Document: NUREG-0800
Document ID: e2737d9a-8e56-46cb-a97d-aaf62a442c6c
Document Type: srp
Title: PRESSURE-TEMPERATURE LIMITS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340637.pdf
Revision Date: 2023-06
Chapter: 5
Section ID: 5.3.2
CFR Part: 
CFR Title: 

Content:
h = 0.25 t and length = 1.5 t), the KI expressions are simpli- fied to multiples that are a function only of wall thickness and stress level. These factors, Mm for membrane stresses and M. for bending stresses, are provided in graphical form in Figure G-2214.1 of the Code. Refer to Figure 1 herein. The criterion recommended by MTEB can be expressed as KI < KIR for the shell region. To get KI, the stress level and wall thickness must be known. The pressure for the hydrostatic test is 1.25 times the design pressure, so that the higher of two simple methods described below to approximate the membrane stress should be accurate enough for this purpose: stress = 1.25 times the Code allowable (SM) stress = Pr t. where P is the test pressure and r is the vessel radius. As an example, assume a vessel with a design pressure of 2500 psig, made of steel with an Sm of 26,700 psi, and a minimum yield strength of 50,000 psi. The stress for the preservice hydrotest is then 26,700 x 1.25 = 33,400 psi, or (1.25) (2500) (95) = 33,400 psi, for a vessel with a radius of 95 inches and a wall thickness of 9 inches. The next step is to determine the factor to apply to this stress to obtain K . Figure G-2214.1 (reproduced here as Fig. 1) provides several curves, depending on the ratio of the stress level to the yield strength of the material. In this case, the stress level is 33,400; the yield strength is conservatively assumed to be 50,000 so the curve for a ratio of .7 should be used. (A ratio equal to or higher than the actual ratio must be used for conservatism.) For a 9-in. thick vessel (41 = 3), the value of Mm from Figure G-2214.1 is 2.94. The KI for this case is then: 5.3.2-6 Rev. 1 - July 1981 K, = (MM) (Membrane Stress) KI = (2.94) (33,400) = 98,300 psi -ji'i From Figure G-2210.1 (reproduced here as Fig. 2), a temperature of at least RTNDT + 120'F is necessary for a KI of this level. If, for example, an original RTNDT of 400F is assumed, the required temperature is then 40 + 120,