EDF Energy (United Kingdom)

The high energy consumption in the building sector and the increasing impacts of climate change have necessitated the transition to net-zero-energy buildings (NZEBs), in which energy retrofit strategies play a key role. However, neglecting moisture transport and climatic design while improving energy efficiency often leads to reduced building performance, material deterioration, worse occupant health, and indoor environmental problems. This review examines in detail the basic mechanisms of moisture transport, including diffusion, capillary action, and airborne moisture transport, and illustrates how poor moisture control affects thermal performance and resident health. Additionally, a comparative analysis of the impact of retrofit strategies implemented in different climatic regions on energy efficiency, carbon emission reduction, moisture-related failures and net-zero goals is conducted. At the same time, the need exists to incorporate awareness regarding the adverse effects on the health of occupants. This systematic review analyzed 120 peer-reviewed studies published from 1994 to 2026, covering different climatic regions (e.g., cold, temperate, warm–humid, etc.). The analysis found that the energy savings rates were reported to range from 18% to 45%, while the moisture-related failures in inappropriately retrofitted buildings were observed to increase by up to 32% in some cold regions. This research review provides a comprehensive advisory framework for domestic residents to take remedial steps until retrofit experts gain access in order to prevent health risks from mold and moisture ingress, which can contribute to a healthy lifestyle and a net-zero-energy building.

Abstract Physics-based models for permeability prediction are essential for ensuring physically consistent reservoir characterization, yet they often fail to capture the full complexity of real geological systems. This study applies an explainable physics-informed machine learning (PIML) framework for discrepancy modeling to a legacy well dataset from a carbonate formation in southern Iraq. The dataset, originally comprising more than 2,400 samples from 10 wells, was heavily contaminated with incorrectly imputed or interpolated core permeability values. Through a rigorous zonation-based cleaning process, 1,130 high-quality samples were retained for modeling. A baseline physics model, built using well log–derived porosity and a porosity–permeability transform, was combined with a machine learning (ML) discrepancy model trained on three physics-informed features: neutron porosity (NPHI), the gamma ray/ bulk density (GR/RHOB) ratio, and depth. Three ML algorithms, Random Forest, XGBoost, and CatBoost, were evaluated, with five-fold cross-validation employed to ensure robustness. The discrepancy model effectively captured systematic biases in the physical model's predictions. When integrated into the boosted-ML frameworks, it delivered substantially higher permeability prediction performance, reducing root mean squared error (RMSE) by 56% and improving the adjusted coefficient of determination (adjusted R2) from −0.27 to 0.76 compared to the original physical model. These results demonstrate the strong potential of discrepancy-based ML-enhancement methodologies for improving permeability prediction in legacy well datasets. Explainable AI analysis using Shapley additive explanations (SHAP) to determine feature influence identified measured depth as the most influential predictor. Compaction effects not captured by the original physical model, GR/RHOB and NPHI also exerted substantial influence on the PIML permeability predictions. These findings not only improve permeability prediction performance but also reveal missing physics in the baseline model, enabling targeted refinement of physical relationships. This work highlights the feasibility and value of applying discrepancy-based PIML to noisy, incomplete legacy datasets, bridging the gap between empirical ML corrections and physically consistent modeling.

Asphaltene precipitation in carbonate reservoirs presents a significant flow assurance challenge. This study investigates a novel ZnO/SiO₂/xanthan/eucalyptus nanocomposite (NCs) for inhibiting asphaltene deposition. A multiscale analysis was employed, incorporating adsorption isotherms, atomic force microscopy (AFM). and core-flooding under realistic reservoir conditions (90 °C, up to 3700 psi). Adsorption isotherm analysis confirmed that the Langmuir model provided the best data fit, indicating monolayer adsorption with a high capacity (Qm = 185.2 mg/g). Interfacial tension (IFT) measurements demonstrated NCs altered the IFT-pressure slope by 45.71%, indicating enhanced inhibition. AFM analysis revealed NCs significantly reduced surface roughness, decreasing average roughness (Ra) from 56.70 to 11.42 nm. Core-flood experiments confirmed NCs mitigated permeability impairment by over 50% and reduced asphaltene precipitation by up to 4.00 wt.% during natural depletion. The results demonstrate that the synthesized NCs are a highly effective inhibitor for mitigating asphaltene-related formation damage in carbonate reservoirs.

