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«Association EURATOM / IPP.CR I N S T I T U T E O F P L A S M A P H Y S I C S, v.v. i. ACADEMY OF SCIENCES OF THE CZECH REPUBLIC ANNUAL REPORT ...»

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were cut using spark erosion and the surfaces were ground and subsequently coated by chromium oxide using plasma spraying using a standard industrial technology procedure.

The phase composition of the as-deposited coating was checked by XRD and characterized by means of analytical scanning electron microscopy. That includes overall microstructure characterization and EDX analyses of existing phases in various regions of coating/substrate system.

In the next step, heat treatment modelling exploitation conditions were performed with the aim to study influence of temperature and the surrounding atmosphere. For this purpose the coated samples were annealed in various regimes (at three temperatures - 550, 650, and 750 °C for 100 hours - and in two types of surrounding atmosphere - either argon or hydrogen).

For conclusions we can summarize following results:

1. Structure of both the substrate and the coating are stable during the annealing in range 550-750 °C in argon and hydrogen.

2. The microstructure of plasma sprayed layers shows a variety of layering and stacking of the coatings. From the plan view of the inner surface of peeled off coating it is seen that some powder particles did not completely melt during spraying. Analysis of the microstructure shows that the bonding between the EUROFER substrate and coating is very good especially at lower applied annealing temperatures. Annealing at 750 °C in hydrogen deteriorates the quality of bonding between substrate and sprayed layer. Chemical composition of the coating is inhomogeneous and this is not smeared out by applied thermal treatment. Large Al-rich particles were found frequently at the interface in annealed samples.

No gradients of chemical composition of metallic elements were found in the substrate near the coating by means of EDX analyses.

3. The concentration curves of the main elements at interface Cr203 layer/EUROFER measured by WDS show redistribution of manganese only. Concentration changes of other elements (Cr, O, V, W, Ta) are insignificant. This result is not valid for sample annealed at 750°C/100h in hydrogen where de-cohesion between L and E along large areas of L/E interface was found. We suppose that hydrogen promotes both a creation of C- and Mn-rich interlayer at L/E interface and the L – E de-cohesion.

~

4. Diffusion coefficients D Mn were calculated for samples annealed in argon only. Obtained ~ value of D at 750 °C agrees very well with known diffusion coefficient D αFe. Other Mn Mn ~ αFe diffusion coefficients D Mn (at 650 and 550°C) are higher than D Mn. This phenomenon is probably a consequence of Mn redistribution during plasma deposition of Cr2O3 layer.

~ Reliable values of D Mn at 650 and 550°C should be obtained from redistribution curves that would be measured after much longer anneals.

5. Negative influence of the hydrogen as the surrounding atmosphere by the annealing at 750°C/100h was observed. It can be important drawback for an application of the Cr2O3 coating due to expected tritium penetration.

References:

[1] Tavassoli AAF, Alamo A, Bedel L, Forest L, Gentzbittel JM, Rensman JW, Diegele E, Lindau R, Schirra M, Schmitt R, Schneider HC, Petersen C, Lancha AM, Fernandez P, Filacchioni G, Maday MF, Mergia K, Boukos N, Baluc, Spatig P, Alves E, Lucon E, J.

Nuclear Mater. 329 (2004) 257.

[2] Boccaccini LV, Giancarli L, Janeschitz G, Hermsmeyer S, Poitevin Y, Cardella A, Diegele E, J. Nuclear Mater. 329–333 (2004) 148.

[3] Smith DL, Konys J, Muroga T, Evitkhin V, J. Nucl. Mater. 307–311 (2002) 1314.

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The Eurofer steel: microstructural degradation and embrittlement Principal investigator: Ivo Dlouhy, IPM AS CR, Brno, Czech Republic e-mail: idlouhy@ipm.cz, tel.: +420 532 290 342, fax.: + 420 541 218 657 Task: IPP-CR_UT7_DEGR_IPM2 Field: Tritium Breeding and Materials, Area: Materials Development Collaborative staff: Hynek Hadraba, Vladislav Kozak, Pavel Cupera, Zdenek Chlup

–  –  –

Part III - TECHNOLOGY Fig. 2. Temperature dependencies of Charpy impact energy of Eurofer´97 steel (left 14 mm sheet, right 25 mm sheet, upper figures – temperature dependence of impact energy, bottom – temperature dependence of Fgy and Fm).

The temperature dependence of impact energy for 14 mm and 25 mm sheet compared with values collected from literature is given in Fig. 2. It is evident that the fracture behaviour of 14 mm Eurofer´97 steel was comparable with published results. The tgy transition temperature of 14 mm sheet was about -75°C. The comparably different fracture behaviour of 25 mm sheet compared with 14 mm sheet was observed: the transition temperature tDBTT and transition temperature tgy were shifted for about +20°C. No difference between temperature dependence of impact energy of 25 mm sheet in as-received state and in state after step-cooling was observed.

