The nuclear interaction at Oklo 2 billion years ago

We re-examine the effort to constrain the time variability of the coupling constants of the fundamental interactions by studying the anomalous isotopi c abundance of Sm observed at the remnants of the natural reactors which we re in operation at Oklo about 2 billion years ago, in terms of a possible d eviation of the resonance energy from the value observed today. We rely on new samples that were carefully collected to minimize natural contamination and also on a careful temperature estimate of the reactors. We obtain the upper bound (-0.2 +/- 0.8) X 10(-17) y(-1) on the fractional rate of change of the electromagnetic as well as the strong interaction coupling constant s. Our result basically agrees with and even suggests some improvement of t he result due recently to Damour and Dyson. Strictly speaking, however, we find another choice of the resonance energy shift indicating a non-zero tim e variation of the constants. However, we find a rather strong but still te ntative indication that this non-null range can be ruled out by including G d data, for which it is essential to take the effect of contamination into account. (C) 2000 Elsevier Science B.V, All rights reserved.