Dommelen, JAW Hans  van

Geers, MGD Marc

Shah, Varun

van Dommelen, J.A.W. (Hans)

Geers, Marc G.D.

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 Spatially dependent kinetics of helium in tungsten under fusionconditionsCitation for published version (APA):Shah, V., van Dommelen, J. A. W., & Geers, M. G. D. (2018). Spatially dependent kinetics of helium in tungstenunder fusion conditions. Poster session presented at Mate Poster Award 2018.Document status and date:Published: 01/01/2018Document Version:Publisher’s PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 08. Jul. 2024Mul�-scale Mechanics of Tungsten :              Structure Evolu�on     V. Shah, J.A.W van Dommelen, M.G.D. GeersV.Shah1@tue.nl/ department of mechanical engineeringV. Shah, J.A.W. van Dommelen, M.G.D. GeersSpa�ally dependent kine�cs of helium in tungsten under fusion condi�onsV.Shah1@tue.nlDEPARTMENT OF MECHANICAL ENGINEERINGMechanics of Materials DivertorHeat NeutronsH, He ionsPlasma facingcomponent3.3 m28 mmTungsten monoblocksNeutron Irradia�on Helium Implanta�onIVIIIIV VV VIVIIIIV VV VPerfect la�ceScale: nm 1. Introduc�onTri�um NDeuterium HeliumNeutron17.6 MeVEnergyFusion N N N N NUnirradiated state In tokamak based nuclear reactors (ITER, DEMO), the divertor component made out of Tungsten (W) (Figure 1 - le�) performs the vital func�on of extrac�ng heat and helium - ash from the burning plasma. Further, predic�ng the life�me of the divertor component requires an in depth understanding of the irradia�on damage mechanisms, where the fast neutrons along with high concentra�on of helium and high temperatures will induce microstructral changes (Figure 1 - right), thereby influencing  the material proper�es. The goal is to predict the long term behaviour of helium in rela�on to the irradia�on damage and the recrystalliza�on process in tungsten. Figure 1: Schema�c of Tokamak inner view (JET) and water cooled tungsten monoblock along with the neutron and helium assisted irradia�on damage mechanisms.    Defect produc�on by neutronsSelf - inters��al atom (I)Clusters - Vn , InFree He diffusion Trapping at neutroninduced defects:Bubble forma�onvs.*Source: EUROfusionVacancy (V)4. Conclusion and OutlookBased on the results for an irradia�on �me of 10 hours, it is observed that  pronounced clustering of helium with vacancies results in the forma�on of small helium bubbles in the sub-surface region. Addi�onally, accoun�ng for the mobility of helium based clusters, has a huge influence on the overall defect evolu�on and the associated  la�ce stored energy. For future work, larger cluster sizes in the current model will be incorporated by using an appropriate averaging scheme and the influence of helium on the kine�cs of recrystalliza�on process will be inves�gated.5. References[4] C. S. Becquart  and C. Domain 2009 J. Nucl. Mater. 385.2 223[3] Y. Li et al. 2012 J. Nucl. Mater. 431.1 26[2] T. Faney and B. D. Wirth 2014 Modelling Simul. Mater. Sci. Eng. [1] T. Jourdan et al. 2014  J. Nucl. Mater. 444.1. 298   2. Methodology: Kine�c rate theory Coupled set of ODE - PDE: Diffusion - Reac�on system.One dimensional diffusion of mobile defect/clusters alongthe monoblock depth.Evolu�on and interac�on of irradi�on induced defects/clustersBoundary condi�ons  - Desorp�on and zero flux.SourceDiffusion Reac�on LossW monoblockabTemporalevolu�onSpa�al domain10 MWm-2n n+1 growth+-shrinkageLoss of mobiledefects at sinksDisloca�ons (ρdisl.)Grain boundaries (gs)ρdisl.gsSink strengthParameteriza�onSource term: BCA and MD simula�ons.Binding energy between defects : DFT and MD simula�ons.Migra�on energy of defects : MD simula�ons.Figure 2: Kine�c rate theory master equa�on: Evolu�on and interac�on of defects under irradia�on condi�ons.ab0 1 2 3 4 5 6 7 8 9 10 11 12 13 1414131211109876543210Number of Helium in cluster [ # n]Number of Vacancies in cluster [ # m ]0 1 2 3 4 5 6 7 8 9 10 11 12 13 1414131211109876543210Number of Helium in cluster [ # n]Number of Vacancies in cluster [ # m ]3. Results   Clustering of helium with vacancies: Nuclea�on of small bubbles (sub-surface)Overall defect evolu�on: highly sensi�ve to mobility of clustersHen Immobile; n > 1 Hen mobile; n > 1Forma�on of He rich HenVm clusters HenVm clusters - n/m ra�o < 1:   ConcHe based clusters:   Conc.V based cluster:     Conc. pronounced He-V clusteringHe based clusters:   Conc.Increased He losses to sinksHenVm distribu�on; x ≈ 20 nm1001051010101510201025a) Influence of Hen clusters mobility on defect evolu�on; tirradia�on = 10 hrs b) Influence of defect conc. on la�ce stored energy; tirradia�on = 10 hrsInfluence of temperatureInfluence of He defect mobilityLa�ce stored energy: Forma�on energies of defectsHen Immobile: Higher Estored owing to lowerI - V recombina�ons events      V immobiliza�onHen mobile: Lower Estored         Hen losses to sinkshigher I - V recombina�on eventsLower temperature: Higher concentra�on of defectsHigher EstoredLower mobility of defects

Spatially dependent kinetics of helium in tungsten under fusion conditions

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