Document: NUREG-0800
Document ID: 7c7e043f-0cf6-4d85-ad06-3f01128bc7f8
Document Type: srp
Title: (ENiCrFe-7), and 5.14 (ERNiCrFe-7)
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0703/ML070380192.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.11
CFR Part: 
CFR Title: 

Content:
e buildup of corrosion product and sludge, which can lead to corrosion of the tubes and the supports. B. Uses appropriate corrosion-resistant materials or employs cladding for materials susceptible to corrosion. To limit the potential for denting the tubes, the tube support structures should use a corrosion-resistant material. Tube denting is a phenomenon associated with corrosion of the tube support structures, creating a hard corrosion product that fills the crevice between the tube and the tube support. Denting of tubes can result in the restriction of primary coolant flow and stress-corrosion cracking of the tubes. To limit the steam generator tube’s susceptibility to corrosion, the tubes should be heat-treated (e.g., thermally treated), as needed, to optimize their microstructure from a corrosion resistance standpoint. To reduce residual stresses in the U-bend region of short-radius tubes (and therefore the material’s susceptibility to corrosion), the U-bend region of short-radius tubes should be stress-relieved after bending. The materials that 5.4.2.1-7 Revision 3 - March 2007 support the tubes and other materials on the secondary side should be sufficiently resistant to degradation to ensure that the tubes will remain adequately supported and to reduce the potential for the generation of loose parts, which can result in a loss of tube integrity. The corrosion-resistant cladding on the tubesheet and on other primary side components should be weld-deposited, fabricated, and inspected according to the requirements in Part QW of Section IX of the ASME Code. C. Limits the crevice and residual stresses in the tubesheet region. The extent of the tube-to-tubesheet crevice should be limited. This can be accomplished by expanding the tube throughout the tubesheet region, if practical (given other design considerations such as the desired preload in the tube for once-through steam generators). The choice of the method for expansion should consider limiting the