Prof. Vladimír Slugeň

Transcription

1 Analytical nuclear methods for assessment of radiation degradation mechanism Presented by Prof. Vladimír Slugeň Institute of Nuclear and Physical Engineering, Slovak University of Technology, Bratislava, Slovakia

2 Goal of presentation -To inform participants about the methods useable for nuclear material studies 2

3 Content of presentation 1. General information about nondestructive nuclear methods 2. Information about effective use of NDT of irradiated materials 3

4 Feritic/martensitic (FM) steels Temperature limit C (ductility loss), Appropriate values of strength (martensite) and ductility (ferrite), Lower content of nickel and cobalt reduced activated FM steels (RAFM). FM steel martensite looks like needles. 4

5 Complementary results Scanning electron microscope (SEM) 1mm Z x SEM results confirms the PLEPS prediction of large voids in the depth >500nm which correspondent to the helium implantation profile maxima 13 October

6 Radiation damage By alpha or helium ion implantation 1. Ionization, 2. Electron excitation X-ray creation, 3. Atom displacement open volume defects formation, 4. Nuclear reaction (α, n) or (α, p). Fig. T91 defects after irradiation 10 dpa. Fig. T91 bubbles. 13 October

7 Overview TEM Transmission electron microscopy XRD X-Ray Difraction SEM Scanning electron microscopy OM Optical Microscopy SANS Small Angle Neutron Scattering APFIM Atom Probe Field Ion Microscopy PAS Positron annihilation spectroscopy Grain boundary Dislocations Dislocation loops, precipitations Frenkel Defects, Small Vacancy clusters ~10mm ~100 nm ~10 nm ~1 nm ~10-5 m ~10-7 m ~10-8 m ~10-9 m ~10 5 Å ~1000 Å ~100 Å ~10 Å

8 Nondestructive Detection of Material degradation DEGRADATION PROCESS Methods - overview DIMENSION [nm] PAS, MS, APFIM SANS, ASAXS, el. Con., therm. el. force us atten. mag. prop, TEM, SANS dislocation loop precipitation dislocationc grain size inclusion atomic spacing Bloch wall defect cluster PAS, el.res., EC, SANS MS, APFIM, ASAXS dis. cross p PAS, MS, APFIM, SANS pre. Of Cu richp., segr. of P rich p. el.res., mag. prop., EC, TEM, SANS PAS, ASAXS, APFIM dislocation loop el.res., EC, TEM dislocationc us atten., TEM precipitation mag. prop., ASAXS, SANS, TEM precipitation of, phases el.res., mag. prop., EC ASAXS anomalous small angle X-ray scattering APFIM atom probe field ion microscopy EC Eddy current MS Mössbauer spectroscopy PAS - positron annihilation spectroscopy SANS small angle neutron scattering TEM transmission electron microscopy US ultrasonic waves

9 Fission and fusion neutrons E n [MeV]

10 Which role can irradiation play? 4. Gamma radiation only ionizes electrons or excites atoms. Neutrons: knock-out atoms from the lattice Epithermal neutrons ( >0,5 ev )and fast neutrons (>100 kev), Primary knock-out atoms with higher kinetic energy produce secondary knock out atoms with smaller kinetic energy, Atom depletion area and local surrounding the place of neutron absorption, Open-volume defect accumulation change of diameters and material swelling. Material transmutation - changes of the nuclear-physical, chemical and mechanical properties Thermal neutrons (<0,5 ev), (n, α) and (n, p) nuclear reaction accumulation of helium and hydrogen nuclei, Defect immobilization by helium residual stress increasing, Hydrogen diffusion to the grain boundaries and segregation - embrittlement and intergranular corrosion Fe( n, Cu( n, ) B( n, ) He( n, p) p) Li( n, ) 7 3 Li H H Mn Co

11 Institute of Nuclear and Physical Engineering (2011- ) Slovak University of Technology Available techniques for material studies: Positron Annihilation Spectroscopy: Conventional PALS 2-det. or 3-det. Setups (for irradiated materials), digital Doppler Broadening set-up, experiences with PLEPS measurements at FRM-II in Garching from past Moessbauer spectroscopy, Atomic force microscopy, X-ray diffraction, Barkhausen Noises measurements, Alfa, beta, gamma spectroscopy including low/background chamber, In collaboration with other institutes: TEM, SEM and Auger spectroscopy

12 The EPR pressure vessel in Olkiluoto 3 (Finland) 2009 VVER-440 annealing facility VVER-440 V-213 Pressure vessel 12

13 Irradiation-induced changes of microstructure Neutron-irradiation Defect production Self-interstitial atom (SIA) & vacancy (V) rich regions x x x x x x Matrix damage SIA-clusters, SIA-loops Micro voids x Solute atom diffusion Precipitates Complex defect-solute configurations x x x x GB segregation

14 Reasons for application of PAS Mechanical tests give not enough information about changes in material microstructure. Therefore, additional methods should be applied. PAS technique is a well-established method for studying open-volume type atomic defects and defect s interactions in metals Ability of PAS to detect very small defects as well as very low defects concentration PAS can give additional information about radiation induced defects, thermal annealing of these defects.

15 What kind of information we can obtain from Positron Annihilation Spectroscopy? Defects density Annealing effectiveness Precipitation Types of defects Report: EUR EN Vladimír Slugeň JRC-Petten, Near surface region study Microstructural changes due to irradiation, ageing,...

