[en] An extreme risk has a very slight probability but potentially heavy consequences. Despite the existence of three accountancy methods for dealing with them (provisions, contingent liabilities and insurance), the transposition of such risks into financial statements is based on a sequential analysis of both the probability of the risk happening and the ability to estimate the effects. This method keeps us from taking into account risks with a highly uncertain probability of occurrence, such as accidents at nuclear power plants - independently of the 'amount' at stake. As management reports from firms concerned by nuclear risks show, the diffusion of qualitative information does not offset this gap in bookkeeping