ORNL has recently published a 125 page report detailing a SMR (small reactor) called Small modular Advanced High-Temperature Reactor (smAHTR) based on the liquid salt graphite moderated reactor design.

ORNL has recently published a 125 page report detailing a SMR (small reactor) called Small modular Advanced High-Temperature Reactor (smAHTR) based on the liquid salt graphite moderated reactor design.

SmAHTR is a 125 MWt, integral primary system FHR concept . . . The design goals for SmAHTR are to deliver safe, affordable, and reliable high-temperature process heat and electricity from a small plant that can be easily transported to and assembled at remote sites. The initial SmAHTR concept is designed to operate with a core outlet temperature of 700°C, but with a system architecture and overall design approach that can be adapted to much higher temperatures as higher-temperature structural materials become available. The SmAHTR reactor vessel is transportable via standard tractor-trailer vehicles to its deployment location . . . .

SmAHTR reactor vessel can be transported via tractor-trailer.

Reactor power, MW(t)                               125
Core volumetric power density, MW(t)/m3            9.4
Primary coolant salt                               FLiBe
Fuel type                                          TRISO, low enriched uranium
TRISO packing fraction, vol. %                     50
Fuel enrichment, wt %                              19.75
Core uranium loading at BOL,a kg                   1600–2020b
Core life, years                                   4.19
Fuel configuration                                 Annular pins
Fuel pin diameters (inside, outside), cm           2.2, 6.5
Fuel surface coating thickness, cm                 0.3
Moderator material                                 Graphite
Moderator configuration                            Pins and blocks
Moderator pin diameter, cm                         6.16
Number of total fuel assemblies/blocks             19
Number of core assembly rings                      3
Number of fuel pins/assembly                       15
Number of graphite pins/assembly                   4
Core height, meters                                4
Core effective diameter, meters                    about 2.2
Reflector configuration and material               Radial, graphite blocks
Reflector diameter, effective inside, outside, m   About 2.2, 3
Vessel height, meters                              9
Vessel diameter, meters                            3.5

SmAHTR salt vault thermal energy storage system.

This initial SmAHTR concept evolution is not sufficiently detailed to support in-depth capital and operating-cost analyses. However, the intrinsic attributes of the SmAHTR system (low pressure, compact system with efficient heat transport characteristics), considered on balance, offer the prospect of attractive nth-of-kind capital costs and competitive unit operating costs both for electricity production and process heat applications for deployment scenarios in the 2030 time period and beyond.

SmAHTR’s operating temperature is currently constrained by the performance limits of the structural materials used in the reactor vessel and non-fuel internal structures. This limitation restricts near-term SmAHTR concepts to operating temperatures of ~700°C. With this in mind, and in view of the benefits to be gained from higher system operating temperatures, a preliminary two-step materials development strategy has been formulated. This strategy targets expansion of the SmAHTR concept to 850°C and ~1,000°C in the coming decades.

 

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