A study was performed to assess the performance of Hanford personnel neutron dosimetry. Measurements were performed in the Plutonium Finishing Plant (PFP), which is the facility with the most significant worker exposures to neutrons on the Hanford site. The study was conducted in two parts: one assessing whole body dosimetry and one assessing extremity dosimetry. For both parts of the study, the Tissue-Equivalent Proportional Counter (TEPC) was used as the principle instrument for characterizing workplace neutron fields.In the whole body study, 12.7-cm-diameter TEPCs were used in ten different locations in the facility. At each location, TLD and TED personnel dosimeters were exposed on a water-filled phantom at the same location to enable a comparison of neutron dose equivalents as measured by the TEPC and as determined from the personnel dosimeters.In the extremity study, 1.27-cm-diameter TEPCs were exposed inside the fingers of gloves worn in gloveboxes. Hanford extremity dosimeters (gamma sensitive ring TLDs) were wrapped around the TEPCs. The glove, loaded with TEPCs and dosimeters, was exposed to six different cans of plutonium, simulating the exposure that a worker's fingers would receive in a glovebox. The comparison of TEPC-measured neutron dose equivalent to TLD-measured gamma dose equivalent provided neutron-to-gamma ratios that can be used to estimate the neutron dose equivalent received by a worker's finger based on the gamma readings of an extremity dosimeter.The study also utilized other neutron instruments including a Snoopy and detectors based on bubble technology for assessing neutron exposures, providing a comparison of the effectiveness of these instruments for workplace monitoring.The study concludes that the TLD component of the Hanford Combination Neutron Dosimeter (HCND) performs adequately overall, with a positive bias of 30%, but exhibits excessive variability in individual results due to instabilities in the algorithm. The electrochemically etched TED response was less variable but only 20% of the TEPC reference dose on average because of the low neutron energies involved. The neutron response of the Hanford Standard Dosimeter (TLD) was more variable than the TLD component of the HCND and biased high by a factor of 8 overall due to its calibration to unmoderated 252 Cf. The study recommends further work to correct instabilities in the HCND algorithm and to explore the potential shown by the bubble-based dosimeters.iii EXECUTIVE SUMMARYThis report describes measurements performed in the Plutonium Finishing Plant (PFP) work environment to validate the recorded neutron dose for Hanford workers. The responses of Hanford dosimeter components, including the Hanford standard dosimeter (HSD), and both the thermoluminescent dosimeter (TLD) and track-etch dosimeter (TED) components of the Hanford combination neutron dosimeter (HCND) have been well characterized under the low-scatter conditions of the Hanford 318 Radiation Standards Laboratory. Hanford whole body personnel dosimeter respon...

SummaryThe U.S. Department of Energy (DOE) requires that environmental monitoring programs be conducted at its Hanford Site in south-central Washington to protect the site's environmental and cultural resources, the public, and site workers by achieving site and contractor compliance with environmental, public health, and resource protection laws, regulations, and DOE Orders. Pacific Northwest National Laboratory (PNNL) manages Public Safety and Resource Protection Projects (PSRPP) for DOE's Richland Operations Office to monitor the Hanford environment, provide assurance that the site is operated in compliance with applicable environmental regulations, and conduct impact assessments to protect public and worker safety and Hanford's ecological and cultural resources. Under the PSRPP, the Surface Environmental Surveillance Project is responsible for measuring the concentrations of radiological and nonradiological contaminants in environmental media and for assessing the potential impacts of these materials on the environment and the public. Various media are collected onsite in the 600 Area, and offsite at perimeter, community, and distant locations. Samples of air, surface water and sediment, farm products, wildlife, and vegetation are routinely collected and analyzed for radionuclides and various chemical constituents. From 1971 through 2005, ambient external radiation was also measured at selected locations on and off the site.This report briefly describes the principles of thermoluminescent dosimetry and the various thermoluminescent dosimeter (TLD) systems that have been used at Hanford for environmental surveillance of external radiation over its operational history largely by PNNL under the so-called Hanford Environmental Surveillance TLD Program, or simply the TLD program. It presents the results of a review of the measurement of external radiation using TLDs outside of industrialized areas on the site, at locations along the river shoreline, and in areas adjacent to and distant from the Hanford Site. Quality assurance practices and independent measures of system performance are discussed, supplemented by summaries of TLD results from January 1971 through December 2005 (when the TLD program was terminated) and analysis of observed trends. Summary figures and narrative discussion of TLD readings at each surveillance location are included for both terrestrial (onsite and offsite) locations and riparian (Columbia River shoreline) locations.An apparent increase in environmental exposure rates was observed from 1985 through 1989 after a large-scale exchange of TLD chips. Part of the increase is believed to be attributable to the greater sensitivity of replacement TLD chips to low-energy photons, and possible changes in calibration practices in the TLD processing laboratory. Analysis of variance showed that there was a significant difference in TLD readings based on dosimeter type and that, historically, there was a significant difference in readings between location groupings of TLDs (i.e., onsite, perimeter, c...

This document was printed on recycled paper. SummaryThe Pacific Northwest National Laboratory (PNNL) conducted neutron measurements at Hanford's Plutonium Finishing Plant (PFP). The measurements were performed to evaluate the performance of the Hanford Standard Dosimeter (HSD) and the 8816 TLD component of the Hanford Combination Neutron Dosimeter (HCND) in the neutron fields responsible for worker neutron exposures.For this study, TEPC detectors and multisphere spectrometers were used to measure neutron dose equivalent rate, and multispheres were used to measure average neutron energy. Waterfilled phantoms holding Hanford dosimeters were positioned at each measurement location. The phantoms were positioned in the same location where a multisphere measurement was taken and TEPCs were also positioned there. Plant survey meters were also used to measure neutron dose rates at all locations.Three measurement locations were chose near the HC-9B glovebox in room 228A of Building 234-5.The multisphere spectrometers measured average neutron energies in the range of 337 to 555 keV at these locations. Personal dose equivalent, H p (10) n , as measured by the multisphere and TEPC, ranged from 2.7 to 9.7 mrem/h in the three locations. Effective dose assuming a rotational geometry (E ROT ) was substantially lower than H p (10), ranging from 1.3 to 3.6 mrem/h. These values were lower than the reported values from dosimeters exposed on a rotating phantom. Effective dose assuming an AP geometry (E AP ) was also substantially lower than H p (10), ranging from 2.3 to 6.5 mrem/h. These values were lower than the reported values from the dosimeters on slab phantoms. Since the effective dose values were lower than reported values from dosimeters, the dosimeters were shown to be conservative estimates of the protection quantities.iii

No abstract

No abstract