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ous situation that requires immediate attention. The consequence could further be broken down into effect for ship, human safety, oil spill, dam- age, ecology, emission and other environmetal impacts. Number 1–10 are assigned according to level of serenity. Risk priority number (RPN) for total serenity is determining as follows:


6.3 ALARP principal, risk acceptability criteria and risk control option

Consequence thresholds priority of value

choice is awarded. The highest Consequence tripped in order of priority give the overall consequence. Catastrophic: Descriptors of catastrophic consequences for 1. People; 2. Infrastructure; 3. Values. Major: Descriptors of major consequences for 1. People; 2. In- frastructure; 3. Values. Moderate: Descriptors of moderate consequences for 1. People; 2. Infrastructure; 3. Values. Minor: Descriptors of minor consequences for 1. People; 2. Infra- structure; 3. Values. Insignificant: Descriptors of insignificant consequences for 1. People; 2. Infrastructure; and 3. Values. Risk acceptability criteria establishment is dynamic because of differences in environ- ment, diversity in industries and choice of regulations requirement to limit the risk. Risk is never acceptable, but the activity implying the risk may be acceptable due to benefits of safety reduced, fatality, injury, individual risk, societal risk, environment and economy. Per- ception regarding acceptability is described by Green et al (1998). The rationality may be debated, societal risk criteria are used by increasing number of regulators. Figure 12 shows prescribed illustrative in- fluence diagram by IMO. Based on region


where the graph falls, step for risk control option and sustainability balancing, cost ben- efit effectiveness towards recommendation for efficient, reliable, sustainable decision can be taken. The frequency (F) of accidents involving consequence (N) or more fatali- ties may be established in similar ways as individual or societal risk criteria. For risks in the unacceptable/intolerable risk region, the risks should be reduced at any cost. Risk Matrix constructed from system and sub sys- tem level analysis can be deduced according to acceptability index defined according to table 5 and figure 12 to deduced measure of ALARP. Within ALARP range, Cost Ef- fectiveness Assessment (CEA) or Cost Ben- efit Analysis (CBA) shown in Figure 13 may be used to select reasonably practicable risk reduction measures.

7.0 RISK ANALYSIS CONSIDERATIONS In addition to a sound process, robust

risk framework and eventual deductive risk model, there are other considerations that should be factored into the design of an ef- fective risk model. These items include the use of available data, the need to address human factors, areas of interest, stakeholder interest and approaches to treating uncertainty in risk analysis. Data required for risk work should involve information on traffic patterns, the environment (weather, sea conditions, and visibility), historical, current operational performance data, and human performance data. The models intentions are highly de- pendent on appropriately selected databases that accurately represent the local situation and the effectiveness of the models. However, there is always issue of missing data or data

Journal of Marine Environmental Engineering

145-173 pp MB_37(Kader)2.indd 160

2/19/2010 11:04:25 AM

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