43 1969 Zero Power Physics Reactor The ZPPR was a low-power physics reactor that started up in 1969 and provided physics data for any type of fast neutron spectrum reactor from the smallest space reactor to the largest fast breeder designs. It consisted of two separate honeycomb lattice assemblies that allowed internal core access for precise physics instrumentation.The two lattice halves were moved together before the reactor was brought to power by conventional control rods. Air circulated through the core to maintain a stable temperature.The type of physics data collected required minimal extrapolation to the full-power designs.The reactor was placed into standby in 1990 and disposed of in 2009.