Integrating Design Strategies and Economic Tools for Enhanced Pressurized Water Reactor Performance
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halimi-ahalimi-phd-nse-2026-thesis.pdf
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Author(s)
Halimi, Assil A.
Advisor(s)
Shirvan, Koroush
Date Issued
February 2026
Publisher
Massachusetts Institute of Technology
Abstract
Global electrification, AI-driven data demand, and industrial expansion are set to sharply increase electricity consumption toward mid-century, requiring firm, reliable, and low-carbon generation at unprecedented scale. Nuclear power, particularly pressurized water reactors (PWRs), which constitute about 80 % of global nuclear capacity, offers unmatched power density, reliability, and low lifecycle environmental impact. Yet its economic competitiveness has eroded under rising construction costs, schedule delays, and financial risk. This thesis demonstrates that restoring and advancing PWR competitiveness demands a coordinated technical–economic–deployment strategy that simultaneously enhances performance, valuation accuracy, and delivery efficiency.
Three complementary pillars structure the research:
(1) Reactor performance: new core design methodologies raise power density and burnup for the existing fleet while maintaining safety limits, achieving operating gains without proportional cost growth. Full-core reactor physics and fuel performance simulations establish achievable discharge burnups of 68–75 MWd/kgU, extended 24-month cycles, and “stretch” and “extended” power-uprate with anticipated post-critical heat flux (CHF) transients yielding gains of $3–9 million per reactor-year. Dynamic operation exploiting CHF margins provides further efficiency and cost gains. For integral and small modular PWRs, a fuel-cycle cost model reveals strong scale effects. Smaller cores incur higher leakage and fuel costs that can be mitigated through power uprates unlocked at the smaller scale. Coupled multi-unit SMR plant architectures and advanced fuel geometries such as high surface-to-volume cylindrical fuels (19×19 to 23×23 lattices) paired with LEU+ enrichment enable recapturing product economies of scale and >40 % power increases leading to up to 30% O&M and 23% CapEx reductions within known thermal-hydraulic limits.
(2) Valuation and finance: a new metric, the Present Cost of Energy (PCOE), replaces the traditional Levelized Cost of Energy, correcting its structural biases for high-CapEx, long-lifetime assets. PCOE distinguishes construction and operational risk, accounts for revenue escalation and cost inflation, and aligns present-valued costs with market prices. Integrated within FORCE, a detailed financial engine combining bottom-up cost, schedule, and revenue models, PCOE enables consistent project valuation across nuclear, natural gas, coal, and renewables. Results show that while combined cycle natural gas (CCNG) dominate in pure merchant markets, nuclear energy competitiveness improves dramatically under project guarantees or tax-credit regimes and with optimized capital financing during construction and operation.
(3) Deployment efficiency: new multi-unit and coupled-SMR site strategies recapture product economies of scale for smaller reactors through shared systems and optimized schedules, capital cost and schedule are estimated for multiple deployment scenarios along with fuel and O&M costs. Beyond the single site, median experience to nth of kind models, a novel development–production cost function links technological learning to site capacity and market demand, identifying capital cost-optimal unit sizes and demonstrating that smaller units are optimal for smaller sites (~2 GWe) and mutualized small reactors can approach gigawatt-scale cost performance under sustained learning for medium to large sites (5-10 GWe). When considering independent units, 1-GW scale reactors are optimal for medium size sites and 2-GW scale reactors dominate for larger sites.
Collectively, these innovations, validated across physics, finance, and project-delivery domains, yield tangible multi-million-dollar annual operating gains and credible cost reductions of tens of $/MWh in total lifetime present cost. The three pillars of the thesis establish a unified framework aligning product design, valuation, and delivery as the foundation for economically viable nuclear power in an electrified, data-intensive, and decarbonizing world.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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