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Title: Criticality accident alarm system

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% {sup 235}U 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 anmore » 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. 13 refs.« less
Authors:
Publication Date:
OSTI Identifier:
5577329
Report Number(s):
LA-UR-91-1979; CONF-910993--4
ON: DE91014746; TRN: 91-021530
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: International conference on nuclear criticality (ICNC) safety, Oxford (United Kingdom), 9-13 Sep 1991
Research Org:
Los Alamos National Lab., NM (United States)
Sponsoring Org:
DOE; USDOE, Washington, DC (United States)
Country of Publication:
United States
Language:
English
Subject:
22 GENERAL STUDIES OF NUCLEAR REACTORS; 07 ISOTOPES AND RADIATION SOURCES; ALARM SYSTEMS; STANDARDS; CRITICALITY; DOSE RATES; EVACUATION; GAMMA RADIATION; MAINTENANCE; MEETINGS; NEUTRONS; PERSONNEL; PERSONNEL MONITORING; RADIATION ACCIDENTS; REACTOR SAFETY; URANIUM 235; URANYL FLUORIDES; ACCIDENTS; ACTINIDE COMPOUNDS; ACTINIDE ISO; ACTINIDE NUCLEI; ALPHA DECAY RADIOISOTOPES; BARYONS; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; EVEN-ODD NUCLEI; FERMIONS; FLUORIDES; FLUORINE COMPOUNDS; HADRONS; HALIDES; HALOGEN COMPOUNDS; HEAVY NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IONIZING RADIATIONS; ISOMERIC TRANSITION ISOTOPES; ISOTOPES; MINUTES LIVING RADIOISOTOPES; MONITORING; NUCLEI; NUCLEONS; RADIATION MONITORING; RADIATIONS; RADIOISOTOPES; SAFETY; SPONTANEOUS FISSION RADIOISOTOPES; URANIUM COMPOUNDS; URANIUM ISOTOPES; URANYL COMPOUNDS 220900* -- Nuclear Reactor Technology-- Reactor Safety; 070500 -- Isotope & Radiation Source Technology-- Health & Safety-- (1990-)