  We consider Z_2-symmetric braneworlds arising from 5-sphere compactifications
with 5-form flux in type IIB supergravity. This Kaluza-Klein reduction produces
a D=5 theory which supports 1/2-supersymmetric Z_2-symmetric domain-wall
solutions. However, upon lifting such solutions back to D=10, one finds that
supersymmetry is broken by 5-sphere Kaluza-Klein effects. This happens owing to
the action on the Killing spinor of the Z_2 \subset SO(1,9) symmetry, which
requires an orientation-reversing transformation in the 5-sphere directions
together with the flip of the orbifold coordinate. We study the consequences of
this supersymmetry breaking for the masses of fermion fluctuation modes about
the brane background and find a natural two-scale hierarchy: some bulk modes
have characteristic masses of order 1/L_5 but other modes more closely
associated to the branes have an additional factor exp(-\rho/L_5), where L_5 is
the AdS_5 length parameter and \rho is the orbifold size.
