SYSTEM OVERVIEW

The CAAS-3S unit is a criticality accident alarm system (CAAS) as defined by the relevant industry standards. The system is designed to monitor areas where a potential criticality excursion could take place and alarm rapidly for the prompt evacuation of personnel in the event of a criticality accident.

The system can simultaneously monitor multiple zones within a building or across a facility with multiple buildings. The detection probes should be located in areas where personnel would be exposed to an excessive radiation dose (as defined by standards).

The CAAS-3S system offers the following significant design features:

• Five detection capabilities through gamma and neutron detection and different sensitivities.
• The neutron and/or gamma detection head and the electronic alert logic module reside in the probe. Continuous state of health monitoring of the scintillator detector is achieved by using a light-emitting-diode with a feedback circuit. This feedback circuit checks the functionality of the entire system (through the full signal chain to alarm), and any electronic inconsistency is communicated back to the control unit (Processing Cabinet).
• The probe architecture is composed of an analog and digital chain. The analog chain comprises the gamma/neutron sensor module, amplifier, test alert, power, and alert signal generators. The analog chain is SIL2 qualified. It is based on the proven EDAC probe design. The digital chain is FPGA based with auto-testing capabilities and accident follow-up, storage of the probe parameters (including calibration), temperature sensing values, and a watch-dog functionality to determine the health of the digital electronics.
• The alert logic in each probe is sensitive to both criticality excursion scenarios: the "prompt-critical" metal system and the "slow-cooker" non-metal accident.
• Redundancy is built in to the system throughout the entire signal chain. Each control unit has a redundant backup with automatic failover.
• The power supplies are provided with battery backup to maintain detection capabilities in the event of a power outage.
• The system is completely autonomous.
• On-board software enables state of health, logged data, testing, and alarm functions to be monitored from the control room.
• Remote network monitoring (guard stations, shift supervisor) is available as an option.