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Forensics in Nuclear Applications

Forensics in Nuclear Applications. Readings: Nuclear Forensics Analysis: Chapter 3 Engineering Issues Nuclear Forensics Analysis: Chapter 5 Principles of Nuclear Explosive Devices Glasstone : Effects of Nuclear Weapons Manipulation of natural radionuclides

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Forensics in Nuclear Applications

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  1. Forensics in Nuclear Applications • Readings: • Nuclear Forensics Analysis: Chapter 3 Engineering Issues • Nuclear Forensics Analysis: Chapter 5 Principles of Nuclear Explosive Devices • Glasstone: Effects of Nuclear Weapons • Manipulation of natural radionuclides • Enrichment (already covered) • Gas • Laser • Solution • General device overview • Single stage • Gun type • Implosion • Two stage • General signatures • Pu Chemistry & Forensics Applications

  2. Technical Mission Areas • Technical Mission Area 1 (TMA 1): In general, the NTNF community is interested in advancements in the analysis and characterization of nuclear and other radioactive materials. Of particular importance are innovations in the speed, accuracy, and precision of determining the physical, chemical, isotopic, micro-structural, and/or morphological properties of materials. Specifically in FY2013, the USG is primarily seeking significant developments in the quantification of micro-structural and morphological measurements of bulk uranium and plutonium materials in both oxide and metal forms. 2. Technical Mission Area 2 (TMA 2): Following the detonation of a nuclear device, solid debris samples to be analyzed are expected to contain trace-level quantities of nuclear materials combined with material from the immediate environment around the detonation site, which may have been activated and is assumed to have been vaporized and recondensed. As such, debris for dissolution is expected to have formed at high temperatures and contain silicates and other hard-to-dissolve materials. Solid fallout debris is typically in a glassy matrix containing parts per million (ppm) quantities of plutonium or uranium with radioactive fission products. Improvements are sought in the characterization and analysis of nuclear and non-nuclear constituents within these nuclear and post-detonation debris materials, including those present in trace quantities. 3. Technical Mission Area 3 (TMA 3): General studies that improve our understanding of how relevant stages of the nuclear fuel cycle create, persist, or modify discriminating material characteristics in the metal or oxide forms of uranium or plutonium. FY2013 activities should focus on identifying discriminating characteristics that help assess the process history and provenance of bulk uranium and plutonium materials produced in the enrichment, conversion to oxides, and conversion to metal stages of the fuel cycle, and developing simulations that predict material characteristics from parameterized processes.

  3. Plutonium isotopics • Pu formed in core or from blanket • U blanket may have a range of isotopic composition • Natural and anthropogenic • Pu formation from neutron capture on 238U • 239Pu becomes a target for higher isotope production • (n,g) up to 241Pu • Also some (n,2n) Emin =5.7 MeV • 238Pu from 239Pu

  4. Plutonium isotopics • 238Pu can also be produced through successive neutron capture on 235U • 235U(n,g)236U • 236U(n,g)237U • 237U beta decay to 237Np • 237Np(n,g)238Np • 238Np beta decay to 238Pu • Mixture of Puisotopics from fuel or blanket can act as a signature • 239Pu dominates at low burnups • Device Pu has 6 % 240Pu

  5. Plutonium isotopics • Neutron behavior and Puisotopics coupled • Puisotopics influence by neutron fluence and energy • neutron kinetic energy effected by reactor operating temperature • Moderator influence due to rate of moderation • Fuel size influences distance between neutron generation and moderator • Fuel composition can influence neutron spectrum • Depletion of neutron in 235U resonance region

  6. Plutonium isotopics • Fluence influence • 240Pu production • Capture on 239Np produces 240Np, which decays into 240Pu • Competition between capture and decay

  7. Plutonium Isotopics • Evaluate ratios with 240Pu • Mass 240:239 (MS) • Activity 238/(239+240) (alpha spectroscopy) • Varied reactor types, 37.5 MW/ton • Large Pu isotopic variation • Obvious variation for blanket and CANDU

  8. Plutonium Isotopics • Comparison to 239Pu concentration • Can provide time since discharge • 241Pu is time sensitive • Change in measure and expect ratio can be used to determine time since discharge

  9. Device general information • Designed to have highest possible k (neutron multiplication factor) • Greatest increase of neutrons and fission from one generation to the next • Cooling from explosion • k goes to zero • Need to complete reaction in short time • Designs maximized neutron interaction with fissile material • Generation time • Average time between neutron release and capture • Neutron energy 1 MeV • 10 n sec per generation • Shake • 50 to 60 shakes to produce 1 kt of fission yield • About 0.5 microseconds • Energy generation exponential • Most energy from last few generations • 30 nsec extra increases yield by order of magnitude

  10. Device general information • Fast neutron reflection important for device • Better use of neutrons, lower critical mass • Reflector material high density • Also slows down material expansion (tamper) • Critical mass • Shape • Composition • Density • Reflection • Minimization of non-fissile isotopes

