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Implementation Concepts for Unattended Measurement Systems at Enrichment Plants

Implementation Concepts for Unattended Measurement Systems at Enrichment Plants. L. Eric Smith, Alain Lebrun IAEA January 2012. IAEA’s “Model Approach for GCEPs”. High-capacity plants pose implementation challenges for c urrent approaches. Safeguards objectives: Timely detection of…

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Implementation Concepts for Unattended Measurement Systems at Enrichment Plants

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  1. Implementation Concepts for Unattended Measurement Systems at Enrichment Plants L. Eric Smith, Alain Lebrun IAEA January 2012

  2. IAEA’s “Model Approach for GCEPs” High-capacity plants pose implementation challenges for current approaches. Safeguards objectives: Timely detection of… • Diversion from declared input and output • Undeclared (excess) production of normal enrichment levels • Higher-than-declared enrichment (e.g. HEU) Implementation objectives • Reduce need for routine measurements, sampling during inspections* • Ease and expedite cylinder release process for facility operators How might unattended measurement systems contribute? *Related work by Boyer, et al. (IAEA Symposium 2010)

  3. Potential Roles: Unattended Measurement Systems Process MBA Storage MBA Load-cell monitoring Online Enrichment Monitor (OLEM) M(t) for each cylinder High-accuracy E(t) for each cylinder Continuous gas monitoring Ecyl = E(t)*M(t) Unattended Cyl. Verification Station (UCVS) High-accuracy net mass “NDA Seal” for CoK on cylinder contents Assay of blended cylinders MU M235 = Ecyl* MU

  4. Concept: Load-Cell Monitoring tstart tend M(t)

  5. Concept: On-Line Enrichment Monitor E(t) ∝Rgas_186keV (t)* rgas(P, T, t) OLEM Cascade 1 CEMO Pressure Temperature NaI(Tl) Cylinder Cascade 2 Cascade 3 P ~ 40 Torr Load Cell Cascade 4 Gas Sampling Header Pump M(t) P ~ 4 Torr UF6 Header Pipe Mass Spec Analysis • High-accuracy E(t) for product and tails • Continuous monitoring of gas

  6. OLEM Viability Studies: Examples Statistical uncertainty only--systematic uncertainties are not addressed.** Low P: 10 Torr High P: 50 Torr Low D: 100 mg/cm2 High D: 1000 mg/cm2 Performance Targets Tails: sT< 3% Feed: sF< 2% Product: sP< 1% **Plot from Smith and Lebrun (IEEE Nuclear Science Symposium, 2011) Related work by Ianakiev (ESARDA 2010) and March-Leuba (personal communication, 2012)

  7. Concept: Unattended Cylinder Verification Station • Apply and verify “NDA Seal” at MBA boundaries (CoK) • Unattended NDA of M235 for blended cylinders • Recovery of CoK on cylinders • Platform for weight, NDA verification during inspections Mass: Shared-use or IAEA scale NDA**: Hybrid (PNNL), PNEM (LANL), other? Cylinder ID: L2IS, Global Bar Code, other? Surveillance: NGSS **from Smith (INMM 2010) **Related Work Smith (IEEE TNS 2010, INMM 2010), McDonald (INMM 2011) Miller (ESARDA 2011)

  8. UCVS Viability Studies: Example“Hybrid NDA” for 235U Assay (30B cylinders) Intl. Target Value:sP~ 5% Hybrid NDA (preliminary) sP~ 2.5% sF~ ?? sT~ ?? Other NDA methods? NDA Seal? sP= 2.5% 8 **Plot from Smith et al. (INMM 2010)

  9. UMS Implementation Concepts “Special” treatment of feed • Challenges • Largest 235U flow rate • Poor assay accuracy (OLEM wall-deposit issues, UCVS > 6%) • Advantages (assuming natural feed) • Isotopics are precisely known • Cylinders should be homogeneous Baseline Concept • No quantitative assay of feed  assume Ecyl= 0.711%  sF ~ 0.0%...if • UCVS verifies that Ecyl_UCVSis consistent with feed-cylinder profile • OLEM only on product and tails header pipes • UCVS quantitative NDA on blended product cylinders

  10. Implementation Concepts: Viability Analysis Overview Scenario: Diversion into MUF or D • 235U bias defect in product and tail cylinders • SQ = 75 kg 235U (LEU, NU, DU) Viability Metric: Fidelity of 235U mass balance (“IMUF”) • Assume no waste, scrap, etc. • IMUF = F – (P + T) • sMUF2 = sF2 + sP2 + sT2 • Threshold = 3*sMUF • PD for 1SQ diversion? PD **from C. Norman, IAEA

  11. Implementation Concepts: Viability Analysis Reference Facility: 4,000,000 SWU/year, 0.711%, 3.0%, 0.25% Analysis variables: OLEM s ,UCVS sP, blend fraction, balance period Balance Period = 1 month = Baseline Concept

