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 NRC TLD DIRECT RADIATION MONITORING NETWORK

NUREG-0837
Progress report

U.S. Nuclear Regulatory Commission (NRC)

The following is taken from the Preface.

The Network was operated by the NRC in cooperation with participating
states to provide continuous measurement of the ambient radiation
levels around licensed NRC facilities, primarily nuclear power reactors.
Ambient radiation levels result from naturally occurring radionuclides
present in the soil, cosmic radiation constantly bombarding the earth from outer space, and the contribution, if any, from the monitored facilities and other man - made sources.

The Network was intended to measure radiation levels during routine facility operations and to establish background radiation levels used to assess the radiological impact of an unusual condition, such as an accident. This report presents the radiation levels measured around all facilities in the Network for a said quarter. Network measured radiation data compiled quarterly. In some instances, two power reactor
facilities are monitored by the same set of dosimeters (e.g., Kewaunee and Point Beach).

All radiation measurements are made using small, passive detectors
called thermoluminescent dosimeters (TLDs), which provide a quantitative measurement of the radiation levels in the area in which they are placed. Each site is monitored by arranging approximately 40 to 50 TLD stations in two concentric rings extending to about five miles from the facility. All TLD stations are outside the site boundary of the facility. A complete description of the program can be found in NUREG-0837, Volume 2, Number 4.

The National Institute of Standards and Technology (formerly the National Bureau of Standards) has performed an independent study of the following characteristics of the NRC dosimetry system;
energy response, angular dependence, temperature and humidity
sensitivity, fading, light dependence, self-irradiation, and reproducibility. NIST has also tested the response of the NRC's dosimetry system against the requirements of ANSI N545-1975 and NRC Regulatory Guide 4.13. Details of this testing can be found in NUREG/CR-3775.

The radiation levels are presented as gross and net exposures. The gross exposure includes naturally occurring background radiation, radiation levels resulting from a facility's operation, and the exposure received during transport and storage of the TLD.
Net exposures are obtained by subtracting an estimate of the exposure received by the dosimeters during transit from the gross exposures.
All exposures are normalized to a 90-day quarter (standard quarter)
and reported in units of milliroentgens (mR).
Station numbers for which no data are reported included stations which have been deleted, stations for which the TLD was lost during the quarter, or stations for which the TLD was damaged. When control dosimeter data are unavailable, no net exposures are calculated.

Three sets of data are presented for each site. The first set includes
the TLD station number, it's direction and distance from the site, the integrated gross exposure for the period, the net exposure normalized to a 90-day quarter (standard quarter), and the historical average and standard deviation for the station. All measurements for the current quarter are listed with their respective random and total uncertainties. The uncertainties are listed in the following format:

X + - Sx; Ux

where X = value of the result

Sx = random uncertainty expressed as one standard deviation

Ux = combined total uncertainty

The second set of data summarizes the average net exposure measured
in each of the 16 standard windrose sectors around the facility, normalized to a standard quarter. The third set of data summarizes the average net exposure measured at three ranges of distances from the facility, normalized to a standard quarter. When average net exposures cannot be reported because of the unavailability of the site's
transit control dosimeter, the average gross exposures, normalized to a standard quarter, are reported in these two sets of data.
The "Std.Dev." refers to the standard deviation of the measurements made in each
 sector and range, respectively.
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The copy we have is:

NUREG-0837
Vol. 17, No. 4
lists 71 sites monitored during the fourth quarter of 1997.
To order the latest copy (Vol. and No.)
Try for contact:

The Superintendent of Documents
U.S. Government Printing Office
P.O. Box 37082
Washington, DC. 20402-9328

As of this date: 10-23-02 I do NOT know the price of a current copy of this publication.
You may want to write and ask at above address.
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