  11. Device general information • Fission spectrum neutrons drive the n,f reaction • Cross sections for fast neutrons orders of magnitude lower than thermal reactions • n, gamma reaction for non-fissile isotopes also lower, but one order of magnitude • Limiting non-fissile isotopes results in material signatures • Less than 7 % 240Pu • More than 20 % 235U • Low 232U in 233U (10 ppm)

  12. Device general information • Low Z material in Pu • React with neutrons • Lowers density • Moderates neutrons • Used as signature • Pu device isotopes in non-metal form indicates storage or starting material • Alloys • Ga in Pu • Nb in U • Fabrication ease and corrosion resistance

  13. Device general information • Shape • Large surface to mass inhibits k>1 • Sphere minimizes surface area to mass • Compression and reflector increases k • Subcritical configuration in storage • Need to consider stray neutrons • Environment • SF from even-even actinides • Supercritical configuration • Addition of neutrons

  14. Device general information • Two methods for formation of supercritical mass • Bring together 2 or more subcritical segments • Gun assembly (Little Boy) • Implosion • Subcritical amount surrounded by explosive • Creates supercritical mass

  15. Gun-Assembly • Explosive pushes subcritical components together in a gun barrel • Neutrons from an external source • Formation of Be-alpha source (210Po) • Initiator • Can only be used with U • 10 kg, low SF rate • 6 % 240Pu, 2.5 SF in 10 microseconds • Fizzle (premature initiation)

  16. Gun Assembly and Implosion • Appropriate for 233U material • 234U has SF half life of 2E16 years • Implosion • Spherical arrangement of high explosive • Detonated externally, fired simultaneously • Spherical fissile material in center of explosive • Compression decreases neutron mean free path • Introduction of external neutrons • Fat Man device • Pu very close to k=1 • Need to limit even A in Pu • Presence of explosive with fissile material can be signature

  17. Boosting • Fusion • Small neutron multiplicity • Cannot sustain reaction • Fusion can be driven by high temperatures and pressures • Fusion has high energy neutrons • Boosting is the introduction of high energy neutrons in late stage of device • Fission used to drive fusion • Reaction of tritium and deuterium • 2H+2H3He +n+3.2 MeV • 2H+2H3H + 1H +4.0 MeV • 2H+3H4He +n + 17.6 MeV (greatest probability) • 3H+3H4He +2n+11.3 MeV

  18. Boosting • High energy neutrons result in more neutrons per fission • 235U • thermal neutrons, 2.4 neutrons per fission • Fission spectrum neutrons, 2.55 n/fission • 14 MeV neutrons, 4.2 n/fission • Even-even fission also occurs • Fat Man with Pu shell filled with D-T • Gas compression, slows Pu implosion • Ignites D-T reaction • Results in 14 MeV neutrons, increase reaction in Pu • Main effect of boost is to increase fission in surrounding material • To prevent hydride formation need to have hydrogen gas only at detonation • Tritium with fissile material can be signatures

  19. Boosted implosion device

  20. Two stage device • Hydrogen bomb • Radiation from primary fission bomb compresses a secondary section containing both fission and fusion fuel • compressed secondary heated from within by a second fission explosion • MIKE device used liquid D2 • Needs coolant • Later devices used 6LiD • 6Li + n4He + 3H + 4.8 MeV

  21. Two-stage device

  22. Post-detonation analysis • Debris provides information on • Function • Source • Efficiency of yield from fuel and fission products • High efficiency indicates sophisticated device • Also with multiple fissile material and (n,2n) reactions • Indication of initial isotopic compositions • Neutron energy influences fission product distribution • Also varies with nuclear fuel • Neutron reactions with device material

  23. Pu Chemistry & Forensics Applications • Pu Oxidations States in various Acids • Visible transitions based on oxidation state and ligand coordination http://dwarmstr.blogspot.com/2005/11/united-colors-of-plutonium.html

  24. Pu Chemistry & Forensics Applications 32 Fractions 1 a. 10 M HCl b. 1.5 M Sulfamic acid 1.5 M Ascorbic acid 3.5 M NaNO3 PuF3(s) Pu(III & IV)(aq) 1. a, b 2. 3. White ppt (PuF4 & PuCl4) Evaporation 30% H2O2 Δ 80 °C Evaporation Pu(organics?) Pu(O2)2

  25. Pu Chemistry & Forensics Applications • Separation of Am-241 from Pu solution • TEVA Resin • Obtain pure Pu(VI) solution • Any desired Puppt • Forensics Interest • PuF4 • PuF3 • Pu(OH)4 • Pu(OH)4 + ZrF4 • Utilize Pu alpha decay • 19F (α, n) 22Na

  26. Trinitite and the Speciation of Melt Glass for Nuclear Forensics Wes Boyd, Ken Czerwinski, Ralf Sudowe Chemical and Radiological Properties of Trinitite http://en.wikipedia.org/wiki/Trinitite http://en.wikipedia.org/wiki/Trinitite

