Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session NF: Applications in Nuclear Physics |
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Chair: Robert Haight, Los Alamos National Laboratory Room: 104AB |
Saturday, October 29, 2011 10:30AM - 10:42AM |
NF.00001: Photonuclear Physics Applications for Isotopic Detection and Assay M.S. Johnson, J.M. Hall, D.P. McNabb, J.J. Gonzalez National security and international safeguards programs are interested in new technologies that utilize gamma-ray sources to detect special nuclear materials (SNM) and/or assay isotopes of interest in a variety of shielded configurations. There are many constraints and caveats that must be addressed such as fast scan times to avoid commercial backlogs. Other challenges include determining the total mass of minute traces of certain isotopes in thick, highly radioactive, nuclear fuel assemblies. This presentation will focus on a high-altitude view of how processes such as nuclear resonance fluorescence (NRF) and photo-fission can function in a variety of applications. We will present an overview of performance estimates for a wide-range of applications. We will also present results from recent validation measurements. [Preview Abstract] |
Saturday, October 29, 2011 10:42AM - 10:54AM |
NF.00002: NUCFRG3: Light ion improvements to the nuclear fragmentation model Anne Adamczyk, Ryan Norman, Sirikul Sriprisan, Lawrence Townsend, John Norbury, Steve Blattnig, Tony Slaba Light ion improvements to the nuclear fragmentation model NUCFRG are reported. Improvements include the replacement of the simple light ion production model with a light ion coalescence model and an improved electromagnetic dissociation (EMD) formalism. Prior versions of the model provide reasonable overall agreement with measured data; however, those versions lack a physics-based description for coalescence and EMD. The NUCFRG3 model has improved theoretical descriptions of these mechanisms and offers additional benefits. Previous work established the improved EMD formalism to be more accurate than the predecessor. The predictive capability of NUCFRG has been improved and strengthened by the light ion physics-based changes. Based on increased capability and better theoretical grounding of NUCFRG3, it is recommended that it replace NUCFRG2 for space radiation assessments and other applications. [Preview Abstract] |
Saturday, October 29, 2011 10:54AM - 11:06AM |
NF.00003: Neutron Capture and Fission Measurements on Actinides at DANCE Andrii Chyzh, Ching-Yen Wu, Elaine Kwan, Rodger Henderson, Julie Gostic, John Ullmann, Marian Jandel, Todd Bredeweg, Aaron Couture, Hye Young Lee, Robert Haight, John O'Donnell Neutron capture and fission measurements on actinides are important in nuclear engineering and physics. DANCE (Detector for Advanced Neutron Capture Measurement build at LANL) together with PPAC (avalanche technique based fission tagging detector designed and fabricated at LLNL) were used to measure the prompt $\gamma$-ray energy and multiplicity distributions in the spontaneous fission of $^{252}$Cf. These measured spectra together with the unfolded ones will be presented. The unfolding technique will be described. In addition the $^{238}$Pu$(n,\gamma)$ cross section will be presented, which was measured using DANCE alone and also is the first such measurement in a laboratory environment. [Preview Abstract] |
Saturday, October 29, 2011 11:06AM - 11:18AM |
NF.00004: Gamma-Ray Output Spectra from $^{239}$Pu Fission John Ullmann, Marian Jandel, Todd Bredeweg, Aaron Couture, Robert Haight, John O'Donnell, David Vieira, Ching-Yen Wu, Andrii Chyzh, Julie Gostic, Roger Henderson, Elaine Kwan A new measurement of the gamma-ray energy spectrum and multiplicity following neutron-induced fission of $^{239}$Pu has been made using DANCE, a highly-segmented, nearly 4$\pi $ BaF$_{2}$ array at the Los Alamos Neutron Science Center. The $^{239}$Pu target consisted of an approximately 2 mg/cm$^{2}$ deposit mounted in a small parallel-plate avalanche chamber inserted into the DANCE in order to tag fission events. The gamma-ray spectra were measured for several strong neutron resonances below 100 eV. The measured spectra were corrected for detector response by using simple parameterizations of the actual fission gamma-ray emission coupled with a GEANT model of the DANCE array. [Preview Abstract] |
Saturday, October 29, 2011 11:18AM - 11:30AM |
NF.00005: Prompt $\gamma$ rays and neutrons from fission E. Kwan, C.Y. Wu, A. Chyzh, J. Gostic, R. Henderson, R.C. Haight, H.Y. Lee, J.M. O'Donnell, B.A. Perdue, T.N. Taddeucci Nuclear data are needed to test the accuracy of calculations from nuclear reaction codes. Information on the prompt $\gamma$-ray distributions from fission is sparse and only a handful of published experiments data that measured the prompt $\gamma$-ray distribution above incident neutron energies of 1 MeV can be found. In addition, improvement on the accuracy and shape of neutron spectrum from the fission of actinides been requested by the nuclear data community\footnote{``Prompt Fission Neutron Spectra of Major Actinides,'' INDC(NDS)-0571, ed. R. Capote Noy, (2010).}. An investigation on the shapes of the neutron and $\gamma$-ray distributions from the spontaneous fission of $^{252}$Cf and the neutron-induced fission of $^{235}$U was undertaken using the Chi-Nu detector array at the Weapons Neutron Research Facility of the Los Alamos Neutron Science Center. Preliminary results will be presented. [Preview Abstract] |
