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  • 1. Airila, M. I.
    et al.
    Jarvinen, A.
    Groth, M.
    Belo, P.
    Wiesen, S.
    Brezinsek, S.
    Lawson, K.
    Borodin, D.
    Kirschner, A.
    Coad, J. P.
    Heinola, K.
    Likonen, J.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Widdowson, A.
    Preliminary Monte Carlo simulation of beryllium migration during JET ITER-like wall divertor operation2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 800-804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Migration of beryllium into the divertor and deposition on tungsten in the final phase of the first ITER-like-wall campaign of JET are modelled with the 3D Monte Carlo impurity transport code ERO. The simulation covers the inner wall and the inner divertor. To generate the plasma background for Monte Carlo tracing of impurity particles, we use the EDGE2D/EIRENE code set. At the relevant regions of the wall, the estimated plasma conditions vary around T-e approximate to 5eV and n(e) 2 x 10(17) m(-3) (far-scrape-off layer; more than 10 cm away from the LCFS). We calculate impurity distributions in the plasma using the main chamber source as a free parameter in modelling and attempt to reproduce inter-ELM spectroscopic BeII line (527 nm) profiles at the divertor. The present model reproduces the level of emission close to the inner wall, but further work is needed to match also the measured emission peak values and ultimately link the modelled poloidal net deposition profiles of beryllium to post mortem data.

  • 2. Allen, S. L.
    et al.
    Wampler, W. R.
    McLean, A. G.
    Whyte, D. G.
    West, W. P.
    Stangeby, P. C.
    Brooks, N. H.
    Rudakov, D. L.
    Phillips, V.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Matthews, G. F.
    Nagy, A.
    Ellis, R.
    Bozek, A. S.
    C-13 transport studies in L-mode divertor plasmas on DIII-D2005Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 337-39, nr 03-jan, s. 30-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    (CH4)-C-13 was injected with a toroidally-symmetric gas system into 22 identical lower-single-null L-mode discharges on DIII-D. The injection level was adjusted so that it did not significantly perturb the core or divertor plasmas, with a duration of similar to 3 s on each shot, for a total of similar to 300 T L of injected particles. The plasma shape remained very constant; the divertor strike points were controlled to similar to 1 cm at the divertor plate. At the beginning of the subsequent machine vent, 29 carbon tiles were removed for nuclear reaction analysis of C-13 content to determine regions of carbon deposition. It was found that only the tiles inboard of the inner strike point had appreciable 1 3 C above background. Visible spectroscopy measurements of the carbon injection and comparisons with modeling are consistent with carbon transport by means of scrape-off layer flow.

  • 3.
    Almjashev, V.I.
    et al.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Barrachin, M.
    Institut de Radioprotection et Suˆrete´ Nucle´aire (IRSN).
    Bechta, Sevostian
    AP Aleksandrov Res Inst Technol, Sosnovyi Bor 188540, Russia.
    Bottomley, D.
    European Commission – DG – Joint Research Centre, Institute for Transuranium Elements.
    Defoort, F.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Fischer, M.
    Framatome ANP GmbH.
    Gusarov, V.V.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Hellmann, S.
    Framatome ANP GmbH.
    Khabensky, V.B.
    A.P. Aleksandrov Research Institute of Technology.
    Krushinov, E.V.
    A.P. Aleksandrov Research Institute of Technology.
    Lopukh, D.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Mezentseva, L.P.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Miassoedov, A.
    Institute for Nuclear and Energy Technologies, Forschungszentrum Karlsruhe.
    Petrov, Yu.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Vitol, S.A
    A.P. Aleksandrov Research Institute of Technology.
    Eutectic crystallization in the FeO(1.5)-UO(2+x)-ZrO(2) system2009Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 389, nr 1, s. 52-56Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Results of the investigation of the FeO(1.5)-UO(2+x)-ZrO(2) system in air are presented. The eutectic position and the content of the phases crystallized at this point have been determined. The temperature and the composition of the ternary eutectic are 1323 +/- 7 degrees C and 67.4 +/- 1.0 FeO(1.5), 30.5 +/- 1.0 UO(2+x), 2.1 +/- 0.2 ZrO(2) mol.%, respectively. The solubilities of FeO(1.5) and ZrO(2) in the UO(2+x)(FeO(1.5), ZrO(2)) solid solution correspond to respectively 3.2 and 1.1 mol.%. The solubilities of UO(2) and ZrO(2) in FeO(1.5) are not significant. The existence of a solid solution on the basis of U(Zr)FeO(4) compound is found. The ZrO(2) Solubility in this solid solution is 7.0 mol.%.

  • 4.
    Almjashev, V.I.
    et al.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Barrachin, M.
    Institut de Radioprotection et Suˆrete´ Nucle´aire (IRSN).
    Bechta, Sevostian
    DSAR, AP Aleksandrov Res Inst Technol, NITI, Sosnovyi Bor 188540, Russia .
    Bottomley, D.
    European Commission – DG – Joint Research Centre, Institute for Transuranium Elements.
    Defoort, F.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Fischer, M.
    Framatome ANP GmbH.
    Gusarov, V.V.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Hellmann, S.
    Framatome ANP GmbH.
    Khabensky, V.B.
    A.P. Aleksandrov Research Institute of Technology.
    Krushinov, E.V.
    A.P. Aleksandrov Research Institute of Technology.
    Lopukh, D.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Mezentseva, L.P.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Miassoedov, A.
    Institute for Nuclear and Energy Technologies, Forschungszentrum Karlsruhe.
    Petrov, Yu.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Vitol, S.A
    A.P. Aleksandrov Research Institute of Technology.
    Phase equilibria in the FeO(1+x)-UO(2)-ZrO(2) system in the FeO(1+x)-enriched domain2010Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 400, nr 2, s. 119-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimental results of the investigation of the FeO(1+x)UO(2)-ZrO(2) system in neutral atmosphere are presented. The ternary eutectic position and the composition of the phases crystallized at this point have been determined. The phase diagram is constructed for the FeO(1+x)-enriched region and the onset melting temperature of 1310 degrees C probably represents a local minimum and so will be a determining factor in this system and its application to safety studies in nuclear reactors.

  • 5. Amme, Marcus
    et al.
    Pehrman, Reijo
    Deutsch, Rudolf
    Roth, Olivia
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Combined effects of Fe(II) and oxidizing radiolysis products on UO2 and PuO2 dissolution in a system containing solid UO2 and PuO22012Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 430, nr 1-3, s. 1-5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stability of UO2 spent nuclear fuel in an oxygen-free geological repository depends on the absence of oxidizing reaction partners in the near field. This work investigates the reactions between the products of water radiolysis by alpha radiation and Fe(II) an the effect on UO2 dissolution. Solid (PuO2)-Pu-238 powder and UO2 pellet were allowed to react in Fe(II) solution in oxygen-free batch reactor tests and kinetics of the subsequent redox reactions were measured. Depending on the concentration of Fe(II) (tests with 10(-5) and 10(-4) mol L-1 were made), the induced redox reactions took place between 20 and 400 h. Dissolved uranium concentrations went first through a minimum caused by reduction, followed by a maximum caused by radiolytic oxidation, and eventually reached another minimum, probably due to sorption on precipitated Fe(III). Plutonium concentrations were decreasing steadily after going through a maximum about 70 h from the start of the experiments. The results show that in the presence of the strong alpha-radiolytic field induced by the presence of solid Pu-238, the behavior of the system is largely governed by Fe(II) as it controls the H2O2 concentration, reduces U(VI) in solution and drives the Fenton reaction leading to the oxidation of Pu(IV).

