Document: NUREG-0800
Document ID: b43625e5-7a9e-473b-bb9a-eaa2ca15ae27
Document Type: srp
Title: -19
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1233/ML12334A360.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.3
CFR Part: 
CFR Title: 

Content:
Draft Revision 3 –June 2013 APPENDIX A STRESS LIMITS FOR ASME CODE SECTION III CLASS 1, 2, AND 3 COMPONENTS AND COMPONENT SUPPORTS, AND CORE SUPPORT STRUCTURES UNDER SPECIFIED SERVICE LOADING COMBINATIONS 1. INTRODUCTION Nuclear power plant components and supports are subjected to combinations of loadings derived from plant and system operating conditions, natural phenomena, postulated plant events, and site-related hazards. Section III, Division 1 of the ASME Code (hereafter referred to as the Code) provides specific sets of design and service stress limits that apply to the pressure retaining or structural integrity of components and supports when subjected to these loadings. Conditions also warranting consideration include thermally stratified flow, thermal striping, and/or thermal cyclic effects and the resulting spatial or temporal stresses on piping and components. Such conditions, where not identified and accounted for in stress analysis and fatigue evaluations of affected piping, can result in unacceptable stresses, pipe movements, deformations, and/or fatigue failures. These phenomena have typically been observed in feedwater piping, at feedwater nozzles, in Pressurized Water-Reactor (PWR) pressurizer surge lines, in piping between PWR pressurizers and associated relief valves, and at locations where piping normally containing relatively cool fluid is connected to the RCS via valves subject to intermittent leakage, such as at residual heat removal and emergency core cooling system connections to the reactor coolant system. The design and service stress limits specified by the Code do not ensure, in themselves, the functionality of components, including their supports, to perform the mechanical motion required to fulfill the component's safety function. Certain of the service stress limits specified by the Code (i.e., level C and D) may not ensure the functionality of components, including their supports, to deliver rated flow and retain dimensional