Measurements of99Tc,137Cs,237Np, Pu isotopes and241Am in sediment cores from intertidal coastal and estuarine regions in the Irish Sea

Long-lived radionuclides,⁹⁹Tc,¹³⁷Cs,²³⁷Np, Pu isotopes and²⁴¹Am were determined in the long sediment cores collected from nine intertidal sites around the west Cumbria of the Irish Sea, UK. The inventories of all nuclides measured varied considerably among the sampling sites, but generally their inventories decreased with increasing distance from Sellafield. Furthermore, the inventory ratios with respect to relationship with distance from Sellafield enabled comparison of transport behavior of⁹⁹Tc,¹³⁷Cs,²³⁷Np and²⁴¹Am compared with^239,240Pu. As a consequence, the apparent fractional rate of solution transport to the intertidal sediment was found to increase as follows:⁹⁹Tc>¹³⁷Cs>²³⁷Np>^239,240Pu≥²⁴¹Am.     

Distribution and behaviour of99Tc,237Np,239,240Pu,and241Am in the coastal and estuarine sediments of the Irish Sea

Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for⁹⁹Tc,²³⁷Np,²³⁸Pu,^239,240Pu and²⁴¹Am. The²³⁷Np activity and²³⁹Pu/²⁴⁰Pu ratio were measured simultaneously by ICP-MS, and⁹⁹Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.The activities of⁹⁹Tc,²³⁷Np,^239,240Pu and²⁴¹Am were distributed over a wide range of 1.5–70.5, 0.01–13.3, 2.3–1589, 2.6–1894 Bq/kg, respectively. Activities of these radionuclides decreased exponentially with distance from the Sellafield source. The²⁴¹Am/^239,240Pu and²³⁷Np/^239,240Pu ratios were almost constant with distance from the Sellafield. This result suggests that the distribution and behavior of Np and Pu are controlled by complicated factors such as the influence of transport, the variation with time of Np/Pu ratio in the Sellafield discharges and sedimentary mixing processes in the Irish Sea.     

Development of a bipolar electrolysis system for tritium accumulation in HTO

Due to the different ²⁴⁰Pu/²³⁹Pu atom ratios from different sources of Pu in the environment, Pu isotopes have been widely used for source identification of radionuclides in sediments. In this work, using sector-field ICP-MS, we investigated Pu inventory and its isotopic composition in a lacustrine sediment core collected in Chenghai Lake, SW China. The ²⁴⁰Pu/²³⁹Pu atom ratios in this sediment core ranged from 0.166 to 0.271 with a mean of 0.195±0.021, which was slightly higher than that of global fallout. The ^239+240Pu/¹³⁷Cs activity ratios ranged from 0.0155 to 0.0411, with a mean of 0.0215, and the ^239+240Pu inventory was 35.4 MBq/km²; both ^239+240Pu/¹³⁷Cs activity ratio and Pu inventory were close to those values of global fallout at 20–30 °N. Three peaks were observed for both ¹³⁷Cs and ^239+240Pu activities in the examined sediment core; they most probably indicated the maximum deposition of global fallout between 1963 and 1964, the fallout from a series of Chinese nuclear tests during the 1970s, and the deposition of resuspended Pu-bearing particles from the Chernobyl accident. Therefore, the vertical profile of Pu isotopes should provide useful time markers for rapid dating of recent sediments. These authors contributed equally to this work.     

Geochemical studies on the Chernobyl radioactivity in environmental samples

Artificial radionuclides in deposition and airborne dust samples in 1986 were measured at Tsukuba and 11 stations in Japan. In May 1986, the Chernobyl radioactivity was observed in rain and air samples in Japan. The Chernobyl-derived Pu isotopes, which are characterized by higher²³⁸Pu/^239,240Pu (85) and²⁴¹Pu/²³⁸Pu (0.5) activity ratios than those of the nuclear test-derived Pu and⁹⁰Sr, were detected in deposition and airborne dust samples in Japan, as well as volatile radionuclides such as¹³¹I and¹³⁷Cs. However, the activities of Pu isotopes and⁹⁰Sr observed in Japan were about two and three orders of magnitude lower than those expected from the activity ratios in the total release at Chernobyl, which means that the residence time of Pu in the air was shorter than that of¹³⁷Cs. In order to understand the fractionation between the Chernobyl radionuclides we studied about individual wet and dry deposition. The results suggest that this cause is due to the difference of the particle size of radionuclide-bearing particles, which may be related to the release process of Chernobyl radionuclides.     

