Dominion Engineering Inc. | Date: 2015-01-16
A method and system detects failures in nuclear fuel assemblies (600). A water treatment device degasses/removes fission gases from water used in the canister (500) of a vacuum sipping device (30). A sipping procedure then detects a failure in a fuel assembly in the canister. The degassing improves a signal-to-noise ratio of the detector used during the sipping process, and improves the failure detection sensitivity of the system. Additionally and/or alternatively, gas may be recirculated through the canister water before the vacuum is applied so that fission gas concentration in the recirculating gas reaches a baseline equilibrium with the canister water. The vacuum is thereafter applied and the sipping procedure proceeds such that an increase in detected radioactivity over the baseline equilibrium indicates a leak in the fuel assembly.
Ligon T.C.,Dominion Engineering Inc. |
Gross D.J.,Dominion Engineering Inc. |
Shepherd J.E.,California Institute of Technology
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2011
This paper reports the results of experiments, analytical models, and finite element simulations on the structural response of piping systems to internal detonation loading. Of particular interest are the interaction of detonations with 90° bends and the creation of forces that lead to axial and bending structural response of the piping system. The piping systems were fabricated using 304 stainless steel, 2-in. (50 mm) diameter schedule 40 commercial pipe with a nominal wall thickness of 0.154-in. (3.8 mm) and welded construction to ASME B31.3 standards. The piping was supported using custom brackets or cantilever beams fastened to steel plates that were bolted to the laboratory walls. Nearly-ideal detonations were used in a 30/70 H 2-N2O mixture at 1 atm initial pressure and 300 K. The detonation speeds were close (within 1%) to the Chapman-Jouguet velocity and detonation cell sizes much smaller than the tube diameter. Pressure, displacement, acceleration and hoop, longitudinal, and support strains were measured using a high-speed (1 MHz) digital data acquisition system and calibrated signal conditioners. Detonation propagation through a bend generates a longitudinal stress wave in the piping that can be observed on the strain gauges and is predicted by both analytical models and finite element simulations. The peak magnitude of the bend force is approximately twice that due to the pressure alone since the peak momentum flux of the flow behind the detonation front is comparable to the pressure in the front. With relatively simple models, quantitative predictions of the bend forces can be made for the purposes of design or safety analysis of piping systems with internal detonations. Copyright © 2011 by ASME.
Broussard J.E.,Dominion Engineering Inc.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP | Year: 2015
The residual stresses imparted by the welding process are a principal factor in the process of primary water stress corrosion cracking (PWSCC) of Alloy 82/182 nickel-alloy (i.e., dissimilar metal or DM) piping butt welds in PWRs. While Section XI of the ASME Code requires that residual stresses are considered in crack growth calculations, there is little guidance or requirement on how to calculate them. Analytical models are frequently used to simulate the welding process in order to predict the residual stress distribution in the weld and base material as an input to crack growth calculations. The crack growth calculations, in turn, have demonstrated a high sensitivity to the welding residual stress distribution inputs. While significant progress has been made in understanding and reducing the variability in calculated residual stress among modelers as well as the variability in measured residual stress among different techniques, there remains some uncertainty regarding any given measured or calculated distribution. A feasible alternative to calculating through-wall stress distributions with analytical models on a case-by-case basis is to develop a set of standardized through-wall stress distributions that are applicable to DM welds. Examples of standardized through-wall distributions for residual stress are found in numerous consensus code and standards. The benefit of established through-wall stress distributions is that evaluations for flaws in welds would start from a uniform basis on one of the key inputs to the crack growth calculation, reducing the time required to perform and review flaw evaluations. This paper presents and describes the technical basis for a set of through-wall distributions for common DM welds found in the US nuclear industry. The basis of the distributions include the results of analytical models, including uncertainty, as well as measured data for through-wall stress in DM welds. Copyright © 2015 by ASME.
Gorman J.A.,Dominion Engineering Inc.
