Conveners
Fission
- Patrick Talou (Los Alamos National Laboratory)
Fission
- Andreyev Andreev (University of York (GB))
Fission
- Nicolas Schunck (Universidad Autonoma de Madrid)
Fission
- Yukinobu Watanabe (Kyushu University)
Since its discovery in the late nineteen thirties, nuclear fission has remained one of the most complex and elusive problems in physics and gaps in our understanding of this phenomena can impact progress in other areas. For example, in basic science accurate knowledge of spontaneous fission half-lives is key to predicting the stability of superheavy elements, and fission fragment charge and...
We propose a framework to calculate the dynamics at the scission
point of nuclear fission based as far as possible on a discrete
representation of orthogonal many-body configurations. Assuming
axially symmetric scission shapes we use the $K$ orbital quantum number
to build a basis of wave functions. In this first exploratory
study, we examine how close to the scission point...
We develop a Hauser-Feshbach Fission Fragment Decay model code, HF$^3$D and demonstrate its application to more than 1,000 primary fission fragments formed in the low-energy neutron-induced fission of $^{235}$U. The HF$^3$D code allows us to calculate the de-excitation of highly excited primary fission fragment by emitting prompt neutrons and $\gamma$ rays, and the sequential $\beta$ decay....
Prompt gamma-ray spectra were measured for the spontaneous fission of 240,242Pu and the neutron-induced fission of 239,241Pu with incident neutron energies ranging from thermal to about 100 keV. Measurements were made using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments using a parallel-plate avalanche counter....
The fission fragment yields are intimately connected to the resulting prompt fission γ-ray spectrum (PFGS). In combination with the prompt neutron emission, the fragment yields determine the fission products that are produced, which ultimately emit the majority of the prompt γ rays in fission. We use a Monte Carlo Hauser-Feshbach model to calculate the de-excitation of the fission fragments...
Nuclear fission is an important process that is not well understood microscopically. The nuclear Time-Dependent Density Functional Theory (TDDFT), which is a microscopic theory accounting for the nucleon degrees of freedom, describes dynamics of atomic nuclei [1]. Recent computational developments enable us to obtain physical quantities systematically from the TDDFT calculations. Those results...
Two major recent developments in theory and computational resources created the favorable conditions for achieving a microscopic description of nuclear fission almost eighty years after its discovery in 1939 by Hahn and Strassmann. The density functional theory (DFT) provides the only microscopic framework suitable for description of heavy nuclei and feasible on today’s computers. Instead of...
Until now, the theoretical description of fission through the effective calculation of potential energy surfaces (PES) has been made in two different approaches: the microscopic approach on the one hand and the macroscopic-microscopic approach on the other hand.
- In the microscopic ones, we assume an effective two-body interaction between the nucleons (e.g. Skyrme or Gogny interaction)....
Predictions of fission observables by solving the Langevin equations are highly dependent on the potential energy surface along which the shape configuration of the nucleus evolves. This potential energy surface is calculated by adding together the liquid drop deformation energy and the shell correction energy. In our recent four-dimension (4-D) Langevin approach [1], the shell corrections...
High-precision measurements of the fission product yields of 235U, 238U, and 239Pu using monoenergetic neutrons between 0.5 and 14.8 MeV have been performed to study the energy dependence. The results confirm the progression towards symmetric fission at higher incident neutron energy, i.e., 14.8 MeV. However, at lower energies (En < ~4 MeV) the experimental data reveal a peculiar energy...
Recent advances in the modeling of the decay of fission fragments have led to the integration of fission event generators in transport simulations. Event-by-event generators follow the decay of each fragment through the successive emissions of neutrons and gamma rays. Natural correlations in energy, multiplicity, angle of those prompt particles with themselves and with their parent nucleus are...
The poor accuracy of microscopic models in the prediction of fission observables constrains nuclear industry to rely on semi-empirical models, which in turns need systematic and accurate experimental data on a significant number of observables. In the last decade, large efforts were made in the fission community to improve models of the fission process and of the de-excitation of fission...
Nuclei in the neutron-deficient region of $^{180}$Hg$_{100}$ are different from the actinides traditionally used for fission studies, from the viewpoint of their fission barriers, separation energies and proton-to-neutron ratios. Fission properties of these nuclei were expected to be similar to those of their heavier isotopes around the stability line, known to fission symmetrically. The...
In this talk we will discuss the use of multi-nucleon transfer (MNT) reactions to study fission properties of a series of exotic nuclei in the neutron-rich actinide region. Most of these nuclei cannot be accessed by the traditional method of complete-fusion reactions. The MNT transfer channels of the $^{18}$O+$^{232}$Th reaction were used to study fission of fourteen nuclei...
The decisive importance of fission-product (FP) decay heat (DH) was far and widely recognized after the core-melt accident at the TMI nuclear power station in 1979. Even before this, in the late 1970s, a lot of experimental and theoretical studies on FPDH were motivated and initiated in Japan, the US and Europe. In these countries, extensive FP decay data libraries to be used in DH summation...
