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Radiation of powdered milk produced at Londrina, PR, Brazil
Radiation Physics and Chemistry 61 (2001) 691–692
Radiation of powdered milk produced at Londrina, PR, Brazil F.L. Melquiadesa,*, C.R. Appolonib a
State University of Center-West, Department of Chemistry and Physics, CP 730, CEP 85015-430, Guarapuava-PR, Brazil b State University of Londrina, CCE, Dep. of Physics, CP 6001, CEP 86051-990, Londrina-PR, Brazil
Abstract This work deals with the measurement of radioactive activities in powdered milk, with high resolution gamma-ray spectrometry, using a HPGe detector. Preliminary measurements were accomplished to define the kind of the system shield, the geometry of the sample recipient, the size of the sampling and the self absorption correction. It was possible to measure the radionuclides 40K, 137Cs and 208Tl. Tukey’s average comparison test was used to check the repeatability of the measurements. r 2001 Elsevier Science Ltd. All rights reserved. Keywords: Gamma-ray spectrometry; Radionuclides; Milk
The measurement of gamma emission lines due to radioactivity in the environment and in food is of fundamental importance for controlling the radiation levels which human are exposed to directly or indirectly. This work deals with the measurement of gamma lines in powdered milk, using a high resolution HPGe gamma spectrometry with a relative efficiency of 10%, coupled to a standard electronic nuclear chain and a multichannel card of 8192 channels. Preliminary measurements were accomplished to define the kind of the system shield, the geometry of the sample recipient, the size of the sampling and the correction of self absorption. Two kinds of powdered milk produced at Londrina, state of Paran!a, southern Brazil, were analyzed: integral powdered milk cativa and the integral powdered milk polly. The samples were properly accommodated in a Marinelli beaker of 2.1 l, sealed and kept for 40 days. The counting time of each measurement was two days. It was possible to identify the radionuclides 40K, 137Cs and 232Th (from 208Tl, because the samples were in secular equilibrium), the activities of which were calculated according to the International Atomic Energy Agency (IAEA) norms. The detector efficiency was measured employing cali-
brated samples, prepared from IAEA certified standards mixed with powdered milk, with the same geometry as the samples. The results are presented in Table 1. Tukey’s average comparison test was used to check the repeatability of the measurements and the absence of significant systematic deviation.
Table 1 Activity statistics results from cativa and polly powdered milk samples (in dry mass)a K
Activity
137
Cs Activity 232Th
Activity
Polly Milk N Mean (Bq/kg) Sr (Bq/kg) RSDr R (Bq/kg)
18 475 12 2.53% 33.6
2 5.1–7.3
5 1.6–3.6
Cativa Milk N Mean (Bq/kg) Sr (Bq/kg) RSDr R (Bq/kg)
18 489 13 2.65% 36.4
3 7.0–11.2
8 1.7–3.7
a
*Corresponding author. E-mail address: [email protected] (F.L. Melquiades).
40
Nuclide
N: number of determinations; Sr : standard deviation; RSDr : relative standard deviation of repeatability; r: repeatability r ¼ 2:8 Sr :
0969-806X/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 6 X ( 0 1 ) 0 0 3 7 6 - 0
692 Table 2 40 K, 137Cs and
F.L. Melquiades, C.R. Appoloni / Radiation Physics and Chemistry 61 (2001) 691–692
232
Th activities in milk samples 40
K (Bq/L)
Cativa Milk 5572 Polly Milk 5372 Hong Kong Milkc 4871 c
137
232
0.82–1.32 0.60–0.82 0.01–0.08
0.20–0.44 0.19–0.42 o0.1
Cs (Bq/L)
Th (Bq/L)
of the literature). On the other hand, the Cativa and Polly milk presented normal 40K radioactivity levels. In general, the activity of radionuclides was below the maximum level permitted by IAEA and CNEN (National Nuclear Energy Center), so these kinds of milk can be normally consumed.
(Yu and Mao, 1994)
It can be concluded that, in general, the implemented technique showed good results when compared with other works (Table 2 shows a comparison with one work
References Yu, K.N., Mao, S.Y., 1994. Appl. Radiat. Isot. 45 (10), 1031–1034.
