This note discusses the use of blank or background counting data that are measured for times that differ from times used for the sample counts. The correct formula for the minimum detectable activity, under this condition, is given as follows: MDA = [3 + 3.29 square root of Rbtg(1 + tg/tb)]/epsilon tg, where Rb denotes background count rate, tb and tg denote background and gross count times, and epsilon denotes counting efficiency. Counting backgrounds for a long time reduces decision levels, uncertainties, and minimum detectable activities. These benefits are fully available only when there is no other source of variability than random fluctuations in count rates.
This report was .prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes a n y legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by t h e United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Summary As part of its ongoing efforts to reduce doses to workers to levels as low as reasonably achievable (ALARA), Westinghouse Hanford Company (WHC) tasked the Health Protection Department of the Pacific Northwest Laboratory (PNL) to review operations at the 105 K-East Fuel Storage Basin (105 K-East). This review included both routine operations and a proposed campaign to encapsulate N-Reactor fuel stored there. This report summarizes the results of PNL's reviews of policy, procedures, and practices for operations at 105 K-East as well as an evaluation of the major sources of occupational radiation exposures. Where possible, data previously collected by WHC and its predecessors were used. In addition, PNL staff developed a threedimensional model of the radiological environment within 105 K-East to assess the relative contributions of different radiation sources to worker dose and to provide a decision tool for use in evaluating alternative methods of dose rate reduction. The model developed by PNL indicates that for most areas in the basin the primary source of occupational radiation exposure is the contaminated concrete surfaces of the basin near the waterline. Basin cooling water piping represents a significant source in a number of areas, particularly the Technical Viewing Pit. This report contains specific recommendations to reduce the impact of these sources of occupational radiation exposure in 105 K-East. Other recommendations to reduce doses to workers during activities such as filter changes and filter sampling are also included. .
The lognormal distribution has a number of properties that do not lend themselves to simple "back-of-the-envelope" calculations. Mathematical relationships are presented for the basic parameters of the large population lognormal distribution as a function of characteristics available to, or needed by, the risk analyst. A freeware computer program called LOGNORM4 has been written to take the tedium out of determining various characteristics of lognormal distributions, given 1 of 15 sets of values that uniquely specify a lognormal distribution.
T his report wao prepared as an accou11l ur work sponsored by tne Un 1ted States Government. Neither the Un ited States nor the Energy Research and Development Adm inistration/ Un ited States Nuclear Regulatory Comm ission , nor any of their employees, nor any of the ir contractors, subcu11ln:tc..;lors, or their employees, makes any warranty. exprP.ss nr imrli.,.d , or assumes any legal liabil ity or responsib ility fof th~:~ accuracy, completeness or usefulness of IIIW information. nflfliUFttlls. rrnrl11rt or process disclosed, or represents that its use would not infringe privately owned rights.
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