Construction began in 1961 in a dedicated building in the Institute for Nuclear Research in Otwock near Warsaw.
The core was additionally surrounded by a reflector and had an external neutron source used for start-up.
The purpose of the Anna reactor was scientific and research work, and for a certain period also small-scale production of radioisotopes.
In particular, the central part of the core was replaced, which was filled with natural uranium without a moderator (and thus becoming fast-neutron reactor).
The Anna reactor was a unit completely designed and built in Poland by Polish engineers and nuclear physicists.