Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session HB: Mini-Symposium: Nuclear Physics Research and Connections to Nuclear Energy II |
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Chair: Alice Mignerey, University of Maryland Room: Room 208 |
Saturday, October 25, 2008 2:00PM - 2:36PM |
HB.00001: Neutron Cross Section Covariances: Recent Workshop and Advanced Reactor Systems Invited Speaker: The recent Workshop on Neutron Cross Section Covariances, organized by BNL and attended by more than 50 scientists, responded to demands of many user groups, including advanced reactor systems, for uncertainty and correlation information. These demands can be explained by considerable progress in advanced neutronics simulation that probe covariances and their impact on design and operational margins of nuclear systems. The Workshop addressed evaluation methodology, recent evaluations as well as user's perspective, marking era of revival of covariance development that started some two years ago. We illustrate urgent demand for covariances in the case of advanced reactor systems, including fast actinide burner under GNEP, new generation of power reactors, Gen-IV, and reactors under AFCI. A common feature of many of these systems is presence of large amount of minor actinides and fission products that require improved nuclear data. Advanced simulation codes rely on quality input, to be obtained by adjusting the data library, such as the new ENDF/B-VII.0, by considering integral experiments as currently pursued by GNEP. To this end the nuclear data community is developing covariances for formidable amount of 112 materials (isotopes). [Preview Abstract] |
Saturday, October 25, 2008 2:36PM - 2:48PM |
HB.00002: Nuclear reaction modeling for energy applications Toshihiko Kawano, Patrick Talou We discuss how nuclear reaction theories are utilized in the nuclear energy applications. The neutron-induced compound nuclear reactions, which take place from in the sub-eV energy range up to tens of MeV, are the most important mechanism to analyze the experimental data, to predict unknown reaction cross-sections, to evaluate the nuclear data for databases such as ENDF (Evaluated Nuclear Data File), and (4) to reduce the uncertainties. To improve the predictive-power of nuclear reaction theories in future, further development of compound nuclear reaction theories for fission and radiative capture processes is crucial, since these reaction cross sections are especially important for nuclear technology. An acceptable accuracy of these cross-sections has been achieved only if they were experimentally confirmed. However, the compound reaction theory is getting more important nowadays as many rare nuclides, such as americium, are involved in applications. We outline future challenges of nuclear reaction modeling in the GNASH/McGNASH code, which may yield great improvements in prediction of nuclear reaction cross-sections. [Preview Abstract] |
Saturday, October 25, 2008 2:48PM - 3:00PM |
HB.00003: Measurement of the Spectrum of Neutrons Emitted in Neutron-Induced Fission Robert Haight The spectrum of neutrons emitted in fission is the source term for neutron transport in fission reactors and other systems. This spectrum is expected to change with incident neutron energy, and the energy dependence is described by the Los Alamos Model and implemented in the ENDF/B-VII evaluated nuclear data file. A collaboration among researchers from LANL, CEA (France), and Lawrence Livermore National Laboratory is measuring the fission neutron spectrum as a function of incident neutron energy using a double time-of-flight technique at the Los Alamos Neutron Science Center. Recent results for that part of the spectrum between 1 and 8 MeV for fission of 235U and 239Pu induced by neutrons from 1 to 50 MeV will be reported, and plans for future measurements will be outlined. [Preview Abstract] |
Saturday, October 25, 2008 3:00PM - 3:12PM |
