Neutron activated criticality alarm system

Conference · Sat Jan 01 04:00:00 EST 1972

OSTI ID:4313265

Zuerner, L V; Weddle, R C; Willis, C A ^[1]

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1. ed.

A system incorporaling BF/sup 3/ type neutron detectors has been designed and is now in use at the Pacific Northwest Laboratory. The monitors have been calculated to alarm to a pulsed fast neutron dose of 50 micro-rem. They have been successfully tested under simulated criticality conditions with a 50 micro-second burst from a pulsed reactor. The alarm is activated when a preset count rate is exceeded. Alarm time is less than 0.5 seconds when the count rate from neutrons exceeds the alarm set point count rate by 5%. Basic sensitivity is determined by the type of BF/sup 3/ tube used; the instrument can be adjusted to alarm in fast neutron fields of 20 to 1000 mrem/hr. The signal from the polyethylene moderated BF/sup 3/ tube is amplifted, shaped and fed to an integrating capacitor in a voltage sensitive trip circuit. This circuit activates the criticality alarms. Failure alarms are energized by circuits which detect high or low operating voltages and loss of signal from the neutron circuits. A self-auditing operating feature is designed around random input from background radiation. The criticality alarms are operated in a 2 out of n system.'' Two monitors must be in the alarm condition before an evacuation alarm is sounded. This minimized false alarms caused by local high level gamma fields, electromagnetic interference, and other spurious signals. (auth)

• Research Organization: Battelle Pacific Northwest Labs., Richland, WA
• DOE Contract Number: AT(45-1)-1830
• NSA Number: NSA-29-029486
• OSTI ID: 4313265
• Country of Publication: United States
• Language: English

Related Subjects

*ALARM SYSTEMS-- OPERATION
*BF3 COUNTERS-- ALARM SYSTEMS
*RADIATION ACCIDENTS-- ALARM SYSTEMS
CRITICALITY
N46110* --Instrumentation--Radiation Detection Instruments-- General Detectors & Monitors
NEUTRON DETECTION