Reference material for radionuclides in sediment IAEA-384 (Fangataufa Lagoon sediment)

A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (⁴⁰K, ⁶⁰Co, ¹⁵⁵Eu, ²³⁰Th, ²³⁸U, ²³⁸Pu, ^239+240Pu and ²⁴¹Am). Information values are given for 12 radionuclides (⁹⁰Sr, ¹³⁷Cs, ²¹⁰Pb (²¹⁰Po), ²²⁶Ra, ²²⁸Ra, ²³²Th, ²³⁴U, ²³⁵U, ²³⁹Pu, ²⁴⁰Pu and ²⁴¹Pu). Less reported radionuclides include ²²⁸Th, ²³⁶U, ²³⁹Np and ²⁴²Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units. Retired from IAEA in 2003.     

Presence of 137Cs, Pu isotopes and 241Am in ligurian and Tyrrhenian Seas sediments

During the last ten years, the Italian Universities of Parma and Urbino collaborated on a special radioecological program having the aim to study the levels and the distribution of long-lived radionuclides in different marine and terrestrial matrixes. This paper summarizes the results concerning the concentrations of ^239+240Pu and ²³⁸Pu, ²⁴¹Am and ¹³⁷Cs in sediments collected in the Ligurian and South Tyrrhenian Seas (Rapallo Harbour, Vado Ligure Canyon, Eolie Islands). Superficial sediments and sediment cores were collected. For cores the vertical distribution was calculated and the sedimentation rate obtained. ¹³⁷Cs was determined directly by gamma-spectrometry, while ^239+240Pu, ²³⁸Pu and ²⁴¹Am were separated by extraction chromatography, electroplating and determined by alpha-spectrometry. This revised version was published online in August 2006 with corrections to the Cover Date.     

Deposition of90Sr and plutonium isotopes derived from the Chernobyl accident in Japan

To clarify environmental effects of the Chemobyl radionuclides, long-lived Chernobyl radioactivity (^239,240Pu,²³⁸Pu,²⁴¹Pu and⁹⁰Sr) in deposition samples in May 1986 was measured at 11 stations in Japan. Temporal variation of weekly deposition of⁹⁰Sr differed from that of volatile radionuclides such as¹³¹I and¹³⁷Cs, which may reflect the released process at Chernobyl. On the other hand, the geographical distributions of the monthly deposition of long-lived radionuclides were similar to those of volatile radionuclides, in which maximum deposits of⁹⁰Sr and plutonium were observed in Akita, a northwestern Japan Sea coast site of Honshu Island. Higher²⁴¹Pu deposition in most of the stations, as well as high²³⁸Pu/^239,240Pu activity ratios were observed. The²⁴¹Pu/²³⁸Pu activity ratios in deposition samples were nearly equal to that in the total release, which is clear evidence that Chernobyl-derived plutonium was transported to Japan in May 1986 together with volatile radionuclides although the contribution of Chernobyl Pu was about three orders of magnitude lower than¹³⁷Cs.     

