Sorption Behavior of Nickel and Palladium in the Presence of NH3(aq)/NH4+

2013 ◽  
Vol 1518 ◽  
pp. 231-236
Author(s):  
Taishi Kobayashi ◽  
Takayuki Sasaki ◽  
Ken-you Ueda ◽  
Akira Kitamura

ABSTRACTIt is necessary to assess the impact of nitrate salts and their reduction products (e.g. NH3(aq)/NH4+) contained in low-level radioactive waste generated from nuclear reprocessing process for the safety assessment of geological disposal of the waste. In the present study, sorption behavior of Ni and Pd on pumice tuff was investigated in the presence of NH3(aq)/NH4+. Under various NH3(aq)/NH4+ concentration, pH and ionic strength conditions, distribution coefficient (Kd) of Ni and Pd on pumice tuff was determined by a batch experiment. For Ni system, the Kd values showed no significant dependence on initial NH4+ concentration ([NH4+]ini < 1 M) in neutral pH region, which agreed with the prediction from thermodynamic data. For Pd system, the Kd values decreased with an increase of [NH4+]ini, suggesting the formation of stable ammine complexes (Pd(NH3)m2+ (m: 1 – 4)). The obtained Kd values for Ni and Pd were analyzed using a surface complexation model. By taking complexes predicted by thermodynamic data into account, sorption behavior of Ni and Pd in the presence of NH3(aq)/NH4+ were well explained.

2000 ◽  
Vol 663 ◽  
Author(s):  
Nobuo Ashikawa ◽  
Takatoshi Tajima ◽  
Hiroshi Saito ◽  
Ai Fujiwara

ABSTRACTLow-level radioactive waste (LLRW) is disposed of by shallow land burial. Reinforced concrete is used as the radioactive waste repository. However, the concrete structure is in contact with water and will gradually degrade over an extended period of time due to leaching.It is important to investigate the interaction between radionuclides and degraded concrete in the safety assessment of nuclear waste disposal. The authors measured the distribution coefficients (Kd) of various radionuclides for calcium-leached mortars. The calcium-leached mortars were prepared by an accelerated leaching test for mortar based on the electrical potential gradient. These degraded conditions are similar to that of degraded concrete in contact with water for a long period of time. The degradation degree of calcium-leached mortar is evaluated by the CaO/SiO2 molarratio (Ca/Si ratio) of calcium silicate hydrate (C-S-H).As a result, the relationship between Kd and the Ca/Si ratio in C-S-H can be roughly grouped into the following three types:1.137Cs and 85Sr – Kd decreases with an increase in the Ca/Si ratio.2. 95mTc and 110mAg – There is no correlation between Kd and the Ca/Si ratio.3. 14C, 241Am and 125I – Kