Successful life management of steam generators requires an ongoing operational assessment plan to monitor and address all potential degradation mechanisms. A degradation mechanism of concern is tube fretting as a result of flow-induced vibration. Flow induced vibration predictive methods routinely used for design purposes are based on deterministic nonlinear structural analysis techniques. In previous work, the authors have proposed the application of probabilistic techniques to better understand and assess the risk associated with operating power generating stations that have aging re-circulating steam generators. Probabilistic methods are better suited to address the variability of the parameters in operating steam generators, e.g., flow regime, support clearances, manufacturing tolerances, tube to support interactions, and material properties. In this work, an application of a Monte Carlo simulation to predict the propensity for fretting wear in an operating re-circulation steam generator is described. Tube wear damage is evaluated under steady-state conditions using two wear damage correlation models based on the tube-to-support impact force time histories and work rates obtained from nonlinear flow induced vibration analyses. Review of the tube motion in the supports and the impact/sliding criterion shows that significant tube damage at the U-bend supports is a result of impact wear. The results of this work provide the upper bound predictions of wear damage in the steam generators. The EPRI wear correlations for sliding wear and impact wear indicate good agreement with the observed damage and, given the preponderance of wear sites subject to impact, should form the basis of future predictions.

The response of buildings to a pressure pulse from a shock wave is becoming more critical to design assessments. The severe loading transients resulting from such events, provides unique challenges to analytical modelling and simulation of building survivability. In this paper, a nonlinear explicit three dimensional blast simulation of a building is undertaken with critical contents located in the most susceptible locations in order to provide an assessment of potential damage and the impact on the contents of interest. In the work described in this paper, the source and orientation of the blast relative to the building are outlined. Using developed blast procedures, the amplitude and impulse of the blast shock wave due to specified blast parameters are determined for the front, sides, roof and rear of the building. These are applied to finite element models of the building. A state-of-the-art, large deformation, non-linear finite element code that is well suited to this class of problem, is used in the blast simulations. The results indicate that the building is severely damaged, however, the internal building area, in the vicinity of the critical contents, is intact and the main roof trusses remain attached.

In order to better understand and predict hydride blister formation and hydride cracking in zirconium alloy CANDU (1) fuel channels, specialized computational methods are required. Hydride blister formation involves the coupled action of gradients in temperature and hydrogen concentration, while hydride cracking involves coupling of stress and concentration gradients. Hydride accumulation and crack growth in a leaking crack involves a complete coupling of concentration, stress and temperature gradients. In all cases, the action of dissolution or precipitation of hydride adds complexity to the numerical analysis procedure. Dedicated finite difference and finite element programs have been developed and applied to blister formation and uniform temperature cracking problems. On the basis of experience gained in the use of such specialized codes, a fully coupled capability has been integrated into a general-purpose finite element program. This program can more realistically address complex load and temperature histories that may be encountered during fuel channel operation. An overview of important computational features is given along with applications relevant to current experimental research and fuel channel assessments. (1) CANDU is a registered trademark of Atomic Energy of Canada Limited.