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Research Reactors

IAEA CRP 1314 (2006-2009)
Developement and Application of the Techniques of Residual Stress Measurements in Materials
Background

The large penetration depth and selective absorption of neutrons make them a powerful tool in non-destructive testing of materials with large samples. Residual stress formed in a material during manufacturing, welding, utilization or repairs can be measured by means of neutron diffraction. In fact neutron diffraction is the only non-destructive testing method, which can facilitate 3-D mapping of residual stress in a bulk component. Such studies are importance to improve the quality of engineering components in production and to optimise design criteria in applications. Anisotropies in macroscopic properties like thermal and electrical conductivities, for instance of fuel elements, and mechanical properties of materials depend on the textures developed during their preparation or thermal treatment. Such textures can be studied using neutron diffraction techniques.

Neutron diffraction (ND) and X-Ray diffraction (XRD) are based on the same principle and are complementary. XRD is suitable for surface measurements while ND can probe thick specimens in bulk. Although XRD is easily available, it is not practically useful for probing real industrial components, as it yields only localized information at the specimen surface, which usually is not representative of the bulk sample. In its simple form the instrument for residual stress measurement is a two axes powder diffractometer with some specific requirements and / or attributes and can be installed on a medium flux research reactor to improve the effective utilization.

There are some facilities having well designed, optimised and characterised instrument. The expertise and infrastructure exists to develop and maintain the facility. For convenience sake such facilities are defined as type A facilities. On the other hand there are many research reactors where either the instrument is not available or is not optimised, basic infrastructure is not available or trained manpower is missing. Such facilities remain under utilised. For convenience such facilities are defined as type B facilities.

Objectives

The main objective of this CRP is to develop the technique including the design of instruments, the process of data acquisition and analysis and expertise in residual stress measurement - an application as a nondestructive probe in material technology and industry. Other aims are:

  • To optimize the neutron beams for residual stress measurement using modern simulation techniques.
  • To enhance the beam intensity using modern neutron optics, like focusing and beam guides, beam convergence.
  • To develop a standardized, low cost, detectors / data acquisition systems
  • Standardization and/or comparison of data from various instruments for comparison
  • Develop collaboration / teamwork

Expected research outputs (results)
  • Instruments for Neutron scattering are installed and used in many MS but the systems are not optimized for attractive potential applications and stakeholders. This fact has been brought out at various discussion meetings. The CRP is aimed at improving the design of beam lines in terms of neutron collimation and intensity.
  • Improvements in resolution are normally achieved at a cost in intensity. This can be compensated by suitable choice and design of detectors. For an instrument exhibiting good resolution, one needs to employ a fast counting system. It is proposed to work along these lines to develop an optimized detection system.
  • This CRP will help to expand the knowledge and understanding of various components for residual stress measuring instrument including their optimization and auxiliary equipments and their applications among the research reactor community in developing Member States. The CRP will be helpful in training qualified specialists who, in addition to operating existing facilities, will be able to take up developmental work in future.
  • The program will help in building long term relationships between scientists from developing and developed countries. This will help in encouraging further bilateral and /or multilateral collaborations among institutions/reactor facilities in various Member States.