This aspect of learning is not very different from the exchange of informa­tion on normal operation as discussed in the previous section. Normal operation also includes a host of small equipment malfunctions and human errors — all of which are examined to find out if they might be precursors of larger malfunctions that could occur in the future.

We must carefully define the usage of the word ‘accident’ in this context, beyond the conventional usage. We are dealing here with a complex tech­nology for which all contingencies are presumed to be subject to careful engineering analysis and design. It is reasonable, therefore, to take the posi­tion that all unfortunate consequences arise from human error at some stage of the process. This classification is somewhat at odds with usual prac­tice; however, taking the example of an equipment failure, one can quickly identify different causes — design error, manufacturing error, installation error, and maintenance error. All of these failures are caused by human failure. Even so-called natural events are expected to be protected against by design (through either prevention or mitigation).

An example

Given the fact that accidents are, at the very least, caused mostly by human error, it is very useful (Duffey and Saull, 2008) to look at serious accidents that occur in other industries and human activities in general. The reason for this is to ‘normalize’ the accident rate in nuclear plants to the usual patterns of human existence. Indeed, Reason (1990) points out that ‘active’ human errors are very rare in the world nuclear industry when compared with the frequency of correct action.

Table 10.1 outlines a ‘typical’ accident sequence. (Note that the specific technology is of secondary importance in this type of analysis.) In this case a sudden tire failure led to failure of one engine during takeoff. The pilot was 1.5 seconds late in applying the takeoff abort procedure, and so the immediate cause of the accident was said to be pilot error. During subse­quent review and analysis it was found that a number of other factors actu­ally had a powerful negative effect on the accident — most especially the continued use of tires that were already beyond their service life. In the end, it became apparent that airline management was strongly implicated through unsafe practices.