Radionuclide and Noble Gas Data Processing and Analysis

Transcription

1 International Data Center 1 Radionuclide and Noble Gas Data Processing and Analysis Ulrich STOELHKER Scientific Methods Unit Software Applications Section, IDC/SA/SM Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, Provisional Technical Secretariat Vienna International Centre P.O. Box 1200, A-1400 Vienna, AUSTRIA

2 International Data Center 2 Radionuclide monitoring in The Treaty Protocol To The Comprehensive Nuclear Test-ban Treaty Part I The International Monitoring System (IMS) and International Data Centre (IDC) Functions C. Radionuclide Monitoring The network of stations to measure radionuclides in the atmosphere shall comprise an overall network of 80 stations, as specified in Table 2-A of Annex 1 to this Protocol. All stations shall be capable of monitoring for the presence of relevant particulate matter in the atmosphere. Forty of these stations shall also be capable of monitoring for the presence of relevant noble gases upon the entry into force of this Treaty. All monitoring stations shall fulfill the technical and operational requirements specified in the Operational Manual for Radionuclide Monitoring and the International Exchange of Radionuclide Data.

3 International Data Center 3 Radionuclide monitoring in The Treaty Draft Operational Manual for the International Data Centre (IDC) Standard Radionuclide Processing, Analysis and Products... The objective of radionuclide analysis is to detect, characterize and report on radionuclides of nuclear explosions. These data include gamma spectroscopic pulse-height data from all particulate and some of the noble-gas monitoring stations, and beta/gamma coincidence counting data from the remaining noble-gas stations.

4 International Data Center 5 Particulate sampling: How are non-gaseous radionuclides transported in the atmosphere? An extremely hot & highly luminous spherical mass of air and gaseous residues is formed after a nuclear explosion. The fireball grow in size as it sucks up particles from surrounding air and ground and becomes a radioactive cloud. As the cloud is cooling, vaporized radionuclides condense and attach to the aerosols in the cloud and are either transported by wind over great distances or washed-out by rain. aerosol vaporized radionuclides condensed radionuclides condensed radionuclides attached to aerosols Particulates slowly precipitate with a rate depending on the particle size. Noble gases stay in the atmosphere and disperse due to atmospheric mixing.

5 International Data Center 6 IMS radionuclide particulate monitoring network In November stations for particulate monitoring systems are installed, 60 of them are certified

6 International Data Center 7 IMS Radionuclide Network Objective of the International Monitoring System (IMS) Radioactivity particulate network: At least 90% detection capability within 14 days after a nuclear explosion in the atmosphere for a 1 kton nuclear explosion. Main nuclides of interest: Nuclide 140 Ba 140 La 131 I 99 Mo T ½ 12.8d 40.3h 8.06d 2.75d Gamma energy [kev] Gamma emission probability [%] Minimum detectable concentration: < 30 Bq/m 3 for 140 Ba

7 Minimum requirements for particulate stations CTBT/PC/II/1/Add.2, CTBT/PTS/INF/INF.58/Rev.7 System Manual or automated Air flow 500 m³ h - ¹ Collection time 24 h Decay time 24 h Measurement time 20 h Time before reporting 72 h Reporting frequency Filter Particulate collection efficiency Measurement mode Daily Adequate composition for compaction, dissolution and analysis For filter: 80% at = 0.2 m Global: 60% at = 10 m HPGe HPGe relative efficiency 40% HPGe resolution 2.5 kev at 1332 kev Base line sensitivity 10 to 30 Bqm -3 for 140 Ba Calibration range 88 to 1836 kev Data format Radionuclide Monitoring System Format (RMS) State of health Status and ancillary data recorded every 10 minutes Communication Two-way Auxiliary data Meteorological and flow rate data recorded every 10 minutes Data availability 95% Down time 7 consecutive days; 15 days annually International Data Center 8

8 International Data Center 9 Essential elements for radionuclide particulate monitoring Sampling equipment - for collection of large volume of airborne particulates. Filter material - for trapping particulates as many as possible and changed into a geometry best suited for gamma radioactivity measurement. Detection equipment - a detector crystal with good resolution, detection efficiency as high as possible, with lead shielding. Multi-channel analyzer, computer system, station operation software - for production of spectral raw data for transmission to the IDC for analysis. State-of-health (SOH) sensors - status of station monitors, i.e., air flow rate, detector temperature, indoor temperature and humidity, filter position monitor, power supply status, lead shield status, that could be used to interpret the measured radionuclide data. Meteorological sensors - meteorological data monitors, i.e., precipitation, temperature, wind speed, wind direction. Transmission of data to IDC via satellite. Uninterruptible power supply & Auxiliary generator - for power stability and alternate source of electrical power.