  • 6. Andrew, P
    et al.
    Coad, J P
    Corre, Yann
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Eich, T
    Herrmann, A
    Matthews, G F
    Paley, J I
    Pickworth, L
    Pitts, R A
    Stamp, M F
    Outer divertor target deposited layers during reversed magnetic field operation in JET2005Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 337, nr 1-3, s. 99-103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Divertor surface temperatures are significantly affected by the presence of deposited surface layers. This phenomenon can be used to monitor deposited layer evolution on a shot-by-shot basis. It was found that during an experimental campaign where the B x del B direction was reversed that the outer target, normally an erosion zone, became a deposition zone.

  • 7.
    Anghel, Clara
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hultquist, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Limbäck, Magnus
    Influence of Pt, Fe/Ni/Cr–containing intermetallics and deuterium on the oxidation of Zr-based materials2005Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 340, nr 2-3, s. 271-283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An in situ gas phase analysis technique and the 18O-SIMS technique are used to evaluate the transport of oxygen and hydrogen in oxidation of Zr-based materials. At 400 °C, it is found that oxygen dissociation efficiency decreases in the order: Pt > Zr2Fe > Zr2Ni > ZrCr2 Zircaloy-2. Two Zr-plates partly coated with 200 Å porous Pt, with and respectively without D in the substrate, were oxidized in two stages at 400 °C. SIMS depth profiles in the Pt area show that an enhanced oxidation takes place mainly by inward oxygen transport. A minimum in the oxide thickness was found near the Pt area on both Zr plates. Two Ar-filled Zircaloy-2 tubes with ZrSn liner were exposed at 370 °C to 22 mbar water, filled in from one side. Our experimental results suggest that a proper choice of the SPP composition and size distribution can lead to reduced hydrogen uptake during oxidation of Zr-based materials in water.

  • 8. Antoni, V.
    et al.
    Bergsåker, Henric
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Serianni, G.
    Spolaore, M.
    Vianello, N.
    Cavazzana, R.
    Regnoli, G.
    Spada, E.
    Martines, E.
    Bagatin, M.
    Drake, James R.
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Anomalous particle transport and flow shear in the edge region of RFP's2003Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 313, s. 972-975Artikel i tidskrift (Refereegranskat)
  • 9. Arnoux, G.
    et al.
    Loenen, J.
    Bazylev, B.
    Corre, Y.
    Matthews, G. F.
    Balboa, I.
    Clever, M.
    Dejarnac, R.
    Devaux, S.
    Eich, T.
    Gauthier, E.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Horacek, J.
    Jachmich, S.
    Kinna, D.
    Marsen, S.
    Mertens, Ph.
    Pitts, R. A.
    Rack, M.
    Sergienko, G.
    Sieglin, B.
    Stamp, M.
    Thompson, V.
    Thermal analysis of an exposed tungsten edge in the JET divertor2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 415-419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the recent melt experiments with the JET tungsten divertor, we observe that the heat flux impacting on a leading edge is 3-10 times lower than a geometrical projection would predict. The surface temperature, tungsten vaporisation rate and melt motion measured during these experiments is consistent with the simulations using the MEMOS code, only if one applies the heat flux reduction. This unexpected observation is the result of our efforts to demonstrate that the tungsten lamella was melted by ELM induced transient heat loads only. This paper describes in details the measurements and data analysis method that led us to this strong conclusion. The reason for the reduced heat flux are yet to be clearly established and we provide some ideas to explore. Explaining the physics of this heat flux reduction would allow to understand whether it can be extrapolated to ITER.

  • 10. Baron-Wiechec, A.
    et al.
    Widdowson, A.
    Alves, E.
    Ayres, C. F.
    Barradas, N. P.
    Brezinsek, S.
    Coad, J. P.
    Catarino, N.
    Heinola, K.
    Likonen, J.
    Matthews, G. F.
    Mayer, M.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    van Renterghem, W.
    Uytdenhouwen, I.
    Global erosion and deposition patterns in JET with the ITER-like wall2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 157-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A set of Be and W tiles removed after the first ITER-like wall campaigns (JET-ILW) from 2011 to 2012 has been analysed. The results indicate that the primary erosion site is in the main chamber (Be) as in previous carbon campaigns (JET-C). In particular the limiters tiles near the mid-plane are eroded probably during the limiter phases of discharges. W is found at low concentrations on all plasma-facing surfaces of the vessel indicating deposition via plasma transport initially from the W divertor and from main chamber W-coated tiles; there are also traces of Mo (used as an interlayer for these coatings). Deposited films in the inner divertor have a layered structure, and every layer is dominated by Be with some W and O content.

  • 11.
    Barreiro Fidalgo, Alexandre
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Sundin, Sara
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Effect of bentonite on radiation induced dissolution of UO2 in an aqueous system2014Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 447, nr 1-3, s. 73-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to elucidate the impact of bentonite on the process of radiation induced oxidative dissolution of UO2 in an aqueous system, the dissolution of U(VI) and consumption of H2O2 over time has been studied. In addition, γ-irradiation experiments were performed to study a more relevant and complex system, serving as a comparison with the previously stated system. In both cases, the experiments revealed that the presence of bentonite in water could either delay or prevent in part the release of uranium to the environment. The cause is mainly attributed to the scavenging of radiolytic oxidants rather than to the adsorption of uranium onto bentonite.

  • 12.
    Bechta, Sevostian
    et al.
    A.P. Alexandrov Research Institute of Technology (NITI).
    Krushinov, E.V.
    A.P. Aleksandrov Research Institute of Technology.
    Almjashev, V.I.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Vitol, S.A
    A.P. Aleksandrov Research Institute of Technology.
    Mezentseva, L.P.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Petrov, Yu.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Lopukh, D.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Khabensky, V.B.
    A.P. Aleksandrov Research Institute of Technology.
    Barrachin, M.
    Institut de Radioprotection et Suˆrete´ Nucle´aire (IRSN).
    Hellmann, S.
    Framatome ANP GmbH.
    Froment, K.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Fischer, M.
    Framatome ANP GmbH.
    Tromm, W.
    FZK, IKET, Karlsruhe, Forschungszentrum Karlsruhe GmbH.
    Bottomley, D.
    European Commission – DG – Joint Research Centre, Institute for Transuranium Elements.
    Defoort, F.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Gusarov, V.V.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Phase diagram of the UO2-FeO1+x system2007Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 362, nr 1, s. 46-52Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phase-relation studies of the UO2–FeO1+x system in an inert atmosphere are presented. The eutectic point has beendetermined, which corresponds to a temperature of (1335 ± 5) C and a UO2 concentration of (4.0 ± 0.1) mol.%. Themaximum solubility of FeO in UO2 at the eutectic temperature has been estimated as (17.0 ± 1.0) mol.%. Liquidus temperaturesfor a wide concentration range have been determined and a phase diagram of the system has been constructed.

