Divjak is visiting Madrid at the invitation of Spanish Science, Innovation and Universities Minister Pedro Duque.
The memorandum will formalise cooperation between two leading science and research institutes -- Croatia's Rudjer Boskovic Institute (IRB) and Spain's CIEMAT institute -- which are taking part in designing DONES (DEMO Oriented Neutron Source).
DONES helps scientists to test materials in an environment of neutron irradiation similar to that of a demonstration fusion reactor (DEMO), the machine that will follow ITER.
Spanish minister Dueque is an astronaut and aeronautics engineer who flew to space for the first time in 1998 as part of a NASA mission.