Abstract Reactor dosimetry (RD) is a tool that provides data for neutron fluence accumulated over the reactor pressure vessel (RPV) during the reactor operation. This information, however, is not sufficient for RPV lifetime assessment. The life management of RPV is a multidisciplinary task. To assess whether the RPV steel properties at the current stage (for actual accumulated neutron fluence) of reactor operation are still “safe enough,” the dependence of material properties on the fluence must be known; this is a task for material science (MS). Moreover, the mechanical loading over the RPV during normal operation and accidences have to be known, as well, for evaluation, if the RPV material integrity in this loading condition and existing cracks is provided. The crack loading path in terms of stress intensity factor is carried out by structural analyses (SA). Pressure and temperature distribution over RPV used in these analyses are obtained from a thermal hydraulic (TH) calculation. The conjunction of RD and other disciplines in RPV integrity assessment is analyzed in accordance with the FFP (fitness for purpose) approach. It could help to improve the efficiency in multi-disciplinary tasks solutions.

Abstract The purpose of this study was to obtain a better understanding of crack initiation at friction stir weld exit holes in no-load transfer coupons as a first-order approximation of the potential performance of friction stir welding (FSW) joints employed for aircraft fuselage applications. In order to meet this goal, the effects of weld exit location on fatigue life in discontinuous friction stir lap-welded panels were documented. Sheets of aluminum alloys 7075-T6 and 2024-T3 were chosen for the FSW lap welds. Constant amplitude fatigue tests were carried out in order to determine the effect of various welding scenarios on fatigue crack initiation. A number of weld exit strategies were investigated, as well as another FSW tool design called a retractable pin tool (RPT). This tool was shown to eliminate the exit hole and reduce the stress concentration around the weld exit location. Prior to this work, none of the attempted exit strategies was found to delay or eliminate the initiation of fatigue cracks at the exit holes of discontinuous FSW lap welds. Only by using the RPT, which is able to eliminate the exit hole completely, was it possible to produce fatigue life results in coupons with a tool extraction zone that were comparable to those in baseline coupons containing no extraction zone.

Abstract This paper presents the experimental outcome of a study of the pool boiling heat transfer characteristics of alumina and CuO nanofluid in distilled water using a 0.19 mm diameter NiCr wire. A series of experiments were conducted in order to visualize the flow, critical heat flux (CHF) enhancement, and transient characteristics of nanofluid. The boiling phenomenon was visualized using a 0.1 g/l concentration of alumina nanofluid. The average bubble diameter was measured and was found to increase with increased heat flux. The average bubble contact angle decreased from 69° during the initial stages of boiling to 33° at CHF. Massive vapour bubbles were observed on the test heater surface near the CHF, inducing vapour blankets and forming hot/dry spots. The increase in the CHF could be well explained by the hot/dry spot theory. Pool boiling experiments conducted using low volume concentrations of CuO-water nanofluid at atmospheric pressure in distilled water showed an increase in the CHF by 30 % at a 0.3 g/l concentration. The transient behaviour of nanofluid, examined by exposing the heater surface at a constant heat flux of 700 kW/m2, indicated CHF enhancement of 5.21 % to 6.77 % for the two time durations. Based on the experimental investigations, it was concluded that the CHF enhancement is due to nanoparticle coating, which changes the thickness of the surface as a function of time and surface wettability and corroborates the hot/dry spot theory.

Abstract Bent glass has garnered increased interest on the part of architects for the realization of curved glass façades. As one method of bending of glass façade units, cold bending is an economically efficient procedure for manufacturing; however, it introduces permanent stresses in the glazing structure, especially in the corner zones of the glass units for warped designs. In a similar manner, high stresses in the corner zones are also generated in general by constant surface loads acting on the panes of the glass unit, which can be explained by thin plate theory. Thus it can be expected that these unsteady loads, e.g., evoked by wind and/or snow loads, unfavorably interfere with the permanent stresses in the adhesives of both the structural glazing sealant and the insulating glass sealant from a durability point of view. The existence of these corner loads is not adequately accounted for by the ETAG 002 guideline for structural glazing applications, which postulates a trapezoidal load distribution in the bonding with diminishing stresses in the corner zones. This paper presents numerical results of a parametric study of pressure-loaded glass units, with a focus on corner loads and stresses. The results show that the stress levels in the corner zones might be significantly higher than the design stress values used for sizing the bonding.

Abstract This paper investigates the effectiveness of froth flotation to remove copper and other heavy metals from dredged anoxic sediments (<250 μm) using a lab scale flotation cell with a selected anionic collector. A sediment fraction selected for flotation tests was potentially contaminated with a copper concentration of about 1763 mg/kg. The sequential extraction study of sediments showed that copper was mainly incorporated, between 70%–85% in the sulfide-organic fraction. The mineralogical analysis of sediment particle by scanning electron microscopy identified that chalcopyrite was the predominant copper sulfide form in the sediments. Flotation tests under controlled, predetermined experimental conditions showed selective flotation removal of copper (70.4%) among other metals with less mass recovery (froth mass).

