Document: NUREG-0800
Document ID: b4808a6f-81dd-45c9-8350-c8d58808bcd4
Document Type: srp
Title: STEAM GENERATOR MATERIALS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070446.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.4.2.1
CFR Part: 
CFR Title: 

Content:
ples of materials that are currently being used for Class 1 components include the following: Tubing - ASME SB-163, Ni-Cr-Fe, annealed (Inconel 600) - ASME SB-163, Ni-Cr-Fe (Inconel 690)7 Tube Sheet - ASME SA-502, C1 2 and 2a, weld-clad with Inconel 600 on the primary coolant side Channel Head Casting - ASME SA-216, Grade WCC, Class 1, or weld-clad with austenitic stainless steel Channel Head Plate - ASME SA-533, Grade A, B, or C Forged Nozzles - ASME SA-508, Class 2, and 2a Examples of materials that are currently being used for Class 2 components include the following: Shell Pressure Plates - ASME SA-533, Grade A, B, or C, Class 1 and 2 Bolting - ASME SA-193, Grade B-7 ASME SA-540, Grade B 23 or B 24 Tube Support Plates or Grids - ASME SA-240 ASME SA-479 The fracture toughness properties and requirements for ferritic materials of Class 1 and Class 2 components are reviewed. 2. Steam Generator Design The design and the fabrication procedures are reviewed to determine that the extent of crevice areas are minimized in the completed steam generators. A "tube denting" phenomenon has occurred in a number of steam generators. Based on operating experience and laboratory testing, it is believed that the denting is associated with the growth of a corrosion product (principally Fe 0 ) in the 3 4 crevice. The corrosion is caused by the concentration of steam generator water impurities in the annulus. The growth of corrosion product puts inward pressure 5.4.2.1-3 DRAFT Rev. 3 - April 1996 on the tube resulting in radial deformation of the tube. As corrosion proceeds and in-plate forces accumulate, there are a number of secondary effects in the steam generator. These include (a) tube support plate hole dilation; (b) tube support plate flow hole distortion, and flow slot hour-glassing; (c) tube support plate 8 expansion with cracking between hole ligaments; (d) wrapper distortion; (e) leg displacement of the smallest radius U-bend heat tube, and (f) tube leakage. The extent of