  12. Implementation Concepts: Viability Analysis Balance Period = 1 week

  13. Conclusions • High-capacity plants require new instruments and approaches • Integrated UMS: “Independent” 235U and U balances on 100% flow • NDA Seal for cylinder CoK • Special treatment of feed • PD values (scoping) for protracted diversion are encouraging • UMS Role: Rule out protracted diversion between inspections • Machines do routine measurements • Inspectors do what humans do best (investigate) • Many questions and issues ahead…for example • Relevance for diversion and excess production scenarios • Realistic OLEM and UCVS uncertainties • Data security for shared-use instruments • Operator impacts, acceptability

  14. Additional Information

  15. Potential Impacts to Operators

  16. Material Flow and Data Streams Unblended Product and Tails Cylinders Storage MBA Process MBA UCVS Load Cell OLEM Load Cell: M(t) OLEM: E(t) Ecyl_OLEM= E(t)*M(t) Ecyl_OLEM: sP < 1%, sT< 3% NDA Seal Scale: Mempty , Mfull , sM< 0.1% M235_OLEM = Ecyl_OLEM * MU M235_OLEM : sP < 1%, sT < 3% Facility-Level Data: MU , M235_OLEM , NDA Seal

  17. Material Flow and Data Streams Feed Cylinders Storage MBA Process MBA UCVS Load Cell Load Cell: M(t) Ecyl= known = 0.711% Ecyl: sF ~ 0.0% NDA Seal: “nominal” feed? Scale: Mempty , Mfull , sM < 0.1% M235 = Ecyl* MU M235 : sF ~ 0.1% Facility-Level Data: MU , M235 , NDA Seal

  18. Material Flow and Data Streams Blended Product Cylinders Storage MBA Process MBA UCVS Blending Station Quantitative NDA of Ecyl_UCVS: sP~ 3 - 6% NDA Seal Scale: Mempty , Mfull , sM < 0.1% M235_UCVS = Ecyl_UCVS* MU M235_UCVS : sP ~ 3 - 6% Facility-Level Data: MU , M235_UCVS , NDA Seal

  19. Implementation Concepts: Viability Analysis Balance Period = 2 weeks

  20. UCVS Technical Objectives • Quantitative assay of cylinder enrichment  M235 in each cylinder • Measurement scenario: Single measurement of many different cylinders • Key metric: Absolute accuracy for quantification of M235 • Preliminary accuracy targets: sP< 3%, sF< 6%, sT< 9% for M235 • Full-volume interrogation (i.e. sensitive partial defect detection) • Unattended operation • NDA Seal  Continuity of knowledge on cylinder contents • Measurement scenario: Repeated measurements on a single cylinder • Key metric: Reproducibility of key signatures and attributes • Candidate attributes: E, MU, 234/235, 232/235, 235 spatial distribution • Preliminary uncertainty targets: TBD, but likely < 0.5% • Full-volume interrogation (i.e. sensitive partial defect detection) • Unattended operation The NDA Seal is a recent addition to the potential roles of the UCVS. The concept requires a viability assessment based on measurements and modeling.

  21. “NDA Seal” Collection of distinguishing signatures and attributes that can be used to provide and recover CoK of the cylinder contents. Reproducibility of these attributes is the key metric.

  22. UCVS: Signatures and Attributes For 235U NDA and NDA Seal Traditional 186-keV g U-235 concentration in outer UF6 Directmeasure of U-235, but weakly penetrating Array of spectrometers  axial distribution of U-235 Induced-fission neutrons  U-235 Directmeasure of U-235 For thermal interrogating neutrons, only outer layer of UF6 Neutrons from F-19 (a, n)  U-234 U-234 is primary a emitter Neutron escape: ~0.80  full-volume Indirectmeasure of U-235 Indicator of feed type Neutron-induced g  U-234 Iron as n  g converter Fe-56 + n  Fe-57 + g (7.63,7.65 MeV) Indirect neutron detection 2614-keV g U-232 “flag” Presence of U-232  reactor recycle feed

  23. Performance Metrics for Quantitative Assay ~ ssys_cal sstat ~ ssys_ran Assay Enrichment (%) sNDA2= sstat2 + ssys_cal2 + ssys_ran2 Declared Enrichment (%) Prediction: ssys_cal > sstat and ssys_ran 23

  24. Performance Metrics for NDA Seal ~ ssys_ran Attribute sseal2= sstat2 + ssys_ran2 Number of Measurements on Same Cylinder Prediction: ssys_ran can be small, so must minimize sstat 24

  25. OLEM Uncertainty Budget Product Material OLEM target for sE *From Smith and Lebrun, IEEE Nuclear Science Symposium, 2011

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