9 Measurement of particulates International Data Center 10

10 International Data Center 11 Manual RN Aerosol systems Filter Filter folded to reduce size Filter compressed to 5cm diameter disc Decay for 24 h Measurement using HPGe for 20h

11 International Data Center 12 Manual aerosol systems (Station PGP51) Detection system Generator and housing Equipment housing Snow White sampler and housing

12 International Data Center 13 RASA (Radionuclide Aerosol Sampler Analyzer) developed by PNNL Automatic aerosol sampler High volume aerosol sampler High resolution gamma spectrometry Detection limit < 30µBq/m³ (Ba-140)

13 International Data Center 14 Data flow from IMS stations to IDC and the process of product generation for state signatories Event Atmospheric transport to IMS station (1 14 days) Data processed at IDC Data review Product generation Total: ~ 3 17 Calendar days IMS particulate station 24 hour collection 24 hour decay 24 hour measurement IDC Transmission to IDC via GCI

14 International Data Center 15 Data flow from IMS stations to IDC and the process of product generation for state signatories In general the same procedures are applied for particulate and noble gas spectra but different analysis tools are used RN data Automatic Processing ATM Interactive Review Data import ARR RRR Data export State signatories Automatic Radionuclide Report (ARR) Reviewed Radionuclide Report (RRR) Atmospheric Transport Modelling (ATM)

15 International Data Center 16 General structure of the RN analysis software Particulate systems HPGe systems Noble Gas Systems SPALAX HPGe systems SAUNA/ARIX Beta-Gamma systems Automatic analysis autosaint Automatic analysis autosaint noble gas analysis Automatic analysis bg_analyze Interactive review SAINT2 Interactive review SAINT2 Interactive review Norfy CAT CAT CAT RRR ARR RRR ARR RRR ARR

16 International Data Center 17 Gamma spectrum collection/analysis of particulate spectra 1. Calibrate the station 2. Collect sample (24h, >500m3/h) 3. Let sample decay (24h) 4. Sample measurement: acquire spectrum (24h) 5. Transmit spectrum to IDC through GCI (<72h) 6. Automatic Analysis Check calibration Locate peaks Quantify peak areas Associate isotopes to peaks Calculate concentrations Categorize 7. Review of spectra by analyst, correct analysis, explain unknown peaks, check categories, check overall correctness of data 8. Results to secure web site/authorized users

17 Counts International Data Center 18 A typical particulate spectrum We want to know: Which number of γ-photons is collected in the detector? What radionuclides and how much are in the sample? 7 Be What energy do they have? 212 Pb keV 40 K 208 Tl 214 Bi Ge Ge 72 Ge Energy [kev]

18 New radionuclide analysis system under LINUX Software for the analysis of particulate gamma spectra Automatic analysis Particulates: autosaint Review of data Particulate: SAINT2 SAINT2 for particulate data review International Data Center 19

19 International Data Center 20 Sample Categorization (particulates) Sample analysis is triggered following an event screening process at the IDC or from a request of a State Party. A Level 5 sample is split into 2 parts and sent to 2 radionuclide laboratories for remeasurement to verify the presence or absence of fission and/or activation products. Spectrum analysis 5 level categorization scheme for particulate data Yes Typical? No Anthropogenic? Yes Typical? No FP? Yes Typical background LEVEL 1 No Non-typical background LEVEL 2 Yes Typical Anomalous anthropogenic anthropogenic LEVEL 3 LEVEL 4 Backtracking Timing Lab analysis Data fusion No Multiple anthropogenic, FP included LEVEL 5

20 International Data Center 21 Why are we looking for radioxenon in addition to particulates? Radioxenon is a volatile substance - a gas Indicates nuclear reactor usage Is not washed out by rain => spread over long distances Is released from underground nuclear tests Ratios of radioxenon isotopes can be used to characterize the source Stable Xenon concentration is constant in atmosphere 0.087ppm Graphics by FOI

21 International Data Center 22 How is Radioxenon released from underground testing? Seeping / Barometric Pumping Prompt: pressurized gas can seep out along fractures Delayed: daily variations in atmospheric pressure give Xenon rise to a pumping effect Barometric pumping can cause gases to advance along fractures or through soil Xe-133 can be measurable for months after an explosion

