Document: NUREG-0800
Document ID: 8afa51d9-10c9-4521-a19c-f082a562bcda
Document Type: srp
Title: -
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1602/ML16029A367.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.4.2.1
CFR Part: 
CFR Title: 

Content:
ed. The detailed evaluation may include reviewing scale testing under the expected operating conditions. B. Limits the crevice between the tube and the tube supports. This can be accomplished by using openings of various shapes (e.g., trifoil or quatrefoil) in tube support plates or by using lattice grid (eggcrate) tube supports. The design of the tube supports should promote high-velocity flow along the tubes. Limiting the crevices will limit the buildup of corrosion product and sludge, which can lead to corrosion of the tubes and the supports. C. 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 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