A Single TLD Dose Algorithm to Satisfy Federal Standards and Typical Field Conditions

Abstract

Modern whole-body dosimeters are often required to accurately measure the absorbed dose in a wide range of radiation fields. While programs are commonly developed around the fields tested as part of the National Voluntary Accreditation Program (NVLAP), the actual fields of application may be significantly different. Dose algorithms designed to meet the NVLAP standard, which emphasizes photons and high-energy beta radiation, may not be capable of the beta-energy discrimination necessary for accurate assessment of absorbed dose in the work environment. To address this problem, some processors use one algorithm for NVLAP testing and one or more different algorithms for the work environments. After several years of experience with a multiple algorithm approach, the Dosimetry Services Group of Yankee Atomic Electric Company (YAEC) developed a one-algorithm system for use with a four-element TLD badge using Li2B4O7 and CaSO4 phosphors. The design of the dosimeter allows the measurement of the effective energies of both photon and beta components of the radiation field, resulting in excellent mixed-field capability. The algorithm was successfully tested in all of the NVLAP photon and beta fields, as well as several non-NVLAP fields representative of the work environment. The work environment fields, including low- and medium-energy beta radiation and mixed fields of low-energy photons and beta particles, are often more demanding than the NVLAP fields. This paper discusses the development of the algorithm as well as some results of the system testing including: mixed-field irradiations, angular response, and a unique test to demonstrate the stability of the algorithm. An analysis of the uncertainty of the reported doses under various irradiation conditions is also presented.

Concentrations and Dose Rate Estimates of 134,137cesium and 90strontium in Small Mammals at Chornobyl, Ukraine

“…The daily dose rate due to external sources of radiation (DR ext ) was measured at one location to examine the relationship between internal and external DR. Sixty-eight Microtus oeconomus were trapped at the Red Forest Enclosure and fitted with collars containing two LiF thermoluminescent dosimeters (TLDs; type TLD 100, Harshaw-Bicron, Newbury, OH, USA). These TLDs absorb radiation in a manner almost equivalent to that of biological tissue [20,21]. Each collar was permanently marked with a unique number and TLDs were housed within a sealed polyethylene tube (0.75-mm wall thickness).…”

Concentrations and dose rate estimates of 134137cesium and 90strontium in small mammals at chornobyl, Ukraine

“…The daily dose rate due to external sources of radiation (DR ext ) was measured at one location to examine the relationship between internal and external DR. Sixty‐eight Microtus oeconomus were trapped at the Red Forest Enclosure and fitted with collars containing two LiF thermoluminescent dosimeters (TLDs; type TLD 100, Harshaw‐Bicron, Newbury, OH, USA). These TLDs absorb radiation in a manner almost equivalent to that of biological tissue [20,21]. Each collar was permanently marked with a unique number and TLDs were housed within a sealed polyethylene tube (0.75‐mm wall thickness).…”