  • 13.
    Bechta, Sevostian
    et al.
    A.P. Alexandrov Research Institute of Technology (NITI).
    Krushinov, E.V.
    A.P. Aleksandrov Research Institute of Technology.
    Almjashev, V.I.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Vitol, S.A
    A.P. Aleksandrov Research Institute of Technology.
    Mezentseva, L.P.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Petrov, Yu.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Lopukh, D.B.
    Saint-Petersburg Electrotechnical University ‘LETI’.
    Khabensky, V.B.
    A.P. Aleksandrov Research Institute of Technology.
    Barrachin, M.
    Institut de Radioprotection et Suˆrete´ Nucle´aire (IRSN).
    Hellmann, S.
    Framatome ANP GmbH.
    Froment, K.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Fischer, M.
    Framatome ANP GmbH.
    Tromm, W.
    FZK, IKET, Karlsruhe, Forschungszentrum Karlsruhe GmbH.
    Bottomley, D.
    European Commission – DG – Joint Research Centre, Institute for Transuranium Elements.
    Defoort, F.
    Laboratoire de Physico-chimie et Thermohydraulique Multiphasiques (LPTM), CEA/Grenoble, DTN/SE2T/LPTM – 17 rue des Martyrs.
    Gusarov, V.V.
    Institute of Silicate Chemistry of Russian Academy of Sciences.
    Phase diagram of the ZrO2-FeO system2006Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 348, nr 1-2, s. 114-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The results on the ZrO2–FeO system studies in a neutral atmosphere are presented. The refined eutectic point has beenfound to correspond to a ZrO2 concentration of 10.3 ± 0.6 mol% at 1332 ± 5 C. The ultimate solubility of iron oxide inzirconia has been determined in a broad temperature range, taking into account the ZrO2 polymorphism. A phase diagramof the pseudobinary system in question has been constructed.

  • 14. Becquart, C. S.
    et al.
    Ngayam Happy, R.
    Olsson, P.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Domain, C.
    A DFT study of the stability of SIAs and small SIA clusters in the vicinity of solute atoms in Fe2018Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 500, s. 92-109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The energetics, defect volume and magnetic properties of single SIAs and small SIA clusters up to size 6 have been calculated by DFT for different configurations like the parallel 〈110〉 dumbbell, the non parallel 〈110〉 dumbbell and the C15 structure. The most stable configurations of each type have been further analyzed to determine the influence on their stability of various solute atoms (Ti, V, Cr, Mn, Co, Ni, Cu, Mo, W, Pd, Al, Si, P), relevant for steels used under irradiation. The results show that the presence of solute atoms does not change the relative stability order among SIA clusters. The small SIA clusters investigated can bind to both undersized and oversized solutes. Several descriptors have been considered to derive interesting trends from results. It appears that the local atomic volume available for the solute is the main physical quantity governing the binding energy evolution, whatever the solute type (undersized or oversized) and the cluster configuration (size and type).

  • 15.
    Bergsåker, H
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Larsson, D
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Brunsell, P
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Möller, A
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Tramontin, L
    Wall conditioning and particle control in Extrap T21997Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 241-243, s. 993-997Artikel i tidskrift (Refereegranskat)
  • 16.
    Bergsåker, Henric
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Egde profiles and limiter tests in Extrap T21999Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 266-269, s. 777-782Artikel i tidskrift (Refereegranskat)
  • 17.
    Bergsåker, Henric
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hydrogen recycling in graphite at higher fluxes1999Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 266-269, s. 856-851Artikel i tidskrift (Refereegranskat)
  • 18.
    Bergsåker, Henric
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Emmoth, Birger
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Ilyinsky, Lev
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    In-situ ion beam analysis and dynamic studies of deuterium retention in graphite exposed to a high flux magnetron plasma1997Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 241-243, s. 1022-1025Artikel i tidskrift (Refereegranskat)
  • 19.
    Bergsåker, Henric
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Emmoth, Birger
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Petersson, P.
    Possnert, Göran
    Coad, J. P.
    Likonen, J.
    Renvall, T.
    Nuclear reaction analysis with ion microbeam of cross sections of surface layers deposited in a tokamak divertor2007Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 362, nr 03-feb, s. 215-221Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ion micro beam analysis has been applied to the investigation of plasma deposited layers covering the divertor tiles in the JET tokamak. Since the layers are about 100 mu m thick they are too thick to be completely investigated by ordinary ion beam analysis. Cross sections of the layers were prepared by cutting and polishing. Elemental depth profiles were determined from the two dimensional images that could be derived by nuclear reaction analysis and resonant backscattering spectrometry, using ion beams focused to a few mu m spot size. A combination of analysis methods are shown, which allow measurements of the concentration profiles of carbon, beryllium, deuterium, oxygen and stainless steel components at levels of a few percent, with an accuracy better than 10%.

  • 20.
    Bergsåker, Henric
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Bykov, Igor
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Possnert, G.
    Likonen, J.
    Koivuranta, S.
    Coad, J. P.
    Widdowson, A. M.
    Microanalysis of deposited layers in the divertor of JET following operations with carbon wall2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, nr Suppl., s. S668-S672Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Elemental mapping of cross sections of deposited layers on inboard tiles in the JET divertor after exposure to plasma operations with carbon wall are presented. The study was made using microbeam ion beam analysis methods in combination with optical microscopy and SEM. The surfaces had been exposed to plasma through different periods of operation (1998-2007, 2007-2009 and 1998-2009). The texture and composition of the layers are non-uniform. The physical structures include columnar, lamellar and disordered globular appearances. The distribution of trapped deuterium was frequently found to be lamellar, with well-defined sub layers with higher deuterium concentration. However, 3D regions with dimensions of about 100 μm with enhanced deuterium content were also found, both at the layer surfaces and in the layer cross sections. The distributions of beryllium and Inconel components were lamellar but did not otherwise show large non-uniformity on the same scale length as the deuterium.

  • 21.
    Bergsåker, Henric
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Ratynskaia, Svetlana
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Litnovsky, A.
    Ogata, Douglas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Sahle, Wubeshet
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Funktionella material, FNM.
    Studies of mobile dust in scrape-off layer plasmas using silica aerogel collectors2011Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 415, nr 1, s. S1089-S1093Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dust capture with ultralow density silica aerogel collectors is a new method, which allows time resolved in situ capture of dust particles in the scrape-off layers of fusion devices, without substantially damaging the particles. Particle composition and morphology, particle flux densities and particle velocity distributions can be determined through appropriate analysis of the aerogel surfaces after exposure. The method has been applied in comparative studies of intrinsic dust in the TEXTOR tokamak and in the Extrap T2R reversed field pinch. The analysis methods have been mainly optical microscopy and SEM. The method is shown to be applicable in both devices and the results are tentatively compared between the two plasma devices, which are very different in terms of edge plasma conditions, time scale, geometry and wall materials.

