  We report the measurement of an inclusive partial branching fraction for
charmless semileptonic B decay and the extraction of |V_ub|. Candidates for B
-> X_u l nu are identified with a novel X_u-reconstruction method based on
neutrino reconstruction via missing 4-momentum and a technique called
``simulated annealing.'' Based on 86.9/fb of data taken with the Belle
detector, we obtain Br (B -> X_u l nu ; M_X<1.7 GeV/c^2, q^2>8.0 GeV^2/c^2) =
  (7.37 +- 0.89(stat.) +- 1.12(syst.) +- 0.55(b -> c) +- 0.24(b -> u)) x
10^(-4) and determine |V_ub| = (4.66 +- 0.28(stat.) +- 0.35(syst.) +- 0.17(b ->
c) +- 0.08(b -> u) +- 0.58(theory)) x 10^(-3).
