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Derivation of Accident Specific Material-at-Risk Equivalency Factors

Derivation of Accident Specific Material-at-Risk Equivalency Factors . Jason Andrus Chad Pope, PhD PE Idaho National Laboratory. Overview. Discussion of problem Proposed solution Mathematical derivation Applied e xample Discussion of ideal applications. Problem Statement.

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Derivation of Accident Specific Material-at-Risk Equivalency Factors

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  1. Derivation of Accident Specific Material-at-Risk Equivalency Factors Jason Andrus Chad Pope, PhD PE Idaho National Laboratory

  2. Overview • Discussion of problem • Proposed solution • Mathematical derivation • Applied example • Discussion of ideal applications

  3. Problem Statement • Need for New Method to Establish MAR Equivalency • Spectrum constraints • Material form relationships • Overly restrictive segmented limits

  4. Proposed Solution • Derive an equivalency method which provides: • Detailed accident comparisons • Process and technical flexibility • Coupling with near-real time tracking system

  5. Solution Methodology • Equate the Committed Effective Dose Equations to a reference material. • Determine a reference nuclide for dose consequence comparisons • Derive equivalency factors to relate different nuclides and accidents to the reference. • Benefits • Establish limits that operators understand • Effectively demonstrates relative hazards

  6. Mathematical Derivation (1/5) • CED Equation /Q= Plume dispersion (s/m3) BR = Breathing rate (m3/s) STi= Source term of nuclide i (Bq) DCFi = Dose conversion factor of nuclide i(Sv/Bq) DDFi = Fraction of nuclide iinplume after dry deposition (no units) N = Number of nuclides contributing to dose (no units)

  7. Mathematical Derivation (2/5) ST Equation ST = Source term (Bq) MAR = Material-at-risk (g) SA = Specific activity (Bq/g) DR = Damage ratio (no units) ARF = Airborne release fraction (no units) RF = Respirable fraction (no units) LPF = Leak path factor (no units)

  8. Mathematical Derivation (3/5) • Equate spectrum CED to reference CED

  9. Mathematical Derivation (4/5) • Cancel common terms and simplify

  10. Mathematical Derivation (5/5) • Equivalency Factor and dose calculation

  11. Applied Example (1/3) • Consider a simple example “psuedo-fuel” • 2 potential accidents drop or fire • Release values known, ASF calculated

  12. Applied Example (2/3) • Calculate Weighting Factors and Equivalency Factors

  13. Applied Example (3/3) • Risks from individual nuclides as well as accidents can be compared. • Single metric available for risk comparisons

  14. Discussion of Ideal Applications • Well characterized and consistent processes • Well tracked inventory • Multiple or varied material forms or similar accidents • Nuclide spectrums where important isotopes can be readily identified. • Comparison of different scenarios and material types that all roll up to one limit.

  15. Conclusion • New methodology for dose equivalency derived which allows comparison of different accidents. • Single metric for comparison of hazards of different accident events, nuclide spectra. • Permits establishment of general limits for events where multiple material forms may roll up into an integral consequence. (i.e. earthquake events)

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