Softwares for radiological assessment of buildings & soils

Transcription

1 Softwares for radiological assessment of buildings & soils Given by Jean-Guy Nokhamzon Julien ATTIOGBE, Didier DUBOT CEA/DSV/USLT/SPRE/SAS Jean-Jacques PERAUDIN Geovariances sales manager

2 Objective and key points Recall the main geostatistical principles, then present how it is possible to optimise sampling strategies for radiological evaluation in nuclear premises Key points : Provide alternatives to exhaustive sampling/control Compare regular and random sampling, sequential sampling Model the spatial continuity of radiological contamination Estimate surface activities together with their uncertainty Evaluate the sampling efficiency in terms of activity estimation and hot-spot detection

3 Context and material Context: Decontamination of nuclear premises requires a radiological assessment of residual activity levels Two steps: 1. systematic control of the surface activity (in situ measurements) 2. analysis of concrete samples (drill-holes) in order to assess the contamination depth Aims: Identify surface hot spots Quantify the average residual contamination level or the residual amount of radionuclide present in the premises Assess the spatial continuity of the radionuclides within the premise, to provide a reliable estimate of activity levels Context & material

4 Software Development Radiological characterization for contaminated sites through data processing (Krigéo) associated to a GIS (Kartotrak) Optimization & decision making aid module (STRATEGE) 4

5 Softwares dedicated to the geographic representation of the measures in the different stages of the clean-up process Real-time data acquisition Data processing through Geostatistics Calculation of the projected impact Preparing the sampling plan Validating the cleanup objective Establishing the theoretical mesh Observing the extension of the pollution Prototype by CEA Interaction of the different softwares 5

6 KARTOTRAK: GEOGRAPHIC INFORMATION SYSTEM GIS component Use of vectorial maps No pixeling effect when zooming in Different layers: vectorial + raster Data management Georeferenced maps Used with a differential GPS + Doppler radar Path of the vehicle CEA prototype Sampling Plan Editing 6

7 Kartotrak : Geographic Information System Different working processes: manual acquisition Collecting measures without any sampling plan Make a sampling-plan denser Data acquisition : - Automatic geographic location - Entering manually the in situ measure Save/ Load a data file 7

8 Kartotrak : Geographic Information System Different working processes: systematic mesh Specify areas to be/not to be measured Specify areas with an historical interest (known location of contamination) Area to be measured 8400 m² Area of interest m² Excluded area (building) 2150 m² 245 georeferenced data 8

9 STRATEGE 9

10 Evaluation objectives and sampling Different sampling plans for different evaluations BRGM data Random sampling Specific search sampling Circular grid sampling Profile sampling Appraisal sampling Regular sampling 10

11 Decision making aid module : STRATEGE STRATEGies d Echantillonnage Module developed in 2007 which covers each step of a sampling campaign Evaluation objective Removal of doubt / Initial cartography Environmental diagnosis Radiological characterization End of remediation controls Determine and optimize the sampling plan Optimized grid Circular grids Drillings distribution PESCAR, Wilks method Forecast measures performances Estimating the projected budget 32% 68% Editing a report of the evaluation preparation 11

12 STRATEGE : Sampling optimization Too much? Not enough? 5000 m² 400 measures m² 270 measures Variability Variability Adjustment Experimental variogram Distance (m) Distance (m) 12

13 STRATEGE : Sampling optimization Analysing the experience feedback Optimizing the systematic grid in order to use geostatistics (highlight the spatial structure of the data) Considering the informations of the area ( historical, geology, topography) and the evaluation constraints (budget, performances ) Graphic indicators: - Probability of hitting a target - Impact/relevance of extra measures Probability of hitting (%) Probabilité de toucher (%) Normal Intérêt Size of the target (m) Dimension de la cible (m) 13

14 GEOSTATISTICS 14

15 Geostatistics : basics Data analysis Known Data Histogram Kriging 3D Experimental variogram and model 2D Interpolation (initial cartography) 3D Interpolation (with drillings) 15

16 Geostatistics: Kriging Method Kriging is a geostatistical method for measurement interpolation It proceeds in different steps : - Understand and quantify the spatial variability - Estimate activities where it remains unknown - Draw the uncertainty map - Analyse the risk Experimental variogram Variogram fitting 16

17 Example of initial cartography - Kriging Interpolation Map Uncertainty Map High variability The Uncertainty Map points out areas that lack measures or where the variability is important. 17

18 Risk analysis Probability maps Allows to estimate the local probability of exceeding a given value. High probability, very likely Intermediary probability, uncertainty Low probability, very likely Complementary to the contaminated surface estimation (through simulation) Helps to establish a relevant drilling positioning 18

