Study on Neutronics of Minor Actinides Transmutation in Accelerator Driven System Reactor
Amer Ahmed Abdullah Al Qaaod;
Abstract
The study of accelerator driven system (ADS) implies the investigation of some important subcritical multiplication parameters which include subcritical multiplication factor ks, neutron multiplication M and external source efficiency φ*, since they play an important role in the ADS neutronic designs. The purpose of the study is to investigate the neutronics design of ADS including several effects, such as, the external neutron source importance, the neutron spectrum and the burnup variation through the evaluation time. This purpose was achieved by studying three topics.
The first is to numerically investigate the effects of changing the external neutron source cylindrical target material, radius, source, position, and the electron beam energy, on the final neutron production and the external source efficiency of the subcritical system of TRIGA Mark II ADS research reactor.
The study showed that the maximum neutron yield for W, Pb, and W-Cu targets was obtained at radii of 3.25 cm, 3.5 cm and 7 cm, respectively. The highest source neutron production was associated with the W, followed by the W-Cu, and then the Pb targets for different radii and incident electron beam energies. The maximum source efficiency φ* for W, Pb, and W-Cu targets was achieved when the source was placed at the center of the core, which may vary for different core configuration and fuel distribution. When the source was placed inside the core, the Pb target clearly produced the maximum source efficiency among the three targets; while outside the core, the W target slightly did. Moreover, although the source neutrons (photoneutron production) were found positively correlated to the incident beam energy on all target materials. The source efficiency do not change significantly with incident beam energy onto the tungsten target.
The second is to study the multiplication characteristics of TRIGA MARK II ADS reactor with Plutonium and minor actinides in heterogeneous and homogenous distributions.
After choosing the best properties and location of the source in the first section of the present thesis, the feasibility of Pu and MA transmutation in the TRIGA Mark II reactor was numerically examined with two core configurations in forms of heterogeneous and homogeneous distributions. The results showed that the neutron spectrum becomes softer along the change of configuration from heterogeneous to homogenous due to the presence of Pu and MA sample, and the neutron flux change significantly with the place and distribution of Pu and MA in the core. The heterogeneous distributions achieve slightly more fission rate for the Pu and MA due to the fast neutrons contribution. additionally, has been observed in case of heterogeneous configuration the neutron flux distribution decreases because the neutrons captured by 239Pu and 241Am, which means there is possibility to transmute that material by the decay process. On the other side at homogenous distribution the total fission rate and the source efficiency was high remarkably. This is due to contribution of fuel fission neutrons. Where that the source efficiency is high, this will providing and decreasing an accelerator current which means the economic feasibility is high. Also, the effectiveness of the incident beam type and its energy on Pu and MA fission rate was studied. As a consequence of our results it is found that the best values for the subcritical multiplication parameters M, ks and φ* achieved with electron beam where the average energy (Eav) of the neutrons was ~1.18 MeV. The external source efficiency is found to be clearly higher for electron beam at the energy range from 20 to 60 MeV than proton beam at the same incident energy.
The first is to numerically investigate the effects of changing the external neutron source cylindrical target material, radius, source, position, and the electron beam energy, on the final neutron production and the external source efficiency of the subcritical system of TRIGA Mark II ADS research reactor.
The study showed that the maximum neutron yield for W, Pb, and W-Cu targets was obtained at radii of 3.25 cm, 3.5 cm and 7 cm, respectively. The highest source neutron production was associated with the W, followed by the W-Cu, and then the Pb targets for different radii and incident electron beam energies. The maximum source efficiency φ* for W, Pb, and W-Cu targets was achieved when the source was placed at the center of the core, which may vary for different core configuration and fuel distribution. When the source was placed inside the core, the Pb target clearly produced the maximum source efficiency among the three targets; while outside the core, the W target slightly did. Moreover, although the source neutrons (photoneutron production) were found positively correlated to the incident beam energy on all target materials. The source efficiency do not change significantly with incident beam energy onto the tungsten target.
The second is to study the multiplication characteristics of TRIGA MARK II ADS reactor with Plutonium and minor actinides in heterogeneous and homogenous distributions.
After choosing the best properties and location of the source in the first section of the present thesis, the feasibility of Pu and MA transmutation in the TRIGA Mark II reactor was numerically examined with two core configurations in forms of heterogeneous and homogeneous distributions. The results showed that the neutron spectrum becomes softer along the change of configuration from heterogeneous to homogenous due to the presence of Pu and MA sample, and the neutron flux change significantly with the place and distribution of Pu and MA in the core. The heterogeneous distributions achieve slightly more fission rate for the Pu and MA due to the fast neutrons contribution. additionally, has been observed in case of heterogeneous configuration the neutron flux distribution decreases because the neutrons captured by 239Pu and 241Am, which means there is possibility to transmute that material by the decay process. On the other side at homogenous distribution the total fission rate and the source efficiency was high remarkably. This is due to contribution of fuel fission neutrons. Where that the source efficiency is high, this will providing and decreasing an accelerator current which means the economic feasibility is high. Also, the effectiveness of the incident beam type and its energy on Pu and MA fission rate was studied. As a consequence of our results it is found that the best values for the subcritical multiplication parameters M, ks and φ* achieved with electron beam where the average energy (Eav) of the neutrons was ~1.18 MeV. The external source efficiency is found to be clearly higher for electron beam at the energy range from 20 to 60 MeV than proton beam at the same incident energy.
Other data
| Title | Study on Neutronics of Minor Actinides Transmutation in Accelerator Driven System Reactor | Other Titles | دراسة على تحولات الأكتنيدات الشحيحة بإستخدام النيوترونات في مفاعل المسرع ذو النظام المدفوع | Authors | Amer Ahmed Abdullah Al Qaaod | Issue Date | 2015 |
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