ALARP application

In the nuclear energy industry, the scope of risk criteria includes the whole range of risk criteria from societal and individual risk, off-site radioactive release, reactor core damage accident and lower level criteria to mnnerical criteria used in various risk-informed applications. Risk criteria have variable status in different coimtries strict regulatory limits are defined in few coimtries, while indicative target values are used in most coimtries. The ALARP principle is sometimes applied, involving a risk criterion with a limit and an objective. 

In the AOP 52 for the calculation of the SSCI it is necessary to know the severity of a hazard. It is categorized in four categories catastrophic, critical, marginal and negligible. These categories are not explicitly defined in the AOP 52 so we guess that these terms can be defined by the user depending on the application, e.g. in the definition of the ALARP approach. This leaves room for interpretations. This holds also true to a lesser extent for the concept of software autonomy of the AOP 52. 

ALARP stands for as low as reasonably practicable. An equivalent term ALARA, as low as reasonably achievable, is also commonly used. The application of radiation can aid the patient by providing doctors and other healthcare professionals with a medical diagnosis. However, keeping exposure reasonably low will reduce probability of cancers or sarcomas and eliminate skin reddening or cataracts. Any radiation exposure, no matter how small, can increase the chance of negative biological effects such as cancer. The probability of the occurrence of negative effects of radiation exposure increases with cumulative lifetime dose (Table 14.2). 

This approach pre-supposes that it is possible to determine independently for each hazard whether the risk is tolerable or not. This may be applicable when the safety target is ALARP, but not so when it is GALE. The risk matrix approach also overlooks the issue that, if there are many hazards that fall into a particular risk class, this should be regarded as less tolerable than if there is only a single hazard in that class. 

It is suggested that the four components of the Accident Tetrahedron may be considered as a new concept of separate lines of defence or layers of protection when considering ALARP Justifications, all of which must be considered during risk assessments. Further research is recommended on the costs of mitigation methods across the four areas of the tetrahedron. A specific retrospective application would also have benefit. 

Requirements 1 to 7 can be met by the application of either qualitative or quantitative hazard and risk analysis techniques as per part 5 of the Standard. The example to date has applied a quantitative analysis employing a number of techniques. In terms of qualitative assessment, an "unlikely failure but with "catastrophic outcome represents an extreme risk necessitating "necessary risk reduction and application of ALARP (as low as reasonably practicable), good practice and continuous risk reduction principles... 

As we proceeded with our studies, we found that developing a distinct, perhaps statistical, universally applicable definition of acceptable risk that did not contain general and judgmentally interpretive terms is not possible. But, with a studied understanding of risk, and risk taking, and the concept of As Low as Reasonably Practicable (ALARP), I dare to offer a practical definition of acceptable risk that can be effectively applied when dealing with workplace hazards, risks, and deficiencies in safety and health management systems. 

Complete application of the ALARP principle fully and accurately is very expensive and time-consuming [6]. 

S. Hughes, Gost Effective Application of ALARP Principle, Safety Engineering Group ERA Technology. 

Many industries will justify the ALARP level with a quantitative risk assessment of how it will impact societal risk. In other words, how many additional lives are saved with this hazard control This application is very common in the United Kingdom especially in rail safety but highly controversial in the United States. But this is changing to some extent in the United States. Trade-off benefits in pollution control in some industries are now using the ALARP method (Figure 2.2). 

The overall application of the ALARP principle to the overall APIOOO design is considered in Chapter 8 of this report. The application of ALARA/ALARP principle to operational radiation exposures is specifically considered in Section 12.1 of the EDCD (Reference 12.1). Asaresultof this process, the APIOOO is expected to have significantly reduced occupational radiation exposures, in the range of 219 man-mSv/year. This exposure is less than the current best practice for Westinghouse plants of the same power rating. 

The proposed system has been assessed and a predicted risk of 8 x 10 pa obtained. Given that the negligible risk is taken as 10 pa then the application of ALARP is required. For a cost of 3,000, additional instrumentation and redundancy will reduce the risk to just above the negligible region (say 2 x 10 pa). 

However some scenarios might need the application of BOTH individual and societal calculations and for ALARP to he satisfied in both cases. 

Axle counter application risk models were developed to support the derivation of Safety Cases for individual axle counter installation projects. In accordance with the UK safety case regime, each project will have to prove that the technological and procedural solution accepted for the project is the As Low As Reasonably Practicable (ALARP) solution. 

It provides a framework so that individual application safety cases can demonstrate that the type of axle counter system that is being commissioned on a particular project reduces the risks to ALARP (relative... 

Application specific issues cannot be addressed at the concept level. To demonstrate ALARP, it is necessary to consider the specific application in conjunction with the Concept Safety Case, as the latter caimot deal with reasonable practicality in all situations and combinations of applications. 

Applicable hazards are managed to closure or are conditionally closed and managed tiirough restrictions. The Safety risk is ALARP and tolerable ... 

Applicable hazards from V2.1 Syst Hazard 1< are closed or conditionally closed and safety risk is ALARP... 

An example of application of the ship performance data regarding the ship roll function in time domain and ALARP risk evaluation criteria for assessment of a ship safety in damage conditions is presented in Figure 8. The vertical axis in Figure 8 regards the angle of heel in degrees and the horizontal axis concerns the time in seconds. 

Finally, there are legislative considerations to take into account. Fortunately, there has been a great deal of harmonisation work in EC directives, which should limit potential areas of conflict. However, there are still variations between EU member states. The most obvious is the application of ALARP in the UK, which has not been adopted to the same extend elsewhere within the EU. There are also domain variations, where historically, system safety has taken differing approaches. The rail industiy is a good example in this respect, with differences due to the historical development within each nation. 

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