In 2011, Westinghouse introduced a new SMR design, the W-SMR. It is rated at 800 MWt with an expected electrical capacity of greater than 225 MWe. The W-SMR design draws heavily from Westinghouse’s AP1000®[1] design experience, although it uses an integral primary system configuration rather than the traditional loop-type configuration used for the AP1000® plant. Except for eight external, horizontally mounted primary coolant pumps, all primary system components are contained within the 3.5 m diameter by 24.7 m tall reactor pressure vessel, including the control rod drive mechanisms, pressurizer, and steam generator. The reactor core is composed of 89 fuel assemblies with 17 X 17 fuel pins and an active core height of 2.4 m. In addition to the 37 control rods, soluble boron in the primary coolant is used for reactivity shim. The internal control rod drive mechanisms are based on the AP1000® plant magnetic jack units. The steam generator is a recirculating once-through, straight-tube bundle that surrounds the central hot leg riser. The low-quality steam produced in the steam generator is passed to a steam dryer drum mounted outside the containment vessel.

The reactor pressure vessel is contained within a 9.8 m diameter by 27.1 m tall steel containment vessel. The passive safety systems and residual heat removal systems are modeled closely after the AP1000® plant systems and are expected to provide a 7-day post-accident grace period without operator action. A W-SMR plant consists of a single reactor, although multiple plants can be constructed at the same site.

Ameren-Missouri has announced the intent to build up to six W-SMR plants at the existing Callaway Nuclear Generation Station site in Missouri. Key parameters and a representative graphic for the W-SMR design are given in Figure 2.13. [11]

Control rod drive mechanisms

Reactor coolant
pumps

Reactor core

Figure 2.13 W-SMR (United States) — Westinghouse Electric Company (used with permission of Westinghouse Electric Company LLC).