Corrosion | Year: 2015
In order to provide background for a review of stress corrosion cracking (SCC) in nuclear power plants, a review is first presented of the history of occurrence of SCC in fossil fired power plants and a few related applications. The historical development of SCC in nuclear power plants is then described. The many materials and components that have been affected by SCC over the years are identified, as are the material, stress, and environmental factors involved. A particular focus of this monograph is the question of how it happened that materials with significant susceptibility to SCC were used for so many important structural applications in nuclear power plants. To address this question, the historical development of both pressurized water reactor designs and boiling water reactor designs is reviewed. The review covers factors such as the material types selected for test and use, the operating temperatures used as the designs evolved, and the qualification tests and prior operating experience that were relied upon for selection of materials. Some conclusions as to the factors involved in the choice of materials that turned out to be susceptible to SCC are presented, together with some suggestions for how to minimize such problems in the future. © 2015, NACE International.
Dominion Engineering Inc. | Date: 2012-12-12
A particulate removal apparatus and method are used to capture and remove particulates from nuclear reactor core coolant during normal operation. Bottom nozzle, particulate removal apparatus and top nozzle structures form an assembly sized to be installed in place of a nuclear fuel assembly. The particulate removal achieved reduces the inventory of corrosion product deposits, foreign objects and other particulates in the reactor coolant system. This in turn reduces activation or deposition of particulates on fuel cladding, with a corresponding improvement in fuel reliability and reduction in ex-core radiation fields.
Dominion Engineering Inc. | Date: 2011-05-16
Provided area cleaning apparatus and an associated method of using the disclosed apparatus wherein the apparatus utilizes one or more nozzles configured to provide a coherent stream of one or more cleaning fluids for removing accumulated fine particulate matter, sludge, from surfaces. The nozzles may be sized, arranged and configured to provide coherent streams that maintain the initial stream diameter for a substantial portion of the maximum dimension of the space being cleaned. The apparatus and method are expected to be particularly useful in the cleaning of heat exchangers incorporating a plurality of substantially vertical and narrowly spaced tubes by directing cleansing streams along a plurality of intertube spaces.
Dominion Engineering Inc. | Date: 2011-07-27
The present invention provides methods and compositions useful for conditioning and removing solid deposits that have formed on or otherwise accumulated within one or more components including, for example, scale formed within a steam generating system. The aqueous cleaning compositions incorporate one or more quaternary ammonium hydroxides characterized by pK_(a) values no less than about 13.5. These quaternary ammonium hydroxides may be used alone or in combination with one or more additives including, for example, chelating agents, reducing or oxidizing agents, pH adjustment agents, surfactants, corrosion inhibitors, complexing agents, dispersants and combinations thereof.
Dominion Engineering Inc. | Date: 2010-12-13
An improved scale conditioning composition and method is disclosed that results in improved dissolution and disruption of tube scale, hardened sludge and other deposits composed primarily of highly densified magnetite such as those found in heat exchange vessels, particularly steam generators. After treatment with the advanced scale conditioning composition, these magnetite rich deposits are more easily removed using known and commercially available high pressure hydro-mechanical cleaning techniques. The present invention further provides effective cleaning in a short period of time and at relatively low temperatures, while reducing the amount of waste produced and reducing the resulting corrosion of carbon and low alloy steel components within the steam generator during the cleaning process.
Dominion Engineering Inc. | Date: 2014-03-14
A method of cleaning a vessel having deposits on an interior surface includes removably bonding an ultrasonic transducer to an external wall of the vessel and using the ultrasonic transducer to produce ultrasonic energy coupled into the vessel wall such that at least a portion of the ultrasonic energy is transmitted to the interior surface.
Dominion Engineering Inc. | Date: 2013-07-25
An aqueous cleaning solution that has been previously used to remove deposits from a nuclear steam generator (or other vessel) is reused after being transferred from the steam generator into an external vessel. The spent cleaning solution may be reconditioned and reused in a further cleaning of the same steam generator or a different steam generator. The different cleanings being accomplished by the cleaning solution may be of the same type or different types (e.g., iron oxide removal and/or copper removal).