Department Of Energy Laboratory Accreditation Program Research Articles

Use of Commercially Available Optically Stimulated Luminescence Dosimeter As Extremity Dose Estimator.

In 2009, Idaho National Laboratory (INL) transitioned to an external dosimetry program using optically stimulated luminescent (OSL) technology. This process led to the introduction of the Landauer, Inc., nanoDot dosimeter and MicroStar reader to INL's radiological control program. At the time, a small, self-contained, single chip OSL dosimeter that could be easily read in the field was recognized as having many potential applications for a radiological control program. The ability to achieve a realistic extremity-dose estimate in the field shortly following work where significant exposure is expected is a much sought-after capability at INL. It was proposed to employ the Landauer nanoDot dosimeter as a supplemental extremity monitor as an alternative to time-motion dose analyses based on direct radiation measurements, which had proven to be inaccurate and operationally inefficient. Additionally, this process does not involve the nanoDot in the US Department of Energy Laboratory Accreditation Program (DOELAP) process, which significantly reduces operational complexity. A dose conversion value for the nanoDot dosimeter was derived from direct comparisons with a DOELAP-accredited extremity dosimeter. The geometry or placement of the nanoDot relative to the accredited extremity dosimeter was kept as proximate as possible to best replicate the expected results from the accredited extremity dosimeter. Upon implementation, the nanoDot has proven to be effective in providing reasonable and timely extremity-dose estimates for operational control.

History of personal dosimetry performance testing in the United States

The basis for personal dosimetry performance testing in the United States is ANSI/HPS N13.11 (2001). Now in its third edition, this standard has been in place since 1983. Testing under this standard is administered by the National Voluntary Accreditation Program (NVLAP), and accreditation of dosimetry processors under this program is required by US Nuclear Regulatory Commission (NRC) regulations. The US Department of Energy (DOE) also maintains a testing program for its laboratories and contractors, administered by the Department of Energy Laboratory Accreditation Program (DOELAP). A focus in recent years has been the modification of ANSI/HPS N13.11 to allow acceptance by both testing programs in order to bring harmonisation to US personal dosemeter processing testing. Since there is no type testing program in the US for personal dosemeters, the testing philosophy of ANSI N13.11 has always combined elements of type testing and routine performance testing. This philosophy is explored in detail in this presentation, along with trends in the development of the document to its present state. In addition, a look will be taken at what the future holds for the next revision of the document, scheduled to begin in 2005.

Determining the Lower Limit of Detection For Personnel Dosimetry Systems

A simple method for determining the lower limit of detection (LLD) for personnel dosimetry systems is described. The method relies on the definition of a critical level and a detection level. The critical level is the signal level above which a result has a small probability of being due to a fluctuation of the background. All results below the critical level should not be reported as an indication of a positive result. The detection level is the net signal level (i.e., dose received) above which there is a high confidence that a true reading will be detected and reported as a qualitatively positive result. The detection level may be identified as the LLD. A simple formula is derived to allow the calculation of the LLD under various conditions. This type of formula is being used by the Department of Energy Laboratory Accreditation Program (DOELAP) for personnel dosimetry. Participants in either the National Voluntary Laboratory Accreditation Program (NVLAP) for personnel dosimetry or DOELAP can use performance test results along with a measurement of background levels to estimate the LLDs for their dosimetry system. As long as they maintain their dosimetry system such that the LLDs are less than half the lower limit of the NVLAP or DOELAP test exposure ranges, dosimetry laboratories can avoid testing failures due to poor performance at very low exposures.

Mixed Field Personnel Dosimetry Using a Nearly Tissue-Equivalent Multi-Element Thermoluminescence Dosemeter

Abstract The method of response interpretation for determining dose equivalents of a new multi-element thermoluminescence dosemeter in mixed photon-beta and photon-neutron fields is described. The four TL chips are LiF:Mg,Ti, each covered by its own unique filter. Experiments to determine the response of the dosemeter and to test the dose calibration algorithm were performed according to the standard established by the US Department of Energy Laboratory Accreditation Program (DOELAP). It has been shown that the dosemeter response can be used to identify the mixture type. The accuracy of the system has been proven in blind testing to be well within DOELAP tolerance limits in all test categories.