Environmental Correction Factor Research Articles

Assessment of environmental fatigue in nuclear power plants: A comparative analysis of the effects of plasticity correction

In accordance with Regulatory Guide 1.207, Rev.1, fatigue assessments must be conducted considering the influence of primary coolant environment in nuclear reactors. Environmental fatigue, resulting from corrosion in the primary coolant, is evaluated in air fatigue life assessments through the application of an environmental fatigue correction factor. This environmental fatigue correction factor depends on sulfur content, operating temperature, dissolved oxygen, and strain rate. It remains constant for sulfur content, operating temperature, and dissolved oxygen, while strain rate introduces potential errors based on the analysis method. The current fatigue evaluation procedure for air, following ASME B&PV Code Sec.III, NB-3200, employs elastic analysis with a simplified elastic-plastic correction factor(Ke). However, Ke factor is considered excessively conservative, prompting less conservative alternatives proposed by JSME, RCC-M, ASME Code Case N-779. This study applied both ASME Ke and JSME Ke for fatigue evaluations considering environmental effects. Additionally, fatigue assessments accounting for elastic-plastic effects were conducted using Neuber and Glinka methods, compared with actual experiments. The analysis systematically examined changes in fatigue life and the environmental fatigue correction factor due to plastic effects in environmental fatigue evaluations.

Estudo da capacidade de carga na trilha do Traíras na Reserva Particular de Desenvolvimento Sustentável Legado Verdes do Cerrado, Niquelândia, Goiás: uma adaptação a partir do método de Cifuentes

In accordance with the method developed by Cifuentes (1992), this research measures the Effective Load Capacity of the Traíras river. Established in the private susteinable development reserve Legado Verdes do Cerrado, in the municipality of Niquelândia-GO, Brazil. Located 366 km from Goiânia Capital. The trail has its biodiversity of native flora and fauna of the Cerrado in a state of conservation since 1947. From the quantification of the daily and annual flow of tourists it was observed that the local management capacity obtained the value of 47.9% far below the ideal value, which is 75% (Arias,1999). In addition to this verification environmental social and physical correction factors are suggested, followed by a management capacity, planning and environmental management proposal in order to minimize future human interference caused by ecotourism activity.

Effects of strain rate on low-cycle fatigue crack growth behavior of 316LN weld metal in high-temperature pressurized water

Corrosion fatigue (CF) tests of 316LN weld metal were investigated in high-temperature water at different strain rates (0.0004–0.4%/s) under strain amplitude of 0.6%. Relationship between CF life and strain rate was proposed and environmental fatigue correction factor Fen was also calculated. It was found that the γ/δ phase boundary was more susceptible to cracking at low strain rates and δ-ferrite worked as a barrier to retard the crack growth at high strain rates. Mechanisms of CF damage involving the effects of strain rate, hydrogen, δ-ferrite and residual strain on crack growth are also discussed.

Effect of environmental media on the fatigue property of Chinese A508-3 steel of AP1000

The fatigue tests of Chinese RPV steel (A508-3) were carried out under the simulated primary coolant environment of AP1000 which is a kind of 3rd generation nuclear power plant. The effects of temperature, strain rate and dissolved oxygen (DO) on fatigue life were analyzed. During the fatigue test, the material exhibited a cyclic hardening followed by cyclic softening behavior, with no obvious cyclic stability region. In logarithmic coordinates, the S–N curve showed a bilinear relationship. As the strain amplitude increased from 0.2 to 0.6%, the fatigue life approximately decreased from 105 to 3 × 102. The environmental correction factor (Fen), which is defined as the ratio of life in air at room temperature to that in the primary coolant environment, decreases as the temperature decreases from 321 to 150 °C. The Fen also decreases as the DO decreases from 0.6 to 0.03 ppm while it increases as the strain rate decreases from 1 to 0.0004%/s. Compared with the NUREG6909 model, the presented model is more applicable for fatigue life prediction of Chinese A508-3 steel.

