Swimming pool reactor

This design has two major advantages: the reactor is easily accessible and the entire primary cooling system, i.e. the pool water, is under normal pressure.

Life preservers are sometimes located around the facility to rescue personnel that may fall into the pool, further adding to the appearance of a swimming pool-like environment.

Normally the reactor is charged with low enriched uranium (LEU) fuel consisting of less than 20% U-235 alloyed with a matrix such as aluminium or zirconium.

Highly enriched uranium (HEU) was the fuel of choice since it had a longer lifetime, but these have been largely phased out of non-military reactors to avoid proliferation issues.

Evacuated, or helium filled horizontal tubes may also be installed to direct a beam of neutrons to targets situated at a distance from the reactor hall.