Design and construction features of OPAL guarantee the effective protection of the reactor personnel, the general public and the environment against radiological hazards.
All facilities comply with safety requirements and standards for research reactors established by ARPANSA (the Australian Radiological Protection and Nuclear Safety Agency) and IAEA (the International Atomic Energy Agency).
The conception of this one reactor applies two well proven design criteria in nuclear installations: "Defense in Depth", and ALARA ("As Low As Reasonably Achievable"). It thus establishes several successive protection levels and multiple physical barriers to prevent radioactive escapes.
The inherent safety of the reactor is based on the open pool concept and the negative reactivity coefficients of the reactor core. The reactor features passive safety, and responses are triggered automatically whenever set limits are attained.
The fission chain reaction may be interrupted any time by the action of two redundant and independent shutdown devices, each based on a different physical principle and each functionally non related to the other.
The reactor safety and protection systems take the reactor to a safe shutdown condition as soon as any anomalous operating condition is detected.
Reactor Shutdown: The first shutdown system quickly inserts five neutron-absorbing plates into the reactor core. The second shutdown system empties the reflector tank of its heavy water, which flows by gravity into a storage tank placed underneath the core.
Core cooling: The primary cooling system pumps feature inertial flywheels for the continuing cooling during the coastdown period of the shutdown process. The reactor pool itself is a large heat sink. In the case of a LOCA ("loss of coolant accident") water in the pool is replenished by a gravity injection system close to the core chimney to cool the core.
Contention: During normal operation, the air both circulating and released to the environment, is continuously checked. Under these conditions, all parameters such as air pressure, temperature and moisture are then kept constant by a special energy dissipation system.