(489g) Solvent Extraction Flowsheet-Level Modeling and Simulation with Radiolysis

Solvent Extraction Flowsheet-Level
Modeling and Simulation with Radiolysis

Valmor
F. de Almeida ^†, Kevin L. Lyon^‡, and Taha Azzaoui ^*

^† University of Massachusetts
Lowell, Dept. of Chemical Engineering, Nuclear Program, Lowell, MA, 01854, valmor_dealmeida@uml.edu

^‡Idaho National Laboratory,
Aqueous Separations and Radiochemistry, Idaho Falls, ID, 83415,
Kevin.Lyon@inl.gov

^* University of Massachusetts
Lowell, Dept. of Computer Science and Mathematical Sciences, Lowell, MA, 01854,
taha_azzaoui@student.uml.edu

ABSTRACT

Hydrometallurgical separation
processes have played a critical role in the nuclear fuel cycle since the inception
of nuclear energy. Solvent extraction has been utilized at the industrial scale
for the recovery of uranium from ore, uranium and plutonium recovery from
irradiated nuclear fuel, and nuclear waste management. Despite widespread
application in the nuclear fuel cycle, development of robust models that aid in
the design, operation, and troubleshooting of advanced separation processes
remains one of the most significant challenges in separation science. The need
for advanced modeling and simulation capabilities is a critical component to
enable successful deployment of advanced nuclear fuel cycle technologies. Furthermore,
developing advanced separation technologies is a crucial step towards
demonstrating proof-of-principle concepts for innovative actinide chemistry. As
such, the present work is aimed at developing an extensive solvent extraction flowsheet
simulation capability using chemical non-equilibrium modules employed in a
variety of cross-cutting applications including nuclear separations,
safeguards, materials protection, special materials for national security and
non-proliferation, critical materials, mining, and metallurgy applications.

A modeling framework is currently
under development that couples multiple stages of solvent extraction equipment
in a counter-current cascade configuration to solve time dependent non-equilibrium
mass balances. A rigorous chemistry module has been implemented using available
literature data for n-tributyl phosphate/dodecane and nitric acid solutions of actinides
and fission products. Actinide and fission product concentrations are computed
from fuel depletion codes such as ORIGEN. The module includes radiolysis
reactions for H₂O and HNO₃; actinide oxidation-reduction
reactions; complexation reactions for actinides, H₂O and HNO₃;
and n-tributyl phosphate degradation reactions by radiolysis and hydrolysis.
Overall, the module considers 152 reactions for a total of 98 chemical species.
The resulting, time-dependent, highly nonlinear system of ordinary differential
equations are solved using the computational framework Cortix,
a python library for system-level modeling.