Engineering Controls

Interlocks - Access to areas in the Proton Treatment Facility are controlled through a system of safety interlocks which prevent beam operation when personnel are present. Search and secure procedures require that each area within the enclosure be visually cleared prior to beam operation. Switches located within each area must be pushed and all doors closed before the switchyard can be operational. Intrusion into any of these areas will disable the beam transport system. Access into the switchyard may be accomplished without shutting down the entire facility with two persons making a controlled access requiring keys from the main accelerator control room. Klaxons sound prior to operation when an access has been made to alert any personnel who may have been missed during search and secure procedures.

Facility Shut Down Buttons - Located throughout the facility are twin sets of shut down or "crash" buttons. The mushroom shaped button may be pushed to shut down an individual area, without shutting off the synchrotron. The smaller, rimmed button shuts down the entire facility. These buttons should be used in emergencies only.

Accelerator Safety Systems - The computer system which controls the accelerator and beam transport system has a number of safety systems which prevent accidents from occurring. A checklist of items must be satisfied at each control console before the beam can be directed to an individual location. This includes such items as doors closed, area secured, proper devices in place, proper energy, etc. Any changes or bypasses must be signed into the main log, and signed out when reconfigured. No bypasses of the accelerator safety system may occur without notification and approval by the RSO or designee.

Shielding - The building structure was designed to intercept and attenuate all primary and secondary radiation produced by the accelerator, switchyard and treatment nozzles. The design criteria for the shielding is 5000 mrem per year to restricted areas and 100 mrem per year to unrestricted areas. In most cases, surveys have shown actual radiation exposure levels to be far below these limits.

Radiation Monitors - Three types of radiation monitoring equipment are in use continuously at the Proton Treatment Facility:

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