, the half-life is too short in comparison to the days elapsed between sample collection andlaboratory measurement, so no confirmation could be expected for these radionuclides.3) Both Tc-99m and I-131 are common radionuclides in the atmosphere, usually originating from medical facilities andthey are both frequently detected at several stations. In order to separate Tc-99m from Ge-75m, which emits a gamma-rayat the same energy, the IDC analysis software includes a specific tool for this purpose, which was developed in-house andis well tested.4) There are a few specific issues that could result in the discrepancies for Co-60. A comprehensive and station specificanalysis of the background at the gamma-ray energies for Co-60 is needed to evaluate the causes of discrepancies betweenstation and laboratory result. In the case of only one of the two gamma-rays from Co-60 is detected, it is identified as Co-60 according to IDC analysis policy.

certified laboratoriesfor measurementandanalysis. This is donein accordanceto Prepcom decisions to exercise and maintain the procedures and practices forhandling Level 5 samples for Treaty verification purposes.

This poster presents the results and findings of QA/QC and Level 5 samplemeasurements from 2008 to 2010.

Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, Provisional Technical Secretariat, Vienna International Centre,P.O. Box 1200, A-1400 Vienna, Austria Telephone: +43 1 26030 6475 - Facsimile: +43 1 26030 5973 - E Email Address: Mika.Nikkinen@ctbto.orgDisclaimer: The views expressed on this poster are those of the authors and do not necessarily reflect the views of the CTBTO Preparatory Commission

100

)()(22

×−=

+

−=

LAB

LABIDCA

cc

LABIDC

A

AAD

uu

AAEn

LABIDCAA

QA/QC metrics

The interpretation of the u-test metric, En, in the report is as follows:

u <1 = results are in good agreement1 ≤u < 3 = results may be in agreementu ≥ 3 = results are in disagreement

The interpretation of the DA% is that deviation below ±15% does not cause warning or action, and that deviations ≥ ±15% do, if they are accompanied with u ≥ 3.

RN66 66200907010511 NZL12 3.51 35.02 The compressedfilter had a nice shape,but some Be-7 remainedon the scrim as verified by gamma-rayspectrometry.

RN70 70200904220311 FRL08 4.07 22.27

Single case for station and lab. The station detector X-cooler was replaced, but failed several times during 2009.Finally, the new type of X-cooler was installed at the station in Feb 2010, with the station being stable ever since. Thetwo QA/QC samples sent in 2010 were in agreement with lab results.

Systematic bias probably related to laboratory problems

RN15RN29

1520080719221129200804170311

AUL023.245.25

-44.79-56.73

Problem with laboratory detector system. Laboratory was undergoing a revalidation process. MCA and analysissoftware were replaced in Feb 2010. Laboratory was back to operation after revalidation in June 2010.

RN37RN38RN77

372009040100113820090813061177200908200111

CAL05

4.775.312.38

-28.63-29.43-15.92

Systematic bias from the Lab due to RASA filter efficiency calibration problem. Recalibration was done with a newcalibration source in 2010 and since then the laboratory andstation results agree fairly well within the QA/QCprogramme.

RN11RN77RN77

1120101024131177200905070111*77201006140211*

ARL0113.770.91.73

1087.7318.7335.78

Laboratory results were questionable due to data quality issues. Laboratory is undergoing revalidation process.

Systematic bias probably related to station problems

RN46462010020200114620100617011146201008230111

ATL03JPL11GBL15

1.162.072.08

-12.63-15.2-16.97

Station detector had long term resolution issue. Detector cooler is to be upgraded.

RN47

47200910282011472010022420114720100612211147201010062011

JPL11USL16CAL05GBL15

5.812.3915.090.31

-15.53-24.7-65.81.95

Start from October 2009, QA/QC sample results from the station RN47 had big deviations compared withlaboratories results. Station had long term resolution issue at the energy range of Be-7. Maintenance actions havebeen taken in September 2010. A sample from October 2010 was sent to Lab and the result was in agreement.

RN15

1520091010221115201004042211 1520100701221115201009232211

JPL11NZL12FIL07GBL15

4.962.072.1112.67

-19.46-22.1-25.16-73.08

QA/QC sample results from the station RN15 had systematic bias compared with laboratory results. Recalibration ofstation detector was done in February 2011. One Level 5 sample in March 2011 was split and sent to two labs. Resultcomparisons showed good agreement for Be-7. Further QA/QC sample results will be observed closely in 2011.

RN7777200905070111*77201006140211*77201010240211

ARL01ARL01JPL11

0.91.733.25

18.7335.7817.63

Consecutive large deviation results indicate possible systematic bias of the station results. Considering two resultswere from ARL01 which had data quality issues, no conclusioncould be taken about the causes. Evaluation of oneQA/QC sample and one Level 5 sample sent in 2011 showed good agreement with laboratory results. No actionsneeded so far and the station is under close monitoring.

Evaluation of station QA/QC sample results is based on Be-7, as it isthe nuclide always present inadequate concentrations in the station samples. The deviation (DA%) of station results from laboratoryresults, and u-test value of the two results are used as metrics forthe evaluation of station results.

SummaryThe current PTS practice for QA/QC and L5 samples analysis atcertified laboratories gives usefulinformation about the radionuclide network performance. From 2008-2010, three stations and twolaboratories were identified having systematic bias in theQA/QC programme, and one laboratoryfailed to meet certification requirements. Corrective actions have been taken or planned.

The discrepancies for Level 5 confirmation can primarily beaccredited to:• due to long delivery times the short lived radionuclides consequently decays away;• sample splitting of Level 5 samples results in smaller amounts of radioactivity for laboratory

measurement, i.e. possibly below the detection limit;• false identification may occur due to difficult backgroundor summation effects and conservative

IDC analysis policies. In these cases, the role of the laboratory to confirm or to deny thepresence of the radionuclides is very important.

A thorough study of the peaks from the strong natural background emitters, should increase thereliability of the radionuclide identification and consequently reduce the risk of false identificationsof CTBT relevant anthropogenic radionuclides.

Station sample spectrumEnergy: 1332.0 keV,Peak significance: 1.43

Identified as Co-60

Lab 1: split sample spectrumNo peak in the energy range

Lab 2: split sample spectrumNo peak in the energy range

Level 5 sample from CAP16, Collection stop 23 Jul 2008

Station sample spectrumEnergy: 1331.0 keV,Peak significance: 1.82

Identified as Co-60

Lab 1: split sample spectrumNo peak in the energy range

Lab 2: split sample spectrumNo peak in the energy range

Level 5 sample from KWP40, Collection stop 13 Aug 2009