  We consider the spontaneous breaking of supersymmetry in five dimensional
supergravity with boundaries where the supersymmetry breaking mechanism is
provided by the even part of the bulk prepotential. The supersymmetric action
comprises boundary brane terms with detuned tensions. The two branes have
opposite tensions. We analyse the possible vacua with spontaneously broken
supersymmetry. A class of solutions corresponds to rotated branes in an $AdS_5$
bulk. In particular parallel branes which are rotated with respect to the bulk
preserve 1/4 of supersymmetry. We analyse more general vacua using the low
energy effective action for gravity coupled to the radion field. Supersymmetry
breaking implies that the radion field acquires a potential which is negative
and unbounded from below. This potential is modified when coupling the boundary
branes to a bulk four--form field. For a brane charge larger than the deficit
of brane tension, the radion potential is bounded from below while remaining
flat when the charge equals the deficit of brane tension.
