bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advanced Structural Integrity Assessment Tools for Safe Long Term Operation - ATLAS+ Project: Status of the Activities of the WP3 on Modelling in 2020 & 2021
Authors: Blouin Arnaud , Marie Stéphane , Nicak Tomas , Timperi Antti , Gill Peter 
Published: November 2022

Abstract
The main objective and mission of the ATLAS+ project was to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems.
ATLAS+ WP3 focused mainly on ductile tearing prediction for large defects in piping and associated components: Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as triaxiality effects, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is currently rather limited to R&D expertise. However, because of the continuous progress in the performance of calculation tools and accumulated knowledge, in particular by members of the ATLAS+ consortium, these models can now be considered as relevant for application in the context of engineering assessments.
WP3 was planned to:
• Illustrate the implementation of these models for industrial applications through the interpretation of large scale mock-ups (with cracks in weld joints for some of them),
• Make recommendations for the implementation of the advanced models in engineering assessments,
• Correct data from the conventional engineering approach by developing a methodology to produce J-Δa curve suitable case by case, based on local approach models,
• Improve the tools, guidance and procedures for undertaking leak-before-break (LBB) assessments of piping components, particularly in relation to evaluating structural representative fracture toughness J-Resistance curves and the influence of weld residual stresses.
To achieve these goals, WP3 was divided into 4 sub-WPs. This paper presents the progress of the work performed in each sub-WP after 48 months of activities.
ATLAS+ European Project - General Method for the Components J-R Curve Derivation
Authors: Nicak Tomas , Blouin Arnaud , Marie Stephane , Ancelet Olivier 
Published: November 2022

Abstract
The main objective and mission of the European Project ATLAS+ project was to develop advanced structural assessment tools to address the remaining technology gaps for the safe and long term operation of nuclear reactor pressure coolant boundary systems. ATLAS+ WP3 was focused mainly on ductile tearing prediction for large defects in components. Several approaches have been developed to accurately model the ductile tearing process and to take into account phenomena such as the triaxiality effect, or the ability to predict large tearing in industrial components. These advanced models include local approach coupled models or advanced energetic approaches. Unfortunately, the application of these tools is today rather limited to R&D or expertise. However, because of the continuous progress in the performance of the calculation tools and accumulated knowledge, in particular by members of ATLAS+, these models can now be considered as relevant for application in the context of engineering assessments.
Although there are analytical solutions for calculation of J-Integral values for many standard specimen geometries (i.e. CT or SENT), limited or no formulas are available for more complex structures such as pipes, elbows, T-junctions, pressure vessels etc.
Therefore, there is a need to develop a methodology which can be used for derivation of J-R curves for an arbitrary component geometry on the basis of experimental results obtained by testing small size laboratory specimens.
To achieve this goal Framatome GmbH used combined local approach (GTN model) and elastic-plastic calculations to determine J-R curves whereas Framatome France used analytical methodologies to derive the J-R curves from local approach results (GTN model). In both cases, the Δa and J values were calculated at the deepest point of the crack front.
This paper shows promising results and concludes there is a significant margin in the fracture mechanics assessment based on material properties obtained by testing highly constrained standard specimens compared to more realistic structural situations.
Assessment of Safety Valve Escape Pipework
Authors: Vorster Willem J. J. , Roy Jonathan , Gilroy Daniel G. , Pollock Jack A. , Clarkson David M. , Beveridge Andrew J. , Strong Alistair 
Published: November 2022

Abstract
This paper discusses fitness for purpose (FfP) structural integrity assessments of Safety Relief valve (SRV) vent pipes that were inadequately designed and maintained. The FfP assessments identified several latent errors with the pipework design. The absence of a fault schedule in combination with the latent errors led to a discernable anomaly in the safety case which was finally address but resulted in long outage delays and spiraling costs due to the large number of assessments, inspections and modifications required to achieve and demonstrate integrity.
The FfP assessments discussed here consider all failure mechanisms which were identified as being relevant during steam discharge. These include plastic collapse, ratchetting, creep rupture and creep-fatigue and required a series of complex assessments to sentence the SRV pipes for return to service. The Computational Fluid Dynamics (CFD), pipe stress analysis and Finite Element Modeling (FEM) required to demonstrate integrity are discussed. The plant modification and repair solutions required to achieve integrity before the pipes could be returned to service are presented. The method used to apply CFD loads to pipe stress models without double accounting for static pressure stresses in the Finite Element Analyses (FEA), is describe here. Novel analysis techniques used to speed up assessments and the historic plant data reviews that were required to substantiate the claims on historic damage are reviewed.
Flanges Impact Testing Exemption Assessment
Authors: Robles Roberto , Muñoz Miguel , Santana Antonio 
Published: November 2022

