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Title: Final Report: Safety of Plasma Components and Aerosol Transport During Hard Disruptions and Accidental Energy Release in Fusion Reactor

Abstract

Safety considerations in large future fusion reactors like ITER are important before licensing the reactor. Several scenarios are considered hazardous, which include safety of plasma-facing components during hard disruptions, high heat fluxes and thermal stresses during normal operation, accidental energy release, and aerosol formation and transport. Disruption events, in large tokamaks like ITER, are expected to produce local heat fluxes on plasma-facing components, which may exceed 100 GW/m{sup 2} over a period of about 0.1 ms. As a result, the surface temperature dramatically increases, which results in surface melting and vaporization, and produces thermal stresses and surface erosion. Plasma-facing components safety issues extends to cover a wide range of possible scenarios, including disruption severity and the impact of plasma-facing components on disruption parameters, accidental energy release and short/long term LOCA's, and formation of airborne particles by convective current transport during a LOVA (water/air ingress disruption) accident scenario. Study, and evaluation of, disruption-induced aerosol generation and mobilization is essential to characterize database on particulate formation and distribution for large future fusion tokamak reactor like ITER. In order to provide database relevant to ITER, the SIRENS electrothermal plasma facility at NCSU has been modified to closely simulate heat fluxes expected in ITER.

Authors:
;
Publication Date:
Research Org.:
North Carolina State University, Department of Nuclear Engineering, Raleigh, NC (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
763378
DOE Contract Number:
FG02-96ER54363
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 14 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCIDENTS; AEROSOLS; DISTRIBUTION; EVALUATION; EVAPORATION; LICENSING; MELTING; PARTICULATES; PLASMA; SAFETY; THERMAL STRESSES; THERMONUCLEAR REACTORS; TRANSPORT

Citation Formats

Bourham, Mohamed A., and Gilligan, John G. Final Report: Safety of Plasma Components and Aerosol Transport During Hard Disruptions and Accidental Energy Release in Fusion Reactor. United States: N. p., 1999. Web. doi:10.2172/763378.
Bourham, Mohamed A., & Gilligan, John G. Final Report: Safety of Plasma Components and Aerosol Transport During Hard Disruptions and Accidental Energy Release in Fusion Reactor. United States. doi:10.2172/763378.
Bourham, Mohamed A., and Gilligan, John G. Sat . "Final Report: Safety of Plasma Components and Aerosol Transport During Hard Disruptions and Accidental Energy Release in Fusion Reactor". United States. doi:10.2172/763378. https://www.osti.gov/servlets/purl/763378.
@article{osti_763378,
title = {Final Report: Safety of Plasma Components and Aerosol Transport During Hard Disruptions and Accidental Energy Release in Fusion Reactor},
author = {Bourham, Mohamed A. and Gilligan, John G.},
abstractNote = {Safety considerations in large future fusion reactors like ITER are important before licensing the reactor. Several scenarios are considered hazardous, which include safety of plasma-facing components during hard disruptions, high heat fluxes and thermal stresses during normal operation, accidental energy release, and aerosol formation and transport. Disruption events, in large tokamaks like ITER, are expected to produce local heat fluxes on plasma-facing components, which may exceed 100 GW/m{sup 2} over a period of about 0.1 ms. As a result, the surface temperature dramatically increases, which results in surface melting and vaporization, and produces thermal stresses and surface erosion. Plasma-facing components safety issues extends to cover a wide range of possible scenarios, including disruption severity and the impact of plasma-facing components on disruption parameters, accidental energy release and short/long term LOCA's, and formation of airborne particles by convective current transport during a LOVA (water/air ingress disruption) accident scenario. Study, and evaluation of, disruption-induced aerosol generation and mobilization is essential to characterize database on particulate formation and distribution for large future fusion tokamak reactor like ITER. In order to provide database relevant to ITER, the SIRENS electrothermal plasma facility at NCSU has been modified to closely simulate heat fluxes expected in ITER.},
doi = {10.2172/763378},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Aug 14 00:00:00 EDT 1999},
month = {Sat Aug 14 00:00:00 EDT 1999}
}

Technical Report:

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  • Power loadings experienced by tokamak plasma facing components during normal operation and during off-normal events are discussed. A model for power and particle flow in the tokamak boundary layer is presented and model predictions are compared to infrared measurements of component heating. The inclusion of the full three-dimensional geometry of the component and of the magnetic flux surface is very important in the modeling. Experimental measurements show that misalignment of component armor tile surfaces by only a millimeter can lead to significant localized heating. An application to the design of plasma facing components for future machines is presented. Finally, thermalmore » loads expected during tokamak disruptions are discussed. The primary problems are surface melting and vaporization due to localized intense heating during the disruption thermal quench and volumetric heating of the component armor and structure due to localized impact of runaway electrons. 44 refs., 9 figs., 2 tabs.« less
  • The release and transport of activated materials-of-construction in a fusion reactor during an accident scenario involving overheating and ingress of oxidants is an important area of safety research. This investigation quantified material release characteristics that result from surface oxide spallation and vaporization from the steel alloys PCA and HT-9 in impure helium and air environments. Flowing air and helium, each containing specific quantities of O/sub 2/ and H/sub 2/O, were used to oxidize test sample surfaces at temperatures of 800/sup 0/ and 1000/sup 0/C for exposure times of <200 h. The changes and features observed are described and include: weight,more » oxide scale morphology, adherence and composition; alloy composition (including decarburization); and vaporization as fractional loss of alloying elements. Oxide scales formed were dominant in Mn and Cr but minor in Fe. The dominant volatilized elements detected were Mo, W, Cr, As, Mn, Sb, and Co. The implications of these data for safety analyses of activated material release are that following an accidental temperature excursion to 800/sup 0/C in an oxidizing environment, material transport by scale spallation and/or volatilization should be minor. Furthermore, the potential material release fractions at 1000/sup 0/C appear to be significantly lower than the release fractions used in early fusion safety analyses.« less
  • Thermal characteristics of a fusion reactor [International Thermonuclear Experimental Reactor (ITER) Conceptual Design Activity] during plasma disruptions have been analyzed by using a comprehensive safety analysis code for nuclear fusion reactors. The erosion depth due to disruptions for the armor of the first wall depends on the current quench time of disruptions occurring in normal operation. If it is possible to extend the time up to {approximately}50 ms, the erosion depth is considerably reduced. On the other hand, the erosion depth of the divertor is {approximately}570 {mu}m for only one disruption, which is determined only by the thermal flux duringmore » the thermal quench. This means that the divertor plate should be exchanged after about nine disruptions. Counter-measures are necessary for the divertor to relieve disruption influences. As other scenarios of disruptions, beta-limit disruptions and vertical displacement events were also investigated quantitatively. 13 refs., 5 figs.« less