Developments in Radioactive Waste Characterization in South Africa. Gert Liebenberg Necsa

Transcription

1 Developments in Radioactive Waste Characterization in South Africa Gert Liebenberg Necsa

2 Contents Introduction Characterization of Uranium Wastes Centralised Drum Storage Facility Waste Tracking System Drum Contents Investigation Drum Measurements IQ3 Scanner Current Status Way forward NBNFL Scanner Conclusion 2

3 Introduction Necsa has been operated the following facilities over the past 50 years Nuclear research Reactor Safari 1 since 1965 Uranium Conversion pilot plants Uranium Conversion processing plant Uranium enrichment plant (high enrichment) Uranium enrichment (semi commercial low enrichment) Fuel manufacturing plant Research laboratories Manufacturing plants for enrichment processes Alternative enrichment process development programmes Isotope Production Facilities 3

4 Introduction Most of the fuel cycle facilities - decommissioned since mid 1990 s All radioactive wastes generated since start of operations kept on site until 2012 Started shipping RA waste to the Vaalputs National RA Waste Management Repository in

5 RA Waste Historical and current wastes consists of nearly 100 different waste streams Compressible wastes (low and high enriched) Bulk uranium wastes (natural and low enriched) Non-Compressible wastes (powders, filters, oil, sediments etc.) Scrap metal (Stainless, mild steel, copper, cast iron, brass etc.) Medical wastes Disused radioactive sealed sources 5

6 Characterization of Uranium in Wastes 1991 South Africa signed Comprehensive Safeguards Agreement IAEA unable to verify part of declaration More than 20,000 waste drums Declaration of waste drums based on material balance calculation. Drums situated all over NECSA site. No satisfactory method to quantify uranium Waste drums with various waste forms Alumina-gel, filters, lime Compressible waste various densities 6

7 Centralization of Waste Drums Purpose: better oversight and control Pelstore Former enrichment plant building Decommissioned by 2000 Size 260m x 60m Regulatory approval for drum storage in 2001 Commissioned for drum storage March drums currently in store 7

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11 Waste Tracking System (WTS) Purpose: Record drum information & traceability in secure, centralised, multiuser database Unique barcode identify drums Typical info recorded: Content description; characteristics Drum size and type; origin and weight Drum position and movements recorded (store and XYZ address) Use of Barcode Reader 11

12 Drum Content Inspections To prevent incorrect and incomplete drum info in WTS Open drum in controlled area Record content and other drum info Take digital photo Update WTS 12

13 Drum Measurement IAEA unable to verify anomaly for 10 years July 2001 IAEA, approached DOE-NNSA to assist IAEA and SA in safeguards measurements Suitable device located at Oak Ridge Canberra IQ3 Loan arranged under the US/RSA agreement for co-operation on the Peaceful Uses of Nuclear Energy. End of 2001 system tested and found acceptable for quantifying SA waste Shipped in March 2002 and installed in April 13

14 IQ3 Description 3 planar and 3 coaxial HPGE detectors Ba transmission sources 15 cm thick steel counting chamber Planar detectors used to determine uranium enrichment Coaxial detectors used to quantify mass 2 matrix correction techniques Transmission Density 14

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16 Challenges Complex system Limited know-how at NECSA New persons with no experience for day to day operation Little local manufacturer support SA remoteness 16

17 Data Capture Started with interim program to capture: Assay type used Uranium results (mass and enrichment) Correction technique used Report number Additional info for later IAEA verification Integrated into WTS (with photos) Data for IAEA retrieved from this database using queries; combines IQ-3 results and WTS drum info 17

18 Routine Measurements Daily calibration verification (QA measurement) Auto mode where drum information is entered and drums are automatically loaded and unloaded Max of 18 drums measured after-hours (extended conveyor) Report not final answer, does need interpretation, checking, decision, and possible correction Procedure written and small program to assist in decision and possible re-analysis 18

19 IAEA Verification & Validation IAEA uses ISOCS system (Germanium Gamma Detector, spectrum analysis and specialised modelling to make waste form corrections) and independently measure. Basically same limitations and uncertainty ISOCS set up and validated using Necsa standards No further verification 19

20 Current status Since Nov 2002 a total of more than drums measured All HEU drums have been declared to IAEA Electronics and detectors have been upgraded recently 20

21 Way forward Reduction of inventory under safeguards Thousands of waste drums still to measure More difficult waste streams to be handled Challenges not enrichment any longer more difficult waste forms such as drums with dense spots here and there 21

22 BNFL Scanner Necsa also has a second scanner for waste characterization 3 Detectors and 3 Transmission sources to detrmine density of waste and corrections of measurements) In operation since early 2000s Drums scanned to date

23 Conclusion Obligations under NPT being addressed Measures in place for traceability and record keeping Improved safeguards Positive Statement in SIR 23

24 Thank You!!! 24