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Title: Extrapolation of Fracture Toughness Data for HT9 Irradiated at 360-390°C

Abstract

Following irradiation in the FFTF-AC01 test at 360°C to 5.5 x 1022 n/cm2, two HT9 samples tested at 30°C were measured to have fracture toughness levels of 28.2 and 31.9 MPa m1/2, respectively, whereas a third identical specimen tested at 205°C gave 126 MPa m1/2. Based on testing of notched tensile specimens from the same irradiation test, the low toughness was a result of brittle fracture. A similar low level of toughness has also been demonstrated in HT9 following irradiation at 250°C and therefore such behavior is reproducible. Using ASTM Standard E1921-02, which characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at instabilities, it is shown that these data can be analyzed by a Master Curve approach, and that the trend of the fracture toughness over a wider range of temperatures can be estimated. Master Curve analysis demonstrates that toughness will remain low over a wide range of temperatures near 30°C, but will degrade only slightly when temperatures drop to –10°C.

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
984680
Report Number(s):
PNNL-SA-43653
AT6020100; TRN: US201016%%1420
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Effects of Radiation on Materials: 22nd International Symposium on Effects of Radiation on Materials, 1475:99-110
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CLEAVAGE; EXTRAPOLATION; FERRITIC STEELS; FRACTURE PROPERTIES; IRRADIATION; RADIATIONS; TESTING; Fracture toughness, Neutron irradiation, Martensitic steel, Master curve analysis

Citation Formats

Gelles, David S., and Kurtz, Richard J. Extrapolation of Fracture Toughness Data for HT9 Irradiated at 360-390°C. United States: N. p., 2007. Web.
Gelles, David S., & Kurtz, Richard J. Extrapolation of Fracture Toughness Data for HT9 Irradiated at 360-390°C. United States.
Gelles, David S., and Kurtz, Richard J. Tue . "Extrapolation of Fracture Toughness Data for HT9 Irradiated at 360-390°C". United States. doi:.
@article{osti_984680,
title = {Extrapolation of Fracture Toughness Data for HT9 Irradiated at 360-390°C},
author = {Gelles, David S. and Kurtz, Richard J.},
abstractNote = {Following irradiation in the FFTF-AC01 test at 360°C to 5.5 x 1022 n/cm2, two HT9 samples tested at 30°C were measured to have fracture toughness levels of 28.2 and 31.9 MPa m1/2, respectively, whereas a third identical specimen tested at 205°C gave 126 MPa m1/2. Based on testing of notched tensile specimens from the same irradiation test, the low toughness was a result of brittle fracture. A similar low level of toughness has also been demonstrated in HT9 following irradiation at 250°C and therefore such behavior is reproducible. Using ASTM Standard E1921-02, which characterizes the fracture toughness of ferritic steels that experience onset of cleavage cracking at instabilities, it is shown that these data can be analyzed by a Master Curve approach, and that the trend of the fracture toughness over a wider range of temperatures can be estimated. Master Curve analysis demonstrates that toughness will remain low over a wide range of temperatures near 30°C, but will degrade only slightly when temperatures drop to –10°C.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}

Conference:
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  • The objective of this task is to provide estimated HT9 cladding and duct fracture toughness values for test (or application) temperatures ranging from -10°C to 200°C, after irradiation at temperatures of 360-390°C. This is expected to be an extrapolation of the limited data presented by Huang[1, 2]. This extrapolation is based on currently accepted methods (ASTM 2003 Standard E 1921-02), and other relevant fracture toughness data on irradiated HT9 or similar alloys.
  • The purpose of this work was to determine the fracture toughness behavior of HT9 and modified 9Cr-1Mo ferritic steels after neutron exposure to high doses. A summary is presented of the entire fracture toughness database for HT9 and 9Cr-1Mo generated at Hanford. Fracture toughness tests were recently performed on miniature specimens of HT9 and modified 9Cr-1Mo irradiated in FFTF to exposures ranging from 35 to about 100 dpa. At test temperatures ranging from 20 to 430{degree}C values of toughness and tearing modulus at 35 to 100 dpa were no lower than those obtained previously in tests conducted on specimens irradiatedmore » in EBR-II, despite differences in orientation between the EBR-II and FFTF specimens. 21 refs., 12 figs., 5 tabs.« less
  • The effect of neutron radiation on the mechanical properties of alloy HT9 was evaluated by conducting postirradiation tensile and fracture toughness tests. Samples of HT9 were irradiated in the Experimental Breeder Reactor 2 (EBR-II) and Fast Flux Test Facility (FFTF) as part of material experiments. In addition, selected samples were obtained from a duct used in fuel pin tests in FFTF. The peak neutron fluence for these samples was 15.9 {times} 10{sup 22} n/cm{sup 2} (E > 0.1 MeV), or about 80 dpa. Results of tests conducted at 205{degree}C and at ambient temperature showed that the irradiation temperature had amore » larger influence on the mechanical behavior than neutron fluence. Irradiation at temperatures below 400{degree}C produces a significant increase in the yield strength of HT9. At 360{degree}C, an increase of more than 80% was found for tests conducted at ambient temperature. Tests on notched tensile specimens that had been irradiated at low temperature exhibited a linear elastic behavior with failure occurring with no yielding or elongation. 9 refs., 20 figs., 4 tabs.« less
  • The temperature dependence of fracture toughness in HT9 steel irradiated to high doses was investigated using miniature three-point bend (TPB) fracture specimens. These specimens were from the ACO-3 fuel duct wall of the Fast Flux Test Facility (FFTF), in which irradiation doses were in the range of 3.2 144.8 dpa and irradiation temperatures in the range of 380.4 502.6 oC. A miniature specimen reuse technique has been established for this investigation: the specimens used were the tested halves of miniature Charpy impact specimens (~13 3 4 mm) with diamond-saw cut in the middle. The fatigue precracking for specimens and fracturemore » resistance (J-R) tests were carried out in a MTS servo-hydraulic testing machine with a vacuum furnace following the standard procedure described in the ASTM Standard E 1820-09. For each of five irradiated and one archive conditions, 7 to 9 J-R tests were performed at selected temperatures ranging from 22 C to 600 C. The fracture toughness of the irradiated HT9 steel was strongly dependent on irradiation temperatures rather than irradiation dose. When the irradiation temperature was below about 430 C, the fracture toughness of irradiated HT9 increased with test temperature, reached an upper shelf of 180 200 MPa m at 350 450 C and then decreased with test temperature. When the irradiation temperature 430 C, the fracture toughness was nearly unchanged until about 450 C and decreased with test temperature in higher temperature range. Similar test temperature dependence was observed for the archive material although the highest toughness values are lower after irradiation. Ductile stable crack growth occurred except for a few cases where both the irradiation temperature and test temperature are relatively low.« less
  • Fracture toughness J-R curve tests were conducted at room temperature on disk-shaped compact-tension DC(T) specimens of three vanadium alloys having a nominal composition of V-4Cr-4Ti. The alloys in the nonirradiated condition showed high fracture toughness; J{sub IC} could not be determined but is expected to be above 600 kJ/m{sup 2}. The alloys showed very poor fracture toughness after irradiation to 4 dpa at 390 C, e.g., J{sub IC} values of {approx}10 kJ/m{sup 2} or lower.