Home Science Solving a mystery: A new model for understanding how certain nuclei split

Solving a mystery: A new model for understanding how certain nuclei split

Scientists at Tokyo Tech have extended an existing mathematical model so that it can be used to more accurately predict the products of fission reactions.

In nuclear fission, an unstable atom splits into two or more smaller pieces that are more stable and releases energy in the process. The fission process also releases extra neutrons, which can then split additional atoms, resulting in a chain reaction that releases a lot of energy. Though the fission has been misused for a considerable length of time to produce vitality in atomic plants all around, our comprehension and models of fission reactions still have numerous gaps.

Researchers have seen that there are four particular fission modes that extensively demonstrate what kind of nuclear species will be created by a fission event. These modes are identified with the state of the two nuclei directly before the nuclei parts totally (scission). Two of them are called standard modes and are topsy-turvy; they deliver lighter nuclei and a heavier one. The other two are called super-long and super-short fission modes, and both deliver two practically indistinguishable nuclei.

One model that has been used for predicting the fission products (and their kinetic energy) for various heavy elements involves the 3D Langevin equations. These 3D equations are based on three variables that are defined for an atomic nucleus that is about to undergo binary fission: the distance between the centers of the left and right fragments, the deformation of their tips, and their difference in mass or volume, called mass asymmetry.

Although this model has been successfully used for many heavy nuclei, its predictions failed to match the experimental data for some fermium (256Fm and 258Fm) and mendelevium (260Md) isotopes.

Experimental and calculated data for the fission products of 256Fm and 258Fm The fission products for 256Fm and 258Fm are shown, according to their mass number. These plots show the discrepancy between the data calculated using the 3D model (blue lines) and the experimental data (red dots). In contrast, the data calculated with the 4D model (black lines) is more true to the experimental findings.
Experimental and calculated data for the fission products of 256Fm and 258Fm
The fission products for 256Fm and 258Fm are shown, according to their mass number. These plots show the discrepancy between the data calculated using the 3D model (blue lines) and the experimental data (red dots). In contrast, the data calculated with the 4D model (black lines) is more true to the experimental findings.

While trying to improve this model and use it to comprehend what’s happening for those isotopes, a group of researchers at Tokyo Tech, including Prof. Satoshi Chiba, utilized 4D Langevin equations. The equations for this new model swapped the variable that showed the twisting of the piece’s tips for two free factors that took into account these disfigurements to be distinctive rather than continually being symmetric.

This extra level of opportunity enabled the new model to represent what was beforehand a riddle while passing by the past model. Test information (appeared in Fig. 2) for 256Fm demonstrated that standard parting modes were overwhelming for this isotope, though information for 258Fm and 260Md demonstrated that super-short splitting modes were considerably more likely.

The group deduced that the states of the two parts comfortable had an applicable impact on the splitting items and their motor vitality, and that compelling the twisting of the section tips to be equivalent brought about incorrect expectations.

Prof. Satoshi Chib said, “3D Langevin equations are unable to solve the observed transition between standard and super-short fission modes for these isotopes. Now, with our 4D Langevin model, this is solved.”

“Our model has allowed us to explain how these transitions happen in a consistent manner.¬†Needless to say, a better understanding and better modeling of nuclear fission are crucial if we are to keep improving existing nuclear technology to secure reliable energy sources.”

The study is published in the journal Scientific Reports.

REFERENCETokyo Tech

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