Radiation of powdered milk produced at Londrina, PR, Brazil F.L. Melquiadesa,*, C.R. Appolonib a
State University of Center-West, Department of Chemistry and Physics, CP 730, CEP 85015-430, Guarapuava-PR, Brazil b State University of Londrina, CCE, Dep. of Physics, CP 6001, CEP 86051-990, Londrina-PR, Brazil
Abstract This work deals with the measurement of radioactive activities in powdered milk, with high resolution gamma-ray spectrometry, using a HPGe detector. Preliminary measurements were accomplished to define the kind of the system shield, the geometry of the sample recipient, the size of the sampling and the self absorption correction. It was possible to measure the radionuclides 40K, 137Cs and 208Tl. Tukey’s average comparison test was used to check the repeatability of the measurements. r 2001 Elsevier Science Ltd. All rights reserved. Keywords: Gamma-ray spectrometry; Radionuclides; Milk
The measurement of gamma emission lines due to radioactivity in the environment and in food is of fundamental importance for controlling the radiation levels which human are exposed to directly or indirectly. This work deals with the measurement of gamma lines in powdered milk, using a high resolution HPGe gamma spectrometry with a relative efficiency of 10%, coupled to a standard electronic nuclear chain and a multichannel card of 8192 channels. Preliminary measurements were accomplished to define the kind of the system shield, the geometry of the sample recipient, the size of the sampling and the correction of self absorption. Two kinds of powdered milk produced at Londrina, state of Paran!a, southern Brazil, were analyzed: integral powdered milk cativa and the integral powdered milk polly. The samples were properly accommodated in a Marinelli beaker of 2.1 l, sealed and kept for 40 days. The counting time of each measurement was two days. It was possible to identify the radionuclides 40K, 137Cs and 232Th (from 208Tl, because the samples were in secular equilibrium), the activities of which were calculated according to the International Atomic Energy Agency (IAEA) norms. The detector efficiency was measured employing cali-
brated samples, prepared from IAEA certified standards mixed with powdered milk, with the same geometry as the samples. The results are presented in Table 1. Tukey’s average comparison test was used to check the repeatability of the measurements and the absence of significant systematic deviation.
Table 1 Activity statistics results from cativa and polly powdered milk samples (in dry mass)a K
Activity
137
Cs Activity 232Th
Activity
Polly Milk N Mean (Bq/kg) Sr (Bq/kg) RSDr R (Bq/kg)
18 475 12 2.53% 33.6
2 5.1–7.3
5 1.6–3.6
Cativa Milk N Mean (Bq/kg) Sr (Bq/kg) RSDr R (Bq/kg)
18 489 13 2.65% 36.4
3 7.0–11.2
8 1.7–3.7
a
*Corresponding author. E-mail address: [email protected] (F.L. Melquiades).
40
Nuclide
N: number of determinations; Sr : standard deviation; RSDr : relative standard deviation of repeatability; r: repeatability r ¼ 2:8 Sr :
0969-806X/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 6 X ( 0 1 ) 0 0 3 7 6 - 0
692 Table 2 40 K, 137Cs and
F.L. Melquiades, C.R. Appoloni / Radiation Physics and Chemistry 61 (2001) 691–692
232
Th activities in milk samples 40
K (Bq/L)
Cativa Milk 5572 Polly Milk 5372 Hong Kong Milkc 4871 c
137
232
0.82–1.32 0.60–0.82 0.01–0.08
0.20–0.44 0.19–0.42 o0.1
Cs (Bq/L)
Th (Bq/L)
of the literature). On the other hand, the Cativa and Polly milk presented normal 40K radioactivity levels. In general, the activity of radionuclides was below the maximum level permitted by IAEA and CNEN (National Nuclear Energy Center), so these kinds of milk can be normally consumed.
(Yu and Mao, 1994)
It can be concluded that, in general, the implemented technique showed good results when compared with other works (Table 2 shows a comparison with one work
References Yu, K.N., Mao, S.Y., 1994. Appl. Radiat. Isot. 45 (10), 1031–1034.