Tolerable
I have just been shown the Nimrod report - isn't it amazing how someone can be so wrong and so self-satisfied about it. Perhaps the QC should have listened to the York safety folk or gone to the local library rather than jetting off to the States at Taxpayers' expense.
There are 3 main elements in an ALARPassessment and a couple of influencing elements. First there is the tolerability measurement. There are 3 levels of tolerability: intolerable, tolerable and broadly acceptable. These are set with one of the influencing elements in mind - the industry sector or the environment (ie what is tolerable in the aviaition industry may be acceptable in a coal mine). Second there is the ALARP judgement. Third there is the acceptability of the risk. These are influenced by the passage of time.
The QC is quite wrong to say that a tolerable risk that is not ALARP is intolerable. It is generally unacceptable - but in principle any risk can be accepted in dire circunmstances - but once it is determined it fits into the tolerable basket there it stays unless the measurment of tolerability changes.
ALARP is more difficult. The 'temporal' bit has 3 ways of interpretation - all valid. The obvious one is that risks change with time and you should re-evaluate then regularly. The second is that just because your competitor has brought in a safer piece of equipment than the one you are using does not mean that you have to retrospectively apply a higher standard to your old kit - relevant to the old Nimrod. The third is that once you have determined that there is a reasonably practicable measure that you could take you are no longer ALARP but clearly there is no reason why your kit suddenly becomes unacceptable - there is a reasonable amount of time allowed to become ALARP again.
As for tyre burst - that is why you have a clear area around a runway as an ALARP measure. Just take care when you put in your runway monitoring radar to allow enough space!