Document: NUREG-0800
Document ID: 967102fd-cb63-4897-b488-1358be1b2640
Document Type: srp
Title: TURBINE DISK INTEGRITY
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350072.pdf
Revision Date: 2023-06
Chapter: 10
Section ID: 10.2.3
CFR Part: 
CFR Title: 

Content:
e made for each forging. Elements that have a deleterious effect on toughness, such as sulfur and phosphorus, should be controlled to low levels. b. The fracture appearance transition temperature (50% FATT) as obtained from Charpy tests performed in accordance with specification ASTM A-370 should be no higher than 0OF for low-pressure turbine disks. Nil-ductility transition (NDT) temperature obtained in accordance with specification ASTM E-208 may be used in lieu of FATT. NDT temperatures should be no higher than -300F. c. The Charpy V-notch (Cv) energy at the minimum operating temperature of each low-pressure disk in the tangential direction should be at least 60 ft-lbs. A minimum of three Cv specimens should be tested in accordance with specification ASTM A-370. 2. Fracture Toughness The low-pressure turbine disk fracture toughness properties are acceptable if in compliance with the following criteria: The ratio of the fracture toughness (KIC) of the disk material to the maximum tangential stress at speeds from normal to design overspeed should be at least two 4Tn., at minimum operating temperature. Bore stress calculations should include components due to centrifugal loads, interference fit, and thermal gradients. Sufficient warmup time should be specified in the turbine operating instructions to assure that toughness will be adequate to prevent brittle fracture during startup. Fracture toughness properties can be obtained by any of the following methods: a. Testing of the actual material of the turbine disk to establish the KIC value at normal operating temperature. b. Testing of the actual material of the turbine disk with an instrumented Charpy machine and a fatigue precracked specimen to establish the Kic (dynamic) value at normal operating temperature. If this method is used, KIc (dynamic) shall be used in lieu of KIC (static) in meeting the toughness criteria above. c. Estimating of KIC values at various temperatures from conventional Charpy and tensile