  • 22.
    Bergsåker, Henrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Bykov, Igor
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Possnert, G.
    Likonen, J.
    Koivuranta, S.
    Coad, J. P.
    Van Renterghem, W.
    Uytdenhouwen, I.
    Widdowson, A. M.
    Microscopically nonuniform deposition and deuterium retention in the divertor in JET with ITER-like wall2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 956-960Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The divertor surfaces in JET with ITER-like wall (ILW) have been studied using micro ion beam analysis (mu-IBA) methods and scanning electron microscopy (SEM). Deposited layers with beryllium as main constituent had been formed during plasma operations through 2011-2012. The deuterium trapping and impurity deposition were non-uniform, frequently enhanced within pits, cracks and valleys, regions reaching in size from 10 mu m to 200 mu m. The impurity deposition and fuel retention were correlated with the surface slope with respect to the direction of ion incidence. Typically more than 70% of the total measured areal density of trapped D was found in less than 30% of the surface area. This is of consequence for the interpretation of other surface analyses and in extrapolation from fuel retention in JET with ITER-like wall and rough divertor surfaces to ITER with smoother surfaces.

  • 23.
    Björkas, C.
    et al.
    Accelerator Laboratory, University of Helsink.
    Nordlund, K.
    Accelerator Laboratory, University of Helsink.
    Malerba, L.
    SCKCEN, The Belgian Nuclear Research Centre.
    Terentyev, D.
    SCKCEN, The Belgian Nuclear Research Centre.
    Olsson, Pär
    Departément Matériaux et Méchanique des Composants, Electricité de France.
    Simulation of displacement cascades in Fe90Cr10 using a two band model potential2008Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 372, nr 2-3, s. 312-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular dynamics (MD) simulations of displacement cascades, with recoil energies up to 50 keV, have been performed in Fe90Cr10 and Fe using a recently developed two band embedded atomic model (2BM) potential that correctly describes the mixing enthalpy and the binding energy of the mixed dumbbell configurations. Comparisons between results obtained with the 2BM potential fitted to different data sets, a one band model (1BM), and another existing FeCr-potential previously used for similar calculations were done, showing differences in the vacancy clustered fraction and the Cr content in interstitials predicted by the potentials. The 2BM potential resulted in roughly the same concentration of Cr in interstitial positions as in the matrix, and the 1BM, which incorrectly predicts a positive heat of mixing, predicted even smaller concentrations. The calculated short range order parameter is around zero for the 2BM, and takes positive values within the 1BM, as expected from the mixing enthalpies.

  • 24. Bonny, G.
    et al.
    Bakaev, A.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Domain, C.
    Zhurkin, E. E.
    Posselt, M.
    Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels2017Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 484, s. 42-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Under irradiation NiSiPCr clusters are formed in high-Cr ferritic martensitic steels as well as in FeCr model alloys. In the literature little is known about the origin and contribution to the hardening of these clusters. In this work we performed density functional theory (DFT) calculations to study the stability of small substitutional NiCr-vacancy clusters and interstitial configurations in bcc Fe. Based on DFT data and experimental considerations a ternary potential for the ferritic FeNiCr system was developed. The potential was applied to study the thermodynamic stability of NiCr clusters by means of Metropolis Monte Carlo (MMC) simulations. The results of our simulations show that Cr and Ni precipitate as separate fractions and suggest only a limited synergetic effect between Ni and Cr. Therefore our results suggest that the NiCrSiP clusters observed in experiments must be the result of other mechanisms than the synergy of Cr and Ni at thermal equilibrium.

  • 25. Bonny, G.
    et al.
    Pasianot, R. C.
    Malerba, L.
    Caro, A.
    Olsson, Pär
    vermore, CA 94550, United States f Department Matériaux et Mécanique des Composants, Electricité de France.
    Lavrentiev, M. Yu.
    Numerical prediction of thermodynamic properties of iron-chromium alloys using semi-empirical cohesive models: The state of the art2009Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 385, nr 2, s. 268-277Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work the capability of existing cohesive models to predict the thermodynamicproperties of Fe-Cr alloys are critically evaluated and compared. The two-band model and the concentration-dependent model, which are independently developed extensions of the embedded-atom method, are demonstrated to be equivalent and equally capable of reproducing the thermodynamic properties of Fe-Cr alloys. The existing potentials fitted with these formalisms are discussed and compared with an existing cluster expansionmodel. The phase diagram corresponding to these models is evaluated using different but complementary methods. The influence of mixing enthalpy, low-energy states and vibrational entropy on the phase diagram is examined for the different cohesive models.

  • 26.
    Boåsen, Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Efsing, Pål
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Ehrnstén, Ulla
    On flux effects in a low alloy steel from a Swedish reactor pressure vessel2017Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 484, s. 110-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study aims to investigate the presence of Unstable Matrix Defects in irradiated pressure vessel steel from weldments of the Swedish PWR Ringhals 4 (R4). Hardness tests have been performed on low flux (surveillance material) and high flux (Halden reactor) irradiated material samples in combination with heat treatments at temperatures of 330, 360 and 390 °C in order to reveal eventual recovery of any hardening features induced by irradiation. The experiments carried out in this study could not reveal any hardness recovery related to Unstable Matrix Defects at relevant temperatures. However, a difference in hardness recovery was found between the low and the high flux samples at heat treatments at higher temperatures than expected for the annihilation of Unstable Matrix Defects–the observed recovery is here attributed to differences of the solute clusters formed by the high and low flux irradiations.

  • 27. Brezinsek, S.
    et al.
    Fundamenski, W.
    Eich, T.
    Coad, J. P.
    Giroud, C.
    Huber, A.
    Jachmich, S.
    Joffrin, E.
    Krieger, K.
    McCormick, K.
    Lehnen, M.
    Loarer, T.
    de la Luna, E.
    Maddison, G.
    Matthews, G. F.
    Mertens, Ph.
    Nunes, I.
    Philipps, V.
    Riccardo, V.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Stamp, M. F.
    Tsalas, M.
    Overview of experimental preparation for the ITER-Like Wall at JET2011Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 415, nr 1, s. S936-S942Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experiments in JET with carbon-based plasma-facing components have been carried out in preparation of the ITER-Like Wall with beryllium main chamber and full tungsten divertor. The preparatory work was twofold: (i) development of techniques, which ensure safe operation with the new wall and (ii) provision of reference plasmas, which allow a comparison of operation with carbon and metallic wall. (i) Compatibility with the W divertor with respect to energy loads could be achieved in N-2 seeded plasmas at high densities and low temperatures, finally approaching partial detachment, with only moderate confinement reduction of 10%. Strike-point sweeping increases the operational space further by re-distributing the load over several components. (ii) Be and C migration to the divertor has been documented with spectroscopy and QMBs under different plasma conditions providing a database which will allow a comparison of the material transport to remote areas with metallic walls. Fuel retention rates of 1.0-2.0 x 10(21) D s(-1) were obtained as references in accompanied gas balance studies.

