04/01/2026
By Danielle Fretwell

The Francis College of Engineering, Department of Energy Engineering - Nuclear, invites you to attend a Master's Thesis defense by Alyssa Puglisi on: "Purification via Solvent Extraction: Single Stage Centrifugal Contactor Modeling and Simulation."

Candidate Name: Alyssa Puglisi
Degree: Master’s
Defense Date: Friday, April 10, 2026
Time: 11 a.m.-12:30 p.m.
Location: Perry Hall 111

Committee:

  • Advisor: Sukesh Aghara, Ph.D., Professor, Chemical (Nuclear) Engineer, University of Massachusetts Lowell
  • Tejaswini Vaidya, Ph.D., Post Doc Research Associate, Chemical (Nuclear) Engineering, University of Massachusetts Lowell
  • Sara Isbill, Ph.D., Nuclear Security Scientist, Oak Ridge National Laboratory
  • Ram Nagarajan, Ph.D., Professor, Plastics Engineering, University of Massachusetts Lowell
  • Erin Bertelsen, Ph.D., Assistant Professor, Radiological Health Sciences, University of Massachusetts Lowell

Abstract:
The Uranium Science and Technology Center (USTC) focuses on replicating the fuel cycle stages after mining and milling but before enrichment. The goal is to expand the uranium processing workforce in the US to meet the growing demand for nuclear fuel processing that is coming with the expansion of the American nuclear reactor fleet. Part of the research and development is a significant focus on the modeling of each step along the front end of the nuclear fuel cycle after mining, before enrichment. This paper discusses the modeling of solvent extraction in centrifugal contactors within the conversion stage. USTC-Solvex is a modular Cortix application used to model solvent extraction processes of interest to uranium processing. While there are 2 models currently used in industry, AMUSE and SEPHIS, USTC-Solvex captures the reaction dynamics of the vapor phase, setting itself apart. This work discusses water extraction into a solution of n-tri-butyl phosphate (TBP) and inert diluent in contact with a gas/vapor phase. The scenario models a three-phase (aqueous, organic, vapor) single-stage, fast mixer/separator at the system-level of theory, wherein species concentrations are computed in all three phases varying with time. Humidification of the gas phase, aeration of the aqueous phase, and complexation of water in the organic phase are quantified in relation to the chemical equilibrium concentrations (stage efficiency). USTC-Solvex is being built to meet nuclear nonproliferation mission needs for uranium processing research and development to meet the growing demand of fuel for the US’s active and expanding nuclear reactor fleet. The TBP-H2O-air single-stage modeling a centrifugal contactor unit produces a TBP monomer hydrate, a TBP dimer, and a TBP trimer hexahydrate in ratios compared to concentrations of free TBP that are equivalent to validation data gathered from a 1994 Naganawa and Tachimori study. When comparing two cases of slow versus fast mass transfer coefficients, the fast mass transfer produced higher stage efficiencies and more total water extracted from the aqueous phase.