Requirements and solutions for laboratory analysis software Mika Nikkinen CTBT NDC Finland
Task - To make full gamma spectrum analysis fulfilling CTBT requirements - Result to be traceable, conclusions well justified - To be able to analyse difficult spectra - Analysis results to be accurate - Results may not lead to false interpretation about compliance/noncompliance of the treaty
CTBT requirements - Time to answer limited - Format of the result is fixed - Authentication - Correctness of the results - Formal messages - Bar codes, locks, information systems, GCI, etc.
Traceability, justification of the results - All the operations performed during spectral analysis should be recorded - Reasons to reject and add peaks during the analysis of the spectra should be well explained - Reason to add or drop radionuclides as well - Error estimations!
Ability to analyse difficult spectra - Typical level 5 contains currently only some radionuclides from non-interesting sources ( 131 I, 99m Tc, 137 Cs) - In case of real explosion or reactor accident, the spectrum may consists 200-300 peaks, high summing effects, parentdaughter relationships etc. - The determination of the event is based on expert analysis of the measurement
Chernobyl fall-out: 220 peaks
Correctness of the results - Calibrations! Correctness of efficiency calibration. - Ability to find and quantify small peaks - Peak area de-convolution, overlapping peaks - Co-incidence summing effect - Precense of rarely seen radionuclides - Activity calculations in case of interfering radionuclides and parent-daughter decay
Solutions - Software to maintain log of all procedures the analyst at laboratory is doing, the log is attached to the result file - The analysis software should be able to Find and quantify overlapping and small peaks Make correct estimation on the activities of the radionuclides including essential physical corrections needed - Special care for calibrations, reasonable error estimations required
Intercomparison by using spectra only - To verify the performance of the data analysis - Avoid multiple uncertainties which might be even compensating each other - Benefit of using synthetic spectra: the peaks, their areas, energies and intensities are well known by organiser - Inexpensive, only data is sent to laboratories
An example, NKS exercise - Synthetic spectra containing traces of severe nuclear event was sent to 25 laboratories - 1h to evaluate the result, 1month to give more comprehensive results - Under pressure (1h) the results had large variation - The exercise did show problems with a number of analysis software and laboratory data analysis procedures
NKS exercise, prompt replies
NKS exercise, prompt results
NKS exercise, prompt results, 132 Te in ubq/ m 3, correct value 3700 ubq/m 3
NKS exercise, final results
NKS exercise, final results 132 Te, correct value 38.2 Bq
NKS exercise, final results 137 Cs, correct value 1.58 Bq
NKS exercise: problems to determine overlapping peaks Only one participant was able to deconvolute this I-133 and Nd-147 duplet (1.1keV apart), the size of the missing peak was about 25 sigma. Therefore, very few participants did report Nd-147.
Recommendations - Let the analysis software to make reporting, formatting and analysis logging for the laboratory - Exercise difficult cases to make sure that the laboratory can analyse them as well if such a case will come to the laboratory - Use synthetic spectra to verify the correctness of data analysis in various laboratories, the data evaluation can result to large differences. - Verify the correctness of data analysis at the laboratory, specially peak area de-convolution, coincidence corrections and small peak quantification
Continuation of the work on TL-2.20 IDC - Laboratory Interaction Mika Nikkinen CTBT NDC Finland
Background - TL-2.20 focus on IDC requirements on laboratories - Brainsstorming on the issue Helsinki -99 - No discussion on WGB on many of these issues - Short overview + open issues:
Decision to dispatch the sample Level 5, State party request, PTS decision Additional needs: - QA - Station back-up No problems
Laboratory selection No policy decision yet Proposed policy: randomizer State party possibility to have an effect on laboratory selection? Need to be addressed
Sample spliting No fixed policy decision, yet. one, two and three parts proposed Political need to split Need to be addressed
Chain of custody - Tagging: bar-code - Tracking, barcode nodes, courier tracking? - Interaction between IDC, Lab and IMS stations, now described. Tracking of the sample during the transportation and in the laboratory
Analysis at the laboratory Non-destructive analysis as the primary analysis Change of sample geometry mechanically Destructive analysis only on TS command No comment on analysis methods
Integration on the IDC - SSREB (FPEB) - Laborastory results? - Multiple results per sample, multiple laboratories analysing the same sample? - Hyperlinks? Release 3/4 issue
Other issues Messages: under construction Archiving: Has been discussed Formats: under costruction Procedures to transmit the result to IDC
Open issues, need to be addressed - Laboratory selection - Sample tracking - Effect on release 3/4 development - Sample splitting - Messages and reporting formats under construction - Sample archiving