  • 28. Brezinsek, S.
    et al.
    Jachmich, S.
    Stamp, M. F.
    Meigs, A. G.
    Coenen, J. W.
    Krieger, K.
    Giroud, C.
    Groth, M.
    Philipps, V.
    Grünhagen, S.
    Smith, R.
    Van Rooij, G. J.
    Ivanova, Darya
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Matthews, G. F.
    Residual carbon content in the initial ITER-Like Wall experiments at JET2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, nr Suppl., s. S303-S308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The residual carbon content and carbon edge flux in JET have been assessed by three independent diagnostic techniques after start of plasma operation with the ITER-Like Wall (ILW) with beryllium first wall and tungsten divertor: (i) in-situ measurements with optical spectroscopy on low ionisation stages of carbon, (ii) charge-exchange recombination spectroscopy, and (iii) residual gas composition analysis in dedicated global gas balance experiments. Direct comparison experiments in L-mode discharges were carried out between references from the previously installed material configuration with plasma-facing components made of carbon-fibre composite (JET-CFC) and the JET-ILW. The temporal evolution of the C divertor flux since installation of the ILW has been studied in the ohmic phase of dedicated monitoring discharges which have been executed regularly throughout the experimental exploitation so far (60000 plasma seconds). The C flux behaviour in the divertor can be divided in three phases: initial fast drop, moderate reduction phase, and a long lasting phase with almost constant C flux. The Be flux in both divertor legs mirrors the behaviour of C. All experiments and diagnostic techniques demonstrate a strong reduction in C fluxes and C content of more than one order of magnitude with respect to JET-CFC which is in line with the reduction in long-term fuel retention due to co-deposition. There is no evidence of an increase in residual carbon in time, thus no indication that a damage of the thin tungsten coatings on CFC substrate in the divertor occurred.

  • 29.
    Bykov, Igor
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Bergsåker, Henric
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Ratynskaia, Svetlana
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Litnovsky, A.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Possnert, G.
    Time resolved collection and characterization of dust particles moving in the TEXTOR scrape-off layer2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, nr Suppl., s. S681-S685Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Moving dust has been collected in the SOL of TEXTOR in a time-resolved way with silica aerogel collectors [1-3]. The collectors were exposed to the toroidal particle flux in NBI heated discharges during the startup and flat top phase. Intrinsic dust was collected in several discharges. Other discharges were accompanied with injection of known amounts of pre-characterized dust (W, C flakes and C microspheres) from a position toroidally 120° away from the collector. Particle flux, composition and dust size distribution have been determined with SEM and EDX. Calibration allowed particle velocity estimates to be made. Upper limits for the deuterium content of individual dust grains have been determined by NRA.

  • 30.
    Bykov, Igor
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Bergsåker, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Possnert, G.
    Heinola, K.
    Miettunen, J.
    Groth, M.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Widdowson, A.
    Likonen, J.
    Materials migration in JET with ITER-like wall traced with a Be-10 isotopic marker2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 773-776Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current configuration of JET with ITER-like Wall (ILW) is the best available proxy for the ITER first wall. Beryllium redistribution in JET-ILW can be used for estimates of its migration in ITER. To trace it, a localized isotopic Be marker has been implemented. A bulk Be-9 tile has been enriched with Be-10 up to atomic concentrations of 1.7 x 10(-9) and installed at the inner midplane of JET before the campaign. During the 2012 shutdown over 100 surface samples were taken non destructively from surfaces of two toroidally opposite limiter beams. The absolute areal densities of the marker were inferred from Be-15 atomic concentration in each sample, measured with Accelerator Mass Spectrometry with sensitivity <10(-14). The results of marker mapping are compared with predictions made with the ASCOT orbit following code.

  • 31.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Terentyev, Dmitry
    Sandberg, Nils
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Dislocation bias factors in fcc copper derived from atomistic calculations2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 441, nr 1-3, s. 357-363Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atomistic calculations were employed in order to calculate the interaction energy of an edge dislocation with different point defects. The bias factor was calculated by applying a finite element method on the interaction energy landscapes obtained from the atomistic calculations. A comparison of the calculated bias factor with a model based on elasticity theory reveals around 30% discrepancy under conditions representative for electron irradiation at 600 degrees C. Possible reasons are discussed. The bias factor dependence on dislocation density and ambient temperature is presented and discussed.

  • 32.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Sandberg, Nils
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik. Swedish Radiation Safety Authority, Sweden.
    Dmitry, Terentyev
    Samuelsson, Karl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Bonny, Giovanni
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Assessment of the dislocation bias in fcc metals and extrapolation to austenitic steels2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic study of dislocation bias has been performed using a method that combines atomistic and elastic dislocation-point defect interaction models with a numerical solution of the diffusion equation with a drift term. Copper, nickel and aluminium model lattices are used in this study, covering a wide range of shear moduli and stacking fault energies. It is found that the dominant parameter for the dislocation bias in fcc metals is the width of the stacking fault ribbon. The variation in elastic constants does not strongly impact the dislocation bias value. As a result of this analysis and its extrapolation, the dislocation bias of the widely applied austenitic stainless steels of 316 type is predicted to be about 0.1 at temperature close to the swelling peak (815 K) and typical dislocation density of 1014 m-2. This is in line with the bias calculated using the elastic interaction model, which implies that the prediction method can be used readily in other fcc systems even without EAM potentials. By comparing the bias values obtained using atomistic- and elastic interaction energies, about 20% discrepancy is found, therefore a more realistic bias value for the 316 type alloy is 0.08 in these conditions.

  • 33.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Terentyev, Dmitry
    Nuclear Materials Science Institute, Belgium.
    Sandberg, Nils
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik. Swedish Radiation Safety Authority, Sweden.
    Samuelsson, Karl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Anomalous bias factors of dislocations in bcc iron2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 461, s. 221-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dislocation bias factors in bcc Fe have been calculated based on atomistic interaction energy maps on three kinds of dislocations, namely the a0/2〈1 1 1〉{1 1 0} screw, a0/2〈1 1 1〉{1 1 0} and a0〈1 0 0〉{0 0 1} edge dislocations. The results show that the dislocation bias is higher for the a0/2〈1 1 1〉 edge dislocation than for the a0〈1 0 0〉 edge dislocation, even though the latter possesses a larger Burgers vector. This indicates the importance of the dislocation core contribution. For the a0/2〈1 1 1〉{1 1 0} screw dislocation, a negative dislocation bias has been obtained, which implies a more efficient absorption of vacancies than of SIAs. The effect of coexistence of both edge- and screw dislocations are assessed by a total bias. A possible complementary mechanism for explaining the long swelling incubation time in bcc metals is suggested and discussed.

