Investigation of the fundamental constants stability based on the
  reactor Oklo burn-up analysis
  The burn-up for SC56-1472 sample of the natural Oklo reactor zone 3 was
calculated using the modern Monte Carlo codes. We reconstructed the neutron
spectrum in the core by means of the isotope ratios: $^{147}$Sm/$^{148}$Sm and
$^{176}$Lu/$^{175}$Lu. These ratios unambiguously determine the spectrum index
and core temperature. The effective neutron absorption cross section of
$^{149}$Sm calculated using this spectrum was compared with experimental one.
The disagreement between these two values allows to limit a possible shift of
the low laying resonance of $^{149}$Sm even more . Then, these limits were
converted to the limits for the change of the fine structure constant $\alpha$.
We found that for the rate of $\alpha$ change the inequality $|\delta
\dot{\alpha}/\alpha| \le 5\cdot 10^{-18}$ is fulfilled, which is of the next
higher order than our previous limit.