Environmental fatigue correction factor model for domestic nuclear-grade low-alloy steel

Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (Fen) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

Investigation on Analysis Method of Environmental Fatigue Correction Factor of Primary Coolant Metal Materials in LWR Water Environment

The environmental fatigue correction factor (Fen) is mainly used to analyze the influence of the coolant environment on the fatigue life of primary metal materials. Because the calculation of the transformed strain rate is related to the stress history of the component structure, how to determine the strain rate is the most critical step in calculating the Fen. The approaches of the detailed method were given by the Electric Power Research Institute (EPRI) guidelines and RCC-M-2017 Edition Section VI- RPP No. 3 separately, so a gap analysis was performed between the two methods. Furthermore, another average method was also proposed to determine the average strain rate and strain range. Based on the analysis benchmark provided in the EPRI guideline, a simple case study was performed to account for the effect on the fatigue life in applications with different strain rate approaches and different Fen expressions. Finally, two industry case studies were also completed, including on materials of low alloy steel, austenitic stainless steel, and nickel-base alloy. We suggest adopting a more accurate detailed method, and its methodology is recommended to provide more reasonable solutions.

255 Island tourism carrying capacity in the UNESCO Site Laurisilva of Madeira

The Laurisilva of Madeira is an important natural resource as well as a location for nature-based tourism and recreational activities. Despite UNESCO’s concerns and recommendations for assessing tourism capacity, the local population is perceived as overusing this resource; yet precisely how many tourists visit its most popular areas remains unknown. Tourism carrying capacity (TCC) was assessed on two Rabaçal trails using a specific formulation relating physical aspects to environmental correction factors. Tourism carrying capacity was found to be below theoretical limits, and trail access was not restricted despite being a major concern in natural resource management.

Gauge-Strain-Controlled Air and PWR Fatigue Life Data for 304 Stainless Steel—Some Effects of Surface Finish and Hold Time

We performed environmental fatigue testing in simulated primary water reactor (PWR) primary water and reference fatigue testing in air in the framework of an international, collaborative project (INCEFA-PLUS), where the effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments are being studied. Our fatigue lives obtained on machined specimens in air at 300 °C lie close to the NUREG/CR6909 mean air fatigue curve and are in line with INCEFA-PLUS air fatigue lives. Our environmental fatigue lives obtained in simulated PWR primary water at 300 °C lie relatively close to the NUREG/CR6909 mean fatigue curve; derived from the NUREG/CR6909 mean air fatigue curve and the applicable environmental correction factor (Fen). The PWR results show that (1) a polished surface finish has a slightly higher and a ground surface finish a slightly lower fatigue life than the NUREG/CR6909 prediction; (2) the ratio of polished to ground specimen life is ~1.37 at 300 °C and ~1.47 at 230 °C; (3) holds—at zero strain after a positive strain-rate—have a slightly detrimental effect on fatigue life. These results are in line with the INCEFA-PLUS PWR fatigue lives. A novel gauge-strain extensometer was deployed in order to perform a true gauge-strain-controlled fatigue test in simulated PWR primary water.

Corrosion fatigue model of austenitic stainless steels used in pressurized water reactor nuclear power plants

Low cycle fatigue behavior of 316LN stainless steel (SS), 304 SS and 308L weld metal was investigated in air and high-temperature pressurized water environment. The effects of mechanical factors and environmental factors on fatigue lives were considered. The fatigue mean curve and design curve for nuclear-grade austenitic SSs in air are obtained by fitting fatigue data. The corrosion fatigue model for nuclear-grade austenitic SSs in high-temperature pressurized water environment is proposed based on environmental fatigue correction factor method, which mainly considers the effects of strain rate, temperature and dissolved oxygen concentration.

