Impact of modularization and site staffing on construction schedule of small and large water reactors

Abstract

Recent nuclear construction project schedules in the US and Europe were 2.5x their original estimates due to productivity misses, supply chain challenges, hiring constraints, and other issues. Small modular reactors are proposed as a remedy. Smaller reactors will require one fourth to one third the person-hours of labor and leverage more common supply chains, putting less strain on each step of the construction process. This study presents a methodology for estimating the construction duration of nuclear projects, so the sensitivity of proposed concepts to staffing and labor constraints can be analyzed. The methodology builds on a previous overnight capital cost estimation tool and builds a Gantt chart out of 226 tasks. The genetic algorithm assigns resources to each task to minimize construction time subject to peak staffing and hiring rate constraints. The results were consistently within 15% of seven benchmark durations. Under tighter labor constraints, the construction duration of large reactors increased 42% on average and only 3% for small reactors. Modularization of systems and structures reduced construction durations 60%, but it increased the sensitivity to labor constraints. Small reactors were more sensitive to the modularization assumptions because of the compact structures and layout, and the power specific cost ($/kW) sensitivity was higher, but the total financial impact was smaller because the total costs were lower.