Risk is most commonly represented on an inverted triangle such as increasing from a ‘broadly acceptable’ risk region, through a ‘tolerable’ region only if shown to be ALARP, to an ‘intolerable’ region, in which the risk cannot be justified on any grounds.
When the assessed risk is above the broadly acceptable level, but below the unacceptable level, then risk reduction is expected to be carried out by a corporation to a level ‘As Low As Reasonably Practicable’ (or ALARP).
As it is generally known that plant operation is undertaken with risks. Risk is the possibility that harm (illness, injury or death) might occur when plant personnel or equipment expose to a hazard. Theoretically, all foreseeable risks must be identified and managed through a structured process. Because risk cannot be completely eliminated, it is however possible to be minimized to a level that is As Low As Reasonably Practicable (ALARP).
ALARP principle is basically represented by the above risk triangle with high risk ( indicated by red color) on the top and low risk (green color) at the bottom. And medium risk is located somewhere in the middle. When a risk is reduced by mitigations or measures, the degree of risk is decreased from high to low. Risks above the Upper Tolerability Limit is intolerable which risk reduction is a must. Between the Upper and the Lower Tolerability Limit, the risk is only tolerable if it is ALARP, which means that all reasonably practicable risk reduction measures have to be identified and implemented. Lastly, below the Lower Tolerability Limit, risk is broadly tolerable or accpetable. ALARP is a point at which a risk is reduced so low that further risk reduction measure is not required. ALARP is simply a balancing of risk reduction and the cost of achieving it.
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