Nuclear facility aging is one of the biggest problems encountered in nuclear engineering. Radiation damage is among one of the aging causes. This kind of damage is an important factor of mechanical properties deterior...Nuclear facility aging is one of the biggest problems encountered in nuclear engineering. Radiation damage is among one of the aging causes. This kind of damage is an important factor of mechanical properties deterioration. The interest of this study is on the Es-Salam research reactor aluminum vessel aging due to neutron radiation. Monte Carlo(MC) simulations were performed by MCNP6 and SRIM codes to estimate the defects created by neutrons in the vessel. MC simulations by MCNP6 have been performed to determine the distribution of neutron fluence and primary knock-on atom(PKA) creation. Considering our boundary conditions of the calculations, the helium and hydrogen gas production in the model at a normalized total neutron flux of 6.62×10^(12) n/cm^2 s were determined to be 2.86 × 10~8 and 1.33 × 10~9 atoms/cm^3 s,respectively. The SRIM code was used for the simulation of defects creation(vacancies, voids) in the aluminum alloy of the Es-Salam vessel(EsAl) by helium and hydrogen with an approximate energy of 11 MeV each.The coupling between the two codes is based upon postprocessing of the particle track(PTRAC) output file generated by the MCNP6. A small program based on the Mat Lab language is performed to condition the output file MCNP6 in the format of a SRIM input file. The concentration of silicon was determined for the vessel by the calculation of the total rate of ^(27)Al(n,γ)^(28)Si reaction. The DPA(displacement per atom) was calculated in SRIM according to R.E. Stoller recommendations; the calculated value is 0.02 at a fast neutron fluence 1.89 × 10^(19) n/cm^2.RCC-MRx standard for 6061-T6 aluminum was used for the simulation of the evolution of mechanical properties for high fluence. The calculated values of nuclear parameters and DPA obtained were in agreement with the experimental results from the Oak Ridge High Flux Isotope Reactor(HFIR) reported by Farrell and coworkers.展开更多
Bituminous sub-ballast is an alternative solution to the unbound granular sub-ballast used in the railway track due to several benefits that it can provide. Indeed, it contributes to maintain the moisture content in t...Bituminous sub-ballast is an alternative solution to the unbound granular sub-ballast used in the railway track due to several benefits that it can provide. Indeed, it contributes to maintain the moisture content in the subgrade unchanged during all year. This decreases the subgrade deterioration process. Moreover, the presence of bituminous sub-ballast can also reduce vertical stiffness variations on the track; it can have a positive effect in the maintenance needs at transition sections （bridge-embankment） and in the attenuation of the vibrations induced by the rail traffic. Despite the importance of the presence of the bituminous sub-ballast to conceive the construction and/or rehabilitation of sustainable infrastructure, in literature, there are only fragmentary information regarding the definition of benchmark criteria for their mix design. The superpave mix design approach used in road domain is applied systematically in the railway domain, without being adjusted for different load configuration of the rail track system. This research work aims at defining the benchmark criteria for the bituminous sub-ballast mix design to reduce the approximations involved in the recipe optimization due to the limitation of applying the superpave system in the railway domain. The methodology proposed aims at selecting the RESAL （rail equivalent single axle load） and therefore, transforming the entire traffic spectrum on the track lines in number of ESALs. Afterwards, the Ndesign has been calculated as function of the rail traffic level. Finally, a case study of bituminous sub-ballast mix design has been investigated for a first verification of the methodology proposed.展开更多
文摘Nuclear facility aging is one of the biggest problems encountered in nuclear engineering. Radiation damage is among one of the aging causes. This kind of damage is an important factor of mechanical properties deterioration. The interest of this study is on the Es-Salam research reactor aluminum vessel aging due to neutron radiation. Monte Carlo(MC) simulations were performed by MCNP6 and SRIM codes to estimate the defects created by neutrons in the vessel. MC simulations by MCNP6 have been performed to determine the distribution of neutron fluence and primary knock-on atom(PKA) creation. Considering our boundary conditions of the calculations, the helium and hydrogen gas production in the model at a normalized total neutron flux of 6.62×10^(12) n/cm^2 s were determined to be 2.86 × 10~8 and 1.33 × 10~9 atoms/cm^3 s,respectively. The SRIM code was used for the simulation of defects creation(vacancies, voids) in the aluminum alloy of the Es-Salam vessel(EsAl) by helium and hydrogen with an approximate energy of 11 MeV each.The coupling between the two codes is based upon postprocessing of the particle track(PTRAC) output file generated by the MCNP6. A small program based on the Mat Lab language is performed to condition the output file MCNP6 in the format of a SRIM input file. The concentration of silicon was determined for the vessel by the calculation of the total rate of ^(27)Al(n,γ)^(28)Si reaction. The DPA(displacement per atom) was calculated in SRIM according to R.E. Stoller recommendations; the calculated value is 0.02 at a fast neutron fluence 1.89 × 10^(19) n/cm^2.RCC-MRx standard for 6061-T6 aluminum was used for the simulation of the evolution of mechanical properties for high fluence. The calculated values of nuclear parameters and DPA obtained were in agreement with the experimental results from the Oak Ridge High Flux Isotope Reactor(HFIR) reported by Farrell and coworkers.
文摘Bituminous sub-ballast is an alternative solution to the unbound granular sub-ballast used in the railway track due to several benefits that it can provide. Indeed, it contributes to maintain the moisture content in the subgrade unchanged during all year. This decreases the subgrade deterioration process. Moreover, the presence of bituminous sub-ballast can also reduce vertical stiffness variations on the track; it can have a positive effect in the maintenance needs at transition sections （bridge-embankment） and in the attenuation of the vibrations induced by the rail traffic. Despite the importance of the presence of the bituminous sub-ballast to conceive the construction and/or rehabilitation of sustainable infrastructure, in literature, there are only fragmentary information regarding the definition of benchmark criteria for their mix design. The superpave mix design approach used in road domain is applied systematically in the railway domain, without being adjusted for different load configuration of the rail track system. This research work aims at defining the benchmark criteria for the bituminous sub-ballast mix design to reduce the approximations involved in the recipe optimization due to the limitation of applying the superpave system in the railway domain. The methodology proposed aims at selecting the RESAL （rail equivalent single axle load） and therefore, transforming the entire traffic spectrum on the track lines in number of ESALs. Afterwards, the Ndesign has been calculated as function of the rail traffic level. Finally, a case study of bituminous sub-ballast mix design has been investigated for a first verification of the methodology proposed.
