Oklo reactors and implications for nuclear science
Abstract
We summarize the nuclear physics interests in the Oklo natural nuclear reactors, focusing particularly on developments over the past two decades. Modeling of the reactors has become increasingly sophisticated, employing Monte Carlo simulations with realistic geometries and materials that can generate both the thermal and epithermal fractions. The water content and the temperatures of the reactors have been uncertain parameters. We discuss recent work pointing to lower temperatures than earlier assumed. Nuclear crosssections are input to all Oklo modeling and we discuss a parameter, the ^{175}Lu ground state crosssection for thermal neutron capture leading to the isomer ^{176m}Lu, that warrants further investigation. Studies of the time dependence of dimensionless fundamental constants have been a driver for much of the recent work on Oklo. We critically review neutron resonance energy shifts and their dependence on the fine structure constant α and the ratio X_{q} = m_{q}/Λ (where m_{q} is the average of the u and d current quark masses and Λ is the mass scale of quantum chromodynamics (QCD)). We suggest a formula for the combined sensitivity to α and X_{q} that exhibits the dependence on proton number Z and mass number A, potentially allowing quantum electrodynamic (QED) and QCD effects to be disentangled if a broader range of isotopic abundance data becomes available.
 Publication:

International Journal of Modern Physics E
 Pub Date:
 April 2014
 DOI:
 10.1142/S0218301314300070
 arXiv:
 arXiv:1404.4948
 Bibcode:
 2014IJMPE..2330007D
 Keywords:

 Oklo;
 natural nuclear reactors;
 Monte Carlo simulation;
 neutron/gamma fluxes;
 core temperature;
 nuclear data;
 nuclear waste depository;
 time variation fundamental constants;
 06.20.Jr;
 07.05.Tp;
 21.10.Sf;
 24.30.v;
 27.20.+n;
 28.20.Gd;
 28.41.i;
 Determination of fundamental constants;
 Computer modeling and simulation;
 Coulomb energies;
 Resonance reactions;
 6<
 =A<
 =19;
 Neutron transport: diffusion and moderation;
 Fission reactors;
 Nuclear Theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology;
 Nuclear Experiment
 EPrint:
 40 pages, 7 figures. Review paper