title: Assessment and modification of an ion source grid design in KSTAR neutral beam system.
abstract: A new 2 MW NB (Neutral Beam) ion source for supplying 3.5 MW NB heating for the KSTAR campaign was developed in 2012 and its grid was made from OFHC (Oxygen Free High Conductivity) copper with rectangular cooling channels. However, the plastic deformation such as a bulging in the plasma grid of the ion source was found during the overhaul period after the 2012 campaign. A thermal-hydraulic and a thermo-mechanical analysis using the conventional code, ANSYS, were carried out and the thermal fatigue life assessment was evaluated. It was found that the thermal fatigue life of the OFHC copper grid was about 335 cycles in case of 0.165 MW/m(2) heat flux and it gave too short fatigue life to be used as a KSTAR NB ion source grid. To overcome the limited fatigue life of the current design, the following methods were proposed in the present study: (1) changing the OHFC copper to CuCrZr, copper-alloy or (2) adopting a new design with a pure Mo metal grid and CuCrZr tubes. It is confirmed that the proposed methods meet the requirements by performing the same assessment.
authors.affiliation: Korea Atomic Energy Research Institute, Daedeok-daero 1045, Daejeon 305-353, South Korea.
authors.forename: Dong Won
authors.initials: DW
authors.lastname: Lee
authors.affiliation: Korea Atomic Energy Research Institute, Daedeok-daero 1045, Daejeon 305-353, South Korea.
authors.forename: Kyu In
authors.initials: KI
authors.lastname: Shin
authors.affiliation: Korea Atomic Energy Research Institute, Daedeok-daero 1045, Daejeon 305-353, South Korea.
authors.forename: Hyung Gon
authors.initials: HG
authors.lastname: Jin
authors.affiliation: Korea Atomic Energy Research Institute, Daedeok-daero 1045, Daejeon 305-353, South Korea.
authors.forename: Bo Guen
authors.initials: BG
authors.lastname: Choi
authors.affiliation: Korea Atomic Energy Research Institute, Daedeok-daero 1045, Daejeon 305-353, South Korea.
authors.forename: Tae-Seong
authors.initials: TS
authors.lastname: Kim
authors.affiliation: Korea Atomic Energy Research Institute, Daedeok-daero 1045, Daejeon 305-353, South Korea.
authors.forename: Seung Ho
authors.initials: SH
authors.lastname: Jeong