The internal structure of SNAP-19 RTGs can be seen in this diagram. The testing process for the RTGs included rigorous functional and safety testing, in order to meet the stringent requirements set for the use of nuclear energy. Not only was it necessary to ensure the confinement during the testing and launch, but also in the event of an abort scenario or possible damage from handling. In fact there was some damage done to one test unit, however the integrity of the capsule was tested and confirmed there was no compromise of the fuel. Even the shipping of the RTGs was highly choreographed, and included complex security and even contingency plans in case the RTG was captured by "bad guys". All transportation was provided by specially designed trucks called SSTs (Safe, Secure Transports) that were designed for the transportation of nuclear weapons. One design feature of the SST was the ability to remotely disable the transport vehicle at any time during shipment. These measures were conservative and extensive despite the fact that the plutonium 238 was not weapons grade.