  We make use of a semiclassical method for calculating the suppression
exponent for topology changing transitions in high-energy electroweak
collisions. In the Standard Model these processes are accompanied by violation
of baryon and lepton number. By using a suitable computational technique we
obtain results for s-wave scattering in a large region of initial data. Our
results show that baryon and lepton number violation remains exponentially
suppressed up to very high energies of at least 30 sphaleron masses (250 TeV).
We also conclude that the known analytic approaches inferred from low energy
expansion provide reasonably good approximations up to the sphaleron energy (8
TeV) only.