  • 34.
    Claisse, Antoine
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Klipfel, Marco
    Lindbom, Niclas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Freyss, Michel
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    GGA plus U study of uranium mononitride: A comparison of the U-ramping and occupation matrix schemes and incorporation energies of fission products2016Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 478, s. 119-124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Uranium mononitride is studied in the DFT + U framework. Its ground state is investigated and a study of the incorporation of diverse fission products in the crystal is conducted. The U-ramping and occupation matrix control (OMC) schemes are used to eliminate metastable states. Beyond a certain amount of introduced correlation, the OMC scheme starts to find a lower total energy. The OMC scheme is chosen for the second part of this study. Furthermore, the influence of the magnetic ordering is studied using the U-ramping method, showing that antiferromagnetic order is the most stable one when the U parameter is larger than 1.75 eV. The effect on the density of states is investigated and elastic constants are provided for comparison with other methods and experiments. The incorporation energies of fission products in different defect configurations are calculated and these energies are corrected to take into account the limited size of the supercell.

  • 35.
    Claisse, Antoine
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Van Uffelen, P.
    Towards the inclusion of open fabrication porosity in a fission gas release model2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 466, s. 351-356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A model is proposed for fission product release in oxide fuels that takes into account the open porosity in a mechanistic manner. Its mathematical framework, assumptions and limitations are presented. It is based on the model for open porosity in the sintering process of crystalline solids. More precisely, a grain is represented by a tetrakaidecahedron and the open porosity is represented by a continuous cylinder along the grain edges. It has been integrated in the TRANSURANUS fuel performance code and applied to the first case of the first FUMEX project as well as to neptunium and americium containing pins irradiated during the SUPERFACT experiment and in the JOYO reactor. The results for LWR and FBR fuels are consistent with the experimental data and the predictions of previous empirical models when the thermal mechanisms are the main drivers of the release, even without using a fitting parameter. They also show a different but somewhat expected behaviour when very high porosity fuels are irradiated at a very low burn-up and at low temperature.

  • 36. Coad, J. P.
    et al.
    Andrew, P.
    Erents, S. K.
    Hole, D. E.
    Likonen, J.
    Mayer, M.
    Pitts, R.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Strachan, J. D.
    Vainonen-Ahlgren, E.
    Widdowson, A.
    Erosion and deposition in the JET MkII-SRP divertor2007Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 363, s. 287-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carbon-13 labelled methane was injected into the outer divertor during a series of H-mode discharges on the last day of operations with the JET MkII-SRP divertor. Tiles from around the vessel were removed during the subsequent shutdown and surface deposits were analysed by IBA techniques and SIMS. First attempts to model the pattern of 13 C deposition using EDGE2D are reported. Erosion of W markers at the outer divertor was observed, with implications for the ITER-like wall experiment planned for JET, whilst thin film growth in the same region has been followed by the effect on infrared measurements. The composition of thick films deposited at the inner divertor during the MkII-SRP campaign, and the migration to the inner corner of the divertor observed by a quartz micro-balance, provide further information on divertor transport. Crown

  • 37. Coad, J. P.
    et al.
    Andrew, P.
    Hole, D. E.
    Lehto, S.
    Likonen, J.
    Matthews, G. F.
    Rubel, Marek J.
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Erosion/deposition in JET during the period 1999-20012003Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 313, s. 419-423Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coated divertor and wall tiles exposed in JET for the 1999-2001 operations have been used to assess erosion/deposition. Deposited films of up to 90 mum thickness at the inner wall of the divertor tiles are, for the most part, enriched in beryllium and other metals, whilst carbon is probably chemically sputtered from these tiles and transported to shadowed regions of the inner divertor. However, from the composition at the surface of the tiles, it appears that the chemical erosion was 'switched off' by reducing the JET vessel wall temperature for the last part of the operations to 200 degreesC. Thick powdery deposits localised at the ion transport limit at each corner of the divertor may be due to physical sputtering. Erosion of the coatings is seen at the outer divertor wall, and on all the inner wall and outer limiter tiles.

  • 38. Coenen, J. W.
    et al.
    Arnoux, G.
    Bazylev, B.
    Matthews, G. F.
    Jachmich, S.
    Balboa, I.
    Clever, M.
    Dejarnac, R.
    Coffey, I.
    Corre, Y.
    Devaux, S.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Gauthier, E.
    Horacek, J.
    Knaup, M.
    Komm, M.
    Krieger, K.
    Marsen, S.
    Meigs, A.
    Mertens, Ph.
    Pitts, R. A.
    Puetterich, T.
    Rack, M.
    Stamp, M.
    Sergienko, G.
    Tamain, P.
    Thompson, V.
    ELM induced tungsten melting and its impact on tokamak operation2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 78-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In JET-ILW dedicated melt exposures were performed using a sequence of 3MA/2.9T H-Mode JET pulses with an input power of P-IN = 23 MW, a stored energy of similar to 6 MJ and regular type I ELMs at Delta W-ELM = 0.3 MJ and f(ELM) similar to 30 Hz. In order to assess the risk of starting ITER operations with a full W divertor, one of the task was to measure the consequences of W transients melting due to ELMs. JET is the only tokamak able to produce transients/ ELMs large enough (>300 kJ per ELM) to facilitate melting of tungsten. Such ELMs are comparable to mitigated ELMs expected in ITER. By moving the outer strike point (OSP) onto a dedicated leading edge the base temperature was raised within similar to 1 s to allow transient ELM-driven melting during the subsequent 0.5 s. Almost 1 mm (similar to 6 mm(3)) of W was moved by similar to 150 ELMs within 5 subsequent discharges. Significant material losses in terms of ejections into the plasma were not observed. There is indirect evidence that some small droplets (similar to 80 mu m) were ejected. The impact on the main plasma parameters is minor and no disruptions occurred. The W-melt gradually moved along the lamella edge towards the high field side, driven by j x B forces. The evaporation rate determined is 100 times less than expected from steady state melting and thus only consistent with transient melting during individual ELMs. IR data, spectroscopy, as well as melt modeling point to transient melting. Although the type of damage studied in these JET experiments is unlikely to be experienced in ITER, the results do strongly support the design strategy to avoid exposed edges in the ITER divertor. The JET experiments required a surface at normal incidence and considerable pre-heating to produce tungsten melting. They provide unique experimental evidence for the absence of significant melt splashing at events resembling mitigated ELMs on ITER and establish a unique experimental benchmark for the simulations being used to study transient shallow melting on ITER W divertor PFUs.

  • 39. Costa, D.
    et al.
    Adjanor, G.
    Becquart, C. S.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik. Etude et Modelisation des Microstructures Pour le Vieillissement des Materiaux, France .
    Domain, C.
    Vacancy migration energy dependence on local chemical environment in Fe-Cr alloys: A Density Functional Theory study2014Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 452, nr 1-3, s. 425-433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The first step towards the understanding and the modelling of the Fe-Cr alloy kinetic properties consists in estimating the migration energies related to the processes that drive the microstructure evolution. The vacancy's migration barrier is expected to depend on the vacancy-migrating atom pair atomic environment as pointed out by Nguyen-Manh et al. or Bonny et al. In this paper, we address the issue of the dependence on the vacancy's local atomic environment of both the vacancy migration energy and the configurational energy change Delta E that occurs when the vacancy jumps towards one of its nearest neighbour sites. A DFT approach is used to determine the ground state energy associated to a given configuration of the system. The results are interpreted in the light of the chromium-chromium and chromium-vacancy binding energies as well as the substitutional chromium atoms magnetic properties.