  27. Trinitite http://www.allpar.com/history/military/a-bomb.html • Gadget device July 16, 1945 • Glassy substance left behind after the Trinity Shot • Broadly applied • Bulldozed and buried by the AEC in 1952 http://jaybarrymore.com/TrinitySite.aspx

  28. Formation of Trinitite • 3.1 s • 4.2kT • Sand on ground heated • Theory proposed in 2005 by Hermes1 • 13.5 kT • 8430 K http://www.omega-level.net/2011/12/12/first-millisecond-of-a-nuclear-explosion-is-the-becoming-of-death/ http://rceezwhatsup.blogspot.com/2011/04/every-nuclear-explosion-since-1945.html

  29. Physical/Chemical Properties • Not a lot available in the public domain • Ross2 reported an index of refraction of ~1.52 • Other areas were 1.46 indicating silica glass • Blast was at least 1470oC • Microprobe analysis Scheffer3 Scheffer3

  30. Trinitite Obtained from MRC

  31. Physical/Chemical Properties

  32. Physical/Chemical Properties • Elemental Composition • O, Si, Na, Mg, Al, S, K, Ca, Ti, Fe • Chemical Composition4 • SiO2, TiO2, Al2O3, FeO, MnO, CaO, MgO, K2O, Na2O Eby et al4

  33. Radiological Properties • Sample • One gram • Finely ground • Filter geometry • Counted on a 40% coaxial HPGe • Counted for twenty hours

  34. Radiological Properties Pittauerova, et al5

  35. Alpha Spectroscopy • Prepare the sample • Not as good resolution as gamma spectroscopy • Alpha energies overlap • Chemical separation • Requires determining chemical yield

  36. Plutonium Alpha Spectra

  37. Identified Radionuclides • * - Indicates sample was from the French test in Algeria. † - Indicates sample was obtained from Semipalatinsk in Russia. ‡ - Indicates analysis was not done. ND - Non-Detect Data for this table was compiled by Pittaurova et al5

  38. Radiological Properties Pittaurova et al5

  39. Abnormalities Fahey and Newbury6 cited abnormalities Zircon rich material near unmelted quartz Whisker of titanium melt Inclusion of other elements (Y, Ba, etc.) What can we learn from these abnormalities? http://www.kilroywashere.org/04-Images/Trinity/J-JumboUnderTower1945.jpg

  40. Methods: Computer Tomography High Z actinide from low Z matrix 0.6 mm Locate Pu hot particle in sediment

  41. Signatures in uranium oxides • Process signatures defined • Research approach and example results • Powders • Pellets • Other features on commercial pellets • Conclusions

  42. Process signatures visualized • 3 production methods, 3 different morphologies • All UO2 samples • How can these differences be explained by the process chemistry?

  43. Process signatures visualized • 3 manufacturers, 3 significantly varied grain structures • All reactor grade uranium dioxide • What accounts for these differences and how can they be quantified?

  44. Process signatures conceptualized • What characteristics continue through the process that can elucidate how the uranium oxide was produced? • Combine this knowledge with other information (e.g., known users of a certain process) to refine the forensic assessment (attribute or eliminate) Interdicted pellet Precursor oxide Precipitate

  45. Research Approach • Develop a methodology to quantitatively compare morphological features in uranium oxide powders and pellets • Utilize scanning electron microscopy and surface area analysis • Synthesize and examine the morphology of various uranium oxides and pellets • Compare with commercially produced materials that have known process histories • Examine commercially produced UO2 fuel pellets for other potential process signatures • Verify the origin of observed features with pellets fabricated in the laboratory

  46. Identify and synthesize relevant derivations of uranium oxides • Precipitants from uranium ore concentration processes • Ammonia gas/ammonium hydroxide • Hydrogen peroxide • Sodium hydroxide, potassium hydroxide • Magnesia • Precipitants from purification or recycling processes • Ammonia gas/ammonium hydroxide • Ammonium carbonate • Hydrogen peroxide • Calcined forms of other process intermediates • Uranyl nitrate • Uranium tetrafluoride • Uranium metal

  47. Powder and pellet synthesis 4. UO2 milled and blended with additives (as required) 2. Separated & dried 3. Powder calcined and reduced 1. Uranium precipitated diameter = 6mm 6. Compacts sintered under H2 at ~1700 °C 7. Pellet examined 5. Powder pressed into green compacts

  48. Collecting reference powder imagery • Systematic synthesis and characterization of oxide products

  49. Leveraging Commercial Powders Typical agglomerate scale bar= 5 μm Typical microstructure scale bar= 5 μm Uranium ore concentrate (as U3O8) from the Rössing Facility in Swakopmund, Namibia. Literature indicates gaseous ammonia was utilized as the precipitation agent. Reference U3O8 powder derived from ammonium hydroxide precipitation. Aids in determining the veracity of signatures observed in laboratory samples

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