2006/08/28 by C. R. Gould, E. I. Sharapov, S. K. Lamoreaux · 6 citations
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #High-pressure geophysics and materials #Nuclear Physics and Applications #Nuclear reactor physics and engineering #nucl-ex
paper · pdf · doi:10.1103/physrevc.74.024607
published as Phys.Rev.C74:024607,2006 · 14 pages, 4 figures. Corrections: minus sign missing in equation 32, changed sign of change in alpha in equations 33 and 34. Also added two new references and corrected minor typographical errors
openalex publication_date 2006/08/28 · arxiv created 2007/04/30 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We reanalyze Oklo 149Sm data using realistic models of the natural nuclear reactors. Disagreements among recent Oklo determinations of the time evolution of \ensuremathα, the electromagnetic fine structure constant, are shown to be due to different reactor models, which led to different neutron spectra used in the calculations. We use known Oklo reactor epithermal spectral indices as criteria for selecting realistic reactor models. Two Oklo reactors, RZ2 and RZ10, were modeled with MCNP. The resulting neutron spectra were used to calculate the change in the 149Sm effective neutron capture cross section as a function of a possible shift in the energy of the 97.3-meV resonance. We independently deduce ancient 149Sm effective cross sections and use these values to set limits on the time variation of \ensuremathα. Our study resolves a contradictory situation with previous Oklo \ensuremathα results. Our suggested 2\ensuremathσ bound on a possible time variation of \ensuremathα over 2 billion years is stringent: \ensuremath-0.11\ensuremath≤\ensuremathΔ\ensuremathα/\ensuremathα\ensuremath≤0.24, in units of 10^\ensuremath-7, but model dependent in that it assumes only \ensuremathα has varied over time.