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Damaging of Materials by Ionizing Pulse Radiation

#2761


Investigations of Mechanisms of Damaging and Microstructure and Properties Evolution of Materials in Conditions of Impact of Extreme Ionizing Radiation Pulse Fluxes for the Purpose of Radiation-Thermal Resistance Increase

Tech Area / Field

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

Status
3 Approved without Funding

Registration date
28.04.2003

Leading Institute
ITEF (ITEP), Russia, Moscow

Supporting institutes

  • VNIITF, Russia, Chelyabinsk reg., Snezhinsk

Collaborators

  • University of Tennessee, USA, TN, Knoxville\nPacific Northwest National Laboratory, USA, WA, Richland\nRuhr Universität Bochum / Institute für Experimentalphysik V, Germany, Bochum

Project summary

The main purpose of the Project: Experimental and theoretical investigations of the impact of powerful pulse fluxes of nano- and micro-second duration ionizing radiation (IR) on processes of damaging, formation and evolution of defects, alteration of structural and phase state, heat- and mass-transfer, and distribution of components in metals and alloys with the purpose of evaluation and prediction of their behavior in conditions of time-dependent extreme duties and increase of their radiation-thermal resistance.

Among modern directions of development of irradiation solid state physics and irradiation material science and technology a special position is occupied by the fundamental problem of interaction of extreme high-density powerful flux of IR with substance. At that, the very important aspect is investigations of various physical effects, radiation- and thermal-induced processes as well as mechanical damaging accompanying the powerful impact considered. Creation on this basis of an effective scientific base for evaluation, prediction and improvement of properties of construction and functional materials working at such extreme conditions is a very important application aspect of this scientific direction.

The specific feature of powerful radiation impact on material in this case is that the radiation dose is compressed to very high extent – firstly in time (in the radiation plant), and then (at absorption in a sample) in space. And if effective volumes of the radiation impact of each inpidual particle in material (for example, micro-volumes containing photo-electrons at absorption of the X-ray photon) are overlapped during a certain time t that is less than the characteristic relaxation time t0 of the radiation-induced process, this process acquires completely new quality. In some cases appearance of various synergy processes can be expected which in their turn can lead to new, unusual alterations of physical and mechanical properties of material.

One of IR sources, based on usage of fast transformation of magnetic energy with help of the sharp current cut-off in inductive devices (including plasma inductive systems) and known as the Plasma Focus (PF), can generate high-current powerful radiations of various nature. The unique feature of the PF is that it allows during one pulse of ~ (10 – 1000) ns duration to affect an investigated sample simultaneously or separately by powerful pulse fluxes (power density up to 1012 W/cm2) of ions, plasma, electrons, soft and hard X-rays as well as neutron radiation. It opens the perspective of studying of influence of combined treatment of a material by IR pulse fluxes on its damaging, structural-phase state, formation and evolution of irradiation defects, re-distribution of components in sub-surface layers. Besides, the PF is the ecologically safe device comparing with such sources of hard radiation as isotopes, reactors and classical accelerators of various types. Therefore, radiations generated in the PF can be used for creation of ecology friendly methods and technologies of studying, treatment and testing of materials.

A number of experimental results concerning impacts of ion and high-temperature plasma fluxes on materials obtained by us and other investigators in recent years using PF plants have shown that the result of interaction between powerful radiation fluxes with material can be new unexpected effects.

1. For example, at irradiation of austenite steel 25Cr12Mn20W by fluxes of deuterium ions and plasma so-called “detachment” effect (screening of irradiated surface by a cloud of evaporated material) has been revealed that has different nature and different manifestation at different levels of power density q. At relatively low q = 105 – 108 W/cm2 the effect was small and did not prevent implantation of low-energy plasma ions into a specimen. At higher densities of energy fluxes (q = 108 - 109 W/cm2) the screening role of the effect increased, and, as the result, the possibility of implantation of low-energy plasma deuterons in material decreased.

By now, the degree of influence of irradiation conditions and properties of material on the “detachment” effect has not been practically studied either in our country or abroad. Whereas the important role of this effect as the mean of protection of material against impact of undesirable radiations of various nature is obvious and detailed investigations of this phenomenon at high-density fluxes of IR in the framework of this Project seem to be very actual.

2. A number of new original results was obtained recently using the Plasma Focus PF-1000 Unit in the framework of the International Project “Copernicus” as the result of cooperation of authors of this Project with scientists of Poland (Institute of Plasma Physics and Laser Micro-Synthesis, Warsaw), Italy (Ferrara University, Ferrara) and Estonia (Tallinn Pedagogical University). A number of experiments have been carried out concerning impacts of concentrated energy fluxes on materials located in cathode area of the discharge chamber of the PF using hydrogen as plasma-forming gas. At multiple pulse impacts with the radiation power density of q = 107 - 109 W/cm2 in the micro-second duration region on poorly-activated chromium-manganese austenite steels of two types (with different carbon content of 0.10 and 0,25 mass%) a completely unexpected result has been obtained. A correlation has been established between surface density of “macroscopic” structural defects on the irradiated plane of material – blisters and craters – and the density of high-energy hydrogen atoms implanted into the sample during one pulse of the impact. In both cases the density mentioned had the value order of 105 cm-2. In addition, in the blisters formation area the increase of light elements concentration (manganese, carbon and oxygen) has been revealed, and in the crater location area – C and O2 increase. These results display a non-traditional mechanism of blisters (craters) formation at surface of investigated steels at realized radiation conditions by fluxes of ions and high-temperature plasma.

