Safety importance

Providing the NRC with new issues that have little safety importance. 

Some corporate sensitivity to investor pressure Product safety important Readiness to stay with project until goal is achieved... 

Vilkomir S.A., Kharchenko V.S. Methodology of the Review of Software for Safety Important Systems// Safety and Reliability. Proceedings of ESREL 99 - The Tenth European Conference on Safety and Reliability, Munich-Garching, Germany, 13-17 September, 1999, vol. 1, pp. 593-596. 

Adequate redundancy of the required instrumentation and equipment has to be defined in accordance with its safety importance. 

Complete preventive maintenance, with priority established on the basis of safety importance and reliability requirements of systems. 

Processes to detect and prevent quality problems as well as ensure quality improvements are established in the RREP-QAPP and implemented through several QA Implementing Procedures. The extent to which each applies to the various activities, operations, projects, and experiments at the Hot Cell Facility is described in the HCF PEQP. Four grouping of safety importance (graded approach) are defined in that RREP ... 

The PEQP assigns a Quality Level to all projects and experiments. Experiments, operations, and other activities (e.g., conduct of operations procedures) that are not included in the PEQP safety importance groups do not require a PEQP or formal quality level assignment. These types of activities are addressed for quality issues on a case-by-case basis or through department instructions that address quality and excellence. 

Rule 14a Human error probability n/10 does represent quite reasonable estimation of failure potential for typical safety important action driven by procedures, including both some information processing and manipulations. 

System reliability parameters (reliability, safety, importance, etc.). 

There are often used back-up systems to control complicated and safety important industrial technologies. It is recommended to make measurements of physical parameters based on different physical principles. This can avoid occurrence of common cause failures. 

Why is safety important Why bother with it There are three general reasons. 

The example of the leaching solution settling has shown that for systems with safety importance, quantitative analyses should be superimposed on qualitative observations. If in the future there is more effort made than in the past to procure an adequate data base for component failure rates, this will favor more intensive utilization of quantitative analysis, which is desirable for safety technology. 

From previous discussions it is seen that there are safety categories and classes as defined by lEC standards. lEC 61226 defines safety categories for nuclear safety 1. C functions (category A, B, C). lEC 61513 also defines three safety classes for 1. C systems (Class 1, Class 2, Class 3). A nonsafety class (NS) can be added to this classification. Based on the safety analysis, all safety I C subsystems will be assigned to a safety class on a case-by-case basis. Safety importance class (SIC) describes a classification scheme for structures, systems, and components that perform a safety function and contribute to the general safety objectives at ITER during incident/accident situations [12]. In the case of fusion technology, these classifications are termed SICl, 2, and SR. The relationship between these is shown in Table XII/3.3.M. 

There are no restraints on the secondary piping either inside or outside the containment. The plant proposes to perform an analysis of the risk of secondary pipe whip and, depending on the results, to consider installing pipe restraints. A further consideration is the mechanical substantiation of the safety important pipings and their supports, also with respect to seismic qualification. 

Identification of the safety importance of particular safety fimetions, which informs the safety categorisation process for SSCs in normal operation and fault conditions. The safety categorisation process is presented in sub-section 4.2.2 of the PCSR. 

Determining safety importance of systems and components at nuclear power plants... 

The evaluation of ageing performed using PSA applications can allow to evaluate the component ageing impact to the unavailability of the safety systems, to show an increasing of core damage frequency due to the ageing of safety important components and structures, and to propose optimal test and preventive maintenance intervals. 

This chapter should provide a description of all plant structures, systems and components that are important to safety and should provide a demonstration of their conformance to the design requirements. The level of detail of each description should be commensurate with the safety importance of the item described. 

It shall be ensured that it is possible to inspect or test either directly or indirectly the components of the reactor coolant pressure boundary, according to the safety importance of those components, so as to demonstrate the absence of unacceptable defects or of safety significant deterioration. 

The level of reliability necessary shall be commensurate with the safety importance of the system. The necessary level of reliabihty shall be achieved by means of... 

The SCL is an index number ranking the relative safety importance of a software module. This ranking implies that in order to make the software safe, greater development rigor must be applied to each successive criticality level. 

The SCL does not identify risk acceptance levels or authorities it establishes the safety importance of a software module and the LOR that is required to assure the software module presents acceptable risk. 

Top level in TLM does not necessarily imply a particular level of safety importance, but rather the common category visible at the system level (i.e., a hazard should fall within a particular TLM category). It should be noted, however, that by their very nature, TLMs have an implied level of safety-criticality. For example, the TLM Inadvertent missile launch has a greater safety-criticality than the TLM Personnel injury due to electrical contact. ... 

Armed with knowledge of the safety importance of a specific degradation area, an inspection programme can be identified which gives clear answers to a set of clear questions. This approach results in a set of in-service inspections that are based on ... 

The final step in the screening process is re-grouping of POSs and initiators. The result of the whole process is a list of safety important POSs and IE groups. The SLP PSA requires iterative processing for redefining and re-grouping POSs and lEs several times during the process. 

Safety systems should be independent of safety related and non-safety systems. Systems of lower safety importance may be associated with a safety Systran, provided that independence is maintained between these systems and that the independence of redundant safety groups is not degraded. 

Assessments should be made, on the basis of deterministic criteria supplemented by risk informed considerations, of the behaviour of passive components (e.g. check valves in discharge lines from accumulators or core make-up tanks) to ensure that their reliability is commensurate with their safety importance. 

The operation of safety systems and safety related systems and components of spent fuel storage facilities shall be subject to QA requirements commensurate with their safety importance. 

The process instrumentation system of the JRR-3M is consists of an instrumentation and control system and a safety protection system It is designed to measure process variables, such as flow rate, temperature, water level, pressure and so on, to provide information which is necessary for reactor operation and safety protection The measuring methods adopted in the system are of conventional ones but safety important components used are specified as reactor grade ... 

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