Characterization of a neutron calibration range
Date
1995
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Texas A&M University
Abstract
A portable neutron survey instrument calibration facility was examined to determine its basic characteristics. The facility uses two, 10 curie 239pu-beryllium neutron sources. The techniques used to assess the facility include a tissue equivalent sealed Rossi chamber, an Andersson-Braun type neutron rem counter, and CR-390 material track etch dosimeters. The theoretical dose equivalent rate, neglecting scattering, was calculated for the purpose of ensuring that the measurements obtained were reasonable. The results were that the Rossi chamber and the Andersson-Braun agreed to within 0.2% at 50 cm (270 mrem h-1) from the source and to within 13% at 400 cm (6.9 mrem h-1) from the source. Using standard error (I a), the error bars from the Rossi chamber overlap the calculated best fit to the Andersson-Braun data. The CR-39(& track etch dosimetry failed to respond to the neutron fluence in several cases. Landauer type CR390 dosimeters were irradiated in neutron dose equivalent rate fields for time periods necessary to deliver an estimated 366 mrem to 5lO mrem. Of the eight dosimeters originally irradiated, Landauer reported six of the eight as having a dose equivalent equal to "m" which is the minimum detectable. Landauer reports that the numerical value of the minimum detectable for this type of dosimeter is 20 mrem. The reason for the discrepancy is not known. The scatter characteristic was computed by fitting the Rossi chamber data to the formulation used by the National Institute of Standards and Technology (NIST). The scatter component varies from about 35% at 50 cm to approximately 100% at 400 cm. Two main conclusions arise from this study. The first is that the sealed Rossi chamber is a valid instrument for use in range calibration. The second is that some information is now known about the scatter characteristics of the facility.
Description
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Includes bibliographical references.
Issued also on microfiche from Lange Micrographics.
Includes bibliographical references.
Issued also on microfiche from Lange Micrographics.
Keywords
health physics., Major health physics.