3. One of the most important problems in development of materials of the first wall of TNR is hydrogen penetration through materials that is connected with problems of possible loss of expensive fuel (tritium) and safety. In this connection, a certain interest has appeared to investigations of influence of treatment of surface of candidate materials of the TNR first wall in PF plants on processes of tritium penetration through materials. Investigations of influence of different factors on hydrogen isotope (protium, deuterium) penetration through construction materials were carried out before, but works on penetration of tritium through materials are practically absent. Such works, unique in the world practice, are being carried out in our country in RF NC-RSRITP.

4. As an applied aspect of experiments carried out using PF plants, we will point out results connected with deposition of anode material on irradiated samples located in the cathode area and the “opposite effect” – deposition of material evaporated from the sample-cathode on the anode surface. It can be assumed that the treatment of a sample-target by pulse fluxes of IR, accompanied by its intensive evaporation and preceding to deposition of coating material on its surface, purifies the irradiated surface from contaminations. It promotes increase of cohesion of the coating with the “substrate”. The considered problem of applied character is not studied enough, and the deficiency can be compensated in the framework of this Project.

Main methods of material investigations will be transmission electron microscopy, atomic-probe, field-ion and scanning tunnel microscopy giving the possibility to investigate structural-phase transformations, evolution of defect structure. Usage of other investigation methods (recoil spectroscopy, optical microscopy, X-ray methods and fractal analysis) will significantly complete results of ultra-microscopic and electron microscopic investigations. Significant efforts will be required to create software for analysis of samples at ultra-microscopic investigations as well as to develop digital methods of evaluation of evolution of the temperature field of the surface layer of material at irradiation.

As the result of the Project fulfillment, new data will be obtained that are necessary for development of fundamental science and its practical applications in the following directions:


- mechanisms of damaging and modification of surface of investigated materials at various types of pulse IR impacts;
- evolution of structure and phase states, re-distribution of components of investigated alloys at various types of pulse IR impacts;
- nature of the effect of screening of irradiated surface by a gas cloud at pulse fluxes of IR impacts on material in PF;
- mechanism of formation of structural defects (blisters, craters, etc.) on surface of investigated materials in realized irradiation conditions in the PF chamber;
- comparison of properties of coatings deposited on materials by the laser evaporation method and in the process of cathode (anode) evaporation in the PF;
- influence of surface treatment of construction materials by pulse IR fluxes in the PF and laser radiation in the LU on diffusion penetration of tritium.

Planned in the Project investigations of mechanisms of damaging of materials and peculiarities of physical-chemical processes of surface melting and crystallization, thermal-mass transfer, formation and evolution of radiation defects, alteration of microstructure in conditions of impacts of extreme high pulse fluxes of IR will be carried out at the interface between several independent scientific directions – solid state physics, radiation chemistry, radiation material science and technology, plasma physics, physics and mechanics of destruction. Such inter-disciplinary approach to the problem considered will allow to study comprehensively and in more details the nature of phenomena investigated as well as specific features of behavior of irradiated materials as a whole in non-equilibrium conditions created in the bulk of material by powerful pulse IR fluxes of short duration.

The proposed program of experiments and investigations will be fulfilled by the team of scientists and specialists representing Institutes of Ministry of Atomic Energy of RF (SSC ITEP, RFNC-RRITP). During many years they have been working successfully in various directions of the irradiation solid state physics, irradiation material science and technology, plasma physics and plasma interaction with materials and are leading specialists in these fields. The Institute of Theoretical and Experimental Physics possesses high-qualified staff and unique equipment allowing carrying out investigations of surface erosion, structural investigations, processes of generation and evolution of irradiation defects on atomic level. The ITEP enjoys international reputation and recognition in the field of investigations of atomic structure of defects in materials and application of field-ion microscopy methods and atomic-probe analysis as well as mathematical simulation of field-ion images of samples of a given defect structures.

The role of international collaborators in the presented Project is cooperative compositions, discussions and corrections of plans, intermediate and final results of the work, carrying out of some cooperative investigations and developments, assistance to executors in marketing, possible future cooperative usage of developed technologies and acting prototypes (for example, implementation in mass production).

Fulfillment of the Project will allow to realize the following goals:

- it will present to Russian scientists and specialists connected with weapon the possibility to re-direct their abilities for peaceful activity;


- it will facilitate further integration of Russian scientist into international scientific community;
- it will allow to use effectively the advantages of PF plants as ecology friendly equipment to solve fundamental and applied problems of irradiation solid state physics and irradiation material science and technology;
- it will support investigation and development of new radiation-resistant construction and functional materials promising for thermo-nuclear plants.


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