Safety Reference Levels

At European level, so-called safety reference levels have been defined by WENRA (2008,2013), originally in the context of the definition of safety requirements for nuclear installations of countries which are potential candidates to join the European Union. These reference levels should be adhered to by all member countries of the European Union. 

Western European Nuclear Regulators Association WENRA. 2008. WENRA reactor safety reference levels, January 2008. 

Western European Nuclear Regulators Association WENRA. 2013. WENRA safety reference levels for existing reactors, update in relation to lessons learned from TEPCO Fukushima-Daiichi accident, November 20, 2013. 

WENRA, Western European Nuclear Regulators Association, 2014. Safety Reference Level for Existing Reactors. Available at http //www.wenra.org/harmonisation/reactor-harmonisation-working-group. 

Enhancement of Process Safety Knowledge—The level of performance in this area can be based on analysis of involvement in internal and external research, including CCPS programs and professional and trade association programs (both domestic and international), improved prredictive systems, such as toxicological data and trend information on maintenance failures, and a process safety reference library. 

General References Guidelines for Hazard Evaluation Procedures, Second Edition with Worked Examples, American Institute of Chemical Engineers, New York, 1992 Layer of Protection Analysis A Simplified Risk Assessment Approach, American Institute of Chemical Engineers, New York, 2001 ISA TR84.00.02, Safety Instrumented Functions (SIF)—Safety Integrity Level (SIL) Evaluation Techniques, Instrumentation, Systems, and Automation Society, N.C., 2002. 

We chose Level 2 as the reference level during our analysis that means that by safe we understand that the system is compliant with the railway safety regulations. And we chose Level 6 as the lowest component level (we did not consider further decomposition levels). Our goal was to analyse how possible failure modes of the components can affect the safety properties expressed with respect to Level 2. 

Answer It is interesting to note that safety regulations specify a certain physical spacing that must be maintained between the primary and secondary sides — in terms of the RMS of the voltage differential between them. The question arises — how do we define a voltage difference between the two sides of a transformer that are supposedly separate What is the reference level to compare their voltages ... 

Resistance to microfissuring is strongly affected by plate structure it is excellent in a plate with fine and fibrous structure, as shown in Fig. 1. Because of severe safety requirements for LNG storage tanks, the quality of the majority of welds is specified to be monitored by ultrasonic inspection. The accuracy of ultrasonic inspection of weld defects depends mainly on the ultrasonic characteristics of the base metal, in which noises and attenuations are important. Distance amplitude correction curves, obtained in accordance with Section VIII of the ASME Boiler and Pressure Vessel Code and NV Rules, are shown in Fig. 1. Since the evaluation level is 20% of the reference level (R.L.), it is difficult to detect defects unless the noise level is below 20% of R.L. at every node. Noises and attenuations of ultrasonic responses increase with coarsened plate structure, and in plates with very... 

Safety instrumented systems (SISs), with their associated Safety Integrity Levels (SILs), play an increasingly important part in assuring the safety of process plants. Referring to the standard example once more, a high-level interlock can be installed on LRC-101 such that when the level... 

Within the framework of [1] the standards [2]-[4] refer to the process industry. In these standards the continuous spectrum of failure frequencies and unavailabilities is divided into four discrete bands, the safety integrity levels, as shown in Tables 11.1 and 11.2. The bands apply to safety-related systems. These are systems which play a role for safety and can therefore in addition to safety systems also comprise elements from the operating level. The bands in Tables 11.1 and 11.2 are targets whose selection and fulfilment are presented below. 

Individual risk criteria are reference levels for evaluating individual risks. Tbe individual risk criteria were given a legal status in 2004 by tbe External Safety Decree. These limits to individual risk prevent dispro-portional individual exposures. Permits for property developments or plant modifications are denied if vulnerable objects would then be located within the 10 contour (Fig. 1). 

SIL refers to Safety Integrity Level. The number 3 is a numeric term that specifies the relative integrity of its safety function performance—the probability that it will perform as designed when required to perform. A SIL 3 compliant brake system means that the system is designed according to the lEC 61508/62061 (lEC, 2014) functional safety standards framework and there is a high probability that it will function as designed and correctly when called upon. 

As noted above, SIL means safety integrity level and a discrete number (1 to 4) is used to indicate the probabihty of the safety system satisfactorily performing the safety related control functions under all stated conditions the higher the level of safety integrity of the item, the lower the probabihty that the item will fail to carry out the safety related control function (Reference 2, P.16). lEC 61508 specifies four SIL levels—SIL 1, SIL 2, SIL 3 and SIL 4, while lEC 62061 does not consider SIL 4. 

The procedure described in Section 6 should be followed to identify any differences between the safety status of a nuclear power plant and current safety standards and practices (a reference level used for comparison). Some differences may actually be strengths because the safety status of a plant on particular issues may be better than for current standards and practices. The procedure does not require that a nuclear power plant meet all current standards however, practicable improvements should be made as steps towards meeting them. It is recognized that some safety features, such as current seismic features, cannot easily be backfitted, and some design aspects, such as plant layout, are difficult to modify. For these cases, the procedure requires that the risk associated with the shortcomings be assessed and that a justification for continued plant operation be provided. 