Plutonium isotopes, 241Am and 137Cs activity concentrations in marine sediments of Gökova Bay, Aegean Turkish Coast

Samples of marine surface sediments of different grain sizes collected in Gökova, a small bay on the Aegean Turkish Coast, have been examined to measure alpha- and gamma-radioactivity. The purpose of this research is to define a baseline study of man-made radionuclides on sediments along Gökova Bay, using a combination of direct gamma-spectrometry, radiochemical separation and alpha spectrometry. The analysis of these samples revealed measurable quantities of some artificial radionuclides namely: ^239+240Pu (from 0.13±0.017 to 0.85±0.15 Bq^.kg^–1). ¹³⁷Cs, ²⁴¹Am and ²³⁸Pu were identified at a very low level. Concentration ratios of ²³⁸Pu to ^239+240Pu obtained seem to confirm that this artificial radioactivity is due mainly to Chernobyl accident.     

Certified reference material for radionuclides in seawater IAEA-381 (Irish Sea Water)

A certified reference material (CRM) for radionuclides in seawater, IAEA-381 (Irish Sea Water), is described and the results of certification are presented. The material has been certified for nine radionuclides (⁴⁰K, ⁹⁰Sr, ¹³⁷Cs, ²³⁷Np, ²³⁸Pu, ²³⁹Pu,²⁴⁰Pu, ^239,240Pu and ²⁴¹Am). Information on massic activities with the corresponding 95% confidence intervals are given for eight radionuclides (³H, ¹²⁵Sb, ²³⁴U, ²³⁵U, ²³⁶U, ²³⁸U, ²⁴¹Pu and ²⁴⁴Cm). Less reported radionuclides include ⁶⁰Co, ⁹⁹Tc, and ²⁴²Pu. The CRM may be used for quality assurance/quality control of the analysis of radionuclides in environmental water samples, for the development and validation of analytical methods and for training purposes. The material is available from the IAEA in 5 kg units.     

Anomalously high237Np in intertidal sediments from the Ribble Estuary in the Irish Sea

Depth profiles and inventories of²³⁷Np in sediment cores from the Ribble Estuary in the Irish Sea have been studied along with those of Pu isotopes,²⁴¹Am and¹³⁷Cs, to allow a more detailed look of anomalously high²³⁷Np content observed in this estuary previously. The comprehensive data obtained showed that the depth profiles of both²³⁷Np contents and²³⁷Np/^239,240Pu activity ratios were clearly different from those of^239,240Pu,²⁴¹Am, and¹³⁷Cs and their activity ratios. As much as 80–90% of²³⁷Np inventories (0.32–1.06 kBq/m²), found in three cores, were estimated to be derived from a source other than Sellafield, on the basis of comparison of the²³⁷Np/^239,240Pu inventory ratio (0.65–1.74%) found in the Ribble Estuary cores with those (0.10–0.16%) in the Ravenglass Estuary cores.     

Studies of the vertical distribution of134Cs,137Cs,238Pu,239, 240Pu,241Pu,241Am and210Pb in ombrogenous mires at mid-latitudes

Six peat cores taken from three unmodified blanket and raised bogs in Ireland were sectioned and analyzed for a range of radionuclides including¹³⁴Cs,¹³⁷Cs,²³⁸Pu,²³⁹Pu,²⁴¹Am, and²¹⁰Pb.¹³⁴Cs and¹³⁷Cs were measured by high resolution gamma-spectrometry, while the transuranium nuclides were determined after chemical separation by alpha-spectrometry.²⁴¹Pu, present on the electroplated discs together with Pu(), was measured directly by low-level liquid scintillation counting. Core chronologies were established by measuring the unsupported²¹⁰Pb component using low energy photon spectrometry (LEPS). From the resulting profiles, relaxation depths and migration rates for the above mentioned radionuclides have been determined and differences in the values of these parameters interpreted.²³⁸Pu/^239,240Pu and²⁴¹Pu/^239,240Pu ratios have been examined carefully and are discussed in some detail. Finally, the contribution from Chernobyl to the total radiocaesium inventory in each core has been established using the¹³⁴Cs/¹³⁷Cs ratio observed in the initial fallout from Chernobyl.     

