Takeo Muroga

PKA spectral effects on subcascade structures and free defect survival ratio as estimated by cascade-annealing computer simulation

Calcul du rapport de survie des defauts libres par simulation dun «recuit de cascade» sur ordinateur a laide des codes MARLOWE et DAIQUIRI modifies dans differents cas de spectres datomes primaires. Calcul du nombre de sous-cascades a laide de MARLOWE

EDS investigation of solute-precipitate interactions in ferritic steels under irradiation

Abstract The local composition at exactly the same position of the specimen is measured before and after irradiation by energy-dispersive X-ray spectrometer (EDS) in a Fe-10Cr-2Mo ferritic/martensitic steel. Microchemical charges are especially analyzed at precipitates and at the nearby matrix (25 nm from boundaries). The precipitates are identified, beforehand, to be Cr-rich (M23C6), Mo-rich (mostly M6C), and Nb-rich (MC). The combination of EDS and microdiffraction techniques has made it possible to identify precipitates with the size of less than 20 nm in infoil conditions. After irradiation to 20 dpa by 1.25 MeV electrons at 500°C, enrichment of Si and depletion of Cr are observed at all precipitates and nearby matrices. By irradiation at 300°C, however, only significant enrichment of Si is observed. Since similar compositional changes are observed at grain boundaries irradiated at 500°C, the above decomposition is expected to be caused by defect-solute interactions. The present results extend our understanding of the mechanisms of precipitate rearrangements during irradiation.

Computer Simulation of Precipitate Recoil Resolution by Energetic Collision Cascades

Computer simulation calculations have been carried out of precipitate recoil resolution under energetic particle irradiations. Using MARLOWE code, recoil range distributions in complete cascade events from primary recoilswith energies between 1 to 100 keV are calculated in pure iron. From these results, precipitate shrinkage rate is estimated in various irradiation conditions. The resolution rate is found to be highly sensitive to projectile mass rather than projectile energy. This suggests a considerable difference of the resolution rate under heavy and light ion irradiations. Remarkable change in the precipitate size begins only after irradiations to several tens dpa. This implies that some precipitates, which are present at low to intermediate doses, can disappear at high doses by recoil resolution. It is shown, by comparison with fission neutron irradiation data, that the recoil resolution of tiny but numerous precipitates can be a factor to determine the incubation dose of void swelling.