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Vol.11 No.4previousAA SP22 (AA165-166-167-168-169-170-171) NT96

Academic Articles
Regular Paper Vol. 11 No. 4 (2020) p.163 - p.171
 

Applicability of ultrasonic-wave based method for integrity assessment of concrete severely damaged by heat

 

Vu Nhut LUU1,3*, Kenta MURAKAMI1, Thi Mai Dung DO1, Masahide SUZUKI1, Tomonori YAMADA2, Takuya SHIBATA2, Hiroyuki DAIDO2

 
1 Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata, 940-2188, Japan
2 Japan Atomic Energy Agency, Nakamaru 1-22, Yamadaoka, Naraha-machi, Futaba-gun, Fukushima, 979-0513, Japan
3 Vietnam Atomic Energy Institute (VINATOM), 59 Ly Thuong Kiet, Hoan Kiem, Hanoi, Viet Nam
 
Abstract
Previous studies on the effect of temperature on various types of concrete have been mainly focused on the case of fire in which the exposure duration is short. Limited data has been obtained regarding the effect of high temperature on concrete properties under severe accident condition in which the concrete structure may be exposed to heat radiation from melting nuclear fuels for a long time. The present study aimed to examine the applicability of the ultrasonic wave based method for concrete damaged extremely by heat simulating a severe accident. The conventional ultrasonic test was conducted in concrete cylindrical with the size of φ100 × 200 mm after exposure to high temperatures 105, 200, 400, 600, 700, 800 ℃. The results revealed that this method is sensitive to indicate thermal damage as results from water content loss and decomposition of portlandite. A strong correlation between dynamic and static elastic modulus was obtained for concrete exposed to temperature range of 25 to 400 ℃, corresponding to dynamic elastic modulus range from 20 - 40 GPa. The degradation within this range is due to water loss. At higher temperatures, the concrete integrity is not maintained due to the formation of cracks and the decomposition of cement paste phases, which cause a significant decay of the ultrasonic waves.
 
Keywords
Reactor Pressure Vessel, Probabilistic Fracture Mechanics, Pressurized Thermal Shock, Structural Integrity, Irradiation Embrittlement, Fracture Toughness, Thermal Transients
 
Full Paper: PDF
Article Information
Article history:
Received 05 December 2018
Accepted 31 January 2020