Document: NUREG-0800
Document ID: 6b7eddf4-f7ce-4821-9f11-e37070221e57
Document Type: srp
Title: DYNAMIC TESTING AND ANALYSIS OF SYSTEMS, STRUCTURES, AND
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1613/ML16133A418.pdf
Revision Date: 2023-06
Chapter: 3
Section ID: 3.9.2
CFR Part: 
CFR Title: 

Content:
ured over narrow frequency bands. Any SMT-based BUFs should be shown to be 3.9.2-22 Revision 4 – March 2017 bounding when compared to previously observed ratios from similar full- scale plants. When plant-specific data are not available, the acceptability of the SMT results needs to be demonstrated by a different method. For example, a slightly modified scale model may be tested to demonstrate the SMT acceptability against available data of another plant, or the SMT results may be confirmed during the startup tests of the specific plant. (ii) CFD simulations can be used to develop unsteady forcing functions, or to compute the distribution of flow velocity which is used to develop the forcing functions (see Section C.2.1.2.3 of RG 1.20, Revision 4 for additional details). Any CFD codes used to determine the forcing functions need to be validated and shown to provide bounding excitation limits. The computation model needs to reflect the details of the fluid domain, and the effects of grid size and time step need to be addressed. The simulated flow cases should include, but not be limited to, the worst- case scenario causing the strongest mal-distribution of reactor flow. In complex flow situations, only conservative assumptions should be made to determine the forcing functions (e.g., correlation length and phase distribution of fluid forces). (iii) Force inference methods have been used in previous EPU applications to aid the vibration analysis of replacement steam dryers in BWRs. These methods use inverse structural and/or acoustic models to estimate fluctuating pressures within the RPV and on BWR steam dryers. The dryer pressures are inferred from alternating strain or pressure measurements on the dryer surface or from hoop strains on the MSLs connected to the RPV (see Section C.2.1.2.4 of RG 1.20, Revision 4, for additional details). Other force inference methods estimate directly the maximum strains and vibrations in a structure. Force inference methods, whether