SYMPOSIA PAPER Published: 01 February 2018
STP159720160040

Effect of Alloying Elements, Cold Work, and Hydrogen on the Irradiation-Induced Growth Behavior of Zirconium Alloy Variants

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In-reactor dimensional changes in zirconium-based alloys result from a complex interplay of many factors, such as (1) alloy type and composition, including the addition of elements such as niobium, iron, and tin; (2) fabrication process, including cold work, texture, and residual stresses; (3) irradiation temperature; and (4) hydrogen levels. In many cases, the observed dimensional changes in light water reactor fuel-assembly components—especially at high exposures—cannot be fully explained based on current growth and creep models. Therefore, a systematic approach was taken in this multiyear (2005–2011) Nuclear Fuel Industry Research Program investigation. The objective was to measure stress-free irradiation-induced growth (IIG) of specially fabricated alloys through irradiation under controlled conditions in the BOR-60 fast-flux test reactor up to a high fluence of approximately 2 × 1026 m−2 (E > 1 MeV)—equivalent to maximum of approximately 37 dpa exposure—followed by postirradiation examinations (PIEs). Irradiation temperature was within a narrow temperature range (320 ± 10°C). The PIEs included dimensional-change and microhardness measurements, metallography and hydride etching, and scanning transmission electron microscopy (STEM) or transmission electron microscopy (TEM).

All irradiation samples (typically flat rectangular coupons or curvilinear cutouts of cladding tubes sized 35 by 6.5 by 0.8 mm) were prefilmed to avoid the uptake of impurity hydrogen from sodium-cooled BOR-60. A wide variety of samples representing standard LWR cladding alloys with and without prehydriding (approximately 116 to approximately 718 ppm) as well as special compositions with iron contents (100 to 4,000 ppm) were irradiated. The irradiation in BOR-60 was done in five different stages (eight microcycles) and lasted approximately 18 months with interim and final growth measurements made using a high precision-length measurement device. Results of the extensive investigation include: significant effects of Fe, Nb, and hydrogen additions; quantification of growth rates from low to very high fluences (dpas); measurement of volume changes; and correlation of growth with -component dislocation densities.

Author Information

Yagnik, Suresh
EPRI, Palo Alto, CA, US
Adamson, Ronald
Zircology Plus, Fremont, CA, US
Kobylyansky, Gennady
Research Institute of Atomic Reactors, RU
Chen, Jen-Hung
Institute of Nuclear Energy Research, Lungtan, Taoyuan, TW
Gilbon, Didier
CEA, Saclay Center, Gif-sur-Yvette, FR
Ishimoto, Shinji
Global Nuclear Fuel, Yokosuka-Shi, Kanagawa-ken, JP
Fukuda, Takuji
Nuclear Fuel Industry, Tokai-mura, Naka-gun, Ibaraki, JP
Hallstadius, Lars
Westinghouse, Vasteras, SE
Obukhov, Alexander
Research Institute of Atomic Reactors, RU
Mahmood, Sheikh
, Pleasanton, CA, US
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Developed by Committee: B10
Pages: 748–795
DOI: 10.1520/STP159720160040
ISBN-EB: 978-0-8031-7642-3
ISBN-13: 978-0-8031-7641-6