Coincidence Logic Modules for Criticality Alarming

Technical Report · Fri Apr 01 04:00:00 EST 1977

DOI:https://doi.org/10.2172/5240258· OSTI ID:5240258

Schaief III, C. C. ^[1]

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1. Atlantic Richfield Hanford Co., Richland, WA (United States)

Criticality alarming at Hanford has traditionally been accomplished using single detector coverage with each detector alarming independently. Recent changes in Energy Research and Development Administration (ERDA) guidelines require a minimum of two detectors per zone and the concurrent response of two or more of them to initiate an alarm. This significantly reduces the probability of a false alarm. In order to meet the requirements of double detector coverage and protect against loss of coverage due to a single failure, Atlantic Richfield Hanford Company (ARHCO) has specified that each zone shall have a minimum of three detectors with the alarm being generated when any two or more detectors are activated. Thus a single detector failure neither inhibits an alarm nor generates a false alarm. Although a commercial analog module for providing coincidence alarming criteria was available, ARHCO Instrument and Equipment Development (I & ED) found certain undesirable features in the circuit. As a result, a digital logic module providing the required alarm signal was developed. One of the design objectives was that simple failure of a single component should not inhibit an alarm nor generate a false alarm. Serial and parallel redundancy were used extensively to achieve this end. In addition to the Logic Module, a Relay Module provides contact closures for audible alarms and outputs for remote sensing. The Logic Module utilizes CMOS digital integrated circuits and will accept up to six detector inputs. The number of detectors can be expanded indefinitely in multiples of six by connecting the modules in a daisy chain fashion. The modules conform physically to the NIM standard, however, certain electrical changes were incorporated to allow compatibility with other equipment supplied by a commercial manufacturer.

• Research Organization: Atlantic Richfield Hanford Co., Richland, WA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP); US Energy Research and Development Administration (ERDA)
• OSTI ID: 5240258
• Report Number(s): ARH-LD-151
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420203* -- Engineering-- Handling Equipment & Procedures
420203* - Engineering- Handling Equipment & Procedures
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440101 - Radiation Instrumentation- General Detectors or Monitors & Radiometric Instruments
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ALARM SYSTEMS
Alarm System
CRITICALITY
Criticality
DESIGN
ELECTRONIC CIRCUITS
FISSILE MATERIALS
FISSIONABLE MATERIALS
LOGIC CIRCUITS
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Nuclear Criticality Safety Program (NCSP)
SAFETY
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