Presentation on theme: "IAEA International Atomic Energy Agency Implementation Concepts for Unattended Measurement Systems at Enrichment Plants L. Eric Smith, Alain Lebrun IAEA."— Presentation transcript:
IAEA International Atomic Energy Agency Implementation Concepts for Unattended Measurement Systems at Enrichment Plants L. Eric Smith, Alain Lebrun IAEA January 2012
IAEA 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 IAEA’s “Model Approach for GCEPs” How might unattended measurement systems contribute? *Related work by Boyer, et al. (IAEA Symposium 2010) High-capacity plants pose implementation challenges for current approaches.
IAEA Potential Roles: Unattended Measurement Systems Storage MBA Load-cell monitoring Online Enrichment Monitor (OLEM) M(t) for each cylinder High-accuracy E(t) for each cylinder Continuous gas monitoring E cyl = E(t)*M(t) Process MBA Unattended Cyl. Verification Station (UCVS) High-accuracy net mass “NDA Seal” for CoK on cylinder contents Assay of blended cylinders M U M 235 = E cyl * M U
IAEA Concept: Load-Cell Monitoring t start t end M(t)
IAEA Concept: On-Line Enrichment Monitor P ~ 4 Torr E(t) ∝ R gas_186keV (t) * gas (P, T, t) NaI(Tl) CEMO Header Pump 1)High-accuracy E(t) for product and tails 2)Continuous monitoring of gas Cascade 1 Cascade 2 Cascade 3 Cascade 4 P ~ 40 Torr Gas Sampling Load Cell UF 6 Header Pipe Pressure Temperature Mass Spec Analysis Cylinder OLEM M(t)
IAEA OLEM Viability Studies: Examples Low P: 10 Torr High P: 50 Torr Low D: 100 g/cm 2 High D: 1000 g/cm 2 Statistical uncertainty only--systematic uncertainties are not addressed.** **Plot from Smith and Lebrun (IEEE Nuclear Science Symposium, 2011) Related work by Ianakiev (ESARDA 2010) and March-Leuba (personal communication, 2012) Performance Targets Tails: T < 3% Feed: F < 2% Product: P < 1%
IAEA Concept: Unattended Cylinder Verification Station 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) 1)Apply and verify “NDA Seal” at MBA boundaries (CoK) 2)Unattended NDA of M 235 for blended cylinders 3)Recovery of CoK on cylinders 4)Platform for weight, NDA verification during inspections **Related Work Smith (IEEE TNS 2010, INMM 2010), McDonald (INMM 2011) Miller (ESARDA 2011)
IAEA UCVS Viability Studies: Example “Hybrid NDA” for 235 U Assay (30B cylinders) 8 P = 2.5% **Plot from Smith et al. (INMM 2010) Intl. Target Value: P ~ 5% Hybrid NDA (preliminary) P ~ 2.5% F ~ ?? T ~ ?? Other NDA methods? NDA Seal?
IAEA “Special” treatment of feed Challenges Largest 235 U 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 E cyl = 0.711% F ~ 0.0%...if UCVS verifies that E cyl_UCVS is consistent with feed-cylinder profile OLEM only on product and tails header pipes UCVS quantitative NDA on blended product cylinders UMS Implementation Concepts
IAEA Scenario: Diversion into MUF or D 235 U bias defect in product and tail cylinders SQ = 75 kg 235 U (LEU, NU, DU) Viability Metric: Fidelity of 235 U mass balance (“IMUF”) Assume no waste, scrap, etc. IMUF = F – (P + T) MUF 2 = F 2 + P 2 + T 2 Threshold = 3* MUF PD for 1SQ diversion? Implementation Concepts: Viability Analysis Overview **from C. Norman, IAEA PD
IAEA High-capacity plants require new instruments and approaches Integrated UMS: “Independent” 235 U 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 Conclusions
IAEA Additional Information
IAEA Potential Impacts to Operators Potential Impact Eased and expedited cylinder release process Reduced physical presence of inspectors Reduced sampling requirements on cylinders Cylinder tracking infrastructure OLEM for process control and criticality control Load-cell (and accountancy scale?) data sharing OLEM nodes installed on header pipes (2 per unit); additional P gauges UCVS installation(s) UCVS scans on cylinders moving in/out of MBAs
IAEA Material Flow and Data Streams Load Cell: M(t) OLEM: E(t) E cyl_OLEM = E(t)*M(t) E cyl_OLEM : P < 1%, T < 3% Process MBA NDA Seal Scale: M empty, M full, M < 0.1% M 235_OLEM = E cyl_OLEM * M U M 235_OLEM : P < 1%, T < 3% OLEM Load Cell UCVS Storage MBA Facility-Level Data: M U, M 235_OLEM, NDA Seal Unblended Product and Tails Cylinders
IAEA Material Flow and Data Streams Load Cell: M(t) E cyl = known = 0.711% E cyl : F ~ 0.0% Process MBA NDA Seal: “nominal” feed? Scale: M empty, M full, M < 0.1% M 235 = E cyl * M U M 235 : F ~ 0.1% Load Cell UCVS Storage MBA Facility-Level Data: M U, M 235, NDA Seal Feed Cylinders
IAEA Material Flow and Data Streams Process MBA Quantitative NDA of E cyl_UCVS : P ~ 3 - 6% NDA Seal Scale: M empty, M full, M < 0.1% M 235_UCVS = E cyl_UCVS * M U M 235_UCVS : P ~ 3 - 6% Blending Station UCVS Storage MBA Facility-Level Data: M U, M 235_UCVS, NDA Seal Blended Product Cylinders
IAEA Quantitative assay of cylinder enrichment M 235 in each cylinder Measurement scenario: Single measurement of many different cylinders Key metric: Absolute accuracy for quantification of M 235 Preliminary accuracy targets: P < 3%, F < 6%, T < 9% for M 235 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, M U, 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 UCVS Technical Objectives 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.
IAEA “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.
IAEA UCVS: Signatures and Attributes For 235 U NDA and NDA Seal Neutrons from F-19 ( , n) U-234 U-234 is primary emitter Neutron escape: ~0.80 full-volume Indirect measure of U-235 Indicator of feed type Traditional 186-keV U-235 concentration in outer UF 6 Direct measure of U-235, but weakly penetrating Array of spectrometers axial distribution of U-235 Neutron-induced U-234 Iron as n converter Fe-56 + n Fe-57 + (7.63,7.65 MeV) Indirect neutron detection 2614-keV U-232 “flag” Presence of U-232 reactor recycle feed Induced-fission neutrons U-235 Direct measure of U-235 For thermal interrogating neutrons, only outer layer of UF 6
IAEA Performance Metrics for Quantitative Assay 23 NDA 2 = stat 2 + sys_cal 2 + sys_ran 2 Declared Enrichment (%) Assay Enrichment (%) stat sys_cal Prediction: sys_cal > stat and sys_ran sys_ran
IAEA Performance Metrics for NDA Seal 24 seal 2 = stat 2 + sys_ran 2 Number of Measurements on Same Cylinder Attribute sys_ran Prediction: sys_ran can be small, so must minimize stat
IAEA OLEM Uncertainty Budget Product Material OLEM target for E *From Smith and Lebrun, IEEE Nuclear Science Symposium, 2011