End Of Design Life Research Articles

Empirical Analysis of the Multi-Mission Radioisotope Thermoelectric Generator Qualification Unit Operated at a Low Thermal Inventory with Potential for Improved End-of-Life Power

Performance predictions for the first multi-mission radioisotope thermoelectric generator (MMRTG) flight unit and engineering unit were recently reported. Both units were produced and operated/tested within specifications [i.e., nominal thermal inventory = 2000 W(thermal)]. In an attempt to study the effect of a deep space cruise on an MMRTG that has been operational for 6.25 years (2.25 years storage + 4 years cruise), the qualification unit (QU) was placed on life test with a below-specification thermal inventory of 1904 W(thermal). Analysis indicates that loading an MMRTG with a lower thermal inventory may result in less power at the beginning-of-life but more power at the end-of-design-life (EODL). The lower thermal inventory in the QU produces a lower operating temperature, which appears to cause a significant reduction in the degradation rate of the thermoelectric couples. Preliminary calculations indicate that a thermal inventory of 1904 W(thermal) could result in a 9 W(electric) power boost at EODL [i.e., 84 W(electric)], which is a 12% improvement over the first MMRTG flight unit and engineering unit predictions. Preliminary degradation analysis suggests that a 1904 W(thermal) unit will begin to produce more power than a 2027 W(thermal) unit approximately 4 years after fueling. This suggests that missions with a primary power requirement more than 4 years after fueling would benefit from a lower thermal inventory. In addition, using a lower thermal inventory has significant benefits for 238Pu stockpile management and may allow for additional MMRTGs to be fueled from our current reserves. Conclusions and hypotheses presented here should be considered preliminary because the QU data set is very small and there are some uncertainties regarding how early-life QU data will translate into later-life performance. More QU testing at a thermal inventory of 1904 W(thermal) is needed to prove that the preliminary conclusions presented here are valid.

Characterization of long-term skid resistance in exposed aggregate concrete pavement

Exposed aggregate and tining surface texture can improve the skid resistance of concrete pavements. These textures should provide not only a sufficient skid resistance at early age but also maintain its adequacy throughout the design life. Tining surface contains both cement binder and aggregates; however, cement paste may not be as durable as aggregate. Thus, skid resistance may be reduced due to cement paste loss when pavement ages. Aggregate particles in exposed aggregate concrete pavement may be vulnerable to polishing effect. This phenomenon attenuates the particle's texture features and consequently decreases the skid resistance before the end of design life. Initial texture condition of EACP is significantly beneficial to the functional pavement performance; however, its long term characteristic may be questionable. Therefore, this research aimed to characterize the long term skid resistance of EACP through surface texture comparison and investigation of stone polishing effect. Moreover, prediction model of skid resistance for aged EACP was also suggested. This study indicated that EACP is an effective alternative to secure the long term skid resistance. Also, accelerated polishing test should be included in the mixture design process to determine the appropriate type of coarse aggregate for EACP. Lastly, the prediction model provided good agreement with measured long-term skid resistance.

Influence of corrosion on reliability-based design of steel grid MSE walls

Design for internal limit states of steel grid reinforcement in mechanically stabilized earth (MSE) walls must provide for loss of steel thickness due to corrosion. The paper combines key features of zinc and steel corrosion models used in North American practice with corrosion rate statistics reported in the literature for the zinc coating on buried galvanized steel strips and for steel rebar. Examples of loss of strength and pullout capacity of steel grid elements constructed with different member diameters and up to 120 years after construction are presented in probabilistic terms. Results of reliability-based analysis for the tensile strength and pullout limit state at design lives of 75 and 120 years are demonstrated for a typical wall under operational conditions using tensile load and resistance models in combination with non-aggressive soils recommended in North American design codes. The results of calculations show that for the wall example the influence of different zinc cover thickness on probability of tensile failure of longitudinal members is detectable at the end of design life. However, the typical minimum specified zinc thickness of 0.086 mm recommended in North American practice is likely sufficient to keep probabilities of failure to 1% or less (i.e., reliability index of 2.33 or greater). The influence of a range of initial zinc thickness reported in the literature on probability of pullout failure of the same steel grid elements was found to be negligible.

