Nuclear

There are few industrial sectors where safety issues have the significance they have in the nuclear sector.

The specialised services in materials characterisation, analysis and structural integrity developed by Inesco Ingenieros allow our clients to determine the safety conditions of their equipment, to establish inspection periods, the need for repairs or replacements or the need for new structural designs.

All this is achieved following advanced techniques of structural analysis and numerical simulation, as well as the most complete codes, standards or procedures used in this sector, including the ASME Code.

Thermal and mechanical analysis

Thermal, mechanical and themomechanical assessments are performed for different components of the reactor: nozzles, pipe joints, vessel internals, etc.

There exists a calculation department made up of doctors, civil engineers and mechanical engineers with a wide experience and knowledge in this type of analysis.

Moreover, ANSYS Mechanical (v12.1) is available for those advanced calculations that require numerical simulations.

Fracture assessments of nuclear plants internals

Inesco Ingenieros performs fracture assessments in any kind of nuclear plant internals (vessel, nozzles, water pumps, shroud, etc.). These assessments allow the safety margins of the different components to be known.

Inesco Ingenieros has a wide experience in both the development of “Flaw Handbooks” (which allow quick decisions to be taken during refuelling shutdowns) and detailed structural integrity assessments from the data obtained during inspections.

Calculation of P-T curves

The definition of operation limit curves or P-T curves (Pressure-Temperature) is one of the specific cases in structural integrity where Inesco Ingenieros has more experience. These calculations are performed following a conventional methodology described in ASME XI (Appendix G), although the latest advances and recommendations are also considered (e.g., P-T curve definition in specific nozzles, the use of probabilistic approaches or the extrapolation of fracture mechanics data under irradiation conditions based on the latest developments on the subject).

Fatigue damage assessments and environmental factor implementation

Fatigue damage assessment in critical components and implementation of the environmental factor.

The analysis is performed in the design stage (following the indications of the corresponding Code, e.g., ASME) and/or in the maintenance stage, through the implementation of monitoring systems. The methodology is based on the use of influence functions, application of the convolution integral, cycle counting, applying the well established guidelines of the different reference codes and documents (NUREGs, MRPs, BWRIPs…).

The implementation of the environmental factor in the fatigue design is performed by using different techniques and following the instructions of the guidelines.

Inspection management and assessment

One of the activities of Inesco Ingenieros within the nuclear industry is that related to the management and assessment of inspections. In this area, Inesco Ingenieros offers a complete service that starts from the planning of inspection programmes, based on both the conventional deterministic approaches and the current methodologies based on risk assessments (RI-ISI).

Once the data obtained in the inspections are available, Inesco Ingenieros performs the assessment and provides the clients with the corresponding detailed reports as well as graphic summaries that allow a quick analysis of the results to be performed.

Support in surveillance programmes

The participation of Inesco Ingenieros in several international projects and networks (Cupriva, AMES ATHENA), the wide experience of our staff in fracture characterisation of metallic materials, and the sound command of the current legislation (10CFR50, RG 1.99 rev.2, etc), allow us to offer our clients detailed advice on the management of their surveillance programmes.

Inesco Ingenieros performs estimations of mechanical property variations in the different materials of the vessel (base material, HAZ, weld) caused by neutronic irradiation, based on the most advanced models, and at the same time, offers advice on the planning and optimisation of the experimental programmes based on the material contained in the nuclear vessels surveillance capsules.

Residual stress calculations

Residual stresses are often involved in degradation and damage mechanisms (e.g, SCC, stress corrosion cracking) that imply the loss of the structural integrity of a component and, therefore, the reduction of its corresponding service life. The analysis and calculation of such residual stresses is an important tool for stress control and for the aging analysis of components.

Weld simulation

Welds may be a problem or a solution for cracking processes in nuclear components.

The residual stresses arising during the welding processes may cause degradation or damage processes (e.g. SCC, stress corrosion cracking) that may reduce the service life of components.

However, over the last years, a technique has been developed for the repair/mitigation of cracking processes based on weld overlays.

The Simulation Department of Inesco Ingenieros has developed a wide variety of parameterised models of weld overlays and welds for the analysis and validation of welding processes.

Fluid and fluid-structure interaction simulations

The simulation of the fluid and fluid-structure interaction behaviours is an assessment technique which is increasingly in demand for the precise knowledge of stress states or for the physical understanding of some fluid dynamic phenomena (e.g., vortex in pipe branches, thermal stratification…).

Due to the conservatism that may arise in certain thermomechanical simulations, it is sometimes necessary to determine more accurately the actual state of a structure containing fluids.

Over the last years, Inesco Ingenieros has specialised in this type of simulations, providing a wide range of services to nuclear plants (e.g., BWRVIP-196, BWRVIP-155…).