Mechanisms of Actinide Isotope Leaching from Monazite

1988 ◽  
Vol 127 ◽  
Author(s):  
Yehuda Eyal ◽  
Donald R. Olander
Keyword(s):  
Radioactive Decay ◽  
Decay Chain ◽  
Alpha Radiation ◽  
High Temperature Anneal ◽  
Leaching Experiments ◽  
High Level ◽  
Satisfactory Prediction ◽  
And Diffusion ◽  
Insoluble Precipitate

The remarkable geological stability of the actinide-containing rare-earth orthophosphate mineral monazite has led to consideration of synthetic analogs of this material as the wasteform for high-level nuclear wastes (1). Monazite is resistant to metamictization in spite of the alpha radiation from decaying actinides to which it has been subjected during its lifetime. This material is also very insoluble in most groundwaters. Consequently, dissolution of the mineral and leaching of its constituent actinides are very small. However, leaching experiments on natural monazite specimens, presented here, show that radioactive decay and radiation damage produce significant differences in the release rates of several isotopes into aqueous solutions. Within the duration of the present experiments, 6.3 to 6.8 years, these effects are particularly prominent in the nuclides in the decay chain of 232-Th. This series includes the alpha-recoil 228-Ra atom (a 5.8-year fT emitter formed directly by 232-Th decay), and its daughter 228-Th (a 1.9-year a emitter, produced by 3 decay). The present experiments exhibit preferential release into solution of 228-Th relative to 232-Th by a factor of 1.3 to 21. This highly enhanced 228-Th release is explained by four different isotope incongruency effects that operate during leaching. One mechanism involves the preferential etching of alpha-recoil tracks. The three other mechanisms depend upon the behaviour of 228-Ra. In particular, dissolution-released, recoil-released and diffusion-released 228-Ra atoms (the latter process is applicable to a high-temperature anneal) are observed to remain with the solid as an insoluble precipitate, possibly loosely attached to the mineral surface. Subsequent decay of this released insoluble 228-Ra immediately leads to the formation of readily dissolved 226-Th. The phenomena may be quite general, so potential wasteforms should be examined for these isotope fractionation effects in order to insure satisfactory prediction of the long-term leaching of actinides from the material.

Long-Term Radioactivity Release From Solidified High-Level Waste -Part I: An Approach To Evaluating Experimental Data

1981 ◽  
Vol 11 ◽  
Author(s):  
Friedrich K. Altenhein ◽  
Werner Lutze ◽  
Rodney C. Ewing
Keyword(s):  
Source Term ◽  
Elevated Temperatures ◽  
Relative Sensitivity ◽  
Reaction Rates ◽  
Waste Form ◽  
High Level Waste ◽  
Leach Rate ◽  
Leaching Experiments ◽  
High Level

Safety and risk analyses for the isolation of radioactive waste in a repository must begin with a source term to quantify the amount of radioactivity released from the waste form under a specific set of conditions. The interaction of the waste form with aqueous solutions is the most important mechanism to consider, as any material released may be dissolved and reach the biosphere. In this regard the behaviour of heat generating high-level waste is of particular importance, because reaction rates are higher at elevated temperatures. A long-term leach rate was derived from previous and continuing experimental work. The purpose of this paper is not to describe the “real case” release but rather to provide guidelines for the design of leaching experiments and determine the required precision for the data. This can be derived from the relative sensitivity of extrapolated leach rates for various parameters measured in laboratory experiments.

scholarly journals Alpha dose rate and decay dose impacts on the long-term alteration of HLW nuclear glasses

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Magaly Tribet ◽  
Caroline Marques ◽  
Sarah Mougnaud ◽  
Véronique Broudic ◽  
Christophe Jegou ◽  
...  
Keyword(s):  
Dose Rate ◽  
Chemical Reactivity ◽  
Alpha Decay ◽  
Glass Block ◽  
Alpha Radiation ◽  
Wide Range ◽  
High Level ◽  
Static Conditions ◽  
Doped Glass

