10.5.1 Modularization

The realization of NPP encompasses the phases of site preparation, construction and start-up. Traditionally, the construction phase of a NPP was performed on site, with specialized workers erecting all the civil structures, nuclear island and balance of plant (BoP) systems starting from raw material and main equipment. Every NPP construction was nearly hand-crafted, specific to the site and the plant design. Conversely, the SMR plant layout may be conceived from its design phase in a number of sub-systems or ‘modules’ that may be fabricated in a parallel way and then shipped and assembled on-site. The construction of the SMR plant systems on-site is reduced and the fabrication activity tends to be shifted in factory, with the following main benefits:

• controlled work conditions and improved quality standards;

• possibility to apply mini-serial production, fostering the learning accumulation and decreasing the overhead cost of the production lines;

• use of less specialized personnel on-site;

• in principle, reduction of the construction schedule due to the shift from series to parallel activities;

• as a consequence of the previous, lower financial cost escalation during construction.

On account of the smaller size of their components and systems, SMRs can achieve higher degrees of design modularization (Carelli et al., 2007b, 2010). The indivisibility of some subsystems and their large scale in the LR plants compels their construction on-site, while the lower physical size of SMRs allows a greater number of systems to be factory-fabricated and then shipped to the site. Modularization requires more project management effort and transportation complexity. Communication and cooperation between suppliers and contractor has to be accurate, in order to create the schedule and ensure synchrony of the shipments. Modularization turns into real cost and time advantages as long as these additional burdens are counterbalanced by a plant layout simplification and a plant design conceived ad hoc to implement and ease the modularization.