Chapter 35
Functionality and Operability Criteria


Chapter 35, authored by Guy H. DeBoo, discusses the functionality and operability criteria, which address evaluations for operating plant systems, structures, or components (SSCs) found to be degraded, nonconforming, or subjected to unanalyzed conditions during nuclear plant operation. This chapter addresses the methodology and acceptance criteria applicable to these evaluations. Guy discusses SSCs that require operability evaluation methods and assessments, failure modes, functionality and operability, and as-built conditions divergent from design. He covers, with the aid of figures, tables, and references, Code requirements as well as short- and long-term operability acceptance criteria for valves, pumps, snubbers, piping, reactor vessels, tanks, heat exchangers and supports (including component standard and linear supports as well as spring hangers), structural bolts, concrete expansion anchors, and integral welded attachments.

The current practice involves a process of consensus among the regulator viewpoints; plant-specific Technical Specification (TS) requirements; and applicable Codes, Standards, rules, and other licensing-basis compliance requirements. Guy discusses the role of related agencies and committees, such as the U.S. NRC, the ASME Code Committees, and the ASME O&M Code Committees. This chapter includes basic concepts, definitions, evaluation methods, and acceptance criteria from these documents. In this chapter, the scope of SSCs is limited to mechanical systems and their components and supporting structures. Guy discusses the role of the CFR-facility TSs as they relate to the topics of this chapter. Guy provides examples of specified safety functions, operating conditions, and events to be considered for some SSCs and piping. His discussion elucidates the often complex, sometimes nonuniform nature of operability concepts and criteria.

  • 35.1 Introduction
  • 35.2 Functionality and Operability Assessments
  • 35.3 ASME Code Requirements for Operability
  • 35.4 Operability Evaluation Methods
  • 35.5 Short-Term Operability Acceptance Criteria
  • 35.6 Long-Term Operability
  • 35.7 Common Term Definitions
  • 35.8 Nomenclature
  • 35.9 References

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