AbstractIn the prospect of deep geological disposal, the long-term behavior of high-level nuclear glasses has to be investigated regarding alpha radiation induced by long-life minor actinides. The present study focuses on the effects of alpha radiation on the long-term chemical reactivity of R7T7-type glasses, by separately considering the alpha dose rate and the alpha decay dose. Old SON68 glasses doped with 238/239PuO2 or 244CmO2 were studied to simulate high alpha dose rates corresponding to an early water ingress and a high level of alpha decay doses corresponding to long-term disposal conditions. A part of the 238/239Pu-doped glass block was annealed to fully recover the irradiation-induced damage accumulated since the glass was fabricated and to dissociate the effect of the alpha dose rate from that of the alpha decay dose. The glasses were then leached under static conditions at 90 °C for several years. The results showed that the residual alteration rate is not affected by the alpha dose rate over a wide range of dose rate values expected under disposal conditions: this glass remained relatively insensitive to the alpha radiolysis phenomena at the glass–water interface. However, over the duration of the experiments, the residual alteration rate of the damaged 238/239Pu-doped glass was enhanced compared to that of the annealed glass. This result is in agreement with those obtained on the 244Cm-doped glass and with reported values in the literature on simplified externally irradiated glasses, indicating that the ballistic effects of the recoil nuclei are responsible for this increase in the residual alteration rate.

Vivid Imagers Are Better at Detecting Salient Changes

2006 ◽  
Vol 27 (4) ◽  
pp. 218-228 ◽  
Author(s):  
Paul Rodway ◽  
Karen Gillies ◽  
Astrid Schepman
Keyword(s):  
Individual Differences ◽  
Change Detection ◽  
Visual Imagery ◽  
Detection Task ◽  
Level Of Detail ◽  
Detection Accuracy ◽  
Change Detection Task ◽  
Term Change ◽  
High Level

This study examined whether individual differences in the vividness of visual imagery influenced performance on a novel long-term change detection task. Participants were presented with a sequence of pictures, with each picture and its title displayed for 17  s, and then presented with changed or unchanged versions of those pictures and asked to detect whether the picture had been changed. Cuing the retrieval of the picture's image, by presenting the picture's title before the arrival of the changed picture, facilitated change detection accuracy. This suggests that the retrieval of the picture's representation immunizes it against overwriting by the arrival of the changed picture. The high and low vividness participants did not differ in overall levels of change detection accuracy. However, in replication of Gur and Hilgard (1975) , high vividness participants were significantly more accurate at detecting salient changes to pictures compared to low vividness participants. The results suggest that vivid images are not characterised by a high level of detail and that vivid imagery enhances memory for the salient aspects of a scene but not all of the details of a scene. Possible causes of this difference, and how they may lead to an understanding of individual differences in change detection, are considered.

scholarly journals Review on Perioperative and Oncological Outcomes of Robotic Gastrectomy for Cancer

2021 ◽  
Vol 11 (7) ◽  
pp. 638
Author(s):  
Giuseppe Giuliani ◽  
Francesco Guerra ◽  
Lorenzo De Franco ◽  
Lucia Salvischiani ◽  
Roberto Benigni ◽  
...  
Keyword(s):  
English Language ◽  
Length Of Hospital Stay ◽  
Radical Gastrectomy ◽  
Robotic Gastrectomy ◽  
Relevant Evidence ◽  
Relative Paucity ◽  
Duration Of Surgery ◽  
High Level ◽  
Standard Laparoscopic Surgery

