The nonmesonic decay of the \Lambda-hyperon has been investigated by observation of delayed fission of heavy hypernuclei produced in proton--U collisions at T_p=1.9 GeV. The lifetime of heavy hypernuclei with masses A \approx 220 obtained in the present work, i.e. \tau _{{\Lambda }}= [138 \pm 6 (stat.) \pm 17 (syst.)] ps,} is the most accurate result for heavy hypernuclei produced in proton and antiproton induced collisions on a U target so far.

PACS numbers: 13.30.--a, 13.75.Ev, 21.80.+a, 25.80.Pw