Abstract
Over the last decade, multiple carbon steel flanges brittle fracture failures have led the industry to issue a global alert on standard ASTM A105 flanges toughness values at temperatures higher than −20°F (−29°C), the minimum temperature allowed by the current editions of ASME B16.5 and ASME B31.3. The ASME BPV VIII Subgroup Toughness penalized these components by assigning the material the UCS-66 Curve A and modified UCS-66(c) to limit the minimum temperature of standard A105 flanges to 0°F (−18°C), unless the flanges have been normalized and manufactured to fine grain practice, after which they can be used down to the temperature permitted by ASME B16.5.
In order to determine whether these changes would provide acceptable toughness values, nineteen (19) flanges were purchased from local manufacturers in both as-forged and normalized conditions and were subjected to several tests including charpy testing at various temperatures, McQuaid-Ehn, hardness testing, metallography, grain sizing, and chemical analysis. The results suggest that complying with UCS-66(c) does not necessarily guarantee acceptable toughness results for flanges that were normalized and manufactured to fine grain practice, and this is attributed to low Mn:C ratios and possibly uncontrolled heat treatment procedure. On the other hand, a number of non-normalized standard flanges have been found to provide very low toughness values at temperatures as high as 32°F (0°C), despite the current state of UCS-66(c) allowing use down to a minimum temperature of 0°F (−18°C).
In view of the above, this paper discusses and evaluates some of the possible additional technical requirements that users could specify to minimize the risk of brittle fracture on standard ASTM A105 flanges, as well as a number of methods to guarantee better toughness performance in standard flanges.
Effect of Trace Water Vapor on Measurement of Fatigue Crack Growth Rates in Hydrogen Gas at Low ΔK
Authors: Nibur Kevin , Somerday Brian 
Published: November 2022

Abstract
Anomalous and inconsistent results were observed while performing fatigue crack growth tests in hydrogen gas on 4130X Cr-Mo steel when the stress-intensity factor range (ΔK) was less than 10 MPa m1/2. Two particular abnormal characteristics were noted: i) sequential measurements of fatigue crack growth rate (da/dN) vs. ΔK from a single test specimen were not repeatable at lower ΔK, and ii) at constant ΔK ∼8 MPa m1/2, da/dN never reached a steady-state level, as crack growth rates continuously increased as a function of time. It was hypothesized that both of these characteristics could be related to water vapor in the hydrogen gas. This hypothesis was tested by varying the environment in the test chamber through modification of the pressure purging and vacuum evacuation procedures. The resulting water vapor levels in the hydrogen test gas were either higher or lower than the nominal value, and measurements of fatigue crack growth rates in these environments confirmed the hypothesis that water vapor governed da/dN at lower ΔK. One consequence of such water vapor-dominated fatigue crack growth rates is that the da/dN vs. ΔK relationship in dry hydrogen gas at lower ΔK cannot be reliably represented by the da/dN vs. ΔK relationship measured in humid air. As a result, when the lower-ΔK portion of the da/dN vs. ΔK relationship in hydrogen gas is constructed from the da/dN vs. ΔK relationship in air, fatigue crack growth rates can be overestimated by as much as an order of magnitude.
Quantification of the Tempering Response for Temper Bead Welding of SA-508 Low Alloy Steel
Authors: Jang Eun , Luo Yuxiang , Alexandrov Boian , McCracken Steven L. , Tatman Jon , Barborak Darren 
Published: November 2022

Abstract
The objective of this work is to demonstrate the tempering response quantification approach for process - property optimization in the heat affected zone (HAZ) of SA-508 Gr. 2 Cl. 1 (formerly designated as SA-508 Cl. 2) subjected to temper bead welding (TBW).
The tempering response in the CGHAZ and ICHAZ was quantified by a series of TBW thermal history simulations, followed by microstructural characterization and hardness measurements. Tempering response predictive equations were developed utilizing a version of the Grange Baughman parameter (GBP), modified to reflect the thermal histories in multi-pass welding.
In parallel, the accuracy of the tempering response quantification and predictive hardness equations were validated. Validation was achieved through experimental welding with thermal history acquisition, determination of a predicted hardness value using the recorded thermal data, and comparison of the predicted values with micro-hardness measurements.
Guidance on the Suitability of Design Codes and Assessment Procedures for Deploying High Temperature Advanced Modular Reactors in the UK
Authors: Chevalier Marc , James Peter , Underwood Nick 
Published: November 2022

