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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.

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.

Kosbab B.D.,Enercon Services Inc. | Kurtis K.E.,Georgia Institute of Technology | Kurtis K.E.,American Concrete Institute
ACI Materials Journal | Year: 2010

Previously unpublished U.S. Bureau of Reclamation (USBR) investigations conducted over a 40-plus year period examined the influence of calcium chloride (CaCl2) addition rate and mixing temperature on the sulfate resistance of concrete. Herein, those data are analyzed and compared with predictions from an existing model, as well as with results from accelerated tests performed in parallel by the USBR to better understand the individual and combined effects of these parameters. Because CaCl2 is more likely to be used during lower temperature construction, the combined effects of these parameters are important to consider. The addition of 1% calcium chloride by weight of cement can significantly decrease the sulfate resistance of samples made using Type V and II cements. Mixing and initially curing at 21.1°C (70°F) resulted in significantly lower sulfate resistance than when mixing at 4.4°C (40°F). Within the ranges considered, both the initial curing temperature and the CaCl2 addition appear equally important to sulfate expansion. Together, these results indicate that higher overall heat generation during the early hydration reactions can significantly decrease the long-term sulfate resistance of concrete. Copyright © 2010, American Concrete Institute. All rights reserved.

Garimella S.,Georgia Institute of Technology | Brown A.M.,Enercon Services Inc. | Nagavarapu A.K.,Georgia Institute of Technology
International Journal of Refrigeration | Year: 2011

A novel cascaded absorption/vapor-compression cycle with a high temperature lift for a naval ship application was conceptualized and analyzed. A single-effect LiBr-H 2O absorption cycle and a subcritical CO 2 vapor-compression cycle were coupled together to provide low-temperature refrigerant (-40 °C) for high heat flux electronics applications, medium-temperature refrigerant (5 °C) for space conditioning and other low heat flux applications, and as an auxiliary benefit, provide medium-temperature heat rejection (∼48 °C) for water heating applications. A thermodynamic model was developed to analyze the performance of the cascaded system, and parametric analyses were conducted to estimate the performance of the system over a range of operating conditions. The performance of the cascaded system was also compared with an equivalent two-stage vapor-compression cycle. This cycle was found to exhibit very high COPs over a wide range of operating conditions and when compared to an equivalent vapor-compression system, was found to avoid up to 31% electricity demand. © 2011 Elsevier Ltd and IIR. All rights reserved.

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.

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.

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.

Jorgenson E.,Enercon Services Inc. | Manning V.,Enercon Services Inc.
International Topical Meeting on Probabilistic Safety Assessment and Analysis, PSA 2015 | Year: 2015

The modeling of human failure event dependencies addresses the dependence between multiple human failure events that occur in the same accident sequence or cutset. The failure to perform one action correctly can affect operator performance for a subsequent action. As part of the Columbia Generating Station PRA update in 2013 and 2014, the human failure event dependency evaluation was updated using the HRA Calculator version 5.1. Based on the update work, this paper enumerates several insights and recommended approaches for performing an HFE dependency evaluation more efficiently and effectively.

Anderson R.C.,Enercon Services Inc. | Dremel R.,Enercon Services Inc.
International Topical Meeting on Probabilistic Safety Assessment and Analysis, PSA 2015 | Year: 2015

This paper reviews experience to date with the draft ANS standard on the technical adequacy of PRA models for shutdown analysis. Benefits of use are addressed, as well as expectations for changes prior to endorsement, their implications andfuture use of the standard. ASME has issued a standard for the technical adequacy of a nuclear plant Probabilistic Risk Analysis (PRA), which has been endorsed by the NRC as an acceptable means of demonstrating model quality. However, this standard does not address Low Power and Shutdown (LPSD) operation. In order to address the unique requirements of LPSD, the American Nuclear Society is drafting a corresponding standard for shutdown PRA model development. Maracor, the PRA division of ENERCON Services, Inc. has used this draft standard in the development of several shutdown PRA models for their clients. Although the standard is only in draft at this time, it is still the best available template for the likely regulatory requirements for technical adequacy for LPSD analysis. This paper discusses similarities of the LPSD standard to, and differences from, the at-power standard; the technical and regulatory benefits of use to date; and the impact of potential changes as the currently draft version is finally endorsed.

Rozga G.,Enercon Services Inc. | Jorgenson E.,Enercon Services Inc.
International Topical Meeting on Probabilistic Safety Assessment and Analysis, PSA 2015 | Year: 2015

A fire PRA plant response model is to be capable of identifying significant contributors to CDF and LERF, including plant initiating events, accident sequences, and equipment unavailabilities. Multi-compartment fire scenarios consist of a fire initiating event andfire damage occurring in one physical analysis unit, followed by propagation of effects from the fire to one or more additional physical analysis units (PAUs) due to barrier failure or unavailability. Based on peer review observations, multi-compartment fire scenario modeling quantifies the likelihood for multi-compartment impacts typically in side calculations, and the contributions from barrier unavailabilities are not explicitly captured as a result. This approach can still meet Capability Category II of the ASME/ANS PRA Standard, if the scenarios in the base model are not risk-significant. This is typically difficult to know in advance, and rework is needed later if any multi-compartment scenario is risk-significant. Furthermore, any PRA applications would need to revisit the risk-significance of multi-compartment scenarios, particularly applications that involve fire barriers. An effective alternative is presented that performs cutset post-processing that explicitly models the exposing compartment scenarios and barrier unavailabilities for all unscreened multi-compartment scenarios and typically requires no additional analysis resources. © 2015 by the American Nuclear Society.

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