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Defects in Reactor Materials

#2677


Role of Hydrogen in Competitive (Counter) Processes of Defect Formation and Repairing of Defects in Constructional Materials of Reactors at Influence of Gamma-Neutron Radiation

Tech Area / Field

  • FIR-MAT/Materials and Materials Conversion/Fission Reactors
  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

Status
3 Approved without Funding

Registration date
23.01.2003

Leading Institute
Research Institute of Scientific Instruments, Russia, Moscow reg., Lytkarino

Supporting institutes

  • Tomsk Polytechnical University, Russia, Tomsk reg., Tomsk

Collaborators

  • CNRS / Ecole Polytechnique / Laboratoire des Solides Irradies, France, Palaiseau\nFraunhofer Institute Zerstörungsfreie Prüfverfahren, Germany, Saarbrücken

Project summary

The purpose of the present Project is the systematic investigation of a hydrogen importance in the defect formation and defect repair in constructional materials of reactors under exposure to gamma-neutron radiation.

One of insufficiently explored processes in materials of nuclear reactors is the interaction of hydrogen and defects during irradiation. By the present time the most part of investigations of ionizing radiation influence on behaviour of hydrogen was carried out on model materials and, as a rule, in absence of radiation defects in materials. Meanwhile, the simultaneous irradiation by neutrons and gamma rays in the presence of hydrogen is specific for the working conditions of reactor materials. Therefore, the systematic investigations of hydrogen behaviour in constructional materials in the presence of radiation defects, and also, defects created by mechanical loads are coming.

The effect of excitation of a hydrogenous subsystem in metals and alloys by ionizing radiation was discovered by participants of the Project, which have been studying the hydrogen behaviour in metals and alloys for a long time. The essence of this phenomenon is that the energy caused by radiation exposure is accumulated in the hydrogenous subsystem, therefore atoms of hydrogen acquire energy by orders of magnitude greater than atoms of a metal matrix, and hydrogen starts intensive migration and leaving the metal. The motion of hydrogen stimulates a diffusion of impurity atoms and defects that leads to reorganization of a defect structure. There are two competing (contrary) processes in constructional materials: on the one hand – the accumulation of radiation defects (disordering of a crystal structure), on the other hand – the annihilation of defects (ordering of the crystal structure) stimulated by the migration of hydrogen. These processes depend on many factors such as: properties of the material, availability of impurities, rate of the hydrogen accumulation, defects and induced activity, irradiation temperature.

Finding-out of the hydrogen importance in ordering of crystal structure under gamma - neutron irradiation and dependence of this process on the above listed factors will allow to determine optimum modes of gamma-neutron irradiation, at which the process of radiation annealing is maximum. The well-grounded forecasts of serviceability of constructional materials of nuclear reactors will be derived from the investigations carried out and scientific foundations of deceleration methods of material degradation processes, including hydrogen corrosion, will be developed.

The investigations will be carried out in the following basic directions:

1. Study of migration, diffusion, rate of hydrogen escape, and interaction of hydrogen with defects in reactor materials, having radiation defects and defects created by mechanical load.


2. Effect of gamma, X-ray and electron irradiation on a rate of hydrogen escape and permeability and concentration of defects in reactor materials having both radiation defects and defects created by mechanical load.
3. In situ investigation of a rate of the defect formation in reactor materials both in the absence and presence of hydrogen during gamma-neutron irradiation.

The Project will be executed at the Research Institute of Scientific Instruments and Tomsk Polytechnic University with the use of the unique equipment, including that designed by the participants of the Project, and standard instruments and installations as well. The methods of non-destructive nuclear-physical assay, including a method of recoil nucleuses (ERDA) and Rutherford backscattering method (RBS), will be used for determination of a hydrogen content in metals. The method of electron-positron annihilation and method of backscattering channeling particles (for single crystals) will be used to determine the presence of defects in material. For investigation of hydrogen and defect motion during irradiation and for study of relaxation phenomena, a method of measuring an output of acoustic emission signals (EADQ) will be applied.

It is supposed that the experts from the Research Institute of Scientific Instruments and Tomsk Polytechnic University in a volume of 175 man-months, including «weapon» specialists in a volume of 90 man-months, will participate in the Project.

The competence of the Project participants is confirmed by availability of more than fifty publications concerned with investigation of the hydrogen problem in reactor materials, including the monographies: Tyurin Y.I., Chernov I.P. Accumulation properties of hydrogen in a solid. M: Energoatomizdat. 2000. 288 p.; Tyurin Y.I., Chernov I.P., M. Kroening, H. Baumbakh. Radiation-induced hydrogen egress out of metals. Tomsk: Publication of the Tomsk University, 2000. 264 p.; Mamontov A.A., Chernov I.P. Effect of small doses of ionizing radiation., M: Energoatomizdat, 2001, 285 p.

During the realization of the main purposes and tasks of ISTC, the Project will allow 14 scientists and experts, bound up with weapon in part of development, production, operation of equipment and components for nuclear tests, nuclear reactors and units for submarines and military space programs, to reorient their abilities on peace activities in the field of development of metals and alloys with improved performances, reactor material management and NPP safety. The project work will support applied investigations and development of technologies in the field of nuclear power, nuclear safety and environmental protection and will promote the integration of scientists and experts from the Research Institute of Scientific Instruments and Tomsk Polytechnic University to the international scientific community.

It is supposed that the foreign collaborators involved in the Project will conduct joint experimental investigations on separate sections of the Project, information exchange, and representation of comments to the technical reports and render assistance in attendance of international conferences.


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