Weibull and Bootstrap-Based Data-Analytics Framework for Fatigue Life Prognosis of the Pressurized Water Nuclear Reactor Component Under Harsh Reactor Coolant Environment

AbstractIn general, the fatigue life of a safety critical pressure component is estimated using best-fit fatigue life curves (S-N curves). These curves are estimated based on underlying in-air condition fatigue test data. The best-fitting approach requires a large safety factor to accommodate the uncertainty associated with large scatter in fatigue test data. In addition to this safety factor, reactor component fatigue life prognostics requires an additional correction factor that in general is also estimated deterministically. This additional factor known as the environmental correction factor Fen is to cater the effect of the harsh coolant environment that severely reduces the life of these components. The deterministic Fen factor may also lead to further conservative estimation of fatigue life leading to unnecessary early retirement of costly reactor components. To address the above-mentioned issues, we propose a data-analytics framework which uses Weibull and Bootstrap probabilistic modeling techniques for explicitly quantifying the uncertainty/scatter associated with fatigue life rather than estimating the lives based on a best-fit based deterministic approach. We assume the proposed probabilistic approach would provide the first hand information for assessing the maximum and minimum effects of pressurized water reactor water on the reactor component. In the discussed approach, in addition to the probabilistic fatigue curves, we suggest using a probabilistic environment correction factor Fen. We assume the probabilistic fatigue curve and Fen would capture the S-N data scatter associated with the bulk effect of material grades, surface finish, strain rate, etc. on the material/component fatigue life.

Air-side heat transfer characteristics under wet conditions at lower ambient pressure of fin-and-tube heat exchanger

Air-side heat transfer performance of plain fin-and-tube heat exchanger under fully wet conditions was experimentally investigated at different ambient air pressure. Test results were compared with three available correlations to examine their applicability in lower pressure. Tested samples had different row numbers of 2–4 and the experimental ambient pressure had a range of 40–100 kPa. The experimental data at atmospheric pressure is basically consistent with the correlations. Air-side jh factors increased by 16.51–40.19% as Re number decreased from 4000 to 1000, and balloon to 112.04–141.37% when Re number declined from 1000 to 200. The row number effect still exists at lower ambient pressure and only become more apparent. Available correlations fails to describe experiment data at lower ambient pressure, maximum average error soar from 15.90% to 137.41% when ambient pressure drop from 100 kPa to 40 kPa. By adding the environmental pressure correction factor to the Re number in correlation, the refined correlation can describe 90.43% of experimental data within ±20%, and have a mean deviation of 1.46%.

Synergistic effect of mechanical and environmental damages of 316LN stainless steel under different fatigue strain amplitudes in high-temperature pressurized water

Corrosion fatigue (CF) behavior of 316LN stainless steel under different strain amplitudes (0.3–0.8%) in 325 °C water was investigated at a strain rate of 0.04% s−1. It was found that the fatigue life and strain amplitude has a linear relation in double logarithmic coordinate. The environmental damage increased with decreasing strain amplitudes. The synergistic effect of mechanical and environmental damages during the CF process in high-temperature pressurized water is discussed, and a calculation equation for environmental fatigue correction factor Fen is proposed to calculate the strain amplitude effect.

Research on the Application of Fen for Environmentally Assisted Fatigue Evaluation of the Austenitic SS Pipe Under Combined Transient Loads

