External risks

Provide External Risk Reduction Facility (ERRF)... 

The methodology for assessment of external events is qualitatively satisfactory but not quantitatively. Little confidence should be placed in any estimates of the risk from external initiators compared to those from internal initiators. This is exacerbated by the fact that the external risk is the larger of the two in many cases. 

The purpose of this section is to enable the reader to identify the potential stability properties of a chemical substance by simply analysing its structural formula. This will be made possible by listing the structural properties of unstable molecules. The reader will see the need to identify two types of structural properties those that bear the hallmarks of an unstable property and those whose presence can increase or alternatively reduce the risk of violent decomposition. Since the latter are the only ones in the molecule, they do not represent any danger for it in terms of stability. But when performing qualitative analysis, one also has to take into account the conditions under which the substance is handled. In addition to the structural properties, the analyst will have to carry out a study on the external risk factors. 

External risk factors an approach to their prevention... 

White (versus black) race External risk factors Intense intermittent sun exposures History of sunburn... 

In the following, only the external risk factors heat and moisture are evaluated. 

Externalized t ratio, 2284 External risks, 45 Extraction, data, 84 Extranets, 220, 256... 

Emerging debt can be issued either in the local currency or in any other external currencies (i.e., Mexico issuing in euro or sterling). These two types of debt do not carry the same risk, and need to be modeled independently. Internal risk was discussed in the interest risk section and we will now address external risk. 

In today s market, factors extraneous to industry fundamentals have been exerting increasing influence on sector performance. The term event risk has traditionally been used to refer to merger and acqnisition (M A) activity, and has been more issuer-specific than affecting the entire sector. However, we take a broad definition of event risk to encompass other external risks, including litigation risk, technological risk, and the like. 

In ANSI/ISA-84.00.01-2004 (lEC 61511 Mod), 3.2.71, a safety instrumented function is defined as a "safety function with a specified safety integrity level which is necessary to achieve functional safety." This standard, 3.2.68, defines a safety function as a "function to be implemented by a SIS, other technology safety-related system or external risk reduction facilities, which is intended to achieve or maintain a safe state for the process, with respect to a specific hazardous event."... 

This Safety Report addresses only the internal events that originate in the reactor or in its associated process systems. Some initiating events that affect a broad spectrum of activities at a nuclear power plant (often referred to as internal or external risks), such as fires (internal and external), flooding (internal and external), earthquakes and local external impacts, such as aircraft crashes, are not discussed in detail. Nevertheless, the guidance provided may be used for analysing the consequences of such events from the viewpoint of neutronics and thermohydraulics. 

These findings can perhaps be explained by reference to the fact that in the industries that have high external risks the extensive historical use of procurement and supply tools and techniques reinforces performance satisfaction since it mitigates the risks that have to be managed and ensures the fulfilment of functional level objectives. The industries with the highest risks appear, therefore, to be using tools and techniques more extensively and with higher satisfaction levels than the medium risk industries, where the lower risks reduce the need for such an extensive use of tools and techniques. 

Safety function Safety instrumented function (SIF) lEC 61508 safety function implemented by E/E/PES, other technology safety related system, or external risk reduction facilities. lEC 61511 ANSI/ISA-84.00.01-2004 flEC 61511 Mod) SIF is imolemented solely by SIS... 

The issuance of ANSI/ISA-84.01-1996 was closely followed by the issuance of lEC 61508. lEC 61508 did not use the term "interlock" but instead, either used the term "E/E/PE safety function" or "E/E/PE safety-related system." This remains significant because many safety products utilize lEC 61508 as their development and documentation guide. In the case of lEC 61508, the term "safety function" applied not only to E/E/PE technology but also to "other technology safety-related systems or external risk-reduction facilities."... 

Consultations with regulatory agency other companies unions Employment of in-house or external risk management consultants... 

The purpose of the W factor is to estimate the frequency of the unwanted occurrence taking place without the addition of any safety-related systems (E/E/PE or other technology) but including any external risk reduction facilities. (Part 5, Annex D - A quaUtative method risk graph)... 

Brdulak points out characteristic areas for the external and internal categories of risk sources. In line with the proposed division, external risk factors cover four areas. The first encompasses factors from the macro environment, i.e. the more distant environment. The second area is the meso environment, which includes the situation in the sector and... 

IFC 61508 Originally functional safety was defined as part of the overall safety relating to the equipment under control (FUC, see Clause 8.1.2), and the EUC control system which depends on the correct functioning of the E/E/PE safely-related systems, other technology safety-related systems and external risk reduction facilities. Later came the generalized definition of functional safety, which is part of the overall safety that depends on a system or equipment operating correctly in response to its inputs. Functional safety is achieved when every specified safety... 

Safety function may be implemented by SIS and/or by passive participants such as other technology safety-related systems and external risk reduction facilities (see Clause 8.1.1). 

Coverage Safety related systems including external risk reduction systems Mainly on safety instrumentation systems... 

The specification of safety requirements is an essential step, with the requirements based on the contribution that the system is making to risk reduction, taking into account the contributions made by other technologies such as pressure relief valves and any other external risk reduction measures. The concept is fundamentally the same as that set out in EN 954-1, although the realisation of it is entirely different. 

In general, the risk is the result of a combination of consequence of the hazardous event and the probability of occurrence of these hazardous events. This combination influences the equipment under control risk. If this risk is higher than the tolerable risk, than necessary risk reduction measures are to apply to reach the tolerable risk level. To reach the tolerable risk level external risk reduction measures, the implementation of safety-related systems and the application of non electrical safety reduction systems are to be considered. 

The actual risk reduction should usually be greater than the necessary. By judicious selection of shown modules the risk reduction achieved by all the safety-related systems and external risk... 

It is important that the distinction between risk and safety integrity be fully appreciated. Risk is a measure of the probability and consequence of a specified hazardous event occurring. This can be evaluated for different situations [EUC risk, risk required to meet the tolerable risk, actual risk (see Fig. A.l)]. The tolerable risk is determined on a societal basis and involves consideration of societal and political factors. Safety integrity applies solely to the E/E/PE safety-related systems, other technology safety related-systems and external risk reduction facilities and is a measure of the likelihood of those systems/facilities satisfactorily achieving the necessary risk reduction in respect of the specified safety functions. Once the tolerable risk has been set, and the necessary risk reduction estimated, the safety integrity requirements for the safety-related systems can be allocated, (see 7.4, 7.5 and 7.6 oflEC 61508-1) (Fig. 2.2). 

---