Background. Minimally invasive gastrectomy is currently considered a valid option to treat gastric cancer and is gaining increasing acceptance. Recent reports have suggested that the application of robots may confer some advantages over conventional laparoscopy, but the role of robotic surgery in clinical practice is still uncertain. We aimed to critically review the relevant evidence comparing robotic to standard laparoscopic surgery in performing radical gastrectomy. Methods. The Pubmed/Medline electronic databases were searched through February 2021. Paper conference and the English language was the only restriction applied to our search strategy. Results. According to the existing data, robotic gastrectomy seems to provide some benefits in terms of blood loss, rate of conversion, procedure-specific postoperative morbidity, and length of hospital stay. Robotic gastrectomy is also associated with a longer duration of surgery and a higher economic burden as compared to its laparoscopic counterpart. No significant differences have been disclosed in terms of long-term survivals, while the number of lymph nodes retrieved with robotic gastrectomy is generally higher than that of laparoscopy. Conclusions. The current literature suggests that robotic radical gastrectomy appears as competent as the conventional laparoscopic procedure and may provide some clinical advantages. However, due to the relative paucity of high-level evidence, it is not possible to draw definitive conclusions.

scholarly journals Mapping of affordability levels for photovoltaic-based electricity generation in the solar belt of sub-Saharan Africa, East Asia and South Asia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sándor Szabó ◽  
Irene Pinedo Pascua ◽  
Daniel Puig ◽  
Magda Moner-Girona ◽  
Mario Negre ◽  
...  
Keyword(s):  
East Asia ◽  
South Asia ◽  
Electricity Generation ◽  
Sub Saharan Africa ◽  
Solar Photovoltaic ◽  
Term Operation ◽  
Sub Saharan ◽  
High Level ◽  
Do So

AbstractLack of access to modern forms of energy hampers efforts to reduce poverty. The provision of electricity to off-grid communities is therefore a long-standing developmental goal. Yet, many off-grid electrification projects neglect mid- and long-term operation and maintenance costs. When this is the case, electricity services are unlikely to be affordable to the communities that are the project’s primary target. Here we show that, compared with diesel-powered electricity generation systems, solar photovoltaic systems are more affordable to no less than 36% of the unelectrified populations in East Asia, South Asia, and sub-Saharan Africa. We do so by developing geo-referenced estimates of affordability at a high level of resolution (1 km2). The analysis illustrates the differences in affordability that may be found at the subnational level, which underscores that electrification investments should be informed by subnational data.

scholarly journals Long Term Interactions of Native and Invasive Species in a Marine Protected Area Suggest Complex Cascading Effects Challenging Conservation Outcomes

Diversity ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 71
Author(s):  
Charalampos Dimitriadis ◽  
Ivoni Fournari-Konstantinidou ◽  
Laurent Sourbès ◽  
Drosos Koutsoubas ◽  
Stelios Katsanevakis
Keyword(s):  
Invasive Species ◽  
Native Species ◽  
High Performance ◽  
Marine Protected Area ◽  
Habitat Degradation ◽  
Population Increase ◽  
Rocky Reef ◽  
Cascading Effects ◽  
High Level

Understanding the interactions among invasive species, native species and marine protected areas (MPAs), and the long-term regime shifts in MPAs is receiving increased attention, since biological invasions can alter the structure and functioning of the protected ecosystems and challenge conservation efforts. Here we found evidence of marked modifications in the rocky reef associated biota in a Mediterranean MPA from 2009 to 2019 through visual census surveys, due to the presence of invasive species altering the structure of the ecosystem and triggering complex cascading effects on the long term. Low levels of the populations of native high-level predators were accompanied by the population increase and high performance of both native and invasive fish herbivores. Subsequently the overgrazing and habitat degradation resulted in cascading effects towards the diminishing of the native and invasive invertebrate grazers and omnivorous benthic species. Our study represents a good showcase of how invasive species can coexist or exclude native biota and at the same time regulate or out-compete other established invaders and native species.

scholarly journals Physical workload and increased frequency of musculoskeletal pain: a cohort study of employed men and women with baseline occasional pain

2021 ◽  
pp. oemed-2020-107094
Author(s):  
Kathryn Badarin ◽  
Tomas Hemmingsson ◽  
Lena Hillert ◽  
Katarina Kjellberg
Keyword(s):  
Survey Data ◽  
Musculoskeletal Pain ◽  
Leisure Time Physical Activity ◽  
Physical Workload ◽  
Job Exposure Matrix ◽  
Men And Women ◽  
Strenuous Work ◽  
High Level