The cleavage mechanism of crack initiation and propagation in Eurofer´97 steel in asreceived state and in step-cooled state under the conditions of brittle fracture (near tgy transition temperature) was identified.

The results obtained by solving this project were published in the proceedings of workshop Fracture and Design of Materials (ISBN 978-80-254-0725-7, in Czech) held in Brno, Czech Republic, in October 31th – November 1th 2007 [1] and in the proceedings of 13th International Conference on Fusion Reactor Materials held in Nice, France, in 10th to 14th December 2007 [2].





The work will be followed by analysis of fracture behaviour of long isothermally aged (up to 5000 h) specimens. The results from this analysis were not available during preparation the report because of continuing thermal ageing exposition.

References:

[1] Hadraba, H., Dlouhy, I.: Thermal ageing of Eurofer´97 steel. Proceedings of workshop Fracture and Design of Materials, Brno (2007) 85-96, ISBN 978-80-254-0725-7.

[2] Hadraba, H., Dlouhy, I.: Effect of Thermal Ageing on the Fracture Behaviour of EUROFER´97 Steel. Proceedings of 13th International Conference on Fusion Reactor Materials, Nice, France (2007) 659-671.

–  –  –

Task : TW6-TVV-SYSEG Field: Vessel/In-Vessel Collaborative staff: L.Vlček PhD.,V. Diviš, M. Slováček,PhD.

The manufacturing of the vacuum vessel requires a lot of the welding operations. The weld joints are very long and contain a lot of welding passes. Each welding operations (weld joints) generate residual stresses (deformation) and distortions. The final distortion has to comply with the very strict manufacturing tolerances and requirements for final size and shape of the construction parts. Due to stated facts the three experimental mock-ups (VMO, LMVMO and VVPSM) have been done and also manufacturing process was numerically analyzed. The final welding technology can be proposed based on the obtained experimental and calculated experiences.

–  –  –

References:

Slováček M., Diviš V.: Assessment of PSM Welding Distortions and Field Welding, [1] Task 1: Modification of VMO and LM VMO Models, report IAM Brno, archive No.

4038 / 07, Brno, February 2007 Slováček M., Diviš V.: Assessment of PSM Welding Distortions and Field Welding, [2] Task 2: Weld joints optimization, report IAM Brno, archive No. 4031 / 07, Brno, February 2007 [3] Diviš V.: Assessment of PSM Welding Distortions and Field Welding, Task 3: PS1 and PS2 of VVPSM, numerical analyses and results comparison, report IAM Brno, archive No. 4082 / 07, Brno, June 2007

–  –  –

Task: TW3-TVB-FWPAMT Field/Area: Vessel / Mechanical Structures Collaborative staff: A. Materna (FNSPE Prague), J. Václavík (ŠKODA Research Ltd., Pilsen) In collaboration with: P. Lorenzetto, A. Furmanek, EFDA- CSU, Garching

–  –  –

References:

[1] Lorenzetto P., Furnmanek A.: Mechanical Testing of a Primary First Wall Panel Attachment System, Technical Specification. Rep. No. EFDA/04-1137, EFDA-VP-SPCSU EFDA Garching, 2007, 13 p.

[3] Oliva V., Materna A., Václavík J.: Mechanical Testing of a PFW Panel Attachment System for ITER, Final Report. Rep. No. V-KMAT-706/07, Dept. of Materials, CTU in Prague - FNSPE, 2007, 152 p.

This research has been supported by MŠMT grant No. OK 483 and MŠMT grant MSM

–  –  –

Task: IPP-CR_ TW4-TVB-TFTEST2, 1 Field: TV – Vessel in Vessel, Area: TVB Blanket Collaborative staff: Vl. Masarik, P. Hájek, O. Zlámal In collaboration with: P.Lorenzetto, F4E, Barcelona, Spain The objective of this task deliverable is to perform thermal fatigue testing of actively cooled Primary First Wall (PFW) mock-ups. This involves designing the facility ensuring thermal fatigue tests of beryllium coated primary first wall mock-ups to compare the fatigue performance of different beryllium/CuCrZr alloy joints simulating Be coated PFW mock-up specimens. The main effort has been devoted to the development and testing of the suitable heat flux generation system. A long-term qualification test of graphite heating panel material has been performed. Qualification test has to prove the feasibility of equipment to achieved 20,000 thermal cycles with heat flux of approx. 0.7 MW/cm2 and resistivity of mock up specimens to thermal fatigue loading.

