Accurate fission yields for future nuclear systems

Ali al-Adili
Ali al-Adili. Photo: Camilla Thulin.

The Swedish Research Council has on October 31, 2019 decided on the applications to be awarded grants within New nuclear technology. The Department of Physics and Astronomy is granted 5 600 000 SEK for the period 2019-2022 for one project grant and one starting grant.

Project description

Project title: Accurate fission yields for future nuclear systems
Main applicant: Ali Al-Adili, Division of Applied Nuclear Physics
Grant amount: 3 200 000 SEK for the period 2019-2022
Funder: New nuclear technology starting grant from The Swedish Research Council

Fission was discovered more than 75 years ago, and still we are lacking a complete fission model. Correlated fission data on fission fragment masses, prompt fission neutron yields and prompt fission gamma yields, are needed in order to constrain and improve fission models.

The nuclear data needs for Gen-IV systems are eminent. In order to ensure a safe and efficient reactor operation, fast-neutron induced data are needed. Fissions Yields (FY) are a major source of uncertainties in decay heat- and burnup calculations. They are vital for delayed neutron calculations, reactor poisoning and waste management. The aim of this project is to improve the current knowledge of fast neutron induced fission yields. By delivering accurate FYs and prompt neutron multiplicities (nubar) we contribute to fission modeling and improve the nuclear data evaluation files (ENDF).

The methodology utilizes the state-of-the-art spectrometer VERDI (VElocity foR Direct particle Identification) via the “2v-2E” method. Both fission fragment energies and velocities are measured simultaneously. Precise FY determination can be achieved with a mass resolution better than two atomic mass units. The method provides another important observable, namely the average prompt neutron multiplicity.

The goal of this project is to finalize the development of VERDI and to perform systematic measurements of FY and neutron emission as a function of neutron energy. First, the induced fission of 235U will be measured, both in thermal and fast neutron fission, as a proof of principle. Thereafter, the focus will be on the reactions 238U(n,f) and 232Th(n,f), since they are suitable isotopes for Gen-IV nuclear fuels.