ObjectivesMusculoskeletal pain (MSP) is prevalent among the workforce. This study investigates the long-term association between physical workload (PWL) and increased frequency of MSP among male and female employees with pre-existing occasional MSP.MethodsThis study uses the Stockholm Public Health cohort survey data from the baseline 2006. The sample includes 5715 employees with baseline occasional MSP (no more than a few days per month). Eight PWL exposures and overall PWL were estimated using a job-exposure matrix (JEM). The JEM was assigned to occupational titles from a national register in 2006. Follow-up survey data on frequent MSP (a few or more times a week) were collected from 2010. Logistic regressions produced sex-specific ORs with 95% CIs and were adjusted for education, health conditions, psychological distress, smoking, BMI, leisure-time physical activity and decision authority.ResultsAssociations were observed between several aspects of heavy PWL and frequent MSP for men (eg, OR 1.57, 95% CI 1.13 to 2.20, among those in the highest exposure quartile compared with those in the lowest quartile for heavy lifting) and women (eg, OR 1.76, 95% CI 1.35 to 2.29, among those in the highest exposure quartile compared with those in the the lowest quartile for physically strenuous work). Small changes were observed in the OR after adjustment, but most of the ORs for PWL exposures among the men were no longer statistically significantly increased.ConclusionA high level of exposure to heavy PWL was associated with increased frequency of MSP 4 years later for men and women with baseline occasional pain.

scholarly journals Adiponectin and its receptors in patients with cardiovascular disease

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
E Belik ◽  
OV Gruzdeva ◽  
YUA Dyleva ◽  
EG Uchasova ◽  
MYU Sinitsky ◽  
...  
Keyword(s):  
Heart Defects ◽  
Post Translational Modification ◽  
Fat Depots ◽  
Funding Sources ◽  
Adiponectin Mrna ◽  
Fat Stores ◽  
Group 2 ◽  
High Level ◽  
Group 1

Abstract Funding Acknowledgements Type of funding sources: None. Aim to determine the features of adiponectin expression, secretion of adiponectin and its receptors in local fat depots in CVD. Materials and methods The study included 90 patients with СAD (Group 1) and 60 patients with heart defects (Group 2). Adipocytes were isolated from samples of subcutaneous (SAT), epicardial (EAT) and perivascular (PVAT) adipose tissue obtained during CABG or heart valve replacement. The expression of adiponectin was determined by qPCR using TaqManTM Gene Expression Assays (Applied Biosystems, USA) in the ViiA 7 Real-Time PCR System (Applied Biosystems, USA), the levels of expression products was determined using enzyme immunoassay (Bender MedSystems GmbH, Vienna, Austria). The data were analyzed using the statistical software Statistica 9.0. Results EAT adipocytes were characterized by the lowest adiponectin expression relative to adipocytes of other localization both in Group 1 and Group 2. In patients Group 1 adiponectin expression in EAT was reduced relative in SAT and PVAT (by 1.2 and 1.5 times). In Group 2, the adiponectin mRNA in the EAT was lower than in the SAT and PVAT (1.4 and 1.5 times). The expression of adiponectin in EAT in Group 2 exceeded the same indicator in Group 1 by 1.2 times. The maximum expression of adiponectin was observed in the PVAT culture in patients of both groups. For Group 2, this indicator exceeded the values of Group 1 by 1.2 times. The content of adiponectin in the culture EAT was lower than in the SAT, both in Group 1 and Group 2 (by 1.3 and 1.13 times). The level of this indicator in Group 2 was 1.4 times higher than in Group 1. PVAT adipocytes of patients with CAD were characterized by the lowest level of adiponectin secretion in comparison with adipocytes of other localization. The adiponectin level in the PVAT of Group 2 exceeded that of fat stores of other localization and in Group 1 patients by 1.8 times. There were no statistically significant differences in the expression and concentration of adiponectin in the culture of adipocytes of the SAT between the groups of patients. In Group 1, the lowest level of AdipoR1 was found in the adipocyte culture of the PVAT. Noteworthy is the decrease in the level of AdipoR1 in Group 1 compared to the level of Group 2, observed in the SAT and PVAT: 1.3 and 1.5 times. There were no significant differences in the concentration of the AdipoR1 in the EAT, as well as AdipoR2 in all types of AT between the groups of patients. Conclusion: in CVD the EAT is characterized by minimal expression and secretion of adiponectin, regardless of nosology. In CAD despite the high level of expression of adiponectin, the adipocytes of the PVAT were found to have the lowest content in comparison with adipocytes of other localization. Dysregulation of the adiponectin/AdipoR axis is observed in PVAT, which may be due to low expression of adiponectin receptors and long-term processes of its post-translational modification and oligomerization in CAD.

