a.a. ghorbanpour khamseh

One of the driving factors for creating axial flow inside the gas centrifuge rotor to increase the separation performance is the scoop. Due to the exposure of the scoop to the high Mach gas flow, the flow will be shocked, and strong gradients will occur in the flow.  In this research, the gas flow around the scoop in a two-dimensional state (r-θ) is simulated by the Direct Simulation Monte Carlo method (DSMC) using the dsmcFoam solver at different distances of the scoop from the rotor wall. The results show that increasing the distance of the scoop from the rotor wall and decreasing the contact angle of the gas flow with the scoop reduces the maximum temperature and drag force. For instance, increasing the distance of the scoop from the wall by 31% (from 8 to 10.5 mm) in 3800 Pa wall pressure and 85° contact angle, causing a maximum temperature decrease of 1.3% (from 596 to 588 K) and also the drag force is reduced by 49.4% (2412 to 1221 dyn). Furthermore, reducing the angle of the gas flow with the scoop by 11.8% (from 85 ° to 75 °) in 3800 Pa wall pressure and at the distance of the scoop from the wall equal to 10.5 mm causes a maximum temperature decrease of 6.8% (from 588 To 548 K) and the drag force is reduced by 50.3% (1552 to 771 dyn).

Among the noble gases, Xenon isotopes are the most widely used. So far, no specific strategy has been published for separating all Xenon stable isotopes with the highest number of stable isotopes. In this research, a computational code, SQCAS, is prepared to determine the target isotope separation strategy in light or heavy current. The prepared code investigates the separation of the natural isotopes in proportion to the feed concentration by changing the parameters of the square cascade and modeling it at each step. All stable isotopes of natural xenon are separated using a square cascade in 32 steps for the certain feed (200kg). The proposed square cascade has 20 stages. In each stage, 10 centrifuges were used. Also, the separation factor for the unit mass difference in this research equals 1.2. Using this strategy, the enrichment of nine isotopes increases from 0.9393, 0.0009, 0.01917, 0.2644, 0.408, 0.2118, 0.2689, 0.1044, and 0.087 to 98.72%, 91.3%, 92.79%, 92.63%, 83.77%, 90.12%, 91.64%, 95.68%, and 99.04%, respectively. The results show that the highest recovery is related to the end isotopes, and the lowest recovery is related to Xe-135 isotope.

One of the crucial parameters in designing the Q model cascade for the multi-component systems is the M* parameter. In this research, a code called MOTACAS has been developed to design a Q cascade, using the optimal value of the M* parameter. In this regard, the enrichment of the 8th isotope of tellurium at the heavy stream to 0.40, 0.7, 0.9, and 0.99, and the enrichment of the 4th isotope to 0.1, 0.3, 0.4, and 0.5 have been investigated. Also, in order to evaluate the effect of the separation factor on M*, optimal Q cascades for the enrichment of the 8th and the 4th isotopes with separation factors of 1.05 and 1.1 have been designed and compared with each other. The results show that the acceptable range of the M* decreases with increasing the desired isotope concentration. The optimal value of the M* does not change with reducing the separation factor. The relative inter-stage flow rate remains constant despite increasing the total inter-stage flow rate. Moreover, the required number of separation stages to reach the end component to a high concentration increased, but the enrichment of the middle component in the one cascade is limited despite increasing the stages.

One of the important parameters in the square cascade, which has a great influence on its performance in the separation of multicomponent isotopes, is the cascade cut. In this research work, at first, the effect of cascade cut on the separation of xenon middle isotopes in a square cascade with 20 stages was studied. These studies were carried out for two cases in which the separation factor was 1.2 and 1.1. Moreover, the minimum length for creating a long cascade by changing the Z/F value and cascade cut has been determined. Based on the calculations, if the separation factor is 1.2 and 1.1, the minimum number of cascade stages will be 55 and 110, that's not simply possible. The results showed that the appropriate cascade cut in the long cascade is different from the short cascade. Using the parametric studies of the short cascade, it is possible to determine the most appropriate cascade cut in which the desired isotope concentration reaches its maximum. In order to maximize the amount of Xe-129 in a 20 stages cascade, the suitable cut is 0.2 in the separation factor of 1.2 and 0.15 in the separation factor of 1.1.

In the present study, for the first time the R cascade under normal and optimal conditions with the constant and specified total number of cascade stages, the feed flow rate to the cascade, the factor of separation based on the unit mass difference, and the maximum and optimal of the feed flow into the centrifuge machine is assessed. The algorithm used for optimization is TLBO algorithm and the objective function is considered as a function of separation work for a single machine and match abundance ratio. The results show that in the cascade with the match abundance ratio for isotopes k1 and k2 the separation work in optimal cascade is more than conventional. If the abundance ratio is adapted for two pair of components, i.e., the “first and third” and the “second and third, the separation power in the optimal mode for the first and second cases is 1% and 9% more than those of conventional, respectively. Finally, a computational code named MISCC is written to determine and analyze the parameters of the match abundance ratio cascade in optimal and normal conditions.