Abstract
The UK government has committed to achieving “net-zero” carbon emissions by 2050. Advanced Modular Reactors (AMRs) are small Generation IV reactor that operate at high temperatures. These reactors could play a significant role in providing low carbon electricity generation and decarbonising other industrial processes by utilising heat directly. However the structural integrity challenges for such high temperature plant have been demonstrated in experimental Generation IV plant and the AGR fleet in the UK.
Ensuring the design codes are fit for purpose to satisfy the UK regulatory requirements, including Generic Design Assessment (GDA) and also producing a reliable design that results in a commercially viable plant, is essential. Therefore, the “Establishing AMR Structural Integrity Codes and Standards for UK GDA” (EASICS) project was established to identify the suitability and shortfalls of existing design codes and assessment procedures.
The headline deliverable from the EASICS project was a guidance document, aimed towards vendors looking to deploy AMRs in the UK. However many of the issues raised are relevant to AMR technology regardless of the regulatory regime. This paper provides a summary of the EASICS guidance document. This includes a review of the regulatory requirements for design substantiation in the UK (which unlike many other countries requires consideration of defect tolerance), status of existing design codes (i.e. ASME III Div. 5 and RCC-MRx) and assessment procedure (i.e. R5/R6), comment on the notable technical differences between the available design codes and assessment procedures, highlighting what has been learnt from previous operation of high temperature nuclear plant (including Generation IV reactors and the AGRs in the UK), and an overview of the conclusions.
The conclusions consider the strengths, weaknesses and gaps in the currently available design codes and assessment procedures for commercial deployment of AMRs. It also identifies the development required to address perceived shortfalls and how design codes and assessment procedures may have to be used congruently to provide a solution on a timescale consistent with the UKs ambition for AMR deployment.
Crack Growth in Carbon and C-0.5Mo Steels in High Temperature Hydrogen: Laboratory Data and Fitness for Service Modelling
Authors: Rollins Brandon C. , Sutton Nathaniel 
Published: November 2022

Abstract
High temperature hydrogen attack (HTHA) is a known degradation mechanism in the refining industry for carbon and low alloy steels operating at temperatures above 400°F in hydrogen service. Historically the integrity of operating equipment subject to these conditions has been ensured by using the empirically derived Nelson Curves to identify safe operating regions. This approach was largely successful, but failures still occurred and, in some cases, required overly conservative operational limits. Additionally, this approach did not allow for a defect tolerance approach to fitness for service (FFS) assessments. An on-going joint-industry project (JIP) has been addressing these issues by generating laboratory crack growth data and developing models to apply the acquired knowledge in FFS assessments.
A testing program was conducted on three (3) C-0.5 Mo steels to generate crack growth data in hydrogen at a range of temperatures (316 to 399°C [600 to 750°F]), 5.52 MPa (800 psig H2) hydrogen pressure, and stress intensity values between (10.5 to 35.4 MPa√m [9 to 32 ksi√in]). These results were used to validate and refine a crack growth model based on the creep crack growth fracture mechanics approach, C*. The results of the test program and modeling efforts are described in detail.
Combining Acoustic Induced Vibration and Flow Induced Vibration
Authors: Izuchi Hisao , Swindell Rob , Mann Adin 
Published: November 2022

Abstract
During testing to support a program to improve acoustic induced vibration (AIV) assessments, it became clear that flow induced vibration (FIV) is excited at the same time; both mechanisms excite the shell flexural modes of the piping system, although their frequency characteristics are different but overlap. Typically, AIV and FIV are evaluated separately. However, review of some of the existing AIV assessment methods, particularly those that rely on empirical correlations with known failure cases, suggests that they effectively include an FIV element. In the case of a PSV tailpipe joining a subheader at a tee, the FIV is primarily present near the tee while AIV also present away from the tee. Therefore, combining the AIV and FIV assessments unwittingly into one assessment can result in significant conservatism away from the tee. Formulations for the FIV prediction and combining AIV and FIV into a pipe fatigue life assessment are presented. Data from a flare header test system is used to demonstrate the formulations and justify simplifications. The flare header test system consists of an NPS6x8 pressure relief valve, an NPS12 tailpipe with a tee connection to an NPS20 header.
Level 3 Fitness for Service Assessment of Dented Pipes With Diameter Less Than 6.25 Inch
Authors: Mostafa Khaled , Alian Ahmed 
Published: November 2022

Abstract
The aim of this paper is to investigate the parameters affecting the structural integrity for piping with dents anomalies. As per the requirements to part 12 of the API 579-1/ASME FFS-1, 2016 [1], level 1 and 2 fitness for service (FFS) assessment procedures can’t be used for dented pipe with diameter less than 6.25 inch. Such small size pipes can only be assessed using level 3 assessment procedure. The pipe was indented in the FEA model with a rigid indenter. The indented pipe was then evaluated under general collapse and local failure criteria under different loading combinations using the elastic plastic analysis approach. The pipe material is defined using a multi-linear isotropic hardening model as per Annex 3-D of ASME BPVC, sec. VIII, div. 2 [2]. The effect of nominal pipe size, pipe schedule, and dent’s radius of curvature and depth on the plastic strain, and strain ratio are studied. Following Taguchi design of experiments methodology [5], a partial factorial design was adopted to allow the investigation of multiple levels value for each parameter. This analysis uses a real-life dent profile which was measured using automatic ultrasound inspection (AUT) and fitted to a spherical profile. The significance of each parameter on the different measured responses is evaluated.
Fatigue Analysis of Nuclear Class-1 Small-Bore Piping Connections in CANDU Reactors
Authors: Rehman Sameer Abdul , Alian Ahmed , Abid Najmul 
Published: November 2022

