Criticality Accident Alarm System

Conference · Mon Sep 09 04:00:00 EDT 1991

OSTI ID:5577329

Malenfant, Richard E. ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

The American National Standard ANSI/ANS-8.3-1986, Criticality Accident Alarm System provides guidance for the establishment and maintenance of an alarm system to initiate personnel evacuation in the event of inadvertent criticality. In addition to identifying the physical features of the components of the system, the characteristics of accidents of concern are carefully delineated. Unfortunately, this ANSI Standard has led to considerable confusion in interpretation, and there is evidence that the "minimum accident of concern'' may not be appropriate. Furthermore, although intended as a guide, the provisions of the standard are being rigorously applied, sometimes with interpretations that are not consistent. Although the standard is clear in the use of absorbed dose in free air of 20 rad, at least one installation has interpreted the requirement to apply to dose in soft tissue. The standard is also clear in specifying the response to both neutrons and gamma rays. An assembly of uranyl fluoride enriched to 5% ²³⁵U was operated to simulate a potential accident. The dose, delivered in a free run excursion 2 m from the surface of the vessel, was greater than 500 rad, without ever exceeding a rate of 20 rad/min, which is the set point for activating an alarm that meets the standard. The presence of an alarm system would not have prevented any of the five major accidents in chemical operations nor is it absolutely certain that the alarms were solely responsible for reducing personnel exposures following the accident. Nevertheless, criticality alarm systems are now the subject of great effort and expense.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5577329
• Report Number(s): LA-UR-91-1979; CONF-910993--4; ON: DE91014746
• Country of Publication: United States
• Language: English

Related Subjects

070500 -- Isotope & Radiation Source Technology-- Health & Safety-- (1990-)
220900* -- Nuclear Reactor Technology-- Reactor Safety
61 RADIATION PROTECTION AND DOSIMETRY
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
96 KNOWLEDGE MANAGEMENT AND PRESERVATION
ACCIDENTS
ACTINIDE COMPOUNDS
ACTINIDE ISO
ACTINIDE NUCLEI
ALARM SYSTEMS
ALPHA DECAY RADIOISOTOPES
Accidental Criticality Alarm System
BARYONS
CRITICALITY
DOSE RATES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EVACUATION
EVEN-ODD NUCLEI
FERMIONS
FLUORIDES
FLUORINE COMPOUNDS
GAMMA RADIATION
HADRONS
HALIDES
HALOGEN COMPOUNDS
HEAVY NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MAINTENANCE
MEETINGS
MINUTES LIVING RADIOISOTOPES
MONITORING
Material Safety Data Sheets (MSDS)
NEUTRONS
NUCLEI
NUCLEONS
Nuclear Criticality Safety Program (NCSP)
PERSONNEL
PERSONNEL MONITORING
RADIATION ACCIDENTS
RADIATION MONITORING
RADIATIONS
RADIOISOTOPES
REACTOR SAFETY
SAFETY
SHEBA
SPONTANEOUS FISSION RADIOISOTOPES
STANDARDS
URANIUM 235
URANIUM COMPOUNDS
URANIUM ISOTOPES
URANYL COMPOUNDS
URANYL FLUORIDES