Accumulative test data indicate that the effects of the light water reactor (LWR) environment could cause the fatigue resistance of primary pressure boundary components materials to be significantly reduced. Environmentally assisted fatigue (EAF) is the abbreviation of the environmentally assisted fatigue. In 2007, Nuclear Regulatory Commission (NRC) issued RG. 1.207. It was updated in 2014. And, it requires that the effects of LWR environment on the fatigue life reduction of metal components should be considered for new design plants. And it suggests to use environmental correction factor, Fen, to account for EAF. NRC regulation (NUREG), NUREG/CR-6909 (NRC, 2013, “Effect of LWR Coolant Environments on the Fatigue Life of Reactor Materials,” U.S. Nuclear Regulatory Commission, Argonne, IL, Standard no. NUREG/CR-6909), presents the detail Fen calculation formula. Fen is a function of temperature, strain rate, dissolved oxygen level in water, and sulfur content of the steel. Accordingly, Fen calculation will present a comparatively conservative result. Depending on the experience of the primary pressure boundary piping transient operation, Fen varies during each transient. More uncertainty and confusion are raised during the application of the Fen method. The research work in this paper includes: first, the typical character of piping thermal transient is derived based on the existing experience. Second, small specimen EAF tests are conducted depending on the above derived combined loading characters. Then effort is taken to improve the application of the Fen method for the combined multitransient loading conditions. And the results are compared with those of the lowest instantaneous Fen method and equalization of the weighted Fen method. Finally, a designed test plan is presented.

Optically stimulated luminescence dating of heat retainer hearths from the Sahara: Insights into signal accumulation and measurement

Abstract Heat retainer hearths are a prominent component of the Holocene archaeological record of a number of drylands. Rocks within these hearths were fired in antiquity, emptying the optically stimulated luminescence (OSL) source traps of mineral grains within the rock. Since partial bleaching and mixing of grains within a lithified heat retainer is impossible, these rocks offer the opportunity to test our understanding of OSL signal accumulation and measurement processes. First, we show that OSL ages calculated using grains size fractions from 4 to 11 μm up to 180–210 μm are indistinguishable for a single heat retainer, indicating that the environmental and instrumental dose rate correction factors routinely used in luminescence dating are accurate. Second, we used single-grain dose recovery and equivalent dose measurements to determine the overdispersion due to beta microdosimetry. For the heat retainers measured in this study, overdiseprsion due to beta microdosimetry ranges from 8.9 ± 1.8 to 20.3 ± 1.6%. Third, we investigate the impact of mechanical crushing on the measured equivalent dose from quartz, to test the potential of using this technique to liberate dateable material from heat retainers which are not acid soluble. A small (

Development of Environmental Correction Factor for Environmental Fatigue Evaluation of Austenitic Stainless Steels in PWR Plant Condition

Development of Environmental Correction Factor for Environmental Fatigue Evaluation of Austenitic Stainless Steels in PWR Plant Condition

Effect of Light Water Reactor Water Environments on the Fatigue Life of Reactor Materials

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) provides rules for the design of Class 1 components of nuclear power plants. However, the Code design curves do not address the effects of light water reactor (LWR) water environments. Existing fatigue strain-versus-life (ε–N) data illustrate significant effects of LWR water environments on the fatigue resistance of pressure vessel and piping steels. Extensive studies have been conducted at Argonne National Laboratory (Argonne) and elsewhere to investigate the effects of LWR environments on the fatigue life. This article summarizes the results of these studies. The existing fatigue ε–N data were evaluated to identify the various material, environmental, and loading conditions that influence the fatigue crack initiation; a methodology for estimating fatigue lives as a function of these parameters was developed. The effects were incorporated into the ASME Code Section III fatigue evaluations in terms of an environmental correction factor, Fen, which is the ratio of fatigue life in air at room temperature to the life in the LWR water environment at reactor operating temperatures. Available fatigue data were used to develop fatigue design curves for carbon and low-alloy steels, austenitic stainless steels (SSs), and nickel–chromium–iron (Ni–Cr–Fe) alloys and their weld metals. A review of the Code Section III fatigue adjustment factors of 2 and 20 is also presented, and the possible conservatism inherent in the choice is evaluated. A brief description of potential effects of neutron irradiation on fatigue crack initiation is presented.

