| 1. |
- Chamizo, E., et al.
(författare)
-
Insights into the Pu isotopic composition (239Pu, 240Pu, and 241Pu) and 236U in marshland samples from Madagascar
- 2020
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 740
-
Tidskriftsartikel (refereegranskat)abstract
- This work provides new insights into the presence of 239Pu, 240Pu, 241Pu, and 236U in the Southern Hemisphere through the study of peat bog cores from marshlands in Madagascar (19°S). 210Pb, 238Pu and 239+240Pu activities were characterized by alpha spectrometry in previous studies. Here, Pu from alpha-spectrometry discs corresponding to 10 peat-bog cores (85 samples) was reassessed for the aim of completing its isotopic composition (239Pu, 240Pu, and 241Pu) by Accelerator Mass Spectrometry. In addition, 236U was studied in a single core exhibiting unusually low 240Pu/239Pu ratios. Integrated 240Pu/239Pu atom ratios in the single cores ranged above and below the (0–30°S) fallout average ratio, 0.173 ± 0.027, from 0.126 ± 0.003 to 0.206 ± 0.002, without a regional pattern, thereby demonstrating the heterogeneous distribution of the 239Pu and 240Pu signal. However, such a variability was not observed for 241Pu/239Pu, ranging from (6 ± 1) · 10−4 to (11 ± 1) · 10−4 and consistently below the (0–30°S) fallout ratio of (9.7 ± 0.3) · 10−4 (2012). The integrated 236U/239Pu atom ratio in the studied core, 0.147 ± 0.005, was also significantly lower than the values reported for the global fallout in the Northern Hemisphere, in the 0.20–0.23 range. Our results point out to stratospheric fallout as the main source of both 236U and 241Pu at the studied site, whereas 239Pu and 240Pu signals show the influence of tropospheric fallout from the low-yield tests conducted in Australia (1952–1958) by United Kingdom and in French Polynesia (1966–1975) by France despite the long relative distances (i.e. about 15,000 and 8500 km). It was also demonstrated that a representative number of samples is necessary in order to assess Pu contamination and its various origins in a specific region in the Southern Hemisphere due to the heterogeneous distribution, and results based on single sample analysis should be interpreted with caution. © 2020 Elsevier B.V.
|
|
| 2. |
- Holm, Elis, et al.
(författare)
-
Fallout of 238 Pu over Madagascar following the SNAP 9 A satellite failure.
- 2015
-
Ingår i: Environmental Radiochemical Analysis V. P. Warwick (ed.). - UK : Royal Society of Chemistry, UK. - 9781782621553 ; :12, s. 44-49
-
Bokkapitel (refereegranskat)abstract
- After the SNAP 9A satellite accident in 1964, the dispersion of Pu was investigated as a function of latitude North and South. It was obvious that most of the fallout of 238Pu was on the southern hemisphere. However no data from Madagascar, where the accident happened, were reported. This paper describes the analysis of peat bog samples for Pu-isotopes by alpha spectrometry after radiochemical separation. To investigate especially the presence of 239Pu, selected samples were analyzed for 239Pu and 240Pu using mass spectrometric analyses, AMS.
|
|
| 3. |
- Rääf, C., et al.
(författare)
-
On the presence of plutonium in Madagascar following the SNAP-9A satellite failure
- 2017
-
Ingår i: Journal of Environmental Radioactivity. - : Elsevier BV. - 0265-931X. ; 177, s. 91-99
-
Tidskriftsartikel (refereegranskat)abstract
- This study examined the Pu-238 and 239+249PU activity concentration and the Pu-240/Pu-239 atomic ratio in peat bogs sampled in 2012 from marshlands in central Madagascar. The purpose was to investigate the., presence of plutonium isotopes, (238,) (239,) Pu-240, from the 1964 satellite failure carrying a SNAP-9A radiothermal generator. With an average Pu-238/Pu239+240 activity ratio of 0.165 +/- 0.02 (decay corrected to 1964), the peat bogs in Madagascar exhibit similar values as the ones found in the southeastern African continent, except they are one order of magnitude higher than expected (0.025) from global fallout in the Southern Hemisphere. The Pu-240/Pu-239 atomic ratio showed a distinct decrease for layers dating back to the mid-1960s (down to 0.069 compared with an anticipated ratio of 0.17 for global fallout), indicating that the SNAP-9A failure also resulted in an elevated deposition of Pu-239. The obtained results demonstrate that further Pu analysis in Madagascar and in southeastern continental Africa is necessary to fully account for the regional Pu deposition from the SNAP-9A event. (C) 2017 Elsevier Ltd. All rights reserved.
|
|
