Acceptable risk ALARP principle

On this basis the concept of so far as is reasonably practicable (SFAIRP) was bom and subsequently enshrined in the 1974 UK Health and Safety at Work Act. SFAIRP, whilst a significant step forward, fails however to precisely acknowledge the notion of risk and its relationship to practicability. As such the slightly modified term as low as reasonably practicable (ALARP) has been widely adopted in the UK and some other countries as the basis for risk acceptability. The ALARP principle can be defined as that level of risk which can be further lowered only by an increment in resource expeuditure that is disproportionate in relation to the resulting decrement of risk [2],... 

The ALARP principle is applied for events in the intermediate area. For those near the broadly acceptable limit, the risks are considered tolerable if the cost of risk reduction would exceed the improvement gained. For those near the maximum tolerable hmit, the risks are considered tolerable only if risk reduction is impracticable or implementation of risk reducing measures would lead to disproportionate costs compared with safety benefits gained. 

The ALARP principle is often applied, involving a safety goal with a hmit (maximum acceptable risk) and an objective (broadly acceptable risk). 

Risk is so small, it can be neglected instead of spending resources or effort to reduce (i.e., acceptable zone in ALARP principle Fig. 1/4.3-1). 

The approach that is being widely promulgated in the UK is that the general form or framework for acceptability criteria should be represented as a three-tier system with (a) an upper bound on individual or societal risk levels, beyond which risks are deemed unacceptable (b) a lower bound on individual or societal risk levels, below which risks are deemed not to warrant concern and (c) an intermediate region between the previous two, where further individual and societal risk reduction are required to achieve a level deemed as low as reasonably practicable, the so-called ALARP principle. To achieve a wide consensus on the acceptable flood risk, it is indispensable that the various methods, rules, and tools to be developed in the advanced ALARP framework are robust and transparent. ... 

Calculations of the total recordable injury frequency rates for the new and the reference platforms showed a small decrease for the new platform. It was concluded that the acceptance criterion was met. The analysis, however, revealed a number of activities where an increase in the injury frequency of more than 20 per cent was expected. The ALARP principle called for actions to reduce the risk of accidents in these activities in particular. They included ... 

The hazard log is therefore used to determine the risk of each hazard turning into an accident (see Fig. 6.2). There is an important decision that senior management must make as to the level of risk the company will accept in order to manage the hazards identified. The ALARP principle demands that if a control is technically possible, is reasonable to do and can be achieved without causing financial distress to the company, then those controls should be set in place. 

ALARP principle. The principle that no risk in the tolerability region can be accepted unless reduced As Low As Reasonably Practicable . 

The notion of ALARP is simple yet fundamental. Firstly it acknowledges that there is a difference between clinical risk being as low as possible and what can realistically be achieved. This important principle brings acceptance that organisations do not have an infinite amount of money, time and effort and that there are practical and technical boundaries on how far, from a safety perspective, one can go to reduce risk. In fact one could argue that to continue to reduce risk beyond what is reasonably practicable becomes an inappropriate use of resources and ultimately of little benefit. 

Contemporary risk management follows a maturing path to the establishment, acceptance and management of a level of risk that is deemed tolerable and as low as reasonably practicable (ALARP). The recent issue of military standards [MoD 2004] describes six processes for risk management hazard identification, hazard analysis, risk estimation, risk and ALARP evaluation, risk reduction and risk acceptance. Whilst these are not the universal descriptions of the processes involved, the underlying principles are consistent with other procedures and handbooks, for example lEC 61 SOS, JSP 4S4 and Mil Stan 882D. 

With initial assessment, all risks are listed and suitable IPLs are deployed. After this the entire system is reassessed. Because we are interested in SIS, in the final assessment only SIS is shown. After each assessment the IPLs and SIS are validated. After final assessment of overall safety requirements it is ensured that the risk level is at an acceptable level, as shown in the figure. This shall be a level equal to or below the ALARP level. In principle, what has been discussed here is more or less the same as discussed earlier, the only difference is that here the basic implementation process is shown. Similarly, SIS in the design phase is shown in Fig. XII/1.0-3. The reason for showing the figure is to recapitulate further details about SIS design. 

Where risks are higher than normally acceptable and all reasonable mitigation measures have been examined to find out value and practicality, the principle of risk as low as reasonably practical apphes. Where the available risk protection measures have been exhausted and the level of risk is still higher than an accepted numerical value, the risk would be considered As Low As Reasonably Practical (ALARP). See Figure 7.4. 

This technique of assessing the potential of accidents can be further developed by also assessing the expected frequency of a reoccurrence of the events. By doing so, a risk score is achieved (low, medium or high), see Table 22.4. A high-risk score means that measures must be taken to reduce the risk of the event to a lower level by reducing frequency and/or consequence. A medium-risk score means that measures ought to be taken to reduce the risk further, based on the ALARP (as low as reasonably practicable) principle. A low-risk score means that the conditions are acceptable and no measures are necessary. 

The risk-based approach to dam safety evaluation should balance the public risk and the limited societal resources available to manage the particular risk. As shown in Fig. 1, it is cmisid-ered generally acceptable that the maximum level of societal risk to fatality is less than 10 per annum for loss of one life and the risk is less than 10 per annum when more than 100 lives would be lost in the event of a dam failure. The principle that the risks should be as low as reasonably practicable (ALARP) is generally followed in practice, and it is thus reasonable to use an annual probability of 10 and 10 for 100 and more fatalities. 

---