19 Mapping Quick Analysis and processing on the field 19

20 REAL TIME ACQUISITION 20

21 Acquiring the measures in real time : Kartotrak RT Intesity of the signal per second DSP 2 DSP 1 Number of the acquisition Intesity of the signal per second NaI Total Average DSP Spectro Gamma Total Number of the acquisition Finding a area of interest Confirmed by all the instruments 21

22 From RT data to areas of interest Highlighting 2800 m² of interest out of a 7050 m² zone Historical Knowledge RealTime Measuring Identifying the areas of interest Sound characterization of the areas of interest 22

23 Optimizing example Area : 7050 m² Total surface area : 2800 m² Additional measures 105 measures (5-meter mesh) Characterization 178 measures (6-m mesh) 23

24 Optimizing example #2 Area : 6800 m² Total surface area : 930 m² Additional measures 87 measures (3-m mesh) Characterization 182 measures (6-m mesh) 24

25 Analysing the RT measures measures of 1 second - Between 3000 & c/s - Average value = 7000 c/s Roads level Grounds level Area of the zone : 2,2 ha. Green spaces, asphalt roads. 2 spots were identified in order to do a gamma in situ spectrometry : (1) : activity 137 Cs = 93 +/- 47 Bq/kg (2) : activity 226 Ra = 186+/- 97 Bq/kg 25

26 Measured area processed data Roads of the area : Green spaces of the area : Signal evolution Data processing by Geostatistics 26

27 K RP: Pedestrian Module acquisition in real time A complement to KRT to be used when access is difficult (forest, areas with no access for vehicles, narrow and steep paths, ) Simple equipment: GPS + NaI 3" linked up to a pc Walking detection limit: 1Bq/g eq. 137 Cs 27

28 3D ANALYSIS 28

29 GEOPHYSICS INVESTIGATIONS SAMPLING TECHNIQUE Confirm the position of drill holes by checking the absence of metallic parts or underground network near the drill holes. Contact : Jean-Christophe SPARFEL anomaly Contact : Stéphane BELBEZE ANTEA Ingénierie 3 Av. Claude Guillemin BP Orléans cedex 2 s.belbeze@anteaingenierie.fr Drillings with auger or Geoprobe Depends on the field, maximal depth: 2m Simple and relatively cheap Unsuitable for chemical measures Unsuitable for containment Drillings with ultrasonic device Every type of soils Maximal depth 50 to 100m Suitable for containment Expensive technique 29

30 From the 2D to the 3D viewing The preliminary 2D mapping leads to a drillhole campaign processed in 3D. Drillholes View from below Isatis 3D Viewer (Geovariances) 30

31 3D Analysis Roads monitoring Underground evaluation Radiological evaluation of walls and floors 31

32 DEPTH EXCAVATION OPTIMIZATION - COST STUDY In depth profile Activity(Bq/g) 0,00 0,01 0,10 1,00 10,00 100,00-7 Drillings and samplings ,02 0,01 0,01 0,01 Remediation scenarios come from -67 0,05 0,3 IRSN methodology guide: Analyses results Profondeur (cm) ,1 0,3 2,1 2,0 0,9 1,3 2,3 0,5 Industrial sites management potentially contaminated by radioactive substances ,1 Typical spectrum determination per zone ,1 somme beta somme alpha Activité totale césium a/b Residence and playgrounds Primary school Market gardening In depth profile plotting Optimisation impact/coût (profil A) Offices Optimization graph functions of a remediation scenario Cost/advantage study Excavation depth choice Impact µsv/an ,8 7 4,8 6,7 6,0 3,3 3, construction batiment coût , , ,0 180,0 135,0 120,0 105,0 90,0 75,0 60,0 45,0 30,0 15,0 0,0 Coût (k ) Public car park Waste land Building site Car park under construction Profondeur (cm) 32

33 CONCLUSIONS Sampling takes a critical place in our project management More than 120 sites characterized and permanent feedback Current industrialization of the software platform Kartotrak Cost/advantage study allows to optimize the remediation in function of the rehabilitation, to justify the remediation choices before the safety authority and to control cost and delays. Relative Cost HIGH Rehabilitation Total Cost The better you characterize upstream with surface and in-depth measures, the better you manage the remediation operations, respecting the projected cost and deadlines. LOW BASIC APPROACH Investigations DETAILED APPROACH HIGH LEVEL APPROACH Edited by BRGM, D. Hubé Scientific promotions, publications, seminars and collaborations : Decommissioning Avignon 2008; SIEN Bucharest 2009; Statgis 2009, SFEN 2009, Intersol Paris 2010, DDR Idaho 2010, Environet program (AIEA), WM Phoenix AZ 2011 Collaboration with China, Russia and South Korea about contaminated sites and soils 33

34 THANK YOU 34