Humans accepted for ideas about what to do, but regarding operations and security, with its three fully independent control systems, OPAL can manage itself quite neatly.

To achieve the utmost safety as well as availability of the reactor, three completely independent systems are provided:

• First protection system of the reactor
• Second protection system of the reactor
• Control and monitoring system of the reactor

The first protection system of the reactor is provided by a last generation, failproof controller, which monitors all safety variables and detects potentially substandard operating conditions. Its main functions are: to trigger the first shutdown system (neutron absorbing bars) and to isolate the confinement.

The second protection system of the reactor is a wired one, which monitors a different set of safety variables and triggers the second shutdown system of the reactor, which is different from the first, as it depends on emptying the heavy-water mirror around the core, to starve the nuclear reaction of neutrons. Each of the above mentioned systems has three independent and redundant measurement channels for each safety-related parameter, guided by a "two of three" logic to trigger the actuation mechanisms of the safety systems.
		Another view of the posh main control room of OPAL, overlooking the operations hall. At INVAP we designed the systems to make operators feel like the owners of a high-end car, totally in control of a very self-controlled thing.

The control and monitoring systems of the reactor are under the supervision of a real time computer system of high availability. These computers monitor every reactor and plant parameter and display it to three different types of manned facilities: to the operator in the main control room, to operator at the emergency control room, and to the local supervision stations. In OPAL's layered and redundant control design, this top system allows to handle the reactor, permitting process orders and the activation of control circuits. This is the ruling system that "talks" to the above mentioned systems, on one side, and to human operators on the other.  

The following are its functions:

• Reactor power control
• Limiting actions (safety-related functions)
• Plant control
• Reactor overview and plant status
• Lock-in generation
• Alarm generation
• Recording of events and signals

Nuclear Instrumentation

The neutron flux is monitored by a very complete set of measuring channels which cover the complete set of possible operating conditions of the reactor, from shutdown to full power.

The system channels are the following:

• Start-up channel: three fission counters
• Wide range logarithmic channel, with three fission chambers
• Power channel, with three compensated ionization counters
• Linear automatic range channel: one fission chamber
• Nitrogen-16 channel, with one ionization chamber