Neutronic Analysis And Design Optimization For Spallation Target Of ADS

Nuclear energy was reconginized as undefiled energy and an advanced approach to replace fossil energy. However, development of nuclear power station may face these troubles:Supplying of fissile anddealing with nuclear waste,15000t nuclear waste was to be appear according to the development plan of Chinese Government, including a large amount of long-lived minor actinides and fission products. And the new developed nuclear device-Accelerator Driven Subcritical system (ADS)just solve these problems for it was good in nuclear fuel multiplication, nuclear waste transmutation and reactor safety, so ADS was reconginized as an promising nuclear device in the future. One of the preliminary differences between ADS and ordinary reactor was the spallation target, and its neutron performance was directly concerned with the power and transmutation performance of system.To supply spallation neutrons of strong intensity for the sub-critical core, high proton energy and high proton current (hence high power) was needed. However, it was difficult for an accelerator to meet such request. So optimization of the target was needed. In additional, as link of the core and the accelerator, the influence of the target to the accelerator should also be considered and avoided.Three points was studied concerning spallation target. First, the generated neutrons of the liquid lead-Bismuth spallation target were studied for an ADS demonstration facility of1000MW thermal power. We have investigated the variation of neutron yield, neutron leadage and spatial energy deposition in terms of the different incident proton energy, target height, buffer height and buffer thickness. The information of generated neutrons, including energy spectrum, neutron angle distribution and neutron spatial distribution of the most effective scheme was studied.The spallation products for different proton energy were also studied for LBE target, including volatile and light nuclides. For the windowless target, volatile nuclides enter the proton tube directly and polluted the vacuum. Even for the windowed target, light nuclides easily permeate the wall of the proton tube. Purpose of this part was to analyses the influence of light spallation productions to the vacuum of the proton tube. First software was used to simulate the spallaiton production yields, then combined the permeation and flow conductance calculation, pressure in the proton tube was got. At last, parameters of PDS-XADS were partly used to give a numerical result to get a visual impression.The last part was to validate the idea that if MA transmutation in the target was possible. For most programs developed and published, the target was in an independent loop. The purpose of this part was to discuss the possibility of taking Minor Actinides (MA,237Np,241Am,243Am and244Cm were included in this work) as target material. To achieve that, the influence on the neutron performance of the target, refueling period, energy deposition, neutron yield and neutron energy and transmutation mass were studied in terms of different fuel and structure material volume proportion. The result figured out adding MA into target was feasible. Moreover, since the target shared the same fuel, structure and coolant with the blanket, and thermal stresses were not greater than that was in the blanket, an independent target loop might not be needed in an ADS, and a well designed subcritical blanket maybe good enough.As a summary, in this paper, we did optimization for the spallation target of1000MW thermal power ADS, then the source term and especially the light nuclides permeate to the proton tube was analysised for target, the numerical result was shown and the weakness of the present design was pointed out. An attractive suggestion was given to simplify the engineering design of ADS at last.