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Title: Surface analysis of TFTR vacuum vessel samples subjected to the post-weld heat treatment

To ensure the dimensional stability of the Tokamak Fusion Test Reactor (TFTR) vacuum vessel, it is necessary to perform a post-weld heat treatment (PWHT). This process consists of heating the vessel segments to approx. 450/sup 0/C for 1.5 h. The large size of the segments precludes a vacuum bake previous to installation. Effects of the PWHT on the vacuum vessel surface were studied using small samples of vessel material which were subjected to a variety of PWHT procedures, including inert gas purges and different oven designs. Changes in topography and near-surface chemistry were investigated with SEM and sputter-Auger electron spectroscopy. These samples were compared with the surface properties of non-baked UHV-quality stainless steel. The primary difference noted between the PWHT samples and the non-baked control was the thickness of the passivation oxide layer. The thickness of this mixed oxide (FeO/Cr/sub 2/O/sub 3//NiO) on the control sample was less than or equal to 100 A. The thickness of the oxide layer on the heat-treated samples ranged between 230 to 350 A, depending on the method of the PWHT. The effect of hydrogen glow discharge cleaning on these thicker oxide layers, and the consequences of such heat treatment procedure relative to oxygenmore » impurity production in fusion devices are discussed.« less
Authors:
; ; ;
Publication Date:
OSTI Identifier:
7090436
Report Number(s):
PPPL-1722
TRN: 81-002502
DOE Contract Number:
AM02-76CH03073
Resource Type:
Technical Report
Research Org:
Princeton Univ., NJ (USA). Plasma Physics Lab.
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; TFTR REACTORS; PRESSURE VESSELS; AUGER ELECTRON SPECTROSCOPY; STABILITY; SURFACE PROPERTIES; CONTAINERS; ELECTRON SPECTROSCOPY; SPECTROSCOPY; THERMONUCLEAR REACTORS; TOKAMAK TYPE REACTORS 700209* -- Fusion Power Plant Technology-- Component Development & Materials Testing