Abstract Austenitic stainless steels used in light water reactor coolant environments can be susceptible to environmentally assisted fatigue due to non-monotonic loading conditions, primarily associated with load-follow, thermal transients, or intermittent plant shutdowns and start-ups. One of the main goals of a five-year INCEFA-SCALE (INcreasing safety in NPPs by Covering gaps in Environmental Fatigue Assessment - focusing on gaps between laboratory data and component SCALE) project, kicked off in October 2020 and supported by the European Commission HORIZON2020 program, is to develop an improved mechanistic understanding behind the effect of a pressurized water reactor (PWR) primary environment on the fatigue behavior of austenitic stainless steels through coordinated extensive characterization of tested specimens at partner organizations. Post-mortem characterization of fatigue specimens tested in air and high-temperature PWR water environments with different loading parameters was performed. In this program, the effects of a PWR environment containing hydrogen and cyclic loading parameters on the low cycle fatigue (LCF) behavior of 316L stainless steel were investigated by comprehensive striation spacing evaluation and microscopic characterizations. The exposure to a PWR environment results in a decreased LCF lifetime, an enhanced fatigue crack initiation and an accelerated fatigue crack growth rate of 316L austenitic stainless steel. The interaction of hydrogen and localized deformation contributes to the accelerated fatigue crack growth rate in a PWR environment. The effect of waveform (periodic underload PUL, periodic overload POL and constant amplitude sawtooth CA) was evaluated. PUL and POL reduce the low cycle fatigue lifetime, accelerate the fatigue crack growth rate and advance the cycle where initiation of fatigue crack occurs compared to CA loading. LCF waveform strongly influences the shear band formation, localization of plastic deformation and stress state.

Abstract INCEFA-SCALE is a five-year project within the European Commission HORIZON 2020 programme starting in October 2020. Nuclear plant operators have generally observed that the number of failure events attributable to Environmentally Assisted Fatigue (EAF) are fewer than predicted by current assessment methodologies. It is recognised that a contributor to this discrepancy is the transferability of data from laboratory-scale tests to real nuclear components. This is the main knowledge gap addressed by INCEFA-SCALE. This is being achieved through the combination of testing, analysis, and materials characterisation to provide laboratory testing data, and the required meta data to understand the resulting behaviour, generated under conditions that are more representative of those experienced by plant components. The EAF assessment methodology described in NUREG/CR-6909 Rev 1 designed for use with the ASME BPVC Section III fatigue design curves (using factors of 12 on life and 2 on stress/strain) provides an international benchmark and technical justification. This benchmark has been the subject of over a decade of research defining the levels of conservatism provided and proposing alternative approaches to clearly define appropriate margins in EAF assessment methods. One such approach, initiated by the Japanese ‘Subcommittee on Design Fatigue Curve’ and further developed by Rolls-Royce, offers modifications to the design curve approach through the use of ultimate tensile strength dependent mean curves, justification of a new approach to transference factors, the use of the Smith-Watson-Topper mean stress correction approach and explicitly accounting for variable amplitude loading in the high cycle regime of fatigue. Substantial research has been conducted and improvements proposed for the low-cycle regime of the design curves (where the factor on life applies for the ASME approach). However, research data in relevant high temperature water environments relating to the transference factors influencing the factor of 2 on stress/strain is limited. Part of this value is defined by loading history and understanding how to account for this phenomenon in a fatigue assessment requires the production of research data that enables the behaviour of materials subjected to variable loading to be understood. Variable loading is known to affect hardening and mean stress behaviour. Additionally, failure modes where a crack can initiate under larger loading amplitudes and grown to failure by sub-endurance limit loading may be important. This means laboratory testing under relevant environments and variable strain amplitudes is required to advance this area and define new benchmark methods that can adequately account for such behaviours while providing an appropriate level of conservatism. This paper focuses on the presentation and analysis of test data produced by the INCEFA-SCALE project. The data investigates the effects of loading history, environment, and surface finish, through the application of single and variable amplitude waveforms to 316L stainless steel uniaxial fatigue specimens in both air and simulated Pressurised Water Reactor primary coolant environments. By altering the above variables, the aim of this paper is to provide an understanding of how the method outlined in NUREG/CR-6909 and the alternative method proposed by the Subcommittee on Design Fatigue Curve accounts for these effects. It is shown that at time of writing the data would provide support for reducing the NUREG transference factor on stress to 1.4, however a recommendation on reducing the factor on cycles requires more analysis. The reduction in the stress factor is consistent with the approach of the Japanese ‘Subcommittee on Design Fatigue Curve’. There is however inconsistency between the use of elastic pseudo stress amplitudes used in fully reversed design life predictions, and the yield stress value used to govern the boundaries of stress-based mean stress corrections which should be considered in any new design curve approaches.

Abstract The primary and secondary PWR (Pressurized Water Reactor) circuits are a complex set of pressure-welded steel piping and components. As the second barrier to the spread of fissile materials is concerned, ensuring the integrity of these circuits is a major safety objective. It must cover all possible loading situations encountered in service (normal operation as well as accidental situations) and all possible failure modes, material functions and associated conditions of use. Fracture mechanics assessment in welded joints in these structures require particular attention. Indeed, welds may present defects (ex. lack of fusion) and generally have a lower fracture resistance than the base metal. Additionally, welding process generate Welding Residual Stresses (WRS) that might be considered in the assessment. Their potential impact on the risk of failure is directly related to material behavior. These WRS have been shown to have an impact on the risk of failure in the brittle domain where the behavior is quasi-elastic, but this impact appears to be overestimated in the upper shelf of the transition curve. Consequently, industry needs to develop criteria adapted to the problem of taking WRS into account in the analysis of fracture mechanics for fracture mechanics assessment, and to validate these criteria through experiments at different scales, then define the areas where these stresses must be taken into account or can be neglected. This paper present experimental results and first analysis of four points bending tests performed on large scale welded C-Mn steel pipe representative of the PWR secondary and auxiliary piping.