22 Noble Gas network November 2012 Total of 34 NG stations 31 IMS (9 certified) 3 Non-IMS International Data Center 23

23 International Data Center 24 CTBTO Noble Gas Measurement System Objective of the International Monitoring System (IMS) Noble Gas Network: At least 90% detection capability within 14 days after a nuclear explosion in the atmosphere, underwater or underground for a 1 kt nuclear explosion. Nuclides of interest: 131m Xe (11.9 d), 133m Xe (2.19d) 133 Xe (5.24 d), 135 Xe (9.10 h) Minimum detectable concentration: < 1 mbq/m 3 for 133 Xe Source Term: range to Bq 133 Xe for a 1 kt nuclear explosion Minimum 40 Noble Gas stations worldwide

24 International Data Center 25 Minimum requirements for Noble Gas stations Characteristics Minimum requirements Air flow 0.4 m 3 h -1 Total volume of sample 10 m 3 Collection time 24 h Measurement time 24 h Time before reporting 48 h Reporting frequency Daily Isotopes measured 131m Xe, 133 Xe, 133m Xe, 135 Xe Measurement mode Beta-gamma coincidence or High resolution gamma spectrometry Minimum Detectable Concentration 1 mbq m -3 for 133 Xe State of health Status data transmitted to IDC Communication Two-way Data availability 95 % Down time 7 consecutive days 15 days annually

25 International Data Center 26 Data flow from IMS stations to IDC and the process of product generation for state signatories Event Atmospheric transport to IMS station (1 21 days) Data processed at IDC Data review Product generation Total: ~ 2 21 Calendar days IMS station 12/24 hour collection, processing & measurement IDC Transmission to IDC via GCI

26 International Data Center 27 General structure of the NG analysis software Particulate systems HPGe systems Noble Gas Systems SPALAX HPGe systems SAUNA/ARIX Beta-Gamma systems Automatic analysis autosaint Automatic analysis autosaint noble gas analysis Automatic analysis bg_analyze Interactive review SAINT2 Interactive review SAINT2 Interactive review Norfy CAT CAT CAT RRR ARR RRR ARR RRR ARR

27 International Data Center 28 Collection & analysis of Noble Gas spectra 1. Calibrate the station 2. Collect sample (period: 12-24h, air volume >10 m3) 3. Process sample, analyze spectrum (24h) 4. Transmit spectrum to IDC through GCI (<48h) 5. Automatic Analysis Check calibration Add peaks to spectrum for Xenon energies Calculate concentrations Categoriztion 6. Review of spectra by analyst, correct analysis, check calibration, check overall correctness of data and recalculate category 7. Results to secure web site/authorized users

28 Noble Gas monitoring systems developed for CTBTO since 2001 SAUNA-II (Sweden) two-dim. β-γ coincidence spectra Since different types of Noble Gas monitoring systems have been developed which are fulfilling the requirements for NG systems in the IMS: Two-dim. β-γ coincidence spectra High resolution γ spectra using HPGe detector ARIX (Russian Fed.) two-dim. β-γ coincidence spectra SPALAX (France) highresolution γ spectra International Data Center 29 International Data Centre Page 29

29 International Data Center 30 The Principle (Radioxenon Measurement) The basic design of beta gamma coincidence detectors: NaI crystal for efficient detection of gamma radiation Scintillation cell for the detection of electrons from beta decay and internal conversion (IC) Electronics to select coincident beta and gamma radiation (simultaneous in time) Photo Multiplier tubes (PM) are attached to the NaI crystal and the beta scintillator for the amplification of light from the interaction of gamma photons and electrons. PM tubes provide a signal proportional to the energy of gamma photons and electrons

30 International Data Center 31 Identifying Xe-isotopes (beta/gamma analysis) 131m Xe (11.9 d), 133m Xe (2.19d) 133 Xe (5.24 d), 135 Xe (9.10 h) Identification technique based on: γ lines, X-rays and conversion electrons 133 Xe and 135 Xe: 81 kev and 250 kev γ lines 131m Xe, 133 Xe and 133m Xe: kev X-rays 131m Xe and 133m Xe: 129 kev and 199 kev conversion electrons from IC 131m Xe and 133m Xe: weak γ lines due to internal conversion (IC)

31 International Data Center 32 Identifying Xe-isotopes (beta/gamma analysis) 1. Perform point-by-point gas/background subtraction (memory effect). 2. Determine amount of 214 Pb in sample from photopeak with centroid at 352 kev. 3. Correct 135 Xe counts at kev for 214 Pb. Determine 135 Xe activity concentration. 4. Correct 135 Xe counts at kev for 214 Pb. Determine 135 Xe activity concentration. 5. Strip 133 Xe counts from 131m Xe and 133m Xe counts at 30 kev. 6. Determine counts for 131m Xe and 133m Xe.

