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Neutron Diffraction Study of Nuclear Reactor Materials

#3074.2


Neutron-Diffraction Study of Micro- and Macrostresses in Structural Ageing Alloys for Nuclear Power Engineering after Thermal and Radiation Exposure and Predicting Resistance to Radiation-Induced Swelling

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics
  • FIR-MAT/Materials and Materials Conversion/Fission Reactors
  • MAT-ALL/High Performance Metals and Alloys/Materials

Status
8 Project completed

Registration date
29.10.2007

Completion date
17.05.2011

Senior Project Manager
Tocheny L V

Leading Institute
Ural Branch of RAS / Institute of Metal Physics, Russia, Sverdlovsk reg., Ekaterinburg

Supporting institutes

  • Joint Institute of Nuclear Research, Russia, Moscow reg., Dubna\nVNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • Hahn-Meitner Institut Berlin, Germany, Berlin\nNuclear Physics Institute AS CR, Czechia, Rez\nJoint Research Centre, The Netherlands, Petten

Project summary

The development of nuclear power engineering with simultaneous ensuring of a proper level of safety and economic efficiency necessitates solving of closely related problems. On the one hand, this involves ensuring reliable operation of nuclear power plants, and on the other hand, development of the methods of reasonable extension of their life expectancy. Nuclear power plants safety and their reliable life management strongly depend on the used structural materials. Knowledge of the fine mechanisms of radiation damageability and radiation resistance of reactor materials is an indispensable requirement of solving such problems. The accumulated experience of investigation of reactor steels and alloys shows that a great role in the development of radiation damage in them belongs to micro- and macrostresses. At that, it is the neutron diffraction methods that open unique opportunities for investigation of radiaiton damage in such materials.

The Project objective is investigation of macro- and microstresses in samples of radiation-resistant steels used for thermal (type PWWR) and fast (SFR, LFR, GFR, etc.) neutron reactors. The final purpose of such investigations is to improve safety of the already existing nuclear power plants and development of new advanced materials for nuclear power engineering. Special emphasis will be made on internal stresses in samples of welds of nuclear reactor structural materials presenting critical elements from the point of view of safety of such structures. The thus obtained information may prove to be quite useful also in solving the problems of enhancing safety of marine gas pipelines of thick-walled pipes welded together.

The Project envisages a comprehensive study of samples of materials under study. For this purpose, high-resolution neutron diffraction analysis was selected as the principal method of investigation allowing measurements to be made of both the microstress developing under irradiation or at solid solution decomposition (with formation of intermetallic compounds, carbides, radiation clusters and other precipitates) in a preset bulk of a sample, and of the stress in a weld. Besides, neutron diffraction analysis is envisaged of the details of formation and the morphology of precipitates under external uniaxial load. The central task of this Project will be measuring internal microstresses in the bulk of samples from radiation-resistant steels with BCC and FCC lattices for reactor vessels, components of inter-reactor structures and fuel element shells in the process of formation, growth and coagulation of second-phase disperse particles noticeably influencing pores formation.

Study will be performed of the following:

Iron-based alloys with precipitates of coherent intermetallides Ni3Ti (type 16Cr-15Ni-3Mo-Ti and 36Ni-3Ti steels) and coherent carbides VC (type 15Cr-2Ni-MoФА and 0.2C-18Mn-V steels). The variation dynamics of microstresses vs. the ageing or irradiation time will be ascertained in the alloys where the lattice parameters of the matrix and those of the disperse phase differ little (the first two alloys) and greatly (the third and fourth alloys). Analysis of the value and sign of microstresses around different types of particles in these ageing alloys will be performed, which will allow the effect of increase or decrease of point defects recombination responsible for alloys swelling to be predicted, and susceptibility of vessel materials to embrittlement to be evaluated. Microdistortions around clusters of defect induced by efectron irradiation and formed in place of displacement cascades under neutron irradiation will be analyzed.

Investigations of residual stresses in the thermally affected zone of weld seams will be carried out on real specimens of shell and pipeline joints of PWWR-1000 nuclear reactors. The dependence of residual microstresses in PWWR reactor vessel steel specimens on neutron fluence will be studied.

The implementation of the Project work will provide new fundamental data on the details of distribution of microstresses near different types of precipitates, which is extremely important for prediction of radiation damage in materials; recommendations on the composition and treatment technology of new radiation-resistant steels and alloys will be formulated. The distribution of macro- and microstresses, as well as structural components in the weld affected region will be found out, and their change in the process of annealing will be analyzed, since this significantly influences the service properties of welded structures.

This Project will pull together the efforts of the teams of researchers from IMP UB RAS (Ekaterinburg), the Laboratory of Neutron Physics at JINR (Dubna), and RFNC-VNIITF (Snezhinsk), who have already accumulated a wealth of experience in studies of radiation damage of structural materials and determination of internal stresses by the neutron diffraction method. The Project fulfillment envisages close cooperation with foreign collaborators, beginning from exchange of information up to performing independent investigations of certified samples submitted by the Project participants.


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