Safety critical monitoring for prompt radiation hazards

At TRIUMF we have used both passive and active methods to protect against potential prompt radiation hazards produced by accidental beam losses in high-intensity proton beam lines. These methods consist of shielding, exclusion areas, and the use of fast acting radiation monitors. The latter are located within the shielded areas and are set to terminate beam production on the detection of abnormal beam loss. A recent risk analysis has suggested a need for higher reliability in the protection against potential prompt radiation hazards where the shielding is relatively thin. To address this requirement TRIUMF has developed a new approach using two systems of independent and redundant monitoring devices located outside the shielding to protect against safety critical events with the required level of reliability. Verification of the system reliability is achieved by weekly testing of the safety critical monitors as well as the trip devices. When used in conjunction with the traditional beam loss monitors we are able to distinguish between safety critical events and non-safety critical beam trips.