Denitrifying Bioreactor Woodchip Recharge: Media Properties after Nine Years

HighlightsWood media harvested from a nine-year-old denitrifying bioreactor were evaluated.Media physical changes had multiple causes and effects.Impacts of the physical changes may have been exacerbated by development of preferential flow.LCIs > 0.6 showed C quality declined but media still supported N removal.Abstract. There is a lack of information on denitrifying bioreactors treating subsurface drainage water at the end of their initial design life due to the relative newness of the technology and the relatively long estimated life. A denitrifying bioreactor (15 m L × 7.6 m W × 1.1 m D) installed in August 2008 in Greene County, Iowa, was recharged with new woodchips in November 2017 (age 9.25 years), providing the opportunity to evaluate the properties of the wood media at the end of design life. The objective was to pair a battery of physical, chemical, and nitrate-N removal tests on the wood media harvested from the bioreactor with field observations to assess likely reasons why denitrifying bioreactors treating tile drainage may need to be recharged. The two types of wood media harvested from the bioreactor (termed woodchips and mixed shreds) had median particle sizes (D50) of 12.1 and 7.7 mm, respectively, and saturated hydraulic conductivities of 4.2 ±3.0 and 3.1 ±1.0 cm s-1 (mean ± standard deviation), which were within the range of reported values for woodchips, albeit at the low end. The wood media carbon content and quality had degraded (e.g., lignocellulose indices of 0.63 to 0.74, nearing the range of decomposition stabilization), although batch tests suggested the robustness of wood as a carbon source to support nitrate removal (e.g., 65% nitrate concentration reduction in drainage water). Woodchip degradation along with sedimentation from the drainage system likely reduced conductivities over time. Development of preferential flow paths through the bioreactor was indicated by low bioreactor outflow rates (i.e., reduced permeability) and reduced hydraulic efficiency based on conservative tracer testing. These changes in media properties and linked impacts resulted in the need to recharge this bioreactor after nine years. Keywords: Denitrifying bioreactor, Hydraulic conductivity, Nitrate, Water quality.

A Review of Field Corrosion Control and Monitoring Techniques of the Upstream Oil and Gas Pipelines

All steel pipelines used in hydrocarbon transportation are susceptible to either electrolytic or galvanic corrosion attack which deteriorate with time leading to failure even before end of design life. Consequences of corrosion attack and eventual failure of pipelines within oil and gas industry has been classified into economic, health, safety and environmental impacts. The present study considers detailed review of practical field corrosion control and monitoring mechanisms necessary to preserve, extend service life of pipelines and reduce corrosion impacts. The corrosion controls are various preventive strategies considered during construction and prior to pipelines’ commissioning which include design, material selection, protective coating, chemical treatment and cathodic protection system. But the corrosion monitoring strategy is aimed at establishing condition of pipelines and environmental variables that may accelerate corrosion process and this includes potential survey, bacteria count, corrosion coupons and intelligent pigging. The identified corrosion control and monitoring techniques are not governed by any industry code and standard but has been generally accepted as best practice within the oil and gas industry as ways of combating corrosion and evaluating pipelines condition. Therefore, effective implementation of the identified corrosion control and monitoring strategies would limit corrosion attack and guide pipelines’ operators to make informed decision and timely respond to corrosion threat before failures. Keywords : cathodic protection, corrosion mechanism, control and monitoring, pipelines, oil and gas.

The Effect of Upscaling and Performance Degradation on Onshore Wind Turbine Lifetime Extension Decision Making

Ever greater rated wind turbine generators (WTGs) are reaching their end of design life in the near future. In addition, first research approaches quantified the impact of long-term performance degradation of WTGs. As a consequence, this work is aimed at discussing and analysing the impact of upscaling and performance degradation on the economics of wind turbine lifetime extension. Findings reveal that the lifetime extension levelised cost of energy (LCOE2) of an 18 MW wind farm comprising of 0.5 MW rated WTGs are within the order of £23.52 per MWh. Alternatively, if the same wind farm consists of fewer 2 or 3 MW WTGs, the LCOE2 reduces to £16.56 or £15.49 per MWh, respectively. Further, findings reveal that an annual performance degradation of 1.6% (0.2%) increases LCOE2 by 34-41% (3.6-4.3%).

A Progress Report on the eMMRTG

A multimission radioisotope thermoelectric generator (MMRTG), developed by the US Department of Energy for the National Aeronautics and Space Administration, powers the Mars Science Laboratory Curiosity rover on Mars. New thermoelectric couples (TECs) have been developed in recent years that offer significant improvements over the TECs used in the MMRTG. The maturity of the new TECs and the design flexibility of the MMRTG enable a low-risk system upgrade that is predicted to substantially enhance the MMRTG’s performance. System design trades are looking at changing the TECs and increasing the hot-side temperature to find the best combination of performance and program cost in this enhanced MMRTG (eMMRTG). Initial studies indicated that a low-risk enhancement would be to use skutterudite (SKD) materials developed at JPL to form TECs for the eMMRTG. Simply replacing the PbTe/TAGS TECs with SKD TECs and making a few low-risk modifications to the MMRTG design could potentially provide a 25% increase in power output at beginning of life (BOL). More important than the BOL power output increase is the end of design life (EODL) power output increase. With the anticipated lower degradation rate of the SKD materials, it is anticipated that the EODL power output will be more than 50% higher than for the MMRTG (with EODL defined as 17 years from fueling). This paper presents an overview of the results of the initial trades leading to the pursuit of the eMMRTG and the progress made since those were concluded.

