Document: NUREG-0800
Document ID: 495c2b41-2832-4900-9000-040f3ae8c835
Document Type: srp
Title: STEAM GENERATOR MATERIALS AND DESIGN
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1614/ML16147A289.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.4.2.1
CFR Part: 
CFR Title: 

Content:
s evaluated and that the analyses accounted for tube plugging and tube bundle fouling. 3. Confirm that for analyses of the steam generator tubes, the flow-induced vibration model shows that sufficient margin to fluid-elastic instability (i.e., at least 25 percent) has been maintained. If conditions 1 – 3 are not met, or if the steam generator design is new or unique, a detailed evaluation of the technical basis should be performed. 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