That was understood and wasn't the question. Assume some lithium titride was obtained via the black market and transported to the US. How big would be the minimum necessary bomb arming and maintenance facility?
A clean room environment big enough to: allow two or three people to work immediately next to the bomb without hitting each other; ensure that the bomb is not exposed to anything but extremely dehumidified air (lithium hydride/deuteride/tritide is amazingly hygroscopic); ensure that all workers are on supplied air (no exhaled moisture hitting the lithium tritide); and ensure that the facility is shielded well enough so that there are no detectable gamma and neutron emissions (gamma shielding is a fairish amount of lead; neutron shielding is LOTS of polystyrene foam) to alert NEST. You'd need to make very noticeable modifications to a largish residential home at a minimum.