PSI - Issue 17

Salatiel Pérez Montejo et al. / Procedia Structural Integrity 17 (2019) 123–130 Salatiel Pérez Montejo et al / Structural Integrity Procedia 00 (2019) 000 – 000

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LEFM NRC

Linear Elastic Fracture Mechanics Nuclear Regulatory Commission

SIF SRP

Stress Intensity Factor Standard Review Plan Stress Intensity Factor Fracture Toughness

USNRC

United States Nuclear Regulatory Commission

K I

K IR

T

Temperature Thickness

t

E α

Young modulus

Thermal expansion coefficient

Δ T

Temperature increment

μ

Poisson Ratio

σ m

Circumferential Stress

2. Statement of the problem

A semi-elliptical crack may be developed in the internal surface of a BWR-5 vessel. The most common place is the beltline zone, because the material is embrittle by the radiation. Accordingly, such crack was postulated along the axial direction of reactor vessel. Under this circumstance, the structural integrity is reduced. Therefore, it is important to determine the adequate levels of pressure and temperature of operation. For the problem at hand, the reactor vessel started its operation at the beginning of the nineties. In a previous paper, Alvarez-Loya et al, evaluated the Stress Intensity Factor (SIF) and compared with the Fracture Toughness of the material, after it has been irradiated. The requirements established in the Appendix G of ASME Code Section XI were taken into account. In the case of this paper, the pressure-temperature limit curves were developed for the proposed case, following this approach. A similar evaluation was done with the Finite Element Method. The solutions of both procedures were compared. 3. Materials and Methods

3.1. Crack dimensions and material of the reactor vessel

A semielliptical crack has been postulated at the internal surface of the reactor vessel (Fig. 2). It is oriented along the axial direction in beltline zone. Its depth is one fourth of the wall thickness and its length is six times its depth.

(b)

(a)

Fig. 2. (a) Semielliptical crack dimensions; (b) Model of the semielliptical crack in ANSYS 2019 R1.