Optimisation of helical geometry of inspection probe for steam generator tubes of the PFBR

The steam generator (SG) tubes of the prototype fast breeder reactor (PFBR) located in Kalpakkam, India, need to be periodically inspected using the remote field eddy current (RFEC) technique. During the pre-service inspection of the SG tubes, it was found that the RFEC probes experienced frequent mechanical breakages. To avoid these failures, changes in the existing structural design of the RFEC probe were required. A helical groove design was proposed to obtain a smooth transition in the variation of stress across the probe during the inspection. It was difficult to calculate the flexural stiffness of the proposed helical geometry probe due to the varying cross-section along its length. In this paper, the smearing approach adopted to calculate the stiffness of the RFEC probe and the sensitivity analysis carried out to determine the optimal design of the probe are discussed. A probe was fabricated based on the helical groove design and tested to qualify its suitability for the SG inspection. The RFEC probe with helical grooves was employed for the pre-service inspection of the SG tubes of the PFBR. More than 200 tubes have been inspected using the proposed design and no mechanical failure of the probe has been observed.

Evolution of Standardized Specifications on Materials, Manufacturing and In-Service Inspection of Nuclear Reactor Vessels

The cataloguing and revision of reactor pressure vessels (RPV) manufacturing and in-service inspection codes and their standardized material specifications—as a technical heritage—are essential for understanding the historical evolution of criteria and for enabling the comparison of the various national regulations, integrating the most relevant results from the scientific research. The analysis of the development of documents including standardized requirements and the comparison of regulations is crucial to be able to implement learned lessons and comprehend the progress of increasingly stringent safety criteria, contributing to sustainable nuclear power generation in the future. A novel methodology is presented in this work where a thorough review of the regulations and technical codes for the manufacture and in-service inspection of RPVs, considering the implementation of scientific advances, is performed. In addition, an analysis focused on the differences between irradiation embrittlement prediction models and acceptance criteria for detected defects (both during manufacturing and in-service inspection) described by the different technical codes as required by different national regulations such as American, German, French or Russian is performed. The most stringent materials requirements for RPV manufacturing are provided by the American and German codes. The French code is the most stringent with respect to the reference defect size using as a criterion in the in-service inspection.

Food Service Inspection Capacity: Needs Assessment in a Philippine Local Government Unit

Applying scientific evidence through risk analysis is an important orientation for the international frameworks that have informed the Philippines’ current food-safety legislation. When implementing this legislation, local government units (LGUs) in the Philippines deal with manifold critical responsibilities using various product-based inspection procedures. This qualitative study was conducted at the end of 2017 with a focus on exploring one LGU’s food service inspection practices. The twofold aim was to find needs in the current food inspection capacity, and to illuminate how risk-based legislation is enacted among LGUs in the Philippines. Taking a discursive approach to help explain and describe the LGU’s practices and needs, the methods included an analysis of administrative documents, focus-group discussions, and observational research. This study explains the LGU’s role in carrying out food agencies’ national responsibilities; it also describes how, if adequate resources were available, new roles could exist for food safety officers and food inspectors. In conclusion, fulfilling the LGU’s needs with respect to national and regional standards would require implementation of a risk-based approach for food inspection.

Improving Mooring Integrity through Standardized Inspection Practices – A DeepStar® 19403 Project

