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Title: Physics basis for the first ITER tungsten divertor

Abstract

On the eve of component procurement, this paper discusses the present physics basis for the first ITER tungsten (W) divertor, beginning with a reminder of the key elements defining the overall design, and outlining relevant aspects of the Research Plan accompanying the new “staged approach” to ITER nuclear operations which fixes the overall divertor lifetime constraint. The principal focus is on the main design driver, steady state power fluxes in the DT phases, obtained from simulations using the 2-D SOLPS-4.3 and SOLPS-ITER plasma boundary codes, assuming the use of the low Z seeding impurities nitrogen (N) and neon (Ne). A new perspective on the simulation database is adopted, concentrating purely on the divertor physics aspects rather than on the core-edge integration, which has been studied extensively in the course of the divertor design evolution and is published elsewhere. Emphasis is placed on factors which may increase the peak steady state loads: divertor target shaping for component misalignment protection, the influence of fluid drifts, and the consequences of narrow scrape-off layer heat flux channels. All tend to push the divertor into an operating space at higher sub-divertor neutral pressure in order to remain at power flux densities acceptable for the targetmore » material. However, a revised criterion for the maximum tolerable loads based on avoidance of W recrystallization, sets an upper limit potentially ~50% higher than the previously accepted value of ~10 MW m-2, a consequence both of the choice of material and the finalized component design. Although the simulation database is currently restricted to the 2-D toroidally symmetric situation, considerable progress is now also being made using the EMC3-Eirene 3-D code suite for the assessment of power loading in the presence of magnetic perturbations for ELM control. Some new results for low input power corresponding to the early H-mode operation phases are reported, showing that even if realistic plasma screening is taken into account, significant asymmetric divertor heat fluxes may arise far from the unperturbed strike point. The issue of tolerable limits for transient heat pulses is an open and key question. A new scaling for ELM power deposition has shown that whilst there may be more latitude for operation at higher current without ELM control, the ultimate limit is likely to be set more by material fatigue under large numbers of sub-threshold melting events.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC); Russian Science Foundation
OSTI Identifier:
1560688
Alternate Identifier(s):
OSTI ID: 1611763
Grant/Contract Number:  
SC0012315; SC0013911; 17-12-01020
Resource Type:
Published Article
Journal Name:
Nuclear Materials and Energy
Additional Journal Information:
Journal Name: Nuclear Materials and Energy Journal Volume: 20 Journal Issue: C; Journal ID: ISSN 2352-1791
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; nuclear science & technology; ITER; tungsten; divertor; heat fluxes; SOLPS

Citation Formats

Pitts, R. A., Bonnin, X., Escourbiac, F., Frerichs, H., Gunn, J. P., Hirai, T., Kukushkin, A. S., Kaveeva, E., Miller, M. A., Moulton, D., Rozhansky, V., Senichenkov, I., Sytova, E., Schmitz, O., Stangeby, P. C., De Temmerman, G., Veselova, I., and Wiesen, S.. Physics basis for the first ITER tungsten divertor. Netherlands: N. p., 2019. Web. https://doi.org/10.1016/j.nme.2019.100696.
Pitts, R. A., Bonnin, X., Escourbiac, F., Frerichs, H., Gunn, J. P., Hirai, T., Kukushkin, A. S., Kaveeva, E., Miller, M. A., Moulton, D., Rozhansky, V., Senichenkov, I., Sytova, E., Schmitz, O., Stangeby, P. C., De Temmerman, G., Veselova, I., & Wiesen, S.. Physics basis for the first ITER tungsten divertor. Netherlands. https://doi.org/10.1016/j.nme.2019.100696
Pitts, R. A., Bonnin, X., Escourbiac, F., Frerichs, H., Gunn, J. P., Hirai, T., Kukushkin, A. S., Kaveeva, E., Miller, M. A., Moulton, D., Rozhansky, V., Senichenkov, I., Sytova, E., Schmitz, O., Stangeby, P. C., De Temmerman, G., Veselova, I., and Wiesen, S.. Thu . "Physics basis for the first ITER tungsten divertor". Netherlands. https://doi.org/10.1016/j.nme.2019.100696.
@article{osti_1560688,
title = {Physics basis for the first ITER tungsten divertor},
author = {Pitts, R. A. and Bonnin, X. and Escourbiac, F. and Frerichs, H. and Gunn, J. P. and Hirai, T. and Kukushkin, A. S. and Kaveeva, E. and Miller, M. A. and Moulton, D. and Rozhansky, V. and Senichenkov, I. and Sytova, E. and Schmitz, O. and Stangeby, P. C. and De Temmerman, G. and Veselova, I. and Wiesen, S.},
abstractNote = {On the eve of component procurement, this paper discusses the present physics basis for the first ITER tungsten (W) divertor, beginning with a reminder of the key elements defining the overall design, and outlining relevant aspects of the Research Plan accompanying the new “staged approach” to ITER nuclear operations which fixes the overall divertor lifetime constraint. The principal focus is on the main design driver, steady state power fluxes in the DT phases, obtained from simulations using the 2-D SOLPS-4.3 and SOLPS-ITER plasma boundary codes, assuming the use of the low Z seeding impurities nitrogen (N) and neon (Ne). A new perspective on the simulation database is adopted, concentrating purely on the divertor physics aspects rather than on the core-edge integration, which has been studied extensively in the course of the divertor design evolution and is published elsewhere. Emphasis is placed on factors which may increase the peak steady state loads: divertor target shaping for component misalignment protection, the influence of fluid drifts, and the consequences of narrow scrape-off layer heat flux channels. All tend to push the divertor into an operating space at higher sub-divertor neutral pressure in order to remain at power flux densities acceptable for the target material. However, a revised criterion for the maximum tolerable loads based on avoidance of W recrystallization, sets an upper limit potentially ~50% higher than the previously accepted value of ~10 MW m-2, a consequence both of the choice of material and the finalized component design. Although the simulation database is currently restricted to the 2-D toroidally symmetric situation, considerable progress is now also being made using the EMC3-Eirene 3-D code suite for the assessment of power loading in the presence of magnetic perturbations for ELM control. Some new results for low input power corresponding to the early H-mode operation phases are reported, showing that even if realistic plasma screening is taken into account, significant asymmetric divertor heat fluxes may arise far from the unperturbed strike point. The issue of tolerable limits for transient heat pulses is an open and key question. A new scaling for ELM power deposition has shown that whilst there may be more latitude for operation at higher current without ELM control, the ultimate limit is likely to be set more by material fatigue under large numbers of sub-threshold melting events.},
doi = {10.1016/j.nme.2019.100696},
journal = {Nuclear Materials and Energy},
number = C,
volume = 20,
place = {Netherlands},
year = {2019},
month = {8}
}

Journal Article:
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https://doi.org/10.1016/j.nme.2019.100696

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