Preliminary Study on Minor Actinide Incineration in RSG-GAS without Isotope Separation

Minor actinides (MA) resulted from nuclear power plants is often considered as nuisance in spent fuel management due to its considerably long half-life. One of available strategies to deal with MA is to incinerate it, in order to reduce its radioactivity. This paper presents a study on MA incineration in RSG-GAS research reactor. Unlike previous study, this work did not separate the MA into individual isotopes, but incinerated as a whole. ORIGEN2.1 code is employed to calculate MA incineration within RSG-GAS core. MA composition used in this study consists of Np, Am, and Cm isotopes. The Central Irradiation Position (CIP) of RSG-GAS is loaded by 6 kg of MA and irradiated for two years. The result shows that about 1 kg of MA were incinerated after two years of irradiation, or 18,87% of the initial concentration. However, the increase of Cm-242 isotope, along with newly-formed Pu isotopes, were found to be significantly increasing short-term radioactivity compared to un-irradiated MA. Thus, two years-worth of MA incineration cannot be considered as effective, and other strategies must be pursued.

Records of plutonium isotopes in marine sediments from the southern Gulf of Mexico

Here we report on new data on plutonium (Pu) isotopes to elucidate activity concentrations, inventories, sources and their transport from the ocean surface to the sea floor from a collection of deep-sea sediment cores (depths ranging from 257 to 3739 m) in the Gulf of Mexico (GoM). Sediment cores collected from the continental shelf and upper slope region of the GoM consistently showed 240Pu/239Pu ratios of 0.15 to 0.26 and Pu-inventories ranging from 15 to 35 Bq m− 2. Inventories and ratios are consistent with global fallout Pu for this tropical region. In the continental shelf and upper slope regions, higher particle concentrations close to the margins favor significant scavenging and removal of Pu from the water column; in contrast with the deep-sea cores that show low 240Pu/239Pu ratios (0.07–0.13) and a much lower Pu inventory (< 7 Bq m-2) implying a small fraction of the expected global fallout inventory has reached into the lower slopes and abyssal plain of the GoM. Low values and a progressive decrease of 240Pu/239Pu ratios and Pu inventories with increasing water depth have been previously reported for the GoM. The low Pu ratios indicate that Nevada tests fallout was an important source of Pu to deep-sea sediments, and that this source was likely more efficiently removed from the water column than global fallout Pu. Analysis of Pu isotopes in two sediment traps from the upper slope regions show 240Pu/239Pu ratios comparable to the ones observed in the global fallout. These results indicate that global fallout Pu is currently the main source of Pu in water column particles. Therefore, a significant fraction of global fallout Pu must still be present; either in a dissolved phase, or as biologically recycled material in the water column, or scavenged on the shelf and shelf break. Our results bring to light important questions on the application of Pu isotopes to establish sediment chronologies, since these radionuclides are shown to be tracers of bioturbation rather than accumulation processes in deep-sea sediments of the GoM, similar to previously reported results from excess 210Pb.

Deposition of plutonium isotopes in glacial environments in the Northern and Southern Hemispheres

