Fission studies at TUNL

Dr. Sean Finch
Duke University and Triangle Universities Nuclear Laboratory

Nuclear fission has been intensely studied since it's discovery 87 years ago. Despite nearly a century of research, there are still large gaps in our description of fission owing to the complexity of this nuclear many-body phenomena. A TUNL-LLNL-LANL collaboration is measuring fission observables of uranium and plutonium isotopes, including fission product yields (FPYs) and how they change as a function the probe inducing fission and its energy. TUNL is uniquely suited to perform these measurements using both mono-energetic neutrons, produced at the tandem accelerator, and mono-energetic photons, produced at the high-intensity gamma-ray source (HIgS). One application of specific interest is the "reactor anti-neutrino anomaly." The Daya Bay, RENO, and Double Chooz collaborations have all reported precision measurements of the reactor antineutrino spectra and observed deviations from predictions in the overall flux and spectral shape (referred to as the "5-MeV bump"). We employed a fast target transfer system to measure cumulative FPYs, for product half-lives ranging from 0.5 s to 100 s, following fission of 235U, 238U, and 239Pu induced by 2 MeV neutrons. Approximately 50 short-lived cumulative FPYs are measured, including most of the key fission products expected to contribute to the “5-MeV bump.” Our newly measured FPY data are compared with the presently accepted evaluations and summation method models are used to produce updated predictions of the reactor antineutrino spectra.

Hosted by Prof. Aprahamian