Transient Modelling of a Pd-Ag Permeator System in Filter Mode: Application to the SORGENTINA-RF Tritium Facility

The SORGENTINA-RF (SRF) project, dedicated to the production of medical radioisotopes, requires a tritium facility to process the exhaust gas of the vacuum chamber, containing a percentage of impurities of around 1%, and to allow for the recirculation of the purified hydrogen isotopes. Inside such a tritium facility, the Pd-Ag Permeator System is conceived to operate in a closed configuration (filter mode), where impurities accumulate inside the membrane. A characterisation of this transient behaviour is required to support the design and safety assessment of the SRF Permeator System. To this end, two numerical models were developed. A Python-based implementation was first introduced to investigate the physical mechanisms governing the hydrogen permeation process. Then, the same mathematical formulations were implemented in a custom component in Simscape, incorporating the control logic in a single-membrane configuration. The models were validated against experimental data collected at the Hydrogen Permeation (HyPe) facility of the ENEA Frascati Laboratories, showing good agreement with average relative errors below 9%. The models were applied to assess system behaviour under the operating conditions of the SRF Facility, considering a H2 reference case. A multi-membrane configuration was developed to achieve continuous operation at the system level by activating the membranes in sequence. The effect of membrane length and number of units on system performance was investigated. A configuration of seven membranes 0.12 m in length was found to achieve continuous operation at the system level, with a mean managed flow rate of approximately 1.02 × 10−5 mol·s−1, satisfying the requirements of the SRF Tritium Facility. A sensitivity analysis on hydrogen permeability was carried out by varying this parameter by ±50% to account for the isotopic difference between hydrogen and D/T operation. Considering higher permeability, the system remained consistent with the reference case. In the case of lower permeability, a membrane length of approximately 0.22 m was required to meet the same performance of the reference H2 configuration. The residual tritium to be discharged during the emptying phase of the membranes was also quantified, corresponding to a total release of approximately 5.60 × 10−3 g·day−1 over 24 h of continuous operation, which increases to 1.06 × 10−2 g·day−1 in the case of lower permeability. These results establish minimum design criteria for continuous filter-mode operation and provide a preliminary estimation of tritium release under the operating conditions considered, which may serve as input for future analyses of tritium inventories and the associated safety aspects of tritium management systems.