Parameters affecting the weld defect acceptance criteria of clad submarine pipelines installed by S-lay or reel-lay

This case study presents a methodology to determine the criticality of defects in submarine pipeline girth welds made of clad carbon steel and to establish weld defect acceptance criteria. The maximum target acceptance criteria are usually given by the applied design code often with additional requirements set by the client. ECA calculations are carried out in order to demonstrate that the target criteria can be met using the relevant material data, geometry and load input. The ECA methodology must follow the defect development from welding fabrication through pipeline installation from the lay barge, as well as consider loads in the as-laid condition during pre-operational and operational phases until the end of design life and verify that leakage or failure will not occur.

GaInP/GaAs/Ge 3중 접합 태양전지 배열기의 정지궤도에서 전력 성능 평가

The satellite on geostationary orbit accommodates multiple payloads into a single spacecraft platform and launched in June 26, 2010. The electrical power required to the satellite during sunlight is generated by a solar array wing. The solar cells are the GaInP/GaAs/Ge Triple Junction cells named Gaget2 cells from RWE Space, which were based on a Spectrolab epitaxy. This paper evaluates solar array power performance at end of design life based on the trend analysis results for the flight data on geostationary orbit. The estimated solar array power performance at end of design life compares with the power performance provided by solar array manufacturer. The solar cells show nominal behavior without significant degradation through the trend analysis results.

Avaliação de vida residual de tubos de forno reformador

Este trabalho avalia a vida remanescente dos tubos catalisadores de um forno reformador devido ao fato do fim da vida de projeto de 100.000 horas estar próximo. O principal mecanismo de dano destes tubos é a fluência, por isso a análise seguiu roteiro da Part 10 do documento API-579/ASME FFS-1 (2007). O material dos tubos é uma liga HP modificada, para a qual existe escassez de dados de propriedades na literatura. Por isso, as propriedades de fluência necessárias para a avaliação foram determinadas experimentalmente utilizando correlação de dados de ensaios de tração a quente e fluência. Os resultados indicam que os tubos não necessitam ser substituídos de imediato e que sua vida residual é estimada em 22,3 anos operando na temperatura de projeto

Design optimization of backup seal for sodium cooled fast breeder reactor

Design optimization of static, fluoroelastomer backup seals for the 500MWe, Prototype Fast Breeder Reactor (PFBR) is depicted. 14 geometric variations of a solid trapezoidal cross-section were studied by finite element analysis (FEA) to arrive at a design with hollowness and double o-ring contours on the sealing face. The seal design with squeeze of 5mm assures failsafe operation for at least 10years under a differential pressure of 25kPa and ageing influences of fluid (air), temperature (110°C) and γ radiation (23mGy/h) in reactor. Hybrid elements of 1mm length, regular integration, Mooney–Rivlin material model and Poisson’s ratio of 0.493 were used in axisymmetric analysis scheme. Possible effects of reduced fluoroelastomer strength at 110°C, ageing, friction, tolerances in reactor scale, testing conditions during FEA data generation and batch-to-batch/production variations in seal material were considered to ensure adequate safety margin at the end of design life. The safety margin and numerical prediction accuracy could be improved further by using properties of specimens extracted from seal. The approach is applicable to other low pressure, moderate temperature elastomeric sealing applications of PFBR, mostly operating under maximum strain of 50%.

Anti-Skid Thin Layer on Asphalt Pavement of Super Long Downgrades

Improving the skid resistance performance of asphalt pavement is an effective way to meet the requirements of safe driving on super long continuous downgrades. The anti-skid performance attenuation of SMA-16 was tested in laboratory. The results showed that SMA-16 could meet the requirement of anti-skid performance in early stage, but the anti-skid performance decreased rapidly on super long downgrades. The long-term anti-skid performance of anti-skid thin-layer had also been carried out in laboratory. We can come to conclusion that anti-skid thin paving layer can meet the requirements of anti-skid performance even in the end of design life. The anti-skid thin paving layer on super long downgrades was designed, which not only satisfied the durability of skid resistance performance but also reflected the demand of economics.