Saturday, October 29, 2011 11:30AM - 11:42AM |
NF.00006: Surrogate measurements of the $^{241,242}$Am($n,f$) cross sections J.J. Ressler, J.T. Burke, J.E. Escher, A. Adekola, R.E.A. Austin, M.S. Basunia, C.W. Beausang, L.A. Bernstein, D. Bleuel, J. Gostic, R.H. Henderson, R.O. Hughes, A. Hurst, A. Kritcher, C.M. Mattoon, J. Munson, L.W. Phair, T. Ross, N.D. Scielzo, M.A. Stoyer New reactor designs and materials, reprocessing efforts, and transmutation of nuclear waste play significant roles in the future of nuclear energy. New or improved neutron measurements on a number of isotopes are needed to determine feasibility, effectiveness, and safety issues for the novel engineering efforts. Data collection is often hampered by the need for radioactive targets; the use of such targets is limited to longer-lived isotopes due to the large background induced by the decay of the material. However, cross sections for isotopes of interest can be obtained indirectly using light-ion reactions on long-lived neighbors. Decay from the compound state is assumed to be independent of the production reaction, allowing reactions with the neighboring isotopes to be used as a surrogate for the reaction of interest. Results from the neutron-induced fission cross sections of $^{241}$Am and $^{242}$Am, performed via surrogates $^{243}$Am($^{3}$He, $\alpha^{\prime} f$) and $^{243}$Am($^{3}$He, $^{3}$He$^{\prime} f$), respectively, will be shown. [Preview Abstract] |
Saturday, October 29, 2011 11:42AM - 11:54AM |
NF.00007: A Measurement of Neutron Polarization Asymmetries in Photofission of Actinides Using Polarized Gamma Rays at HI$\gamma$S J.M. Mueller, M.W. Ahmed, S.S. Henshaw, H.J. Karwowski, L. Myers, B.A. Perdue, S. Stave, J.R. Tompkins, H.R. Weller, B. Davis, D. Markoff Photofission of $^{235}U$, $^{238}U$, $^{232}Th$, and $^{239}Pu$ has been studied using 100\% linearly polarized, high intensity ($\sim 10^{7} \gamma/s$), and nearly-monoenergetic gamma-ray beams of energies between 5.6 and 7.0 MeV at the High Intensity Gamma-ray Source (HI$\gamma$S). An array of 18 liquid scintillating detectors was used to measure prompt fission neutron angular distributions. The ratio of prompt neutron yields parallel to the plane of beam polarization to those perpendicular to this plane was measured as a function of beam and neutron energies. A ratio close to unity was found for $^{235}U$ and $^{239}Pu$ while a significant ratio ($\sim 3$) was found for $^{238}U$ and $^{232}Th$ at a scattering angle of 90$^{\circ}$. A phenomenological model of near threshold photofission is being developed in an attempt to explain this large difference for these isotopes. A simulation, based on our model and using previous measurements of fission fragment angular distributions, is being used to interpret our experimental results. [Preview Abstract] |
Saturday, October 29, 2011 11:54AM - 12:06PM |
NF.00008: ABSTRACT WITHDRAWN |
Saturday, October 29, 2011 12:06PM - 12:18PM |
NF.00009: Observations of Fallout from the Fukushima Reactor Accident in San Francisco Bay Area Rainwater Eric Norman, Christopher Angell, Perry Chodash We observed fallout from the Fukushima Dai-ichi reactor accident in samples of rainwater collected in the San Francisco Bay area beginning approximately 1 week after the earthquake. Gamma ray spectra measured from these samples show clear evidence of fission products -- $^{131,132}$I, $^{132}$Te, and $^{134,137}$Cs. The activity levels we have measured for these isotopes are very low and pose no health risk to the public. Soon after the observation of fallout in rainwater, we also observed low levels of Fukushima fallout in plant and food specimens collected in the the San Francisco area. [Preview Abstract] |
Saturday, October 29, 2011 12:18PM - 12:30PM |
NF.00010: Nuclear Physics of DNA: Evidence for Mutations of Free DNA Nucleotides in Nuclear Inelastic Scattering with 14 MeV Neutrons and Applications Bogdan C. Maglich, Luz Marie Aquino, Chris Druey, Anna Z. Radovic First experimental study of interactions between \textit{nuclear} particles whose $\lambda _{DeBroglie} \quad \sim $ 10$^{-15}$ m and \textit{nano}particles (r $\sim $ 10$^{-9}$ m) of free DNA nucleotides is presented. Each collision knocks out 1 atom and creates mutated DNA or DNA breakup. Targets: dAdenosine (C$_{10}$O$_{6}$N$_{5}$H$_{13}$P), dCytodine (C$_{9}$O$_{7}$N$_{3}$H$_{14}$P) and dThymidine (C$_{10}$O$_{8}$N$_{2}$H$_{15}$), differing by 1 O or 1 C atom. We measured high-resolution prompt $\gamma $ spectra of $\sim $ 10$^{7}$ inelastic scatterings of 14 MeV n's: n+O $\rightarrow$ O+n'+ $\gamma $ (6.128 MeV) and n+C $\rightarrow$ C + n' + $\gamma $ (4.44 MeV). C or O ejection from 3 DNA's should manifest itself as 3 (2) $\gamma $ peaks corresponding to 6, 7, 8 O (9, 10 C). We observed 3 O $\gamma $ peaks containing 8,526$\pm $400, 10,495$\pm $ 402, 11,448 $\pm $405 each; and 2 C peaks, as expected; and decoded stoichiometry of 3 DNA's with 3-5 $\sigma $ in 30', signal/background $\sim $2{\%}. Applications of \textit{femto atometry} to genometrics, genetic engineering and noninvasive cancer diagnostics will be presented{\ldots} (maglich@calseco.com) [Preview Abstract] |
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