Kramers relaxation times tau (K) and relaxation times tau (R) and tau (G) for the end-to-end distances and for center-of-mass diffusion are calculated for dense systems of athermal lattice chains. tau (K) is defined from the response of the radius of gyration to a Kramers potential which approximately describes the effect of a stationary shear flow. It is shown that within an intermediate range of chain lengths N the relaxation times tau (R) and tau (K) exhibit the same scaling with N, suggesting that N-dependent melt-viscosities for nonentangled chains can be obtained from the Kramers equilibrium concept.