Evaluating in-vessel composting in treating sewage sludge and agricultural waste by examining and determining the kinetic reactions of the process

This paper presents the evaluation of the performance of an in-vessel composting system by examining the kinetic reactions of the processes developed for the treatment of sewage sludge and agricultural waste. The aim of this work is (a) to describe the composting process using a kinetic model that is based on the biodegradable organic matter losses during decomposition of the substrate, (b) to evaluate the efficiency of the bioxidation process that takes place in the system and (c) to determine the factors and the rate at which they limit the composting process. The simulation of the composting process considers a first-order kinetic model including the environmental parameters (environmental correction factors) that influence bioxidation of the biodegradable organic matter (BOM) of the substrate namely temperature, moisture content and oxygen concentration. The experimental results, recorded and monitored throughout the composting processes, were fitted using the proposed model. The results obtained suggest that the system operates efficiently by recording increased levels of BOM losses, high decomposition rates while composting limitations, due to the environmental conditions, is not significant during the main stages of the processes.

The Current Status of New Czech Corrosion Fatigue Evaluation Proposal for WWER Nuclear Power Plants

Presented paper introduces an innovative principle of fatigue life assessment suggested for WWER nuclear power plants. The subject of this work is to take into account the corrosion environment influence in actual methodology of low-cycle fatigue (LCF) assessment and prediction. The aim of this paper is to summarize the current status of the Czech proposal of corrosion fatigue assessment and prediction. The first project focused on base steel materials, which are used in primary circuit of WWER-440, started in 2010. The basic idea of Czech environmental fatigue correction factor has been introduced on international PVP conference in 2013. The new project linked to the previous one is focused on the additional area of welding joints. Theoretical base is completed by experimental verifications of proposed environmental correction factor. The subject of actually running theoretical-experimental program covers similar metal welds of austenitic stainless steel 08CH18N10T and results will be available in 2015. Moreover LCF tests in corrosion environment of dissimilar metal welds are under preparation. Experimental work is based on LCF strain-controlled tests in primary water environment of WWER-440.

Full-scale 3-D finite element modeling of a two-loop pressurized water reactor for heat transfer, thermal–mechanical cyclic stress analysis, and environmental fatigue life estimation

This paper discusses a system-level finite element model of a two-loop pressurized water reactor (PWR). Based on this model, system-level heat transfer analysis and subsequent sequentially coupled thermal–mechanical stress analysis were performed for typical thermal–mechanical fatigue cycles. The in-air fatigue lives of example components, such as the hot and cold legs, were estimated on the basis of stress analysis results, ASME in-air fatigue life estimation criteria, and fatigue design curves. Furthermore, environmental correction factors and associated PWR environment fatigue lives for the hot and cold legs were estimated by using estimated stress and strain histories and the approach described in US-NRC report: NUREG-6909.

A Fundamental Study and Modeling of the Micro-Droplet Formation Process in Near-Field Electrohydrodynamic Jet Printing

Near-field electrohydrodynamic jet (E-jet) printing has recently gained significant interest within the manufacturing research community because of its ability to produce micro/submicron-scale droplets using a wide variety of inks and substrates. However, the process currently operates in open-loop and as a result suffers from unpredictable printing quality. The use of physics-based, control-oriented process models is expected to enable closed-loop control of this printing technique. The objective of this research is to perform a fundamental study of the substrate-side droplet shape-evolution in near-field E-jet printing and to develop a physics-based model of the same that links input parameters such as voltage magnitude and ink properties to the height and diameter of the printed droplet. In order to achieve this objective, a synchronized high-speed imaging and substrate-side current-detection system is implemented to enable a correlation between the droplet shape parameters and the measured current signal. The experimental data reveals characteristic process signatures and droplet spreading regimes. The results of these studies served as the basis for a model that uses the measured current signal as its input to predict the final droplet diameter and height. A unique scaling factor based on the measured current signal is used in this model instead of relying on empirical scaling laws found in prior E-jet literature. For each of the three inks tested in this study, the average error in the model predictions is under 10% for both the diameter and the height of the steady-state droplet. While printing under nonconducive ambient conditions of low relative humidity and high temperature, the use of the environmental correction factor in the model is seen to result in a 17% reduction in the model prediction error.