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Portsmouth, NH, United States

Cavallo J.R.,Enercon Services Inc.
NACE - International Corrosion Conference Series | Year: 2011

This paper discusses a methodology to be used in evaluating existing coatings on buried piping in nuclear power plants and selection of repair and remediation coatings. In many cases, the same coating can be used for either repair or rehabilitation work. Coatings for buried piping in nuclear power plant installations are selected based on accelerated laboratory screening testing and in situ field testing of both existing coatings and soil conditions surrounding the buried pipe. ©2011 by NACE International. Source


Knighton J.,Enercon Services Inc.
World Environmental and Water Resources Congress 2015: Floods, Droughts, and Ecosystems - Proceedings of the 2015 World Environmental and Water Resources Congress | Year: 2015

Two dimensional flow models typically route flows over a mesh or grid of land surface elevations. This research presents a spatial stochastic simulation methodology to quantify the effects of topographic uncertainty on hydrologic simulations. Uncorrelated elevations errors are determined through a residual-variogram analysis of digital elevation models and a normal approximation of the underlying errors. The effects of uncorrelated and the reported correlated error distribution of National Elevation Dataset (NED) of the White Clay Creek (PA, USA) headwaters are evaluated. The spatially uncorrelated (random) errors of the NED are determined to be negligible compared to the reported root mean square error (RMSE). Monte Carlo flood simulations are performed to evaluate the effects of topographic uncertainty. Model uncertainty is quantified with respect to the 24 hour 200 year return period precipitation. The peak water surface elevation and peak velocity results at each model node are aggregated to determine the spatial variability of the model uncertainty as related to topographic uncertainty. © 2015 ASCE. Source


Hurff J.B.,Enercon Services Inc. | Kahn L.F.,Georgia Institute of Technology
Journal of Structural Engineering (United States) | Year: 2012

Precast structural concrete beams have become longer and more slender, increasing the likelihood of a stability failure. Although there are methods to determine the lateral-torsional buckling load for reinforced and prestressed concrete beams, there has been no conformity as to which is the more accurate method, nor do they account for initial imperfections. Six slender, rectangular pretensioned concrete beams were tested and showed that the lateral-torsional stability behavior was similar to that of reinforced concrete beams except for (1) changes in material properties owing to a different stress state and (2) the effects of prestressing on the cracking behavior of the cross section. The stability behavior proved to be sensitive to initial imperfections; therefore, both a geometric nonlinear stability analysis and a simplified equation were developed. The predictive methods were compared with the current and past results, and the analytical methods showed good correlation with all structural concrete experimental results. The results indicate that prestressed concrete beams are susceptible to lateral-torsional buckling and the initial imperfections serve to reduce the buckling load owing to nonlinear geometric behavior and a nonrectangular compression zone. © 2012 American Society of Civil Engineers. Source


Morgan T.A.,Enercon Services Inc. | Ritter J.E.,Xcel Energy Inc.
International Topical Meeting on Probabilistic Safety Assessment and Analysis, PSA 2015 | Year: 2015

To support a steam generator replacement outage on the Xcel Energy Prairie Island Nuclear Generating Plant's Unit 2, an Outside Lifting System (OLS) was to be installed near the Unit 2 Containment Building equipment hatch. As various heavy load lifts and movements were conducted in that area during the outage, an evaluation was performed to determine what the potential risk impacts of these lifts might have been on the two-unit station, and what potential Risk Management Actions (RMAs) could be considered to offset any risk increases. There were a number of possible operating states each unit could be in during the time when the OLS was in use. Each scenario that could occur during each operating state was categorized. Conditional core damage probabilities were calculated for certain scenarios that could impact Unit I while it was in operation. Most evaluated scenarios were able to be classified into low risk categories; however, several specific scenarios were identified as having a heightened risk level. Possible RMAs were identified for key scenarios, and the feasibility of these RMAs was reviewed with the Steam Generator Replacement Project and Operations staff. The majority of the proposed RMAs were able to be implemented. Based on the positive experience from the steam generator replacement project, additional analyses are being conducted for the plant's Main Generator and Main Transformer replacement projects. © 2015 by the American Nuclear Society. Source


Lavelline J.,Enercon Services Inc. | Peterman A.,Xcel Energy Inc.
International Topical Meeting on Probabilistic Safety Assessment and Analysis, PSA 2015 | Year: 2015

An important aspect of a plant site's Maintenance Rule (MR) program is the establishment and verification of the suitability of Performance Criteria (PC). There are several methods that are used in the industty for verifying the suitability of performance criteria. The method that is presented in this paper is called the "Sensitivity Method". The rationale for the selection of this method is that it is deemed to be a good choice for assessing the integrated effects of all of the performance criteria. The overall objectives of analyses which use the "Sensitivity Method" are: 1. Ensure established performance criteria are compliant with JOCFR5O.65. 2. Ensure that guidance in NUMARC 93-01 for the establishment of performance criteria is followed. 3. Ensure that Maintenance Rule performance criteria are appropriately structured to maintain adherence to accepted nuclear safety concepts. 4. Ensure that the established performance criteria aid in the identWcation of equipment performance "outliers". 5. Ensure that performance criteria strike the appropriate balance between equipment availability and reliability. 6. Ensure (to the extent practical) that the performance criteria established do not place unnecessary burdens on the operation and maintenance of the plant (within the confines of Items I through 5 above). © 2015 by the American Nuclear Society. Source

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