Permission to operate is granted if and only if the operator is reasonably certain that though the plant might be upset, he has demonstrable reasons to know or expect the upset to be manageable. If he determines or begins to suspect that the upset might not be manageable, then permission to operate is withdrawn. The only manageable upsets are those that are routinely seen and for which
procedures that are expected to work exist. This case is quite a bit more subjective and requires substantial operator competence to employ.