The investigations have been focused on the development and testing of the suitable heat flux generation system. This activity has been performed both for this task and for the task TW3TVB-INPILE, D3. The thermal fatigue tests of beryllium coated primary first wall mock-ups of dimensions 250 mm x 110 mm x 70 mm were used to compare the fatigue performance of different beryllium/CuCrZr alloy joints. The task shall consist of two test campaigns of 4 mock-ups, each tested in parallel. The tests shall be performed at 0.8 MW/m2 surface heat flux for a total number of 30,000 cycles each of about 300 s duration. The inlet water temperature shall be about 120 °C with a water velocity of about 5 m/s. Ultrasonic testing should be performed on each mock-up to check the integrity of the Be/CuCrZr joints before starting the thermal fatigue testing, after 15,000 cycles and at the end of each test campaign of 30,000 cycles.

–  –  –

Pre - test thermal fatigue experiments were performed with beryllium specimen and cooper specimen and 12 000 cycles was achieved. Homogeneity and output thermal on Be tile surface were evaluated and results correspond to required testing parameters and required lifetime conditions.

References:

[1] T. Klabík, Vl. Masařík, J. Hájek, Kahle: Berylium Laboratory Operating Safety Instructions, NRI Řež, April 2007 [2] I. Buldra: Results of Mechanized Ultrasound Examinations of Berylium Tiles – Copper Plate Interface of the PFW specimens, NRI Řež, November 2007 [3] O. Zlámal, J. Hájek, J. Kysela: Calorimetry Report, NRI Řež, February 2008 [4] Qualification Testing of ITER PFW mock-ups at the NRI BESTH Facility, NRI Řež – EFDA Garching, February 2008

–  –  –

Task: IPP-CR_ TW2-TTMS-001, D3 Field: Tritium Breeding and Materials, Area: Materials Development Collaborative staff::, M. Falcnik M. Kytka, K. Splichal Reduced activation ferritic and martensitic (RAFM) steals are considered as structural materials for the fusion reactor applications. At the present time experimental studies are focused on effects of neutron irradiation at lower temperatures 230° C on fractural properties of martensitic steel EUROFER 97 which was developed as a structural material for the first wall TBM (Test Blanket Module). Fracture toughness testing at the transition temperature should be performed and static and dynamic fracture toughness should bee valuated in as received state and after irradiation.

Static and dynamic toughness at the transition temperature of plates and weldments are measured at room temperature and the temperature of about 250°C with KLST sub size specimens 4 x 3 x 27 mm. Neutron irradiation was performed at the temperature of 235° C up to neutron dose of 2.5 dpa. Böhler Bleche GMBH manufactured plate IMF I-E 14 of EUROFER 97 steel from Heat E 83698. EUROFER segment No 4/15 was cut and steel sample plate 330 x 300 x 14 mm was delivered to NRI by Forschungszentrum Karlsruhe.

For dynamic fracture toughness testing, the cells have been equipped with a Tinius Olsen Model 74, Zwick RKP450 and RKP50 impact test machines, instrumented with data acquisition and analysis system. The equipment has been fitted with a resistance furnace and a cooling box working with liquid nitrogen for test temperatures from –170° C to +310° C.

For fatigue pre-cracking of the specimens, Alfred J. Amsler model 421 machine of 20 kN

–  –  –

Part III - TECHNOLOGY capacity is used. Static fracture toughness samples are measured using INSTRON tensile testing machine, PC control stations using Instron’s software control their function. This standard equipment was tailored for hot-cell operation by adding stainless steel pull rods and opening furnaces and cooling boxes (operated by manipulators) of NRI’s own design. The heating and cooling system covers test temperatures from -170 oC to +310 oC. During the tests, the load point displacement is measured by LVDT transducer gauges mounted on pull rods outside the furnace or cooling box.

Irradiation experiment was performed in Chouca rig at the temperature of 235°C with fast neutron flux 4.4 1013 cm-2 s-1 under He atmosphere of 100 kPa. The temperature and He pressure are online monitored. Total irradiation time from the beginning of the experiment was 11,246 hours, total reactor work about 96,924 MWh and total radiation level about 2.51 dpa.

Testing of dynamic fracture toughness was finished and the transition temperature curves of base and weld metals in as received state and after irradiation at the temperature of 235°C were evaluated (Fig. 1).

References:

[1] M. Falcnik, Kytka M., Laboratory Report 2007/ 37, NRI, 2007 [2] E. Lucon, M. Decreton, E.van Walle, Mechanical characterization of EUROFER 97 irradiated (0.32 dpa, 300°C), J, Nucl. Mat., 2004

–  –  –



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