Abstract The approach of improved uncertainty-accounted conservative evaluation of vodo-vodyanoi energetichesky reactor (VVER) (reactor-) pressure-vessel (RPV) radiation loading parameters has been proposed. This approach is based on the calculational–experimental procedure, which takes into account C/E ratio, depending on over- or underestimation, and uncertainties of measured and calculated results. An application of elaborated approach to the full-scale ex-vessel neutron dosimetry experiments on Russian VVERs combined with neutron-transport calculations has been demonstrated in the paper.

Abstract The Ringhals site is situated on the Swedish southwest coastline. At the site, there are four operating nuclear power plants. Historically, the Swedish policy has been that the nuclear power plants were to be closed in 2010. The present position is to operate the units until their technical and economic lifetime has run out. The units shall be maintained and invested in to ensure a lifetime of at least 50 years, but the actions taken shall not limit the time to this date. When the initial surveillance capsules were evaluated, it was noted that the material properties of the weld material of unit 3 and 4 showed some deviations from the expected behaviour. Currently there is an extensive project running for re-evaluating the embrittlement situation from a long-term operating perspective. One part of the project is aimed at more accurately determining the fluence levels of the reactor pressure vessels (RPVs). The basis for the early evaluations of the dosimeters in the surveillance capsules and the corresponding fluence evaluation had an operating lifetime of 25 years as a target value. Therefore, the accuracy and refinement of the measurement and calculation were taken to be good enough to suit this life span. Looking back at the results from the dosimetry measurements there are a few discrepancies. Some of the dosimeters were disintegrated and some measurements had comparatively large uncertainties. When starting this project there were some re-evaluations done with the old fluence prediction model. For every new run and refinement there appeared new difficulties, and the decision was to start the evaluation from scratch. Then there are two questions remaining regarding the fluence: What is the current fluence level? What will the resulting fluence be after 60 years of operation, when we have up-rated output power of both reactors? This paper aims to describe the view of the fluence evaluation in the surveillance program of the RPV, both in a historical and prospective view.

Abstract Dynamic-mechanical material analysis as a basis for a general performance exploration complemented by system testing under superimposed climatic and mechanical loading seems to be a promising interdependent test approach addressing the performance behavior of construction sealants under more realistic conditions. With this contribution an attempt is made to adapt dynamic-mechanical material analysis, which has been already successfully validated for different construction types of expansion joint systems in road and bridge engineering, to the field of construction sealants for building façades. Test results from dynamic-mechanical material analysis characterizing the temperature-dependent, deformation-dependent, and frequency-dependent behavior of structural sealant materials are presented and exemplarily discussed for three different sealant products. An attempt is made to address unknown material characteristics in the multi-dimensional loading matrix representing practical use conditions. Furthermore, the applicability of this test approach and its various complex test modes for the exploration of technological performance and especially estimation of fatigue behavior is verified in several examples. Based on this fundamental material exploration, it is planned to complement the dynamic-mechanical assessment methodology by means of system tests on a section of a structural glazing system subjected to a simplified but superimposed loading function. The technical fundamentals and the procedure proposed to develop an adequate system test mode are introduced. The motivation for these investigations is to identify the actual mechanical system behavior under load combinations and for specimens that both closer resemble reality. The objective is to achieve a consistent and interdependent test program complementary to the existing methodology. Finally, the study is meant to initiate further progress toward a performance-related methodology which considers the design, specification, material, and system selection.

Abstract Radioactivation of sulfur is a common technique used to measure fast neutron fluences in test and research reactors. Elemental sulfur can be pressed into pellets and used as monitors. The 32S(n, p)32P reaction has a practical threshold of about 3 MeV and its cross section and associated uncertainties are well characterized [1]. The product 32P emits a beta particle with a maximum energy of 1710 keV [2]. This energetic beta particle allows pellets to be counted intact. ASTM Standard Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32 (E265) [3] details a method of calibration for counting systems and subsequent analysis of results. This method requires irradiation of sulfur monitors in a fast-neutron field whose spectrum and intensity are well known. The resultant decay-corrected count rate is then correlated to the known fast neutron fluence. The Radiation Metrology Laboratory (RML) at Sandia has traditionally performed calibration irradiations of sulfur pellets using the 252Cf spontaneous fission neutron source at the National Institute of Standards and Technology (NIST) [4] as a transfer standard. However, decay has reduced the intensity of NIST’s source; thus lowering the practical upper limits of available fluence. As of May 2010, neutron emission rates have decayed to approximately 3e8 n/s. In practice, this degradation of capabilities precludes calibrations at the highest fluence levels produced at test reactors and limits the useful range of count rates that can be measured. Furthermore, the reduced availability of replacement 252Cf threatens the long-term viability of the NIST 252Cf facility for sulfur pellet calibrations. In lieu of correlating count rate to neutron fluence in a reference field the total quantity of 32P produced in a pellet can be determined by absolute counting methods. This offers an attractive alternative to extended 252Cf exposures because it can be performed regardless of the characterization of the exposure environment. Count rates produced by sulfur pellets are correlated to the measured quantity of separated 32P. A posteriori spectral and cross section determination can be used to correlate the quantity of phosphorus back to a neutron fluence in a reference field. This paper outlines a method for the setup, calibration, and use of the detector systems, 32P sample preparation, and analysis of the beta spectrum. An uncertainty analysis and comparison to ASTM E265 is also included.