Vapor shielding models and the energy absorbed by divertor targets during transient events

Skovorodin, D. I.; Pshenov, A. A.; Arakcheev, A. S.; Eksaeva, E. A.; Marenkov, E. D.; Krasheninnikov, S. I.

doi:10.1063/1.4939537

Title: Vapor shielding models and the energy absorbed by divertor targets during transient events

Journal Article · Mon Feb 01 00:00:00 EST 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4939537· OSTI ID:1469154

Skovorodin, D. I. ^[1];

^[2]; Arakcheev, A. S. ^[1]; Eksaeva, E. A. ^[2]; Marenkov, E. D. ^[2]; Krasheninnikov, S. I. ^[3]

Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation)
National Research Nuclear Univ. MEPhI, Moscow (Russian Federation)
National Research Nuclear Univ. MEPhI, Moscow (Russian Federation); Univ. of California, San Diego, CA (United States)

The erosion of divertor targets caused by high heat fluxes during transients is a serious threat to ITER operation, as it is going to be the main factor determining the divertor lifetime. Under the influence of extreme heat fluxes, the surface temperature of plasma facing components can reach some certain threshold, leading to an onset of intense material evaporation. The latter results in formation of cold dense vapor and secondary plasma cloud. This layer effectively absorbs the energy of the incident plasma flow, turning it into its own kinetic and internal energy and radiating it. This so called vapor shielding is a phenomenon that may help mitigating the erosion during transient events. In particular, the vapor shielding results in saturation of energy (per unit surface area) accumulated by the target during single pulse of heat load at some level E_max. Matching this value is one of the possible tests to verify complicated numerical codes, developed to calculate the erosion rate during abnormal events in tokamaks. The study presents three very different models of vapor shielding, demonstrating that E_max depends strongly on the heat pulse duration, thermodynamic properties, and evaporation energy of the irradiated target material. While its dependence on the other shielding details such as radiation capabilities of material and dynamics of the vapor cloud is logarithmically weak. The reason for this is a strong (exponential) dependence of the target material evaporation rate, and therefore the “strength” of vapor shield on the target surface temperature. As a result, the influence of the vapor shielding phenomena details, such as radiation transport in the vapor cloud and evaporated material dynamics, on the E_max is virtually completely masked by the strong dependence of the evaporation rate on the target surface temperature. However, the very same details define the amount of evaporated particles, needed to provide an effective shielding to the target, and, therefore, strongly influence resulting erosion rate. Finally and thus, E_max cannot be used for validation of shielding models and codes, aimed at the target material erosion calculations.

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Research Organization:: Univ. of California, San Diego, CA (United States); Budker Inst. of Nuclear Physics, Novosibirsk (Russian Federation); National Research Nuclear Univ. MEPhI, Moscow (Russian Federation)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES); Russian Foundation for Basic Research (RFBR); Russian Ministry of Education and Science

Grant/Contract Number:: FG02-04ER54739; 15-32-20669; 14.Y26.31.0008

OSTI ID:: 1469154

Alternate ID(s):: OSTI ID: 1236524

Journal Information:: Physics of Plasmas, Vol. 23, Issue 2; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 23 works

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Simulation study on the vapour shielding at solid walls under transient heat loads using weighted particle model Ibano, K.; Kikuchi, Y.; Tanaka, A. Contributions to Plasma Physics, Vol. 58, Issue 6-8 https://doi.org/10.1002/ctpp.201700160	journal	July 2018
Validating heat balance models for tungsten dust in cold dense plasmas Vignitchouk, L.; Ratynskaia, S.; Kantor, M. Plasma Physics and Controlled Fusion, Vol. 60, Issue 11 https://doi.org/10.1088/1361-6587/aadbcb	journal	September 2018
Diagnostics of the dynamics of material damage by thermal shocks with the intensity possible in the ITER divertor Vyacheslavov, L. N.; Arakcheev, A. S.; Bataev, I. A. Physica Scripta, Vol. 93, Issue 3 https://doi.org/10.1088/1402-4896/aaa119	journal	February 2018
Power handling limit of liquid lithium divertor targets Rindt, P.; Morgan, T. W.; Jaworski, M. A. Nuclear Fusion, Vol. 58, Issue 10 https://doi.org/10.1088/1741-4326/aad290	journal	July 2018
Power handling and vapor shielding of pre-filled lithium divertor targets in Magnum-PSI Rindt, P.; Morgan, T. W.; van Eden, G. G. Nuclear Fusion, Vol. 59, Issue 5 https://doi.org/10.1088/1741-4326/ab0560	journal	March 2019
Estimation of suppressed erosion by vapor shielding at Be and W walls under transient loads Ibano, Kenzo; Kikuchi, Yusuke; Togo, Satoshi Nuclear Fusion, Vol. 59, Issue 7 https://doi.org/10.1088/1741-4326/ab0977	journal	May 2019
Influence of a magnetic field on plasma energy transfer to material surfaces in edge-localized mode simulation experiments with QSPA-M Garkusha, I. E.; Makhlai, V. A.; Petrov, Yu. V. Nuclear Fusion, Vol. 59, Issue 8 https://doi.org/10.1088/1741-4326/ab1932	journal	June 2019
Vapor shielding of liquid lithium divertor target during steady state and transient events Marenkov, E.; Pshenov, A. Nuclear Fusion, Vol. 60, Issue 2 https://doi.org/10.1088/1741-4326/ab5eb5	journal	January 2020

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