This chapter details all standards which have to be addressed, failure rate targets, allocated safety integrity levels, a description of requirements handed over from other safety cases and emerging from the hazard analysis and a reference forward to where each requirement is addressed. It also includes operational safety requirements. 

In Safety Series No. 89, a trivial risk is evaluated firstly, by choosing a level of risk and the corresponding dose which is of no significance to individuals secondly, by using the exposure to the natural backgroimd, to the extent that it is normal and imavoidable, as a relevant reference level. After evaluating these approaches, it was concluded that for the purpose of exemption, a level of individual dose of some tens of microsieverts in a year could reasonably be regarded as trivial by competent authorities. 

The concept of safety refers to a reasonable certainty of no harm per the FD C Act to safe and adequate levels of nutrients, including essentiality, stability, history of use, and toxicity per LSRO or, in some circumstances, a reasonable balance between costs (e.g., risks, harm) and benefits. Safety, therefore, is not an inherent biological property, but rather a point on a continuum that is influenced by intellectual concepts and judgment. Generally, a hazard refers to a substance or combination of substances that produce undesired outcomes in the case of infant formulas, the undesired outcome is health related. Risk implies that an adverse event will be expressed under specified conditions, and harm refers to the nature of an undesired outcome associated with a hazard. Details about the concept of safety and surrounding issues are provided in Chapter 2. 

Refer to lEC 61508-1, table 2 (for low demand mode operation) or table 3 (for continuous or high demand mode operation) to determine the safety integrity level (SIL). The SIL then guides the selection of the techniques used for the avoidance of systematic faults in both hardware and software, so that as the risk reduction increases, or the hazard rate decreases, there is a reduction in the likelihood that systematic failures (including those resulting from incorrect specification) will result in a hazard. 

Behaviors = Action of people taken at all levels of the organization. What they do or do not do in the workplace affects safety. Refer to Figures 17-2 and 17-3 for more on the input, outputs, and consequences. 

Random failure usually refers to permanent failure due to non-functioning of system components, and these are more related to hardware failure. Probabilistic performance-based approach could be one way to address this. For E/E/PE systems, safety integrity level (SIL) is considered for such purposes. 

Table VI/4.0.6-1 Safety Integrity Level Assignment Table (Also Refer to ...

For any safety loop comprising several components, the safety integrity level (SIL) achievement is a joint responsibility of end-user and supplier, as will be clear from Table IX/1.0-1. Why discussing this here These are discussed here to show that equipment manufacturer/system integrator or end-user is not only responsible for the same in isolation. In a safety life cycle, there are several phases involving several activities. So, at various stages there will be involvement of either end-user or sup-plier/manufacturers. The same issue has been elaborated in Clause 1.0.1 refer to Fig. IX/1.0-1 also. 

With the introduction of safety standards lEC 61508 and 61511 (for process industries), there is a defined need for proper implementation of safety systems embedded into the main system. The safety life cycle has various phases. Phases 1 and 2 have been discussed at length in previous chapters (Chapter VI and Chapter VII and to a certain extent in Chapter IX). In this part, detailed discussions have been presented to include Phases 3—7, that is, from safety-related systems (SRSs) to modifications. This has been done purposefully so that prior to looking at the detailed implementation part of the standard, readers need to have some knowledge of the safety instrumented system (SIS), safety integrity level (SIL), and their implementation in various instrumentation components. So, this part of the discussions in conjunction with previous chapters will complete the topic of lEC 61508/61511. Safety instrumentation cannot be complete without discussions on explosion protection. With reference to lEC 60079-(0,10,14,15,17, etc.) and NEC (497,499,70, etc.), electrical area, classification of plant, explosion protection, etc. also have been included as part of this chapter to make the system complete in all respects. In view of this, these are presented in two sections. Section 1 for lEC implementation and Section 2 for explosion protection. 

Per Trent, volume relates to the amount of inventory a company owns at any time and key indicators will relate to total units on hand, including safety stock levels. Velocity refers to how quickly raw material and work-in-process inventory is transformed into finished goods that are accepted... 

In Part G of these reference levels, the safety classification of Structures, Systems and Components (SSCs) is described. The goal is to identify all safety related SSC and to classify them according to their importance for safety. Part Q reflects changes in a Nuclear Power Plant (NPP) and it is requested that no change reduces the abihty of the reactor for safe operation in any form. In addition, national regulations and international agreements within the European Union are supplemented by a directive of the European Commission (2009b) which had to be implemented by July 2011 into national... 

In this study there are six non-parameterised strategies which are applied and evaluated in the SC model using simulation, including (1) JIT (lot-for-lot) (2) JIT (lot-for-lot) with safety stock (3) Kanban (fixed WIP) (4) Kanban (fixed WIP) + safety stock (5) VMl (based-stock policy) and (6) VMl (based-stock policy) with safety stock. The case company B s original strategy will also be evaluated and used as a base reference point. There are two fixed safety stock levels 20% and 30%. The reason for their choice is based on the consideration of inventory capacity, the raw material product cycle time and the financial flow information (from the interview discussions). 

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