Reactor antineutrino spectra and their application to antineutrino-induced reactions. II

The antineutrino and electron spectra associated with various nuclear fuels are calculated. While there are substantial differences between the spectra of different uranium and plutonium isotopes, the dependence on the energy and flux of the fission-inducing neutrons is very weak. The resulting spectra can be used for the calculation of the antineutrino and electron spectra of an arbitrary nuclear reactor at various stages of its refueling cycle. The sources of uncertainties in the spectrum are identified and analyzed in detail. The exposure time dependence of the spectrum is also discussed. The averaged cross sections of the inverse neutron β decay, weak charged and neutral-current-induced deuteron disintegration, and the antineutrino-electron scattering are then evaluated using the resulting ν̅_e spectra. [RADIOACTIVITY, FISSION 235U, 238U, (^239)Pu, (^240)Pu, (^241)Pu, antineutrino and electron spectra calculated. σ for ν̅ induced reactions analyzed.

Reactor antineutrino spectra and their application to antineutrino-induced reactions

The knowledge of reactor antineutrino spectra is necessary for the interpretation of weak-interaction experiments located at nuclear reactors. We calculate the antineutrino and electron spectra accompanying thermal neutron fission of 235U and 239Pu for various irradiation times. It is stressed that the higher energy part (E≳4 MeV) of the spectra depends sensitively on the β-decay characteristics of fission products with experimentally unknown decay schemes. We also discuss the accuracy of a semiempirical conversion of the electron spectrum into the antineutrino spectrum. The resulting ν̅ e spectra are used to calculated cross sections and reaction rates for the inverse neutron β decay, weak charged and neutral current induced deuteron disintegration, and the antineutrino-electron scattering

ENDF/B-IV fission-product files: summary of major nuclide data

The major fission-product parameters [sigma/sub th/, RI, tau/sub 1/2/, E- bar/sub $beta$/, E-bar/sub $gamma$/, E-bar/sub $alpha$/, decay and (n,$gamma$) branching, Q, and AWR] abstracted from ENDF/B-IV files for 824 nuclides are summarized. These data are most often requested by users concerned with reactor design, reactor safety, dose, and other sundry studies. The few known file errors are corrected to date. Tabular data are listed by increasing mass number. (auth

Nuclear data needs for FMIT

The Fusion Material Irradiation Testing Facility (FMIT) is designed to test samples in a high energy neutron environment so that data obtained in fission reactors can be extrapolated to that needed in fusion devices. Although most of the flux is centered around approx. 14 MeV, the neutron distribution will extend from thermal energies to 50 MeV. Data needed in design include total, elastic, and removal cross sections for shielding, neutron yields for source calculations, and selected transmutation cross sections for dose determinations. Data needed for operation include transport and dosimetry cross sections for flux determinations, damage energy, transmutation, and gas production cross sections for damage analyses, and selected data for machine operation and maintenance. Detailed reaction lists are given

Status of ENDF/B-V fission yields

The features of ENDF/B-V with respect to fission yields are described. Yields for approximately 1100 nuclides are given for each of 11 fissioning nuclides at one or more fission-neutron energies, plus the yield uncertainties. Selected chain yields and uncertainties are illustrated. Aspects of the evaluation process are discussed. 4 figures, 3 tables. (RWR

Charge Transfer from Regularized Symmetry-Adapted Perturbation Theory

16 pages, 16 figure

Search for Neutrinoless Double-Beta Decay in 136^{136}Xe with EXO-200

We report on a search for neutrinoless double-beta decay of $^{136}$Xe with EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background of ~1.5 x 10^{-3} /(kg yr keV) in the $\pm 1\sigma$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0\nu\beta\beta}$($^{136}$Xe) > 1.6 x 10$^{25}$ yr (90% CL), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation

Massive stars as thermonuclear reactors and their explosions following core collapse

Nuclear reactions transform atomic nuclei inside stars. This is the process of stellar nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars are reviewed. How stars manage to burn their fuel so slowly most of the time are also considered. Stellar thermonuclear reactions involving protons in hydrostatic burning are discussed first. Then I discuss triple alpha reactions in the helium burning stage. Carbon and oxygen survive in red giant stars because of the nuclear structure of oxygen and neon. Further nuclear burning of carbon, neon, oxygen and silicon in quiescent conditions are discussed next. In the subsequent core-collapse phase, neutronization due to electron capture from the top of the Fermi sea in a degenerate core takes place. The expected signal of neutrinos from a nearby supernova is calculated. The supernova often explodes inside a dense circumstellar medium, which is established due to the progenitor star losing its outermost envelope in a stellar wind or mass transfer in a binary system. The nature of the circumstellar medium and the ejecta of the supernova and their dynamics are revealed by observations in the optical, IR, radio, and X-ray bands, and I discuss some of these observations and their interpretations.Comment: To be published in " Principles and Perspectives in Cosmochemistry" Lecture Notes on Kodai School on Synthesis of Elements in Stars; ed. by Aruna Goswami & Eswar Reddy, Springer Verlag, 2009. Contains 21 figure