16 Difficulties with irradiated RPV steels and advantages for implantation Radioactivity > special rules for handling, transport, polishing, storage... (PROBLEMS), Reducing of volume, Reducing of number of samples, Application of other techniques if possible. PAS disturbing 60 Co contribution (photopiks 1.17 and 1.33 MeV) 1. Measurement using PLEPS (very thin samples of about 20 μm are necessary), 2. Measurement using 3 detector set-up in coincidence mode (takes about 2 weeks), 3. To wait... (T 1/2 (Co-60)=5.27 a). Ion implantation none transmutations = none 60 Co, very short half-time of decay for radionuclides, only 2 detectors measurement equipment for PAS In ODS steels 0 Co content (theory)

17 PAS Theory Scheme of positron experiments (A), Quantitative illustration of positron annihilation -rays from different environments (B) 13 October

18 Positron annihilation lifetime spectroscopy (PALS) specime n b.) a.) Capton foil =0.8mm drops of 22 Na solution Al supporting structure Sandwich set up of the sample and the 22 Na source source specime n Measuring equipment set up 13 October

19 Pulsed low energy positron system (PLEPS) remoderated positrons [1] P. Sperr, W. Egger, G. Kögel, G. Dollinger, Ch. Hugenschmidt, R. Repper, C. Piochacz, Applied Surface Science 255 (2008) [2] Hugenschmidt C., Dollinger G., Egger W., Kögel G.,Löwe B., Mayer J., Pikart P., Piochacz C., Repper R., Schreckenbach K., Sperr P., Stadlbauer M., Applied Surface Science, Volume 255, Issue 1, p October

20 PAS and TEM results are useble for microstructural evalution of new materials SLUGEŇ, V. KURIPLACH, J. - BALLO, P. DOMONKOŠ, P.: Nuclear Fusion 44, 2004, p October

21 Depth (nm) PAS Results - Annealing temperature for WWER-steels at 475 C is acceptable, but PAS gives more information t ( C) (ps) Slugen et al: NTD&E Int. 37 (2004) Kryukov et al: JNM 416 (2011) The 3D presentation of PLEPS results (Tau1) of irradiated (1.25x10E24m -2 ) and annealed Sv-10KhMFT steel (WWER-440 weld). The effectiveness of the annealing process to removing of small defects (mono/divacancies or Frenkel pairs) can be followed via significant decrease of parameter tau1. This figure also shows rapid increase of mentioned small defects in WWER type of RPV steels after about 480 ºC t ( C) Depth (nm)

22 PLEPS results Dependency of intensity in large defects (positron lifetime > 350 ps) e.g. voids, shows peak in depth of ~ 500 nm which correspond well with depth profile of helium implantation. 13 October

23 Tired? wake me up when September ends. 13 October

24 Lattice parameter vs. positron lifetime in defects in helium implanted Fe-Cr alloys. a.) Fe2.56%Cr; b.) Fe11.62%Cr a. ) b.) 13 October

25 Mössbauer spectrum of as-received and two levels of implanted Fe11.62%Cr alloy There are no visible any changes in magnetic structure due to irradiation. sxt 5 sxt 4 sxt 3 sxt 2 sxt 1 spectra fit Dose = 0C Dose = 0,2C Dose = 0,4C 13 October velocity [mm/s]

26 Mössbauer spectroscopy - was confirmed as a good for distinguishing between materials (due to different Cr content), however the surface study in backscattered geometry showed only very slight changes in Mössbauer parameters due to helium implantation X-Ray diffraction Complementary non-destructive results - possible distinguishing between materials and observable changes (increasing) in lattice parameter due to helium implantation (near surface study in grazing incidence geometry) Metallography, SEM, TEM Any relevant information from different experimental techniques can contribute to the creation of complex image about material microstructure processes under radiation treatment. 13 October

27 Experimental treatments Helium ion implantation with kinetic energy 500 kev. Charge per square (C/cm 2 ) Ion counts per cm x x October Fig. Implantation depth

28 Slow Positron Beam Positron stopping depth: x [ g / cm 3 ] E 1.6 mm 13 October

29 Coincidence Doppler broadening S 13 October 2014 A A s o 29

30 (%) Irradiation effects Helium Why is the He/dpa ratio important for fusion materials R&D? He bubbles 50 nm He bubbles can cause severe grain boundary embrittlement at high temp. (fcc alloys) can severely enhance fracture toughness degradation at low temp. (bcc alloys) 13 October 2014 Materna-Morris, FZK, IMF-I Swelling V/V 0 Zinkle, ORNL He/dpa ratio (appm He/dpa) 30

31 Ion implantation of ferritic/martensitic steels Reduced activation ferritic/martensitic (RAFM) steels are candidate for application in Gen. VI and fusion nuclear facilities Expected high radiation damage (>150 DPA) by high energy particles (neutrons) Due to neutron activation and high costs were, for laboratory experiments, chosen charged He ++ ions. SRIM code simulations of radiation damage caused by He ions showed high level of damage (~100 DPA) as expected after neutron irradiation Therefore, from the cascade collisions and vacancy type defects production and behavior point of view, can be reached valuable results of materials behavior under ion irradiation Linear accelerator at Slovak University of Technology was used for He ions implantation 13 October

32 Ion implantation of ferritic/martensitic steels Binary Fe-Cr model alloys were implanted by 250 kev He ions. Group of chosen specimens was afterwards implanted also with 100 kev in order to observe two peaks of maximum damage Five levels of implanted dose were chosen: Dose [C/cm2] Dose [ions/cm 2 ] 6.24x x x x x10 18 Calc. damage [DPA] October

33 Ion implantation of ferritic/martensitic steels Chemical composition of implanted Fe-Cr alloys Specimen Cr [wt%] P [wt%] Si [wt%] Al [wt%] Ti [wt%] Mn [wt%] Ni [wt%] Cu [wt%] C [wt%] N [wt%] V [wt%] L L L L Manufactured at Dept. of Metallurgy at Ghent University, Belgium Specimens preparation: Dimensions 10x10x0,4 mm, One side mirror-like polished 13 October