[en] This report aims to analyze the investment behavior of an enterprise producing nuclear origin electric power in an european market opening to the competition. In this context, the industrial structure controlled by the governor decides the investment in a marginal equipment: either an integrated monopole structure which leads to a regulation at the cost price rate of return; or a pool structure in which the governor intervene to fix the cost price at the marginal cost level given by the main technology of the gas combined cycles. (A.L.B.)