Huge (pun intended)! Making a standard design constructed off-site will lead to huge cost benefits for licensing, construction, operation, and maintenance of future nuclear plants.
NuScale has more details on their website but the goal is that power plant facilities house 12 self-contained reactors that can provide "154 MWe to a mission critical facility micro-grid for 12 years without new fuel following a catastrophic loss of offsite grid and transportation infrastructure."
They estimate the cost of production for the n-th plant to be in the range "approximately $40/MWh to $65/MWh" and their first project has a contractual cap on costs at $58/MWh, all of which is price-competitive with large, established reactors like Diablo Canyon, though their small plant footprint generates a tenth of the electricity output.
They also support air-cooled designs, "which can reduce plant water consumption to as little as 1.1 gal/MWh" and the "high-temperature heat can be directly used to produce hydrogen through electrolysis, thus reducing efficiency losses". "Hydrogen produced by a NuScale HTSE system is forecasted to be cost competitive with high capacity factor renewable hydrogen cost estimates while also providing continuous, controlled hydrogen production."
Used fuel will be stored on-site:
NuScale reactor building and VOYGR plant design incorporates a proven safe, secure and effective used fuel management system. A stainless steel lined concrete pool holds used fuel for at least 5 years under 60 feet of water. The used fuel is protected both by the ground and the Seismic Category 1 reinforced concrete reactor building designed to withstand an aircraft impact, and a variety of natural and man-made phenomena.
After cooling in the spent fuel pool, spent fuel is placed into certified casks, steel containers with concrete shells, on site of the plant. The NRC Waste Confidence Rule states that this is a safe and acceptable way to store used fuel for an interim period at the plant up to 100 years. The NuScale's standard facility design includes an area for the dry storage of all of the spent fuel for the 60-year life of the VOYGR plant.
The plant also supports recycled fuel, or mixed uranium-plutonium oxide (MOX) fuel, helping to reduce nuclear waste.