Skid Resistance Performance Optimization of Asphalt Pavement on Super Long Continuous Downgrades

The skid resistance performance of asphalt pavement on super long continuous downgrades should be designed specially. According to characteristics of super long continuous downgrades which is 52 kilometers long, the skid resistance performance of pavement in end of design life was designed as control index; combined with longitudinal slope distribution, anti-skid control standard were be brought up which was based on the stopping sight distance requirements; The equivalent conversion method for anti-skid axle load was obtained by anti-skid attenuation test; The analysis of skid resistance performance indicate that SMA-16 can’t meet the skid resistance requirements and need to optimize it by using thin anti-skid paving.

Effect of Irradiation on the Fracture Properties of Zr-2.5Nb Pressure Tubes at the End of Design Life

Abstract To determine the fracture properties of Zr-2.5Nb pressure tubes irradiated until the end of design life, cantilever beam, curved compact toughness, and transverse tensile samples were prepared from a typical pressure tube and irradiated in the high flux reactor OSIRIS at CEA, Saclay, France. Experiments were conducted on two batches of samples mounted in two irradiation inserts. Each insert held sixteen samples of each type of specimen. The first insert was irradiated to a fluence corresponding to approximately half of the design life in a CANDU3 reactor. The experimental results were reported in [1]. Samples in the second insert were irradiated for 10.5 years in OSIRIS and received a maximum neutron fluence of 2.61 × 1026 n/m2 (E > 1 MeV), being equivalent to 2.98 × 1026 n/m2 (E > 1 MeV) in a CANDU reactor, i.e., corresponding to ∼30 years operation in CANDU reactors at 80 % capacity factor. The present report describes the results of tensile, fracture toughness, and Delayed Hydride Cracking (DHC) tests and XRD microstructure analysis from the second batch of specimens. A continuous and gradual evolution in tensile, fracture, DHC properties, and dislocation densities is demonstrated without any evidence of a sudden change following the initial transitient at very low fluence. In the whole high fluence range, there is a very slow rate of increase in c-component dislocation density, strength, and DHC velocity and a slow reduction in elongation and Nb concentration in the β-phase. The a-type dislocation density and fracture toughness remain approximately constant. The results from the second insert of specimens confirm that, following the initial transient at very low fluence, there is little further change in the fracture properties of Zr-2.5Nb pressure tube material. Therefore, material properties behave in a stable and predicable manner to the end of a 30 years design life for CANDU reactor pressure tubes.

Qualification of Cables to IEEE Standards 323-1974 and 383-1974

Wire and Cable manufacturers generally qualify products for class IE application by envelope type testing to user specifications and environmental conditions recommended by IEEE Standards 323-1974 and 383-1974. The General Electric Wire and Cable Business Department recently completed two such qualification programs. Cable constructions tested were 600V control cables and 600V, 2KV, and 15KV power cables insulated with flame resistant mineral filled crosslinked polyethylene. The 15KV samples included taped field splices. To determine the ability of samples to withstand a loss of coolant accident (LOCA) both early in and at the end of design life, both thermally aged and unaged cables were irradiated and subjected to a 100 day plus 10 day margin simulated LOCA test. Samples were heat aged to a time-temperature condition in excess of 40 years of service life. The aging criterion was determined from experimental data fitted to an Arrhenius curve by the Regression Method of IEEE Standard 101-72. All test specimens were irradiated using a Cobalt 60 source to a total integrated dose of 220 Mrad. The simulated LOCA conditions of one test program followed the combined requirements for Boiling Water Reactors and Pressurized Water Reactors. In the second test program, the steam pressure-temperature profile included a simulated main steam line break. Test specimens were wrapped on grounded mandrels and were electrically loaded throughout the simulated LOCA tests. After completion of environmental testing, samples were subjected to the IEEE 383 simulated post-LOCA test.

Effect of antireflection coatings and coverglasses on silicon solar cell performance

The high reflectivity of the polished silicon surface of the newer N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /P silicon solar cells has emphasized the need for properly designed antireflection coatings to obtain improved solar cell performance. The problem is complicated by the facts that solar cells are generally tested in air, but are for their final application covered with a glass or quartz slide which is adhesive-bonded to the cell surface, and further, that solar cells operating in a nuclear particle radiation environment change their spectral response and are frequently optimized for performance at the end of design-life. Experiments have been performed to explore the antireflection characteristics of thin films of silicon monoxide which have been evaporated on the solar cell surface. The effect of the antireflection coating thickness on cell response as a function of wavelength has been determined and the improvement in cell short circuit current for Air Mass Zero space sunlight evaluated. Included in this study was the evaluation of the antireflection characteristics after the application of a coverglass with adhesive over the antireflection coating. For comparison, coverglasses were also applied to bare cells with no antireflection coating present. In all cases the various coating comparisons were based on the cell short-circuit current performance in Air Mass Zero sunlight.