32 International Data Center 33 Identifying Xe-isotopes by γ-spectra (II) X-Rays 133 Xe (81 kev) 133 Xe (160.1 kev) 131m Xe (163.9 kev) 133m Xe (233.2 kev) 135 Xe (249.8 kev) Ge escape peak (71 kev)

33 Identifying Xe-isotopes by γ-spectra (III) International Data Center 34

34 New Noble Gas analysis system under LINUX Software for the analysis of Noble Gas spectra Automatic analysis NG: bg_analyze for beta-gamma autosaint for SPALAX Review of data NG: norfy for beta-gamma and SAINT2 for SPALAX norfy for beta-gamma noble gas review International Data Center 35

35 New software for the analysis of Noble Gas spectra Automatic analysis autosaint for SPALAX Review of data SAINT2 for SPALAX Saint2 for noble gas review of gamma spectra International Data Center 36

36 International Data Center 37 Characterization of Noble Gas data Evaluation of the four Xenon isotopes provides information on the activity concentration and isotopic ratios which are used to distinguish between releases from nuclear reactors and nuclear tests. experimental data from IMS Isotope plot with theoretically derived two domains and the empirical separation line Isotope plot with experimental data

37 International Data Center 38 Noble Gas reports for States Parties Noble gas event screening does not have laboratory component due to short half-life of the substances Final categorization scheme with 3 levels has been implemented in August Flags are important, they provide information on possible source and reliability of the sample. Flags: Xenon concentrations Flag: Backtracking indicates known source Clean background A NG Spectrum analysis No Xe present? Yes Typical? Yes No Flag: Quality Indicators on Sample reliability 3 level categorization scheme for NG data Typical for station B Anomalous for station C Flags: Isotopic ratios Xe-133m/131m Xe-135/133

38 International Data Center 39 Noble Gas reports for States Parties Automatic Radionuclide Report (ARR) and Reviewed Radionuclide Report (RRR) - ARR and RRR for Noble Gas spectra are available in XML format - XML/HTML based products are available through secure WEB and AUTODRM & subscription

39 International Data Center 40 Processing of data from Noble Gas stations Status: In total, 34 IMS Noble Gas stations are transmitting data to IDC in testbed. Data from all Noble Gas stations are processed in the IDC testbed. 9 Noble Gas stations are certified. Data from certified Noble Gas stations are processed and reviewed in the IDC operational environment. Data flow of Noble Gas stations is monitored in accordance with operational procedures.

40 International Data Center 41 New RN processing software at IDC New software has been developed and tested by the IDC over many years. On 3 June 2011 the software was moved into operation replacing the legacy applications that were used in IDC routine RN operations. The promotion provided IDC operations with the capability to process and review Noble Gas data for the first time which thus presents a complete makeover of the Radionuclide Monitoring System. Before installation, the new software is compared on a scientific basis and a independent benchmarking environment has been implemented at IDC. Benchmarking of the IDC radionuclide analysis software will be performed in future every year. In 2012 the software was improved with respect to automatic energy calibration of particulate and noble gas systems. In addition the three level noble gas categorization scheme has been implemented.

41 International Data Center 42 Atmospheric transport modeling for NG stations Software tool is available for Xenon flagging in RRR. Takes into account release from all known potential sources and calculates impact on NG stations The tool takes into account specific sampling times of NG stations (12h sampling time) and performs 21 days backwards ATM calculations. Plans: Connect ATM flagging with categorization continue development of Web-grape tool. Web-grape tool, a typical Xe-133 network coverage map for noble gas network

42 International Data Center 44 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV EU-JA III project Initiative funded by the European Union to improve knowledge of the global Xenon background. Two mobile Noble Gas container based systems were purchased: - mobile SPALAX system - mobile TXL-based SAUNA system Objectives of EU JA III Noble Gas project 1. Supplement knowledge through longer and thus more representative time periods in selected sites (measurement period: six months) 2. Detection of local sources - if present 3. Provide empirical data for validating network performance 4. Testing xenon equipment and logistics, providing PTS access to portable equipment that can also be used for training purposes 5. Data analysis and training of local experts

