UNDERGROUND SPACE RESOURCE IN GRANITIC PLUTONS AND THE CONCEPT FOR AN UNDERGROUND NUCLEAR POWER PLANT WITH COLLOCATED FACILITIES FOR LONG-TERM STORAGE AND DEEP BOREHOLE DISPOSAL OF SPENT FUEL

Granitic plutons occur in the Blue Ridge and Piedmont physiographic provinces of the southeastern U.S. and in granitic terrains worldwide. Large, dry, stable, self-supporting caverns can potentially be constructed in portions of the interiors of these granitic plutons where the rock mass has sufficient size, high mechanical strength, low permeability, and favorable in situ stress conditions. These plutons, therefore, represent a global geological resource that several nations could use to develop underground space for siting critical infrastructure facilities. Especially attractive are granitic plutons that outcrop as large domes or other topographically-elevated landforms and thereby permit tunnel access, which—relative to shaft access—should reduce excavation cost and simplify operations related to underground transport of personnel, equipment and material. A hypothetical 1200MWe underground nuclear power plant (UNPP) based on an advanced-design, pressurized, light-water small reactor is used to illustrate the utility granite plutons for siting critical infrastructure facilities. The UNPP concept is based on a 1.3 million cubic meter room-and-pillar network with 25meter wide x 25meter high rooms within which the reactors, other equipment and short and long term spent fuel storage pools could be installed and operate under extraordinary high levels of physical security and safety. In addition, exploratory confirmation of a suitable deep geohydrologic system at the UNPP site offers the potential for deep borehole disposal of spent fuel from the UNPP reactors, thereby allowing on-site closure of the back end of the nuclear fuel cycle. Estimated cost for the room-and-pillar network and related excavations is $280 million and the estimated cost for the deep disposal boreholes is $240 million. Nations considering new nuclear power plant construction based on advanced design small reactors in areas where topographically-elevated granite-pluton landforms occur should consider granite-cavern-based UNPPs. This could be an especially attractive option in global regions having high risks of terrorist or enemy nation attack and/or extreme risks from natural phenomena.