Analysis of 36Cl in Savannah River Site radioactive waste

The present work shows the activity levels of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that ⁴⁰K and ²²⁸Ra concentration is nearly uniform throughout the studied area while ²²⁶Ra and ¹³⁷Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of ²²⁶Ra/²²⁸Ra ratio (0.72) in the sediments indicates that ²³⁸U has relatively greater solubility and mobility than ²³²Th. Similarly, low activity ratio (0.18) for ¹³⁷Cs/⁴⁰K reflects the presence of very high content of ⁴⁰K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between ²²⁶Ra and ²²⁸Ra and ¹³⁷Cs and ⁴⁰K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.     

Simultaneous determination of238Pu,239+240Pu,241Pu,241Am,242Cm,244Cm,89Sr,and90Sr in vegetation samples,and application to Chernobyl-fallout contaminated grass

A radiochemical procedure is described for the simultaneous determination of²³⁸Pu,^239+240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm,²⁴⁴Cm,⁸⁹Sr, and⁹⁰Sr in vegetation samples. The method was applied for the determination of these, radionuclides in grass, collected near Munich after the fallout from the reactor accident at Chernobyl, USSR. The specific activities observed were (in Bq kg^–1 dry weight):²³⁸Pu, 0.077;^239+240Pu, 0.15;²⁴¹Pu, 3.9;²⁴¹Am, 0.031;²⁴²Cm, 3.0;²⁴⁴Cm, 0.008;⁸⁹Sr, 2000;⁹⁰Sr, 99.     

A new reference material for radionuclides in the mussel sample from the Mediterranean Sea (IAEA-437)

A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (⁴⁰K, ²³⁴U, ²³⁸U, and ^239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (¹³⁷Cs, ²¹⁰Pb(²¹⁰Po), ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁰Th, ²³²Th, ²³⁵U, and ²⁴¹Am). Results for less frequently reported radionuclides (⁹⁰Sr, ¹²⁹I, ²³⁸Pu, ²³⁹Pu, and ²⁴⁰Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.     

Radioactivity of plutonium isotopes, <Superscript>137</Superscript>Cs and their ratio in sediment,seawater and biota from the east coast of Peninsular Malaysia

This study with sampling expeditions of marine sediment, seawater and biota were performed at 30 stations within Malaysian Exclusive Economic Zone (EEZ). A total of >400 samples were collected to determine the activity concentration of anthropogenic radionuclides (^239+240Pu, ¹³⁷Cs) and their activity ratio (^239+240Pu/¹³⁷Cs) in sediments, seawater and biota. The purpose of this study was to determine the concentration levels for these radionuclides and to evaluate any occurrence of radioactive contamination. Sediment cores were obtained using multicorer device, while water samples via co-precipitation techniques and biota was purchased from local fishermen. The activity concentrations of ^239+240Pu in sediment, seawater and biota were ranged 0.21–0.45 Bq/kg dry wt., 2.33–7.95 mBq/m³ and <0.008 Bq/kg fresh wt., respectively. Meanwhile, the values of ¹³⁷Cs were ranged <1.00–2.71 Bq/kg dry wt. in sediment, 3.40–5.89 Bq/m³ in seawater and <0.05–0.41 Bq/kg fresh wt. in biota, respectively. Activity ratios of ^239+240Pu to ¹³⁷Cs obtained seem to confirm that these artificial radioactivities were mainly due to global nuclear fallout.     

Depth profiles of long lived radionuclides in Chernobyl soils sampled around 10 years after the accident

Depth profiles of the long-lived radionuclides, ¹³⁷Cs, ⁹⁰Sr, Pu isotopes and ²⁴¹Am were examined in undisturbed sandy, peaty and Podsol soils in the Chernobyl 30 km exclusion zone sampled around 10 years after the accident. Two Podsol soils, which have different radioactive deposition characteristics, have also been examined. Activity ratios of ^239,240Pu/¹³⁷Cs, ⁹⁰Sr/¹³⁷Cs, and ²⁴¹Am/¹³⁷Cs in the 0-1 cm layer of the two Podsol soils differed very much. Speciation of the radionuclides by sequential selective extraction was examined in the soils. Depth profiles of the soils have been analyzed according to the speciation results and soil characteristics.     

