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Using Nuclear Resonance Fluorescence to Isotopically Map Containers

This work, conducted under the U.S. Department of Energy by Lawrence Livermore National Laboratory, explores the application of Nuclear Resonance Fluorescence (NRF) technology for isotopic mapping of materials within containers. The study outlines methods for detecting isotopes such as 239Pu, 235U, and 237Np using NRF techniques. Key advancements include the development of the FINDER system for transmission detection, demonstrating the feasibility of NRF measurements, and discussing various applications in contraband detection, safeguards, and fuel assay. Future measurements are planned to enhance isotopic sensitivity and detection capabilities.

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Using Nuclear Resonance Fluorescence to Isotopically Map Containers

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  1. Using Nuclear Resonance Fluorescence to Isotopically Map Containers Micah S Johnson, D.P. McNabb This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  2. Outline • Motivation for isotopic mapping • Nuclear Resonance Fluorescence • NRF scanning technologies • FINDER - transmission detection • Feasibility test at Duke • NRF measurements on Pu • Future NRF measurements

  3. Current systems: radiography

  4. Limitation: density silhouette

  5. NRF  isotopic sensitivity

  6. Programmatic Needs • Applications of NRF detection technology • Contraband detection • Safeguards • Fuel assay • Waste assay • Examples of some materials that may be of interest • 239Pu, 235U, 233U, 237Np • NRF scanning technologies will detect: • Presence of materials • Amount of material

  7. AZ AZ Nuclear Resonance Fluorescence (NRF) • An energetic photon (-ray) at a resonant energy of a particular isotope can excite that isotope. • The excited nucleus then will decay by emitting a set of -rays • Dipole excitations (e.g. scissors mode) Level sensitive to -ray excitations -ray or

  8. Proposed NRF scanning methods • Reflective • Detectors are arranged at back-angles relative to the -ray source and facing the container • Directly detect NRF scatter from within the container • Positive result occurs when the detected NRF photon is identified with a material of interest • Transmissive • Witness foil is placed on the opposite side of the container relative to the -ray source • Detectors are at back-angles focused on the foil • Positive result occurs when no NRF scatter is detected from foil Each has its own advantages and disadvantages

  9. Schematics of proposed NRF scan techniques Container Reflection: Transmission: Detectors -ray source Witness Foil Transmission: scatter occurs in container OR from witness foil

  10. Transmission technique Container Witness Foil -ray source If material is present then the incident spectrum obtains a notch

  11. Transmission technique Container Pass: Fail: Witness Foil -ray source Scatter from witness foil exposes NRF lines OR not

  12. LLNL concept: FINDER FINDER has quantifiably low false positive and false negative rates -- concept details are published: Pruet et al., J. Appl. Phys. 99, 123102 (2006).

  13. FINDER Demo: setup at HIgS Recent feasibility test at Duke University’s FEL with HIgS Detectors Cargo: W and/or DU Witness Foil: DU HIgS -ray source Flux Monitor NRF scatter for DU occurs in cargo area OR from witness foil

  14. HIgS

  15. FINDER Demo: cargo area Cargo

  16. FINDER Demo: witness foil

  17. FINDER Demo: flux monitor

  18. FINDER Demo: HIgS results Gated spectra:

  19. FINDER Demo: HIgS results (continued) • Different cargo configurations listed on left. Raw counts and counts normalized to fluence in the dominant peak at 2176 keV are shown. • Results are consistent with no notch refilling • More statistics are needed.

  20. Pu measurements at HVRL at MIT The FINDER/NRF technique seems to work (with additional study required). Therefore, we need to identify NRF states in different materials, e.g. Pu, U, etc… *This effort can be done in parallel to fine-tuning of FINDER.

  21. Pu target: Pu Mass: 3.8-grams Diameter: 1.4-cm Thickness: 1.5-mm Nitronic-40 holder: 25-g (63%Fe, 21%Cr, 6%Ni, 9%Mn) We used 2 of these lollipops for 7.5 g of Pu

  22. Experimental Setup: (Passport) Radiator: 102-m Au on 1-cm Cu (cooling and e- cleanup) e-beam

  23. Experimental End Station Collimator/Radiator NRF target HPGe X-ray Imager

  24. Previous NRF measurements NRF measurement on Pu at MIT with bremsstrahlung source

  25. Ex E= Ex E= Ex-7.9 7.9-keV 0.0 GS NRF results for 239Pu Transition Energy Sigma Cross-section (eV barns) Systematics imply these resonances are magnetic dipole

  26. Higher lying resonances? • Systematics of actinides and rare-earths indicate that magnetic dipole strength is closer to 3 MeV • Sensitivity region for HVRL measurement is less than 2.5 MeV • Will perform NRF measurements at UCSB • Electron accelerator maximum ~ 6 MeV • For average strengths: • Sensitivity range is 500 keV below endpoint • Sensitivity range is 500 keV wide

  27. Status of UCSB work • Passport has completed upgrade to their end-station at UCSB that includes 7 HPGe detectors • Collaborating with UC Berkeley, Rick Norman. • Try to get 56Co source to measure absolute efficiency. • Subcontract with Passport Systems is in place • Pu target (3 grams) at UCSB August Measurements

  28. HPGe Detectors X-ray Imager Photon Beam NRF Target Bremsstrahlung Source UCSB setup

  29. Future work • Future measurements at HIgS: • Pu and U isotopes • 237Np and 241Am • Will be able to extract M1 versus E1 • Pending funds from DOE

  30. Summary • NRF measurements have been performed on 239Pu and 13 new (~dipole) levels have been discovered in 239Pu < 2.5 MeV • Measurements on 239Pu will be performed in August at UCSB to search for resonances > 2.5 MeV • Feasibility test of the NRF technique to scan containers has been performed at Duke • Future measurements of NRF states will be performed at Duke pending DOE funding

  31. Collaboration • M.S. Johnson, D.P. McNabb, C.A. Hagmann, E.B. Norman, LLNL • W. Bertozzi, S.E. Korbly, R.J. Ledoux, W.H. Park, Passport Systems Inc. • Facilities at UCSB and HVRL/MIT

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