Setting ALARP

Due to the subjective namre of risk, no external agency—whether it be a regulatory body, a professional society, or the author of a book such as this—can 

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Finally ALARP introdnces a basis for justifying risks, to make a case for them being present but tolerable. To justify something in this way reqnires carefnl analysis and logic set out as an evidence-based argument. The vehicle for this jnstifica-tion is a document known as a safety case. 

Some risk analysts use the term as low as reasonably practical (ALARP) for setting a value for acceptable risk. The basic idea behind this concept is that risk should be reduced to a level that is as low as possible without requiring excessive investment. Boundaries of risk that are definitely acceptable or definitely not acceptable are established as shown in Figure 1.16, which is an FN curve family. Between those boundaries, a balance between risk and benefit must be established. If a facility proposes to take a high level of risk, then the resulting benefit must be very high. 

Acceptable risk is that risk for which the probability of an incident or exposure occurring and the severity of harm or damage that may result are as low as reasonably practicable (ALARP) in the setting being considered. 

Target 5 sets the limit on the risk of death for any person on site from an on-site accident that releases ionising radiation. Section 5 of this PCSR concludes that the risks for an APIOOO are about two orders of magnitude below the Basic Safety Objective, and thus further ALARP justification would be grossly disproportionate. 

Target 8 sets the maximum value allowed for the total predicted frequency of accidents in the facility that results in a specific dose to an individual offsite. Section 5 of this PCSR reviews the various release bands, and concludes that the fiequeney is below the Basic Safety Objective for each, usually by a few orders of magnitude. At this level, further ALARP justification would be grossly disproportionate. The target is thus satisfied. 

Setting integrity (SIL) targets The ALARP eoncept (by inferenee)... 

Apportionment of Safety targets and quantification of requirements. To demonstrate that the risks resulting from the changes to the railway are tolerable, ALARP and no greater than the level of risk in the current Railway System, quantitative risk assessments are carried out, and a set of requirements related to the new hardware system constituents have been quantified. 

The conclusion of the Safety justification was that a set of restrictions, dependencies and other safety measures had been identified which enabled the train operations, associated with V2.01 testing, to be performed at a level of risk which is tolerable and ALARP. This Safety justification can thus be seen a subset of the reasoning model that is the System Safety Case for VLUP. 

Confirm that the identified set of mitigations yields an ALARP compliant method of world]... 

The contractor updates the REPA to include the results of concept optimisation. Norskoil s project SHE manager supervises this work. It is shown that the concept meets all appUcable acceptance criteria, provided that a number of assumptions are met. These define the accidental loads from fire, explosion, dropped objects and ship collisions that the semi mnst be able to withstand. Another set of assumptions defines the safety and communication systems that have to be operable during an accident. There are also assumptions regarding the collision warning system and the withdrawal of the platform from the snbsea wells in case of blow-out. The REPA also results in a number of recommendations based on the ALARP principle. The assumptions and recommendations serve as input to design development and to specifications and need to be followed up in later project phases. 

It is central to the goal-setting approach to safety regulation that the employer or operator should make an assessment of risks and then take appropriate measures to ensure health and safety "so far as is reasonably practicable", in the words of HSWA. This is usually expressed as making risks As Low As Reasonably Practicable, or ALARP in the words of HSE s guidance on the tolerability of risks from nuclear installations. ALARP is associated with the concepts of intolerable and broadly acceptable risks. 

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. 

The ALARP approach can assist in setting priorities for investment by indicating which opportunities for designing out a safety risk or adding a safety feature give most benefit. 

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