Low Alkaline Cement Used in the Construction of a Gallery in the Horonobe Underground Research Laboratory

2010 ◽  
Author(s):  
Masashi Nakayama ◽  
Haruo Sato ◽  
Yutaka Sugita ◽  
Seiji Ito ◽  
Masashi Minamide ◽  
...  
Keyword(s):  
Fly Ash ◽  
Research Laboratory ◽  
Concrete Lining ◽  
Energy Agency ◽  
Tunnel Support ◽  
Long Term Stability ◽  
Alkaline Conditions ◽  
High Level ◽  
Underground Research Laboratory

In Japan, any high level radioactive waste (HLW) repository is to be constructed at over 300 m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various admixtures. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly Fly-ash Contained Silicafume Cement), containing over 60 wt% of silica-fume (SF) and fly-ash (FA). HFSC was used experimentally as the shotcrete material in construction of part of the 140m deep gallery in the Horonobe Underground Research Laboratory (URL). The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40 wt% OPC (Ordinary Portland Cement), 20 wt% SF, and 40 wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC. The total length of tunnel using HFSC shotcrete is about 73 m and about 500 m3 of HFSC was used. The workability of HFSC shotcrete was confirmed in this experimental construction.

scholarly journals The effect of long-term treatment with steroid hormones or tamoxifen on oestrogen receptors (alpha and beta) in the endometrium of ovariectomized cynomolgus macaques

2002 ◽  
Vol 175 (3) ◽  
pp. 673-681 ◽  
Author(s):  
H Wang ◽  
E Isaksson ◽  
B Von Schoultz ◽  
JM Cline ◽  
L Sahlin
Keyword(s):  
Hormone Treatment ◽  
Term Treatment ◽  
Response To Treatment ◽  
Oestrogen Receptors ◽  
Minor Variation ◽  
Protein Levels ◽  
Long Term Treatment ◽  
High Level ◽  
Er Alpha

The effects of oestrogen are mediated by two specific intracellular receptors, oestrogen receptors (ER) alpha and beta, which function as ligand-activated transcriptional regulators. Ovariectomized macaques (Macaca fascicularis) were used to study the regulation of ERalpha and ERbeta in the endometrium by immunohistochemistry and in situ hybridization after long-term hormone treatment. Animals were treated continuously for 35 Months with either conjugated equine oestrogen (CEE), medroxyprogesterone acetate (MPA), combined CEE/MPA, or tamoxifen (TAM). Treatment with CEE/MPA down-regulated ERalpha in the superficial glands. In the superficial stroma the ERalpha level was lower in the CEE/MPA group than in the CEE and MPA groups. ERbeta immunostaining was faint with minor variation in response to treatment, but increased in the superficial stroma after MPA treatment. The ratio of ERbeta/ERalpha increased in superficial stroma and gland after CEE/MPA treatment, and also in stroma after MPA and TAM. Cystic endometrial hyperplasia was observed in TAM-treated animals, in combination with a high level of ERalpha protein expression. The present data show that long-term hormone treatment affects the ERalpha and ERbeta protein levels in the endometrium. The balance between ERalpha and ERbeta seems to be important for the proliferative response to oestrogen.

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