"Center for Advanced Intelligence Project, RIKEN, RAIDEN" is a large GPU cluster operated by RIKEN, located in Japan, in the public sector. It came online around June 2018. At that moment it ranked number 17 among known clusters.
It is built on 416 NVIDIA V100. That amounts to about 26.28 H100e of AI compute. The cluster draws roughly 0.2 MW. Its hardware is estimated at $8M.
Epoch AI rates the certainty of this record as confirmed.