Taking human action into account in risk control measures

To prevent or limit the consequences of an accident scenario, manufacturers implement risk control measures (RCMs). Some RMCs consist solely of technical devices whose performance levels are generally quantifiable. However, the use of totally technical RMCs is not a panacea. In fact, manufacturers sometimes prefer to keep people involved in MMR implementation. For example, a diagnostic phase carried out by an operator, who may or may not decide to take the plant into safety, can help limit the number of MMRs triggered, and thus improve plant availability. On the other hand, this raises the question of the value of man as an MMR or part of an MMR.

• If the performance of technical MMRs is "insensitive" to the stress of an accident situation, what can be said about human performance?

• How can we make the most of human actions as part of a hazard study?

• What performance levels should be associated with MMRs involving human actions?