
DIIS: A 1990s Hybrid Upgrade for Chornobyl NPP
In the 1990s, the Chornobyl Nuclear Power Plant modernized its remaining RBMK reactors not by a full rebuild of the Soviet-era mainframe, but by wrapping a new auxiliary information-measurement system (DIIS) around the 1970s SKALA mainframe. The upgrade linked a Ukrainian SM-1210 minicomputer and an ARCnet-connected 80386 PC to run real-time reactor-core modeling and visualization via the PRIZMA program, letting data stay local instead of being sent to Moscow. Unit 2 operated until 1991 (turbine fire), Unit 1 until 1996, and Unit 3 until 2000, yielding a pragmatic, hybrid upgrade that pushed the plant toward 21st-century capabilities.