HB.00004: Recent Advances in Resonance Region Nuclear Data Measurements and Analyses for Supporting Nuclear Energy Applications Michael Dunn For over 30 years, the Oak Ridge National Laboratory (ORNL) has performed research and development to provide more accurate nuclear cross-section data in the resonance region. The ORNL Nuclear Data (ND) Program consists of four complementary areas of research: (1) cross-section measurements at the Oak Ridge Electron Linear Accelerator; (2) resonance analysis methods development with the SAMMY R-matrix analysis software; (3) cross-section evaluation development; and (4) cross-section processing methods development with the AMPX software system. The ND Program is tightly coupled with nuclear fuel cycle analyses and radiation transport methods development efforts at ORNL. Thus, nuclear data work is performed in concert with nuclear science and technology needs and requirements. Recent advances in each component of the ORNL ND Program have led to improvements in resonance region measurements, R-matrix analyses, cross-section evaluations, and processing capabilities that directly support radiation transport research and development. Of particular importance are the improvements in cross-section covariance data evaluation and processing capabilities. The benefit of these advances to nuclear science and technology research and development will be discussed during the symposium on Nuclear Physics Research Connections to Nuclear Energy. [Preview Abstract] |
Saturday, October 25, 2008 3:12PM - 3:24PM |
HB.00005: The Fission TPC Project Tony Hill, Jenn Klay, Mike Heffner New high-precision fission experiments have become a priority within the nuclear energy community due to a growing, world wide, interest in nuclear reactors. In particular, the design of the next generation reactors requires a reduction in the errors on a number of cross section measurements. Most of the required nuclear data has been measured over the last 50 years, although improvements in the accuracy of the data appear unlikely with the current technology. A potential breakthrough is the deployment of a detector developed within the particle physics community called the Time Projection Chamber (TPC). A group of 6 universities and 3 national laboratories have undertaken the task of building the first TPC for this purpose. In this talk we will present the fission TPC concept, and why we think we can make an improvement on 50 years of fission study. [Preview Abstract] |
Saturday, October 25, 2008 3:24PM - 3:36PM |
HB.00006: Distinguishing fissions of $^{239}$Pu and $^{235}$U with low-resolution detectors E. Swanberg, E.B. Norman, S.G. Prussin, H. Shugart, E. Browne When $^{239}$Pu and $^{235}$U undergo thermal neutron-induced fission, both produce significant numbers of $\beta $-delayed gamma rays with energies in the several MeV range. Experiments using high energy-resolution germanium detectors\footnote{R. E. Marrs \textit{et al.,} Nucl. Instr. {\&} Meth. A (in press).} have shown that it is possible to distinguish the fission of $^{239}$Pu from that of $^{235}$U. Using differences in the temporal behavior and in the shapes of the gamma-ray energy spectra, we show that these two isotopes can also be differentiated using low-resolution plastic or liquid scintillators. It is likely this method could be extended to homeland security applications, such as screening of cargo containers for $^{235}$U and $^{239}$Pu, using a neutron source and such scintillators. [Preview Abstract] |
Saturday, October 25, 2008 3:36PM - 3:48PM |
HB.00007: Using (d,p$\gamma$) as a Surrogate for Neutron Capture with $^{75}$As W.A. Peters, J.A. Cizewski, R. Hatarik, P. O'Malley, D.J. Vieira, M. Jandel, J.B. Wilhelmy, C. Matei, D.W. Bardayan, M.S. Smith, S.D. Pain, K.L. Jones, B.H. Moazen, K.Y. Chae, R.L. Kozub, J. Shriner, J.C. Blackmon Arsenic is used as a radiochemical neutron fluence detector for nuclear reactions and other applications. The abundances of the residual isotopes $^{73,74}$As allow one to calculate the total neutron activity through (n,2n) or (n,$\gamma$) reactions along the isotopic network chain. The neutron capture reaction cross sections used for these calculations cannot be directly measured for the radioactive isotopes, but the (d,p$\gamma$) reaction as a surrogate for the (n,$\gamma$) reaction can be measured. An experiment at Oak Ridge National Laboratory using As beams in inverse kinematics and a deuterated target will first measure the $^{75}$As(d,p$\gamma$) reaction with stable beam to test the efficacy of our surrogate experimental techniques. With a tight geometry, eight ORRUBA silicon-strip detectors will detect recoil protons in coincidence with $\gamma$-rays detected by four high-purity segmented Ge clover detectors. Status and future goals for the As(d,p$\gamma$) surrogate campaign will be presented. [Preview Abstract] |
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