INL will design, fabricate, and irradiate a second fueled pebble experiment, XPeRT-2 (X-energy Pebble Reactor Test 2), in the Advanced Test Reactor (ATR).
Office of NEPA Policy and Compliance
June 4, 2026
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Idaho National Laboratory (INL) is supporting X-energy in the development and licensing of the Xe-100, a 200 MWth high-temperature gas-cooled pebble-bed reactor. As part of this effort, INL will design, fabricate, and irradiate a second fueled pebble experiment, XPeRT-2 (X-energy Pebble Reactor Test 2), in the Advanced Test Reactor (ATR). The objective of XPeRT-2 is to generate irradiation performance data for TRISO-fueled pebbles under prototypic conditions to support the Xe-100 licensing basis and inform fuel qualification. This effort also serves as a precursor to a follow-on post-irradiation examination (PIE) campaign to further characterize fuel behavior that will be an additional revision to this ECP.