Spontaneous fission chemistry made easy full#

In the first step, the system tunnels through a multidimensional space of collective coordinates. Specifically, in case of SF, the dynamics of a fissioning system can be divided into two successive steps as depicted in Figure 1. The same approach is adopted in a static nuclear density functional theory (DFT) based model, where the collective motion is simulated by incorporating the DFT inputs within an appropriate equation of motion. Consequently, majority of the fission models are implemented within the adiabatic approximation that segregates the collective degrees of freedom from the intrinsic coordinates. In general, the collective dynamics of a nucleus is believed to be a much slower process than the random motion of the constituent nucleons. The exascale computing platforms may open up the avenues to overcome such restrictions.

Spontaneous fission chemistry made easy full#

Besides, current implementations of TDDFT simulate only a single fission path for a given initial condition reconstruction of a full yield distribution requires large-scale Monte Carlo sampling, which is beyond the current computational capabilities. Primarily, the quantum tunneling is energetically forbidden within this semiclassical approach. Albeit very promising, TDDFT poses several limitations in its application to SF. Specifically, in the characterization of fission yields, nuclear dissipation plays a crucial role near the scission configuration and would be best accounted for by TDDFT.

Ideally, the time-dependent density functional theory (TDDFT) provides the most realistic microscopic framework to deal with such large amplitude collective dynamics. In the SF process, a fissioning nucleus undergoes quantum tunneling through a single or multiple potential barriers generated by the coherent motion of strongly interacting nucleons. The present scenario and the prospects of fission theory are described in a recent review. Therefore, for both basic science and applications, predictive modeling of SF observables is of utmost interest. However, measurements in actinide nuclei are restricted due to safety issues. In the application frontier, SF data are important to calibrate the nuclear material counting techniques relevant to power generation and international safeguards. Further, as suggested in a recent study, the precise estimation of fission yields is indispensable for a better understanding of the chemical evolution of r-process elements produced in binary neutron-star mergers. Specifically, distributions of fission-fragment yields from different fission modes (SF, beta-delayed fission, and neutron-induced fission) are essential components of the r-process abundances and, therefore, very accurate prediction of these yields is required to improve the r-process network calculations. In the case of nuclear astrophysics, SF strongly impacts the abundances of heavy elements in stars by participating in the r-process recycling mechanism. Moreover, in comparison to α-emission, SF is predicted to be the preferred decay mode for neutron-rich superheavy nuclei. This type of decay sequences are experimentally observed for isotopes of Fl and Ts. Although superheavy nuclei predominantly decay via α-emission at the beginning of a decay chain, SF leads to terminate the chain. Particularly, the stability of very heavy and superheavy nuclei strongly depends on the SF probability. Nuclear spontaneous fission (SF) is a unique decay mechanism that has crucial applications in both basic and applied sciences.