The technical details of the reactor are given in the references. Maria is a
pool-type reactor with a power of 30 MW (thermal). Despite being a pool reactor, it contains channels (aluminum tubes) individually connected to the primary coolant. The water pool provides cooling for elements (e.g., fuel elements) that are not otherwise cooled, and also acts as radiation shielding. Maria uses
enriched uranium as fuel (80% enrichment in
235U till 1999, and 36% since). The fuel elements and channels are vertical but arranged conically. Water and
beryllium blocks serve as the moderator (70% and 30% of the moderation, respectively). Elements of
boron carbide sheathed in aluminum are utilized for control, compensation, and safety. The use of beryllium blocks permits a comparatively large fuel lattice pitch, and consequently large volume for payload targets. There is also a
graphite reflector (aluminum sheathed). Maria supplies a
neutron flux of 4×1014 n/cm2s (
thermal neutrons) and 2×1014 n/cm2s (
fast neutrons). There are six horizontal channels for controlled use of neutron beams. There is also a window of lead-containing glass through which the core can be viewed. The reactor is housed in a
sealed containment. Following preparation which started in 2004, Maria was converted to use
low-enriched uranium (LEU) fuel by 2012. ==History==