In-service inspection is a critical element in confirming the integrity of permanent floating production unit mooring systems. Over the unit's operating life, which will typically span 20 years or more, these inspections provide the majority of the condition information on the mooring components and overall system. This information enables operators to proactively address mooring issues caused by degradation mechanisms or deviations in mooring line tensions that could reduce the system capacity and potentially result in premature failure. However, detailed guidance on inspection intervals, and in particular inspection scope, is limited for permanent mooring systems. To address this identified industry need, the DeepStar® technology consortium initiated Project 19403, "Improving Mooring Integrity through Standardized Inspection and Fit-For-Service Assessment" to develop best inspection practice guidance for permanent mooring systems [1]. This paper describes the content and benefits of this new mooring inspection guidance document developed as part of the DeepStar® 19403 project [1] with the support of subject matter experts from major operator companies, Class societies and mooring consultancies. The paper will describe how this new guidance compliments and expands current industry Recommended Practice (RP) guidance. Key aspects related to in-service survey intervals, component inspection work scopes and inspection methods will be discussed as well as the execution planning of in-service mooring inspections. To facilitate inspection work, the predominate deterioration mechanisms are introduced which are corrosion, wear and fatigue. Other types of deteriorations are also summarized. Default in-service survey intervals (frequencies) and component inspections are recommended. In-service inspection methods are reviewed, from General Visual Inspection (GVI) and Close Visual Inspection (CVI) to advanced Non-Destructive Testing (NDT). Guidance on assessing the residual capacity of a damaged or flawed mooring component, known as fitness-for-service, is also covered within the new mooring inspection guidance.

Optimization of Maintenance Strategy for Sea Water Pumps in Nuclear Plants

Probabilistic Safety Analysis (PSA) methodology is a significant supplement to the deterministic safety analysis in the nuclear power plant. PSA can be used to evaluate the NPP device change, equipment maintenance, in service inspection. The practicability of modifying sea water pump maintenance programme is evaluated in this paper by determining the initial event probability in fault-tree and modifying the PSA calculation model. Based on the evaluation results, the preventive maintenance of sea water pump and 6kv switch can be changed from executed in the plant overhaul to executed in the routine maintenance. This could make a great contribution in optimizing the NPP sea water pump maintenance program.

A fracture mechanics framework for optimising design and inspection of offshore wind turbine support structures against fatigue failure

Offshore wind turbine (OWT) support structures need to be designed against fatigue failure under cyclic aerodynamic and wave loading. The fatigue failure can be accelerated in a corrosive sea environment. Traditionally, a stress–life approach called the S–N (stress–number of cycles) curve method has been used for the design of structures against fatigue failure. There are a number of limitations in the S–N approach related to welded structures which can be addressed by the fracture mechanics approach. In this paper the limitations of the S–N approach related to OWT support structure are addressed and a fatigue design framework based on fracture mechanics is developed. The application of the framework to a monopile OWT support structure is demonstrated and optimisation of in-service inspection of the structure is studied. It was found that both the design of the weld joint and non-destructive testing (NDT) techniques can be optimised to reduce in-service inspection frequency. Furthermore, probabilistic fracture mechanics as a form of risk-based design is outlined and its application to the monopile support structure is studied. The probabilistic model showed a better capability to account for NDT reliability over a range of possible crack sizes as well as to provide a risk associated with the chosen inspection time which can be used in inspection cost–benefit analysis. There are a number of areas for future research, including a better estimate of fatigue stress with a time-history analysis, the application of the framework to other types of support structures such as jackets and tripods, and integration of risk-based optimisation with a cost–benefit analysis.

In-service Piping Inspection Work-aid Tool for Oil & Gas Industries

Piping systems are important in the oil and gas plant’s operation, but continuous damage is harming the piping system due to extensive usage resulting in the increase of accident cases. API 570 Piping Inspection Code: In-service Inspection, Rating, Repair, and Alteration of Piping Systems has proposed an in-service piping inspection practice to ensure the in-service piping is functionable by identifying the remaining life of the piping system. However, the in-service piping inspection process is numerous and complicated where certain steps may be skipped, and data collected may lost along the process. The in-service piping inspection framework followed by a work-aid tool is developed in this study based on API 570 to guide the user the piping inspection process along with providing a depository database for document storage. Validation test is conducted by collecting feedback from professional piping engineer using System Usability Scale followed by conducting a case study using secondary data and sample attachment to test the functionality of the work-aid tool. The work-aid tool can guide the piping inspection process and provide a systematic documentation method for corresponding inspection documents. Case study in the industry is recommended to test the usability of the tool in the industry.