2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35100Thin shells in general relativity have been used in the past as keystones to obtain realistic models of cosmological and astrophysical situations. A crucial role for these developments was played by the compact description of their dynamics in terms of Israel's junction conditions. Starting from this geometrical formulation we present a problem related to the WKB regime of shell dynamics and suggest a possible solution.5 pages, 3 EPS figures, to appear in the proceddings of the 6th International Symposium on Frontiers in Fundamental and Computational Physics (FFP6), September 26-29, Udine, ITALYGeneral Relativity and Quantum Cosmologytext