Numerical study of the applicability of the η-factor method to J-resistance curve determination of steam generator tubes using non-standard specimens

Degraded steam generator tubing can affect its safety functions. Therefore, its integrity should be maintained for each degradation form and all detected degradation must be assessed to verify that if adequate integrity is retained. Determination of tube integrity limits includes identifying acceptable structural parameters such as flaw length, depth, and amplitude of signals. If we consider just single-cracked tubes, short and deep flaws are not likely to threaten structural integrity of tubes. But if it has multiple-cracks, we have to consider interaction effects of multiple adjacent cracks on its burst pressure. Because adjacent multiple cracks can be merged due to the crack growth then it can challenge against the structural performance limit. There are some studies on the interaction effects of adjacent cracks. However, existing works on the interaction effect consider only through-wall cracks. No study has been carried out on the interaction effects of part-through cracks. Most cracks existing in real steam generator tubing are not through-wall cracks but part-through cracks. Hence, integrity of part-through cracks is more practical issue than that of through-wall cracks. This paper presents experimental burst test results with steam generator tubing for evaluation of interaction effects with axial oriented two collinear and parallel part-through cracks. The interaction effect between two adjacent cracks disappeared when the distance exceeds about 2 mm.

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Numerical Study of the Deposition of Radioactive Nucleoids (Aerosol) in PWR Steam Generator

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4051618 ◽

2021 ◽

Author(s):

Muhammad Aadil ◽

Rab Nawaz ◽

Ajmal Shah ◽

Kamran Rasheed Qureshi

Keyword(s):

Steam Generator ◽

Numerical Study ◽

Deposition Efficiency ◽

Decontamination Factor ◽

Radioactive Nuclide ◽

Discrete Phase Model ◽

Velocity Magnitude ◽

Discrete Phase ◽

Steam Generator Tubes ◽

Secondary Side

Abstract This research presents numerical study of deposition efficiency and decontamination factor of radioactive nuclide in steam generator tubes of a typical 325 MWe PWR. To find out the deposition of aerosol, the discrete phase model (DPM) has been used. The flow has been characterized as compressible, adiabatic, turbulent and wall bounded. When steam generator tube gets ruptured, the radioactive nuclides can escape from primary side and create a radioactive field in the secondary side. This can be harmful for the personnel working at the plant. Therefore, in order to ensure the safety of the plant and personnel, it is important to study the particles deposition on the wall of steam generator tubes. In the present study, a CFD methodology has been first developed and validated with the published results. After methodology validation, it has been applied to the U-tube of a typical PWR steam generator. It has been observed that due to the action of centrifugal force near the bent, the velocity magnitude is high towards the inner wall and the flow separates at the bent entrance. Furthermore, the flow inside the tube is rotational with vortices throughout the domain due to the presence of the bent. Finally, the deposition efficiency and decontamination factor have been calculated and it has been observed that both increase with the increase in particle size due to inertial effects.

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Experimental determination of J-resistance curves of nuclear steam generator tubes

Engineering Fracture Mechanics ◽

10.1016/j.engfracmech.2016.07.008 ◽

2016 ◽

Vol 164 ◽

pp. 1-18 ◽

Cited By ~ 6

Author(s):

Marcos A. Bergant ◽

Alejandro A. Yawny ◽

Juan E. Perez Ipiña

Keyword(s):

Experimental Determination ◽

Steam Generator ◽

Resistance Curves ◽

Steam Generator Tubes

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Estimation of Plastic Collapse Load of Steam Generator Tube With Two Parallel Axial Through-Wall Cracks

Residual Stress, Fitness-For-Service, and Manufacturing Processes ◽

10.1115/pvp2003-2067 ◽

2003 ◽

Author(s):

S. I. Moon ◽

Y. J. Kim ◽

J. H. Lee

Keyword(s):

Steam Generator ◽

Local Failure ◽

Plastic Collapse ◽

Steam Generator Tube ◽

Coalescence Model ◽

Collapse Model ◽

Failure Models ◽

Optimum Model ◽

Steam Generator Tubes

The 40% of wall criterion, which is generally used for the plugging of steam generator tubes, is applied only to a single crack. In the previous study, a total number of 9 failure models were introduced to estimate the local failure of the ligament between cracks and the optimum coalescence model of multiple collinear cracks was determined among these models. It is, however, known that parallel axial cracks are more frequently detected during an in-service inspection than collinear axial cracks. The objective of this study is to determine the plastic collapse model which can be appfied to the steam generator tube containing two parallel axial through-wall cracks. Three previously proposed local failure models were selected as the candidates. Subsequently interaction effects between two adjacent cracks were evaluated to screen them. Plastic collapse tests for the plate with two parallel through-wall cracks and finite element analyses were performed for the determination of the optimum plastic collapse model. By comparing the test results with the prediction results obtained from the candidate models, a COD base model was selected as an optimum model.

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A Numerical Study on Graphite Dust Deposition on Steam Generator Tubes in the High-Temperature Gas-Cooled Reactor (HTGR)

Volume 6B: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-82043 ◽

2018 ◽

Author(s):

Mingzhe Wei ◽

Yiyang Zhang ◽

Zhu Fang ◽

Xinxin Wu ◽

Libin Sun

Keyword(s):

High Temperature ◽

Steam Generator ◽

Deposition Rate ◽

Numerical Study ◽

Fem Simulation ◽

Dust Deposition ◽

Lagrangian Simulation ◽

Large Particles ◽

Steam Generator Tubes ◽

High Temperature Gas

Graphite dust is an important issue for the operation and maintenance of high-temperature gas-cooled reactor (HTGR), because the transport of fission product (FP) is coupled closely with graphite dusts. For instance, vapor phase FP could condense as flowing through the steam generator (SG) and deposit on the surface of graphite dusts that are either air-borne or already deposited on SG tubes. In water ingress or loss-of-coolant accidents, these dusts may re-suspend and contribute to the source term. Despite the importance of graphite dusts in HTGRs, the transport and deposition of dust particle are far from being fully understood, neither particle-fluid nor particle-wall interactions. In this work we present a numerical study on the particle transport through upper 5 layers of SG tubes. Particularly, the particle impaction process is simulated by Finite Element Method (FEM) with adhesion and dissipation specially accounted. The FEM simulation predicts the critical adhesion velocity and restitution coefficient when rebound occurs. Then we substitute the particle impaction model into Eulerian-Lagrangian simulation of flow field and extract the deposition rate statistically. The result shows that for small particles (< 5 μm), the deposition rate is controlled by the collision rate, which is mainly determined by the interaction between turbulence and thermophoresis. The particle-vortex interaction is essentially important for the distribution of particles near wall and thus influences the deposition rate. For large particles the deposition rate is more affected by the sticking efficiency, which is simultaneously controlled by both the critical adhesion velocity and normal impaction velocity. Therefore, the deposition rate first increases then decreases with particle size and reaches maximum at about 5 μm.

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