Abstract
Class 1 nuclear piping systems, small-bore piping branch connections are susceptible to high thermal fatigue stresses, particularly in cases where harsh thermal transients are present. Calculating the Cumulative Usage Factor (CUF) using the procedure defined in the ASME Boiler and Pressure Vessel Code in Section III NB-3600 can limit the permissible cycle life (i.e., fatigue life) of the piping component. As per NB-3630(c), when a design does not satisfy the requirements of NB-3640 and NB-3650, a more detailed alternative analysis defined in NB-3200 can be used. This work compares the code requirements, analysis methodology, and results of a typical small bore branch connection connected to a piping header that is assessed against the requirements of NB-3600 and NB-3200. Piping is modeled using beam elements by utilizing PIPESTRESS piping analysis software for the NB-3600 based analysis. In comparison, a finite element model in Ansys Workbench is developed for the NB-3200 transient thermal and structural analysis. Representative pressure and thermal transients applicable to the heat transport system of a typical CANDU reactor are utilized in the analysis. The analysis results show that a significant drop in the Cumulative Usage Factor is achieved with the NB-3200 approach when compared with NB-3600.
An Assessment of the Significance of Design Factors in CUF-Based Fatigue Performance and Related Margins
Authors: Garud Yogendra 
Published: November 2022

Abstract
Fatigue assessment, including the development of a crack of engineering significance, is an integral and important part of design as well as life assessment/extension for long term operation of pressurized components. Additionally, in some cases, environmental effects on fatigue need to be taken into account. These areas are also part of several engineering Codes, such as the ASME B&PV Code, in which the related design margins and decision making are influenced by inherent material/physical variability, uncertainty in inputs, and modeling uncertainty. The code procedures are based on the use of a deterministically calculated measure — the cumulative usage factor (CUF) for a specified service envelope of load transients — to assess the component fatigue performance.
This paper presents the results of an assessment on the relative significance of key S–N adjustment factors (material variability, surface roughness, size, and load history) on the estimation of the CUF. The assessment is based on the recently proposed uncertainty quantification (UQ) and sensitivity analysis (SA) [PVP2017-65850], including the environmentally assisted fatigue. It takes into account the expected uncertainty in the key adjustment factors with sample limiting cases. The significance of these results is discussed in relation to their implications for design/analysis based on the CUF approach and the related fatigue margins.
Mechanical Properties and Metallurgical Examination Results for a Batch of Powder Metallurgy - Hot Isostatically Pressed Low Alloy Steel Grade 508 4N
Authors: Stewart David , Sulley John , Warner Ted , Wallace Phil , Jones Gary , Thatcher Dan 
Published: November 2022

Abstract
This paper presents the work conducted by Rolls-Royce to investigate the mechanical and metallurgical properties of a Low Alloy Steel (LAS) grade 508 alloy batch of material. The material was manufactured using the Powder Metallurgy – Hot Isostatic Pressing (PM-HIP) method. The LAS was an ASME 508 4N model alloy. Rolls-Royce has used PM-HIP extensively for the manufacture of nuclear grade components such as valves, piping and pump bowls, and is now investigating its use for the manufacture of LAS pressure vessels in order to provide an alternative sourcing route to forgings to reduce costs and manufacturing lead-times. A key part of this work is to assess whether mechanical properties can be achieved that meet the specification requirements and that are also comparable to the forged equivalent. In this regard, the toughness of the material is of particular interest, with it being extremely important for LAS pressure vessel applications. This paper reports, that for this particular batch of material, the Charpy toughness was significantly below the minimum room temperature specification requirement, but that the tensile properties were well above the minimum specification requirements for proof and ultimate tensile strength. The Charpy toughness at room temperature was only at 38% of the specification requirement, and only at 21% of forged equivalent material. The reason for the poor Charpy results is potentially attributed to prior austenite retention given the highly faceted nature of the fracture faces and the size of the facet faces. Oxides and other precipitates, such as nitrides, are not believed to have significantly contributed to the low Charpy values in this powder batch. This is because inclusion assessments against other powder HIP material, which had exhibited higher Charpy values but produced with higher oxygen content, did not show a significantly different variation in non-metallic inclusion count, and there was no clear evidence of prior particle boundaries being evident in the cross-sectional studies of the microstructure. Hence, it is hypothesised that increased prior austenite formation was due to the increased nitrogen levels in the gas atomised powder.