DERIVATION OF TECHNICAL SAFETY REQUIREMENTS

Structures, systems, and components (SSCs) that are important to safety and that are identified as Safety SSCs are based on criteria contained in DOE-STD-3009 (p. xix) and the results of safety analyses, which determine the safety contributions of specific SSCs. The degree of consequence mitigation is the basis for identification of Safety SSCs and associated Safety Functions". These Safety Functions are the essential performance requirements that are imposed on Safety SSC s which maintain the consequences of accident scenarios within bounds that are described in the SAR accident analysis. The use of the term Safety Function will be limited to these essential performance requirements in this SAR. While many SSCs provide a material safety benefit and could be considered to perform a safety function, SSCs that are not relied upon to effect an acceptable outcome will not have an associated Safety Function as the term is used in this S/VR. Safety SSCs and associated Safety Functions are based on the results of hazard evaluation and accident analysis described in Chapter 3, and are specifically identified in Section 3.3.2.3. The specific safety functions important to safety are described in Chapter 4, and form the basis of the derivation of Technical Safety Requirements presented in Chapter 5. 

Initial startup testing procedures have been prepared and implemented to demonstrate that structures, systems, and components (SSCs) and processes will perform as intended. Initial testing includes, as appropriate, bench tests and proof tests prior to installation, mockup tests, pre-operational tests, post-maintenance tests, post-modification tests, and operational startup tests. Safety-related items are subject to the quality-assurance requirements of SNL/NM Research Reactor and Experimental Programs (RREP) Quality Assurance Program Plan (SNL 1998a), as implemented by the facility Project/Experiment Quality Plan (PEQP). Testing inciudes those initial tests mandated by applicable Technical Safety Requirement (TSR) surveiilance requirements (see Chapter 5.0, "Derivation of Technical Safety Requirements") and Operational Readiness Review (ORR) requirements (see DOE O 425.1 and DOE-STD-3006-93). 

DOE Order 5480.22 (DOE 1992a), Derivation of Technical Safety Requirements. DOE Order 5480.23 (DOE 1992b), Derivation of a facility Safety Analysis Report. DOE O 151.1, Chg. 2 (DOE 1995a), Comprehensive Emergency Management. 

This chapter provides the bases for the Technical Safety Requirements (TSRs), derived from the safety analyses presented throughout this SAR, which, when Implemented, will ensure the safe operation of the HCF. The content of this chapter provides the iink between the assumptions made in the hazard/accident analysis, operational safety commitments, plant configuration, and the TSR document as required by DOE Order 5480.22, Technical Safety Requirements (DOE 1992a). 

Another safety-related metric is the fraction of functional safety concepts that are matched by a technical safety concept. This can be computed based on derivation relations between functional and technical safety requirements combined with realization relations between analysis functions and design functions making up the architectural aspects of the functional and technical safety concepts, respectively. 

Chapter 7, part 4 addresses the system design, the technical safety concept and their verification, which should be derived from the functional and technical safety requirements. Therefore, in requirement 7.4.3.1 the inductive (for all ASILs) and deductive (for the higher ASILs) safety analysis is required. In this context of product development on system level it is primarily a matter of the analysis of systematic failure. In one indication (note 1) it says that a quantitative analysis can support the results. 

US Pharmacopeia 29/NationaI Formulary 24,1086, Rockville, MD, 2006, p. 2921. International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use, ICH S6 Preclinical Safety Evaluation of Biotechnology-derived Pharmaceuticals, 1997. 

Event-tree models in a Level 1 PSA generally account for the order of demands of safety system functions at set points and for the (stochastic) failure behaviour of the required functions. It is common practice to consider just two alternative states at each set point, namely required function is successful and required function fails . No satisfactory consideration is given, for instance, to situations where technical safety systems which are successfully started fail to function with the required capacity and / or fail to run within the required mission time. What is the consequence, if sequences accounting for stochastic failure times of safety system functions are not considered Is the resulting spectrum of event sequences still sufficient enough to obtain an adequate probabilistic assessment for (core) damage states How reahstic are the probabilistic assessments for damage states derived from static event tree models ... 

Functional and technical requirements are not different by its nature, the allocation within the architecture characterize them as such. Figure 4.25 shows that if the logical and technical perspectives are separated, the common usage of element 3 (E3) becomes transparent. We can describe functional correlations from technical as well as logical elements and we can also functionally describe the internal correlations or a technical element. This is why it is important to determine a specific description level for the technical system architecture and specify flie implemented element and their interfaces. As a result the safety requirements are derived from the functional safety concept to the elements and the interfaces of the technical architecture, whereas the system interfaces do not necessarily have to be described by technical elements. 

Thus it is also in the second interpretation, the request itself is really what is required, according to ISO 26262 in deriving the functional safety concept for technical safety concept through to the component requirements. Here ISO 26262 calls the activity also verification of requirements. 

Following the completion of the first draft design of the planned installation, the necessary requirements derived from experience must be established. Applicable laws and technical rules must be observed. In the event that requirements based on experience cannot adequately guarantee system safety, special attention must be devoted to failure effect on the environment. Qualitative analysts will be continued step by step until unequivocal assessment is possible. In the event that qualitative analysis does not furnish a clear statement concerning system safety, and if the expected danger for the environment due to the behavior of the system under consideration requires it, quantitative analysis should follow qualitative analysis. As a rule, quantitative analysis concerns only particularly critical subsystems indicated in the scope of qualitative analysis. 

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