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Conference Article: Variability of irradiation creep and swelling of HT9 irradiated to high neutron fluence at 400-600 deg.C

Toloczko, M.B.;Garner, F.A. (Pacific Northwest National Lab., Richland, WA (United States))

Abstract

Four tube-sets constructed from a combination of three lots of HT9 and two heat-treatments were examined after irradiation in FFTF-MOTA at four different temperatures between 400 and 600 deg. C. Diametral measurements indicated that small amounts of swelling occurred at 400 deg. C, with the magnitude of the swelling varying from tube-set to tube set. At 495, 550, and 600 deg. C no indications of swelling were observed. Over a limited stress range that decreased with increasing irradiation temperature, the irradiation creep was found to be proportional to the stress level and mirrored the swelling behavior, confirming the Bo + DS creep model. The creep compliance, Bo, appears to be about half of the observed in austenitic steels, whereas the creep-swelling coupling coefficient D, appears to be comparable to that of austenitics. At the highest stress levels examined, the value of the stress exponent became much greater than 1.0. Higher irradiation temperatures resulted in creep behavior with pronounced thermal creep characteristics: a primary creep transient was observed at the three higher irradiation temperatures and increased in magnitude with increasing irradiation temperature, while a stress exponent between 1.0 and 2.0 was observed at 550 deg. C.

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key words: Fast Neutron Spectrum Systems, Nuclear Technology
Reference:
Influence of high dose irradiation on core structural and fuel materials in advanced reactors. Technical committee meeting, Obninsk (Russian Federation), 16-19 Jun 1997
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--1039, pp:197-209