43 International Data Center 45 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Mobile system improvements Standard SPALAX adapted to be transportable: Mechanical parts, electrical connections, electronic boards rugged against vibrations, shocks. SPALAX 15 container PNNL developed container-based solution for a Transportable Xenon Laboratory (TXL) integrating a SAUNA system : 1 st TXL is operated by PNNL 2 nd TXL is operated by PTS Schematics by Environnement S.A the SAUNA is integrated in this TXL Standard SAUNA adapted to be transportable: Mechanical parts, electrical connections, electronic boards rugged against vibrations, shocks. Schematics by PNNL 20 ISO Container / PNNL Double Doors SAUNA in Operating Position

44 International Data Center 46 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Mobile TXL2/SAUNA II Mobile TXL/SAUNA system Manufacturing: Dec to June 2011 (6.5 months) Delivered to PTS: 6 June 2011 System installation: 7 to 17 June 2011 Initial testing: 16 June to 12 Sep Training courses: 13 to 23 Sep in Vienna and 14 to 18 May in Jakarta The mobile SAUNA installed at PTS on 6 June 2011 Shipment by airfreight to Singapore and by sea freight from Singapore to Jakarta: 21 Dec. to 14 Jan Start of measurement campaign: 22 March 2012 System not installed by PTS staff (instead by Gammadata due to warranty issues) The mobile SAUNA in Singapore on the way to Jakarta, Indonesia

45 International Data Center 47 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Noble gas detections in Jakarta (7.5 months) Xe-135 and MDC Xe-133 and MDC

46 International Data Center 48 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Noble gas detections in Jakarta (7.5 months) Xe-131m and MDC Xe-133m and MDC

47 International Data Center 49 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Early phase of campaign 22 March 26 April 2012 Noble gas detections in Jakarta Second period 1 June - 2 Aug Third period 3 Aug Oct Xe-135 < 500 mbq/m3 Xe-133 < 1200 mbq/m3 Xe-133m < 75 mbq/m3 Xe-131m < 10 mbq/m3 < 10 mbq/m3 < 10 mbq/m3 < 0.5 mbq/m3 < 1 mbq/m3 < 200 mbq/m3 < 500 mbq/m3 < 40 mbq/m3 < 10 mbq/m3 Clear detections of all four Xenon isotopes were observed during the measurement campaign: 133 Xe : 1200 mbq/m Xe 500 mbq/m 3 The short duration of increased xenon levels indicates that the main sources for xenon isotopes are close to the measurement site. SAUNA station in Jakarta is close to radiopharmaceutical facility Local ATM clearly links emission profile and detections To confirm these observations and to correlate release and SAUNA data by local ATM installation of a stack monitoring system was initiated.

48 International Data Center 50 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Manufacturing: Dec to Sep (10 months) Initial testing in Vienna: 22 Nov. to 10 Jan Training of PTS staff in Vienna: 5 to 9 Dec Shipment preparation ~ 5 months Shipment to Kuwait: 3 to 11 May 2012 Start of measurement campaign: 15 May 2012 Mobile SPALAX System installed by PTS staff: 13 to 18 May 2012 The mobile SPALAX installed at PTS on 6 Oct The mobile SPALAX picked-up at PTS on 3 May 2012

49 International Data Center 51 EU JA III CFSP/2008/027/CTBTO III EU Council Decision IV CFSP/2010/036/CTBTO IV Measurement campaign in Kuwait started mid-may Data are transmitted are on a regular basis and successfully processed in IDC. Significant detections of Xe-133 (1 mbq/m3) Only Xe-133 detections were seen locally Work on possible source region continues Noble gas detections in Kuwait Network coverage July 5-15, Xe-133 detection confirmed in several samples since 17 May Preliminary activity concentration (decay corrected): up to 1 mbq/m3)

50 International Data Center 52 Conclusion Radionuclide monitoring is essential part of CTBT verification network. Detections of nuclear weapon testing is based on radioactive substances (activation and fission products). Radioactive gasses and particles can travel long distance in the atmosphere, Atmospheric transportation modelling is essential part of the verification effort. Xenon background is dynamic because of medical isotope production which is the biggest contributor to the background. Measurement campaigns with mobile noble gas systems are performed to gain better understanding of the background on a global scale. The detection of radioactive gasses or other substances together with nuclear explosion typical characteristics is a strong indicator for nuclear weapon testing, and may be supported by the detection from other verification methods (infrasound, hydroacustic or seismic).

51 Thank you Questions?