&lt;p&gt;Glaciers are temporary repositories for radionuclides and other airborne contaminants (eg. heavy metals). Retreat of glaciers results in the release of these contaminants to downstream ecosystems where they can be accumulated by biota, with further consequences along the trophic chain. Fallout radionuclides, and especially Pu released from nuclear weapons testing and nuclear accidents, concentrates on glacier surfaces in cryoconite granules. These aggregates of mineral and organic components are associated with biological consortia composed of archaea, algae, cyanobacteria, fungi and heterotrophic bacteria (Cook et al., 2016). Cryoconite is also responsible for local decrease ice albedo and is responsible for formation of water-filled holes. Contaminants are effectively trapped in cryoconite granules for long periods (up to decades) due to the &amp;#8220;sticky&amp;#8221; nature of the material. Cryoconite can thus be useful in monitoring of radionuclide deposition on glaciers (&amp;#321;okas et al., 2019; Giovanni et al., 2020).&lt;/p&gt;&lt;p&gt;Our collective research reveals widespread incidence of Pu isotopes in cryoconite across multiple sites on both hemispheres, including Svalbard, Sweden, Norway, Iceland, Greenland, British Columbia, Alaska, the European Alps, the Caucasus, Siberia, Tien Shan, Altai, South America and Antarctica. The levels of plutonium isotopes (238,239,240Pu) found in cryoconite at these sites are orders of magnitude higher than those detected in non-glaciated environments, raising important questions around the role of glaciers, and specifically cryoconite, in concentrating levels of Pu isotopes above those found in the surrounding environment. The activity ratios of 238Pu/239+240Pu show that the plutonium-related radioactivity of cryoconite from the Northern hemisphere is compatible with the worldwide signal from the global radioactive fallout (0.025) but in some samples from Svalbard higher activity ratios are associated with an additional source of pure 238Pu, pointing to an influence of the SNAP-9A satellite burn up in the atmosphere occurred in 1964. Also activity ratios from South America and Antarctica are consistent with the global radioactive fallout ratio (including SNAP 9 re-entry) in the southern hemisphere (0.14), with an exception concerning cryoconite from the Exploradores Glacier (Chilean Patagonia, ratio 0.35). There are no known nuclear test sites near this glacier which could explain this anomalous value. However, there is also no information about the atmospheric re-entry of the automatic Interplanetary Station &amp;#8220;Mars&amp;#8217;96&amp;#8221; which was launched on 16 November 1996. It fell off the coast of Chile near the border with Bolivia and was not found so far. There were considerable quantities of 238Pu on board of the station, with a total activity of 174 TBq (IAEA, 2001). We hypothesize that this event could explain the anomaly observed at Exploradores Glacier, confirming the unmatched potential of cryoconite to study environmental radioactivity in glacial contexts.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;This study was supported by the National Science Center grant no. NCN 2018/31/B/ST10/03057.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Cook et al., 2016. Progress in Physical Geography,&amp;#160;40(1), 66-111.&lt;/p&gt;&lt;p&gt;Giovanni et al., 2020.&amp;#160;CATENA,&amp;#160;191, 104577.&lt;/p&gt;&lt;p&gt;IAEA, 2001.&amp;#160;International&amp;#160;Atomic&amp;#160;Energy&amp;#160;Agency&amp;#160;IAEA,&amp;#160;Vienna).&lt;/p&gt;&lt;p&gt;&amp;#321;okas et al., 2019.&amp;#160;The Cryosphere,&amp;#160;13(7), 2075-2086.&lt;/p&gt;

Exploring the ability of triple quadrupole inductively coupled plasma mass spectrometry for the determination of Pu isotopes in environmental samples

The monitoring of Pu isotopes in environmental samples was essential for radioactive assessment and tracing the geochemical processes. Triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS) has shown strong ability...

Propagation Analysis of Pu Radionuclides as a Result of Fire Incidents in the Exclusion Zone of the Chernobyl NPP in April 2020

In consequence of nuclear accidents that have occurred in various parts of the world, radioactive contamination of the environment is observed. The risks of spreading pollution can increase during floods, fires and some natural disasters. The lack of effective measures that aimed at eliminating possible sources of fire in the meadow zone and forest lands in the Chernobyl exclusion zone (ChEZ) leads to a high risk of fire emergence. The temporal and spatial distribution of fires shows that they occur throughout the ChEZ, including in the most contaminated areas. The risk of fires increases with climate change and measures to prevent them should be considered in emergency programs. ChEZ area is contaminated with long-lived radionuclides such as 137Cs, 90Sr, Pu isotopes (238Pu, 239 + 240Pu, 241Pu) and 241Am. As a result of forest fires radionuclides contained in wood and underlying surface are carried out into the atmosphere along with smoke. Diseases arising under the influence of ionizing radiation from Pu and 241Am isotopes pose a serious problem for human health. To assess of the spatial distribution of Pu isotopes and 241Am we used data on forest fires that occurred in the Chernobyl zone in April 2020. To evaluatе the dynamics of the release of radioactive substances into the atmosphere during fire incidents on the ChEZ territory, the following software products were used: NASA WorldView, HYSPLIT program. The HYSPLIT program allows to reconstruct the trajectories of radionuclide propagation in the atmosphere using meteorological data and to obtain a reliable picture of the distribution of radionuclides in the study area. The maps of the volumetric activity of Pu isotopes in the air and the fallout on the soil as a result of fires were obtained. It was found that the radioactivity due to the presence of this element in the air and during the fallout of radioactive particles on the soil is low (it reaches 1.0E-7...0.1 Bq/m3 in the air, 1.0E-6...1 Bq/m2 on the soil). The analysis of the propagation of Pu isotopes as a result of the movement of air masses in the places of fires in the exclusion zone of the Chernobyl nuclear power plant and the associated dangers for the population and the environment has been carried out.