Effect of helium production on swelling of F82H irradiated in HFIR

Vacancies and interstitial type dislocation loops of two fusion reactor candidate materials (V-4Cr-4Ti and F82H) after fission and fusion neutron irradiation were studied by positron annihilation lifetime spectroscopy. Fusion neutron irradiation was performed in the FNS of JAERI, and fission neutron irradiation was performed in the KUR of Kyoto University. The neutron irradiation dose was about 1 Â 10 À6 -1 Â 10 À4 dpa, and the irradiation temperatures were room temperature and 673 K. In the irradiation at room temperature, the defects (mainly dislocation loops) in both alloys were detected even at a low irradiation dose of 10 À6 dpa and the mean lifetime of positrons increased as the irradiation dose increased. The effects of the fission and fusion neutron irradiation on the point defect production were almost the same if they were compared at the same dpa. This can be explained by the fact that the number of subcascades, which is an important factor for the defect formation at room temperature, is proportional to dpa in these metals. In contrast, an effect of cascade size was found for the irradiation at 673 K. Dislocation loops were detected only in the fusion-neutron-irradiated F82H at 673 K.

Section: Specimensmentioning

confidence: 99%

Point Defect Formation in V-4Cr-4Ti and F82H Irradiated with Fission and Fusion Neutrons

Sato

Yoshiie

et al. 2005

“…Radiation hardening is induced by the formation of defect clusters, and it can be evaluated by Orowan's theory for athermal bowing of dislocations around obstacles on a slip plane. 38,39) The formation and growth of defect clusters depends on irradiation parameters such as temperature, dpa, dpa rate and helium production rate, 18,22,23,40,41) and the microstructures of the irradiated F82H+ 10 B, F82H+ 11 B, and F82H+…”

Section: Introductionmentioning

confidence: 99%

Effects of Helium Production and Heat Treatment on Neutron Irradiation Hardening of F82H Steels Irradiated with Neutrons

Wakai¹,

Taguchi²,

Yamamoto³

et al. 2005

The influcence of addition of 10 B and 11 B on radiation hardening as a function of irradiation temperature was examined in reducedactivation martensitic F82H+B steels (8Cr-2W-0.2V-0.04Ta-0.1C-0.006B). Specimens used were 10 B doped, 10 B+ 11 B doped and 11 B doped F82H steels. Helium concentration produced in the specimens through 10 B(n, ) 7 Li reaction was measured from about 15 to about 330 appm. Radiation hardening of the specimens irradiated at 300 C to 2.3 dpa and 150 C to 1.9 dpa was observed. Increment of radiation hardening possibly due to helium in the specimen irradiated at 300 C tended to increase slightly with increasing helium production in tensile test at 20 C, but it was not observed for 150 C irradiation. Therefore, it can be mentioned that the enhancement of radiation hardening in the 10 B( 11 B) doped steels depends on irradiation temperature. The dependence of radiation hardening on tempering time was also examined for F82H-std irradiated at 150 C to 1.9 dpa. Increment of yield strength of F82H-std tended to increase with increasing tempering time. The relation between the shift of DBTT and the increment of yield strength due to irradiation suggest that the extension of tempering time or the increase of tempering temperature would be beneficial for mechanical properties of F82H-std.

“…In order to examine the effect of gas atoms on materials properties, one is possible to use the reaction of 10 B(n; ) 7 Li in steels doped with 10 B and irradiating with thermal neutrons in a mixed-spectrum fission reactor, such as the high flux isotope reactor (HFIR) and Japan Materials Testing Reactor (JMTR). 6) The roles of boron addition were investigated to obtain higher strength with heavy thickness for boron treatment and superior toughness of weld bond of large heat-input welded steel plane. The effect of additions of B, N and Ti elements on the toughness and microstructures was very effective.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties and Microstructure of F82H Steel doped with Boron or Boron and Nitrogen as a Function of Heat Treatment

Wakai¹,

Sato²,

Sawai³

et al. 2004

Effect of heat treatment on mechanical properties and microstructures of Fe-8Cr-2W-0.1C-0.2V-0.04Ta martensitic steel F82H doped with about 60 mass ppm B or both of 60 mass ppm B and 200 mass ppm N has been examined. The normalization was heated at temperatures from 950 to 1250 C for 1.8 ks, followed by air cooling or water quenching. After tempering treatment at 780 C or 750 C, the distributions of boron, boron nitride and oxygen were measured by a secondary ion mass spectrometry (SIMS). Optical microstructural observation and tensile and Charpy impact tests were performed also. In the boron doped F82H the tensile properties were similar to the non-doped F82H, but the ductilebrittle transition temperature (DBTT) shifted from À43 C to 15 C. SIMS images with high intensity of boron were observed in localized regions of the boron doped F82H. Water quenching reduced the DBTT shift, about 30 C, and the localized boron intensity was slightly decreased. In the boron and nitrogen doped tempered-F82H heat-treated by the water quenching from the normalizing temperature, the properties of tensile and Charpy impact were similar to the non doped F82H, and no pronounced localized boron image was observed in the SIMS image and no intensities of oxides and boron nitride were observed either.