The construction of two reactors in the US using Lego-style modular parts has met with major difficulties, casting doubts over the efficacy of the innovative building method and its viability for the nuclear industry in future.

Southern Co’s Vogtle plant in Georgia and SCANA Crop’s VC Summer plant in South Carolina are building new reactors for the first time in over a decade, both of which are AP1000 models designed by Westinghouse Electric Co. The individual modules of the AP1000 reactor can weigh hundreds of tons and can rival buildings in size.

Given their exorbitant size, the plant developers have opted for the use of modular parts to build the new reactors, large chunks of which are pre-fabricated off-site before being conveyed to the plant location for welding and assembly.

Advocates of the construction method hope the use of pre-fabricated modules will increase the quality of the completed facility and reduce building time and cost overruns – a crippling problem for the nuclear power industry during its initial phase of development.

These hopes may have been dashed however, given the problems that both facilities are already facing during the construction phase.

The two plants are already well behind schedule. The first reactors of both sites were scheduled to come online in 2016, but those dates have now been deferred to 2017 or even early 2018.

The construction delays have been accompanied by huge cost blowouts that the use of modular building method was originally intended to avoid. Southern Co. now expects the plant in Georgia to run $646 million beyond its initial budget of $6.1 billion.

The chief reason for the lengthy delays and cost overruns has been the difficulties experienced by the manufacturer of the modular parts in meeting the exacting quality standards required of nuclear power facilities.

The Shaw Modular Solutions factory, based in Lake Charles, Louisiana, was enlisted by the developers of both plants to build large sections of the pre-fabricated modules. The company has struggled, however, with quality assurance and fabrication problems, which analysts believe are at least partially the fault of engineering designs which are difficult if not impossible for manufacturers to produce.

Shaw has compounded its difficulties with slovenly work practices. Inspectors from the US Nuclear Regulatory Commission threatened the Shaw Group with a fine of $36,400 after it fired a quality insurance supervisor from another part of the company who warned that a potentially defective component may have been shipped to a project in New Mexico.

The NRC also found that workers at the Lake Charles factory had expressed concerns over safety and quality, and that a welder had taken a qualification test on behalf of a colleague in 2010 with the full knowledge of a supervisor, who refrained from reporting the matter.

Production of the modular parts has since been shifted to other factories in Oregon, Florida and Virginia, with the Lake Charles factory still entrusted with the manufacture of smaller parts, including instrumentation, piping and valves.

While executives from Southern Co. concede that the use of the modular method has failed to save time or money in this instance, they remain confident that it retains promise for the future, given the productivity gains achieved by manufacturing components in a closed environment.