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Spectrometry characteristics of photon fields and atmospheric radionuclide deposits monitoring in one part of Southern Bohemia
International Congress Series 1276 (2005) 418 – 419
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Spectrometry characteristics of photon fields and atmospheric radionuclide deposits monitoring in one part of Southern Bohemia J. Kluson, L. Thinova*, T. Cechak, T. Trojek CTU, Faculty of Nuclear Sciences and Physical Engineering, Praha, Czech Republic
Abstract. The (bio)monitoring in the neighborhood of Nuclear Power Plant (NPP) Temelin started in the year 2000—1 year before the initial power plant operation. In the years 2000, 2002, and 2004, the spectrometry characteristics of photon-spectra measurement were included in biomonitoring. The area of interest contained 29 sampled locations along eight radial profiles intersecting the area at distances from 2 to 20 km around Temelin NPP. Laboratory, as well as in situ, gamma spectrometric method enables to determine presence of natural and manmade radionuclides with very good limits of detection. In situ gamma spectrometry consists of direct air kerma rate measurements and air kerma rate calculations from photon-spectra measurement. The laboratory gamma spectrometric measurement (geometry of Marinelli containers) is used for the determination of radionuclides in the samples of pine bark, Shreber’s moss, forest humus, edible mushrooms, and forest berries. The trend analysis of measurement results enables the completion of the main task of this project: to describe the influence of NPP Temelin on the radiation increase in its neighborhood. Only 137Cs of manmade radionuclides has been identified. D 2004 Elsevier B.V. All rights reserved. Keywords: Gamma spectrometry; Biomonitoring; Trend analysis; Nuclear power plant; Dosimetry
1. Introduction For the past 5 years, FNSPE CTU in Prague took part in monitoring the influence of Nuclear Power Plant (NPP) Temelin on the environment within 20-km radius of the plant. Using ecological principles, the changes in environment quality are indicated by biological indicator changes. We chose forest humus, surface of pine bark, Shreber’s moss, edible mushrooms, and forest berries. The year 2000 was designated as the reference year before the start of the NPP operation, and 2001 was the year of the initial operation. The biomonitoring for years 2000, 2002, and * Corresponding author. Tel.: +42 224 358 235; fax: +42 224 811 074. E-mail address: [email protected] (L. Thinova). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.11.113
J. Kluson et al. / International Congress Series 1276 (2005) 418–419
419
2004 also included assessment of the dosimetry and spectrometry characteristic of the photon fields. 2. Monitored area Monitored area contains 29 sampled locations along eight radial profiles intersecting the area of interest (the measuring points are located 2, 5, 10, 20 km from NPP, distance of 20 km is a comparison area). The pine bark and moss were sampled at the selected sites twice yearly, forest humus once during spring months, mushrooms and berries once in growing season. The top 3 mm of tree bark was taken at reference height of 1 m. The moss samples were cut by scissors. Forest humus was sampled with respect to resolution of surface layers, according to the degree of hummification. In total, 203 samples in 2000, 222 samples in 2001, 223 samples in 2002, and 251 samples in 2003 were collected. In situ gamma spectrometry is conducted at selected 15 points in order to sufficiently cover the area of interest. 3. Materials and methods In the gamma spectrometry laboratory, the samples were, after drying, enclosed in Marinelli containers (0.5l), surrounding during the measurements a coaxial HPGe detector. Processing of measured spectra in the range up to 3 MeV provided mass-related activity (Bq/ kg) of naturally radioactive elements (40K, 226Ra, and 232Th) and contaminant 137Cs (resulting from nuclear weapon tests in the fifties of last century and from Chernobyl accident fallout) using program SP DEMOS. The resulting data were used for the trend analysis. Two methods of the gamma fields in situ measurements of the dosimetric characteristics were selected (all measurements made at a height of 1 m above ground): (1) determination of air kerma rate by direct measurement (Fig. 1A); (2) air kerma rate calculation from photon spectra measurement using a portable spectrometer with scintillation detector NaI(Tl) 3U3U in the energy range up to 3 MeV (Fig. 1B). 4. Conclusions The measured spectra represent characteristic spectra of natural background. In the calculated energy distribution of air kerma rate, it is not possible to identify (with the exception of the abovementioned 137Cs) any significant contribution of any manmade radionuclide. Based on the so-far obtained results of monitoring, as well as of the trend analysis, it can be stated that it was confirmed that JETE operation does not have any impact on the level of natural background in the measured reference points.
