Use of two dosimeters for better estimation of effective dose /
Obviously, a single dosimeter on the chest can ty Microfilm Inc. underestimate effective dose (E) and effective dose equivalent (Hs) significantly when radiation comes from the back because the dosimeter on the chest is shielded by the body of a radiation worker. This problem can be solved by using...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1998.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=733039261&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Obviously, a single dosimeter on the chest can ty Microfilm Inc. underestimate effective dose (E) and effective dose equivalent (Hs) significantly when radiation comes from the back because the dosimeter on the chest is shielded by the body of a radiation worker. This problem can be solved by using an extra dosimeter on the back so that at least one dosimeter is always directly exposed to radiation. In this work, the use of two dosimeters was studied using the MCNP code and mathematical phantoms. First, an optimal combination of dosimeter weighting factors was found to be 0.58 and 0.42 for chest and back dosimeters, respectively, through a systematic optimization process. The optimal algorithm, which uses these weighting factors, was algorithms reported superior to other in the literature. The underestimation problem when using a single-dosimeter approach for posterior incident radiation was completely solved by using two dosimeters and the optimal algorithm. The two-dosimeter approach also estimated E and HE very well for a broad range of frontal incident photon beams, neither underestimating E or HE by more than 1 1%, nor overestimating by more than about 50%. Although the use of two dosimeters effectively solved the underestimation problem of the single-dosimeter approach for posterior incident radiation, this approach overestimated E and HE for lateral, overhead, and underfoot beam directions. However, this overestimation can be reduced by using suitably selected anisotropic-responding dosimeters. To study the effect of anisotropic-responding properties of personal dosimeters on the estimation of E and Hs, this work considered several types of anisotropic-responding dosimeters. In practical exposure situations, radiation workers move during exposure, which results in less overestimation of E and HE than static lateral, overhead, and underfoot exposures. To quantify the reduction of the overestimation by the movement of radiation workers, we averaged photon beam results over various ranges of incident beam directions. Generally, the overestimation problem significantly decreases when the results are averaged over even a very small range of incident beam directions. Finally, we present a set of ideal angular response actors, which can be used to improve angular response properties of personal dosimeters for use in the two-dosimeter approach. |
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| Item Description: | Vita. "Major Subject: Nuclear Engineering". |
| Physical Description: | xiv, 132 leaves : illustrations ; 28 cm. |
| Bibliography: | Includes bibliographical references (leaves 118-122). |