Lifetime Evaluation of Nuclear Grade Graphite in Advanced Very High Temperature Gas-cooled Reactor(VHTR) Core Environment Using HRTEM Microstructural Analysis

• Main Authors: Tsai, Shuo-Cheng, 蔡碩承
• Other Authors: Kai, Ji-Jung
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/90037126645186268046

博士 === 國立清華大學 === 工程與系統科學系 === 101 === In this work, Nuclear grade graphite were irradiated by 3 MeV C2+ ion under high temperatures(>600℃) and ultrahigh vacuum (<5x10-7torr) environment to simulate the same radiation damage level in High Temperature Gas-Cooled Reactor(HTGR) environment. Graphite {0002} and {21 ̅1 ̅0} plane were investigated by FEG-TEM high resolution images. Fast Fourier transform was applied to calculate the average lattice parameters after irradiation. Microstructural evolution analyzed in this study including change of lattice parameters、disorder coefficients were intergraded with structure factor、pore generation factor to develop a model for lifetime and volume change evaluation inside nuclear grade graphite after different irradiation temperatures and fluences. Our model estimated that IG-110 irradiated at 600℃, its maximum volume change reached -6.02% and its lifetime is about 30.5dpa which is very close to experiment carried by neutron. For ATR-2E graphite, its lifetime reaches 25.5dpa in the same irradiated temperature(600℃). At higher irradiated temperature (800), both the lifetime of two graphite decayed seriously. (lifetime is 25.5dpa for IG-110 and 18.5dpa for ATR-2E). According to calculation, graphite block in the highest irradiation fluence region should be replaced every 5 years to insure the structural integrity under irradiation. Another part of this study showed calculation results of the energy storage inside graphite at high temperature irradiation. At high temperature irradiation condition(>600℃), stored energy is less than 10cal/g. This value is quite small compared to previous study (500cal/g at 150℃). From our results, energy storage in graphite would no longer be a problem in VHTR environment.