This study investigates a modular nuclear cogelabneration system that couples a 50 MWth fast-spectrum microreactor with a supercritical CO2 (sCO2) Brayton cycle and a Multi-Effect Distillation (MED) unit for simultaneous electricity and freshwater production. Thermodynamic simulations were performed using Aspen HYSYS to evaluate three operational scenarios that reflect distinct thermal coupling strategies between the reactor and the desalination unit. The system performance was analyzed through key parameters including the Power Loss Factor (PLF) and Gain Output Ratio (GOR), while the economic model integrated these metrics to determine the Levelized Cost of Heat (LCOH) and the Levelized Cost of Water (LCOW). Results show clear tradeoffs between electricity generation, water output, and exergetic efficiency. Scenario 3, which utilizes waste heat from the precooler outlet, achieved 17.41 MWe, 9,101 m3/day of freshwater, and an overall exergetic efficiency of 52.9%, with LCOH = 0 $/MWth and LCOW = 0.82 $/m3, representing the Pareto-optimal configuration. Scenario 1, a flexible cogeneration mode, produced 11,280 m3/day and 8.73 MWe at LCOH = 13.65 $/MWth, while Scenario 2 (heat-only mode) delivered 14,485 m3/day but no electricity, with LCOH = 55.88 $/MWth. Scaling analysis confirmed that modular replication significantly reduces costs, lowering LCOE from 59 $/MWh to 55.6 $/MWh for a ten-module configuration. The results highlight the technoeconomic potential of modular nuclear microreactors as a sustainable, scalable, and dispatchable solution for integrated desalination and power generation, offering a flexible framework for addressing water-energy security in arid regions.