Plutonium Activity Ratios in Plankton: New Evidence of Hold-Up Time in Irish Sea Sediments

The determination of activity ratios for radioisotopes of different half-lives can be used to estimate transit times from a point source to locations further away. For conservative elements, this time is approximately equivalent to the net hydrological transport. However, for non-conservative elements such as plutonium, the additional influence of biogeochemical processes decreases the net transport time. In this study, ²⁴¹Pu and ^239,240Pu concentrations in Irish Sea plankton samples, collected in May 1994, were determined and the ²⁴¹Pu/^239,240Pu ratios calculated. Plutonium-239,240 was measured using a standard method by ion exchange chromatography and alpha counting, and ²⁴¹Pu was determined by liquid scintillation counting using the disk-supported technique. The latter showed some methodological problems, which are briefly discussed. The ²⁴¹Pu/^239,240Pu ratios gave an estimate of the "transit time" from Sellafield to the different sampling points. In fact, this time represents the age of plutonium in plankton, i.e., the time lag between release from Sellafield and detection at the different sampling stations. The mean plutonium age was 17±2 years (n = 10) and 18.6±0.8 years (n = 13) in phytoplankton and zooplankton, respectively. The spatial distribution was reasonably homogeneous over the Irish Sea. The assimilation-elimination processes of plutonium in plankton are rather rapid. Therefore, it may be assumed that, in this time scale, the plutonium concentrations were in equilibrium with surrounding waters. Thus, it is concluded that plutonium was rather old because resuspension-sedimentation processes had occurred that delayed its transport within the Irish Sea. Therefore, the age of plutonium in plankton represented the hold-up time of plutonium in the sediments from the Irish Sea.     

Study on the Horizontal Transport of Some Radionuclides in the Wieprz River Valley

A horizontal transport of radionuclides was studied by the analysis of the radioactivity of the surface soil samples from valleys of Wieprz river and its bottom sediments. Natural gamma-isotopes (⁴⁰K, ²³⁸U and ²³²Th series) antropogenic (¹³⁴Cs and ¹³⁷Cs) and alpha-isotopes ²³⁸Pu and ^239,240Pu were measured. The different kind of bed rock and terrain configuration, influenced the radionuclide transportation from the soil to river bottom sediments. Radioactivity of the sediment samples is definitely lower than the soils. Very strong adsorption of isotopes in soil hinders their horizontal migration. Calculated ²³⁸Pu/^239,240Pu ratio is characteristic for global fallout and about 90% of the ¹³⁷Cs comes from Chernobyl.     

Further results in search for transuranium elements in effluents discharged to air from nuclear power plants

In this work we present data on transuranium nuclides ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ²⁴⁴Cm in effluents discharged to air (activity concentrations and annually discharged activities of individual radionuclides) from 7 stacks in 2004–2009. In the effluents discharged to air from one stack low activities of transuranium nuclides were observed throughout the studied period. Transuranium nuclides had been discharged to air from this stack also in previous years since 1996 when defect in the cladding of a fuel element and consequent contamination of the primary circuit occurred. In the effluents discharged to air from another stack transuranium nuclides were observed only in some monitoring periods of studied years. We could not prove the presence of transuranium nuclides in the effluents of the other stacks up to 2006. The transuranium nuclides in discharged effluents were registered in the second half-year of 2006. In 2007–2008 especially low activities of ²⁴¹Am were found in these effluents.     

Analysis of radioactive metal ions in environmental and liquid effluent samples

This paper describes the development and validation of analytical procedures for the separation and determination of⁹⁰Sr,⁹⁰Y,²³⁸Pu,^239/240Pu,²⁴¹Am,²⁴¹Cm and^243/244Cm in liquid effluents and environmental samples. The procedures use supported reagents for extraction chromatography (reversed phase partition chromatography) that enable the separation of the analytes from a large number of other radionuclides present.