Fig. 1. Determination of air kerma rate by direct measurement and by calculation from photon spectra.
www.ics-elsevier.com
Spectrometry characteristics of photon fields and atmospheric radionuclide deposits monitoring in one part of Southern Bohemia J. Kluson, L. Thinova*, T. Cechak, T. Trojek CTU, Faculty of Nuclear Sciences and Physical Engineering, Praha, Czech Republic
Abstract. The (bio)monitoring in the neighborhood of Nuclear Power Plant (NPP) Temelin started in the year 2000—1 year before the initial power plant operation. In the years 2000, 2002, and 2004, the spectrometry characteristics of photon-spectra measurement were included in biomonitoring. The area of interest contained 29 sampled locations along eight radial profiles intersecting the area at distances from 2 to 20 km around Temelin NPP. Laboratory, as well as in situ, gamma spectrometric method enables to determine presence of natural and manmade radionuclides with very good limits of detection. In situ gamma spectrometry consists of direct air kerma rate measurements and air kerma rate calculations from photon-spectra measurement. The laboratory gamma spectrometric measurement (geometry of Marinelli containers) is used for the determination of radionuclides in the samples of pine bark, Shreber’s moss, forest humus, edible mushrooms, and forest berries. The trend analysis of measurement results enables the completion of the main task of this project: to describe the influence of NPP Temelin on the radiation increase in its neighborhood. Only 137Cs of manmade radionuclides has been identified. D 2004 Elsevier B.V. All rights reserved. Keywords: Gamma spectrometry; Biomonitoring; Trend analysis; Nuclear power plant; Dosimetry
1. Introduction For the past 5 years, FNSPE CTU in Prague took part in monitoring the influence of Nuclear Power Plant (NPP) Temelin on the environment within 20-km radius of the plant. Using ecological principles, the changes in environment quality are indicated by biological indicator changes. We chose forest humus, surface of pine bark, Shreber’s moss, edible mushrooms, and forest berries. The year 2000 was designated as the reference year before the start of the NPP operation, and 2001 was the year of the initial operation. The biomonitoring for years 2000, 2002, and * Corresponding author. Tel.: +42 224 358 235; fax: +42 224 811 074. E-mail address: [email protected] (L. Thinova). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2004.11.113
J. Kluson et al. / International Congress Series 1276 (2005) 418–419
419
2004 also included assessment of the dosimetry and spectrometry characteristic of the photon fields. 2. Monitored area Monitored area contains 29 sampled locations along eight radial profiles intersecting the area of interest (the measuring points are located 2, 5, 10, 20 km from NPP, distance of 20 km is a comparison area). The pine bark and moss were sampled at the selected sites twice yearly, forest humus once during spring months, mushrooms and berries once in growing season. The top 3 mm of tree bark was taken at reference height of 1 m. The moss samples were cut by scissors. Forest humus was sampled with respect to resolution of surface layers, according to the degree of hummification. In total, 203 samples in 2000, 222 samples in 2001, 223 samples in 2002, and 251 samples in 2003 were collected. In situ gamma spectrometry is conducted at selected 15 points in order to sufficiently cover the area of interest. 3. Materials and methods In the gamma spectrometry laboratory, the samples were, after drying, enclosed in Marinelli containers (0.5l), surrounding during the measurements a coaxial HPGe detector. Processing of measured spectra in the range up to 3 MeV provided mass-related activity (Bq/ kg) of naturally radioactive elements (40K, 226Ra, and 232Th) and contaminant 137Cs (resulting from nuclear weapon tests in the fifties of last century and from Chernobyl accident fallout) using program SP DEMOS. The resulting data were used for the trend analysis. Two methods of the gamma fields in situ measurements of the dosimetric characteristics were selected (all measurements made at a height of 1 m above ground): (1) determination of air kerma rate by direct measurement (Fig. 1A); (2) air kerma rate calculation from photon spectra measurement using a portable spectrometer with scintillation detector NaI(Tl) 3U3U in the energy range up to 3 MeV (Fig. 1B). 4. Conclusions The measured spectra represent characteristic spectra of natural background. In the calculated energy distribution of air kerma rate, it is not possible to identify (with the exception of the abovementioned 137Cs) any significant contribution of any manmade radionuclide. Based on the so-far obtained results of monitoring, as well as of the trend analysis, it can be stated that it was confirmed that JETE operation does not have any impact on the level of natural background in the measured reference points.
Fig. 1. Determination of air kerma rate by direct measurement and by calculation from photon spectra.