  • 40.
    Delandar, Arash Hosseinzadeh
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gorbatov, O. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering. KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi. KTH Royal Inst Technol, Mat Sci & Engn, SE-10044 Stockholm, Sweden..
    Gornostyrev, Yu. N.
    Ryssland.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi. KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Ab-initio based search for late blooming phase compositions in iron alloys2018Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 509, s. 225-236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a systematic analysis, based on ab initio calculations, of concentrated solute arrangements and precipitate phases in Fe-based alloys. The input data for our analysis are the calculated formation and interaction energies of point defects in the iron matrix, as well as the energies of ordered compounds that represent end-members in the 4-sublattice compound energy model of a multicomponent solid solution of Mg, Al, Si, P, S, Mn, Ni, and Cu elements and also vacancies in bcc Fe. The list of compounds also includes crystal structures obtained by geometric relaxation of the end-member compounds that in the cubic structure show weak mechanical instabilities (negative elastic constants) and also the G-phase Mn-6(Ni,Fe)(16)(Si,P)(7) having a complex cubic structure. A database of calculated thermodynamic properties (crystal structure, molar volume, enthalpy of formation, and elastic constants) of the most stable late-blooming-phase candidates is thus obtained. The results of this ab initio based theoretical analysis compare well with the recent experimental observations and predictions of thermodynamic calculations employing Calphad methodology.

  • 41. Dudarev, S. L.
    et al.
    Boutard, J. -L
    Laesser, R.
    Caturla, M. J.
    Derlet, P. M.
    Fivel, M.
    Fu, C. -C
    Lavrentiev, M. Y.
    Malerba, L.
    Mrovec, M.
    Nguyen-Manh, D.
    Nordlund, K.
    Perlado, M.
    Schaeublin, R.
    Van Swygenhoven, H.
    Terentyev, D.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Weygand, D.
    Willaime, F.
    The EU programme for modelling radiation effects in fusion reactor materials: An overview of recent advances and future goals2009Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 386, s. 1-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The EU fusion materials modelling programme was initiated in 2002 with the objective of developing a comprehensive set of computer modelling techniques and approaches, aimed at rationalising the extensive available experimental information on properties of irradiated fusion materials, developing capabilities for predicting the behaviour of materials under conditions not yet accessible to experimental tests, assessing results of tests involving high dose rates, and extrapolating these results to the fusion-relevant conditions. The programme presently gives emphasis to modelling a single class of materials, which are ferritic-martensitic EUROFER-type steels, and focuses on the investigation of key physical phenomena and interpretation of experimental observations. The objective of the programme is the development of computational capabilities for predicting changes in mechanical properties, hardening and embrittlement, as well as changes in the microstructure and phase stability of EUROFER and FeCr model alloys occurring under fusion reactor relevant irradiation conditions.

  • 42. Eckle, M
    et al.
    Eloirdi, R
    Gouder, T
    Colarieti Tosti, Massimiliano
    Wastin, F
    Rebizant, J
    Electronic structure of UCx films prepared by sputter co-deposition2004Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 334, nr 1, s. 1-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin layers of UCx (x = 0-12) have been prepared by sputter co-deposition of uranium and carbon in an Ar atmosphere. The films were investigated in-situ by ultraviolet and X-ray photoelectron spectroscopy (UPS and XPS, respectively). Special interest was put on the evolution of the electronic structure with the composition of the films, as deduced from the U-4f, C-1s and valence region spectra. With increasing carbon content, three types of carbon species were detected according to C-1s core level line, at 282, 282.6 and 284.5 eV binding energy (BE). They are attributed to the UC, UC2 and graphite phases, respectively. The U-4f core levels do not change strongly with increasing carbon content, showing well-itinerant U-5f electrons. Similarly, valence region spectra show three types of carbon species for different UCx films, which are differentiated by their C-2p signals. A strong hybridisation between C-2p and U-5f states is detected in UC, while the C-2p signal in UC2 appears only weakly hybridised, and for higher carbon contents a pi band characteristic of graphite appears.

  • 43. Edmondson, P. D.
    et al.
    Parish, C. M.
    Zhang, Y.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Miller, M. K.
    Helium bubble distributions in a nanostructured ferritic alloy2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 434, nr 1-3, s. 210-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 14YWT nanostructured ferritic alloy (NFA) was implanted with He + ions to fluences of 6.75 × 1021 He m-2 at 400 °C in order to simulate the effects of high He concentrations produced in advanced fission and future fusion reactors at an accelerated timescale. The He bubble size distributions associated with specific microstructural features were characterized by a combination of transmission electron microscopy and atom probe tomography. Helium bubbles were observed on grain boundaries, dislocations, and on the surfaces of nanoclusters and larger Ti(N,C) precipitates. A polydisperse distribution of bubble sizes was observed in the ferrite matrix. With the exception of He bubbles on dislocations, bubbles were observed to increase in size with increasing fluence. The combined TEM and APT data indicates that ∼4.4% of the bubbles are located on coarse precipitates, ∼12.2% at dislocations, ∼14.4% at grain boundaries, and ∼48.6% on nanoclusters, and the remainder as isolated bubbles in the ferrite matrix. The abundances of these different trapping sites, especially the nanoclusters, might reduce the availability and mobility of He, and possibly the susceptibility of these alloys to He embrittlement.

  • 44.
    Efsing, Pål
    et al.
    Pacific North West Laboratories, Richland, WA, USA.
    Edwards, Dan
    Pacific North West Laboratories, Richland, WA, USA.
    Garner, Frank
    Pacific North West Laboratories, Richland, WA, USA.
    Bruemmer, Steve
    Vattenfall AB Ringhals, SE-430-22 Väröbacka, Sweden.
    Nano-cavities observed in a 316SS PWR flux thimble tube irradiated to 33 and 70 dpa2009Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 384, nr 3, s. 249-255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The radiation-induced microstructure of a cold-worked 316SS flux thimble tube from an operating pressurized water reactor (PWR) was examined. Two irradiated conditions, 33 dpa at 290 degrees C and 70 dpa at 315 degrees C were examined by transmission electron microscopy. The original dislocation network had completely disappeared and was replaced by fine dispersions of Frank loops and small nano-cavities at high densities. The latter appear to be bubbles containing high levels of helium and hydrogen. An enhanced distribution of these nano-cavities was found at grain boundaries and may play a role in the increased susceptibility of the irradiated 316SS to intergranular failure of specimens from this tube during postirradiation slow strain rate testing in PWR water conditions.

