Gamma-ray fluxes in Oklo natural reactors

الأصل · EN

Uncertainty in the operating temperatures of Oklo reactor zones impacts the precision of bounds derived for time variation of the fine structure constant α. Improved ¹⁷⁶Lu/¹⁷⁵Lu thermometry has been discussed but its usefulness may be complicated by photo excitation of the isomeric state ¹⁷⁶ᵐLu by ¹⁷⁶Lu(γ,γ′) fluorescence. We calculate prompt, delayed and equilibrium γ-ray fluxes due to fission of ²³⁵U in pulsed mode operation of Oklo zone RZ10. We use Monte Carlo modeling to calculate the prompt flux. We use improved data libraries to estimate delayed and equilibrium spectra and fluxes. We find γ-ray fluxes as a function of energy and derive values for the coefficients λᵧ,ᵧ′ that describe burn-up of ¹⁷⁶Lu through the isomeric ¹⁷⁶ᵐLu state. The contribution of the (γ,γ′) channel to the ¹⁷⁶Lu/¹⁷⁵Lu isotopic ratio is negligible in comparison to the neutron burn-up channels. Lutetium thermometry is fully applicable to analyses of Oklo reactor data.