  • 45.
    Ejenstam, Jesper
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Halvarsson, M.
    Weidow, J.
    Jönsson, B.
    Szakalos, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Oxidation studies of Fe10CrAl-RE alloys exposed to Pb at 550 C for 10,000 h2013Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 443, nr 1-3, s. 161-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Five experimental FeCrAl-RE alloys have been exposed up to 10,000 h in stagnant liquid Pb at 550 C. The test matrix consisted of three 10 wt.% Cr alloys, with an Al content ranging from 4 to 8 wt.% (10Cr-4Al, 10Cr-6Al and 10Cr-8Al), one alloy without additions of reactive elements (RE) (10Cr-6Al), and one reference alloy with 21 wt.% Cr and 5 wt.% Al (21Cr-5Al). The evaluation showed a clear difference in oxidation properties, and it was possible to divide the alloys into two distinct groups. A critical Al concentration in the interval of 4-6 wt.% at the given RE content was required to form a thin protective oxide. However, the absence of RE addition in one of the two 10Cr-6Al alloys resulted in a significant reduction in oxidation resistance, comparable with 10Cr-4Al. None of the alloys were severely corroded, however Pb penetrated to a relatively large extent into the porous oxide of the low performing alloys. A 100 nm thick oxide scale, partly consisting of alumina (Al2O 3), was observed for the high performing 10Cr-6Al alloy. The Fe10CrAl-RE alloys showed overall very good corrosion resistance and are hence a promising new alloy category for liquid Pb applications.

  • 46.
    Ejenstam, Jesper
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Szakalos, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Long term corrosion resistance of alumina forming austenitic stainless steels in liquid lead2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 461, s. 164-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alumina forming austenitic steels (AFA) and commercial stainless steels have been exposed in liquid lead with 10-7 wt.% oxygen at 550 °C for up to one year. It is known that chromia forming austenitic stainless steels, such as 316L and 15-15 Ti, have difficulties forming protective oxides in liquid lead at temperatures above 500°C, which is confirmed in this study. By adding Al to austenitic steels, it is in general terms possible to increase the corrosion resistance. However this study shows that the high Ni containing AFA alloys are attacked by the liquid lead, i.e. dissolution attack occurs. By lowering the Ni content in AFA alloys, it is possible to achieve excellent oxidation properties in liquid lead. Following further optimization of the microstructural properties, low Ni AFA alloys may represent a promising future structural steel for lead cooled reactors.

  • 47.
    Ejenstam, Jesper
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thuvander, Mattias
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Rave, Fernando
    Szakalos, Peter
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Microstructural stability of Fe–Cr–Al alloys at 450–550 °C2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 457, s. 291-297Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iron–Chromium–Aluminium (Fe–Cr–Al) alloys have been widely investigated as candidate materials for various nuclear applications. Albeit the excellent corrosion resistance, conventional Fe–Cr–Al alloys suffer from α–α′ phase separation and embrittlement when subjected to temperatures up to 500 °C, due to their high Cr-content. Low-Cr Fe–Cr–Al alloys are anticipated to be embrittlement resistant and provide adequate oxidation properties, yet long-term aging experiments and simulations are lacking in literature. In this study, Fe–10Cr–(4–8)Al alloys and a Fe–21Cr–5Al were thermally aged in the temperature interval of 450–550 °C for times up to 10,000 h, and the microstructures were evaluated mainly using atom probe tomography. In addition, a Kinetic Monte Carlo (KMC) model of the Fe–Cr–Al system was developed. No phase separation was observed in the Fe–10Cr–(4–8)Al alloys, and the developed KMC model yielded results in good agreement with the experimental data.

  • 48.
    Ekeroth, Ella
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Jonsson, Mats
    KTH, Tidigare Institutioner                               , Kemi.
    Oxidation of UO2 by radiolytic oxidants2003Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 322, nr 03-feb, s. 242-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetics of UO2 oxidation by H2O2 has been studied using aqueous suspensions Of UO2-powder. The second order,rate constant for the reaction between H2O2 and UO2 has been determined to 8 x 10(-7) m/min (based on the surface to solution volume ratio) in the absence of carbonate. By studying the reaction between UO2 and other oxidants, it is possible to draw conclusions concerning the mechanism. The logarithm of the second order rate constant, ln k, for UO2 oxidation appears to be linearly related to the one-electron reduction potential, E-0, of the oxidant. This indicates that the rate limiting step in the oxidation of UO2 is one-electron transfer. A Fenton like mechanism is plausible for the reaction between UO2 and H2O2. The diffusion controlled rate constant in this particular system is approximately 10(3) m/min, and therefore the reactions with OH- and CO3- are estimated to be diffusion controlled.

  • 49.
    Ekeroth, Ella
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Jonsson, Mats.
    KTH, Tidigare Institutioner, Kemi.
    Eriksen, Trygve
    KTH, Tidigare Institutioner, Kemi.
    Ljungqvist, Kristina
    KTH, Tidigare Institutioner, Kemi.
    Kovacs, Sandor
    Puigdomenech, Ignasi
    Reduction of UO22+ by H-22004Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 334, nr 1, s. 35-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reactivity of H, towards UO22+ has been studied experimentally using a PEEK coated autoclave where the UO22+ concentration in aqueous solution containing 2 mM carbonate was measured as a function of time at p(H2) similar to 40 bar. The experiments were performed in the temperature interval 74-100 degreesC. In addition, the suggested catalytic activity of UO2 on the reduction of UO22+ by H-2 was investigated. The results clearly show that H-2 is capable of reducing UO22+ to UO2 without the presence of a catalyst. The reaction is of first order with respect to UO22+. The activation energy for the process is 130 +/- 24 U mol(-1) and the rate constant is k(298K) = 3.6 x 10(-9) l mol(-1) s(-1). The activation enthalpy and entropy for the process was determined to 126 kJ mol(-1) and 16.5 J mol(-1) K-1, respectively. Traces of oxygen were shown to inhibit the reduction process. Hence, the suggested catalytic activity of freshly precipitated U02 on the reduction of UO22+ by H-2 could not be confirmed.

  • 50.
    Ekeroth, Ella
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Roth, Olivia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    The relative impact of radiolysis products in radiation induced oxidative dissolution of UO22006Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 355, nr 1-3, s. 38-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relative impact of radiolysis products in radiation induced oxidative dissolution Of UO2 has been studied experimentally. The experiments were performed by y-irradiating an aqueous solution containing HCO3 and a UO2-pellet. The U(VI) concentration in the solution was measured as a function of irradiation time. The aqueous solution was saturated with Ar, N2O, N2O/O-2 (80/20), air and O-2 in order to vary the conditions and the initial oxidant yields. The measured rate of oxidation was significantly higher for the O-2- and air saturated systems compared to the other systems. Using oxidant concentrations derived from numerical simulations of the corresponding homogeneous systems and previously determined rate constants for oxidation Of UO2, the relative trend in rate of oxidation in the different systems was reproduced. The results from the simulations were also used to estimate the relative impact of the oxidative radiolysis products as a function of irradiation time, both for gamma- and alpha-irradiated systems. For 7-irradiated systems saturated with Ar, air or 02, the most important oxidant is H2O2 while for N2O- and N2O/O-2-saturated systems the most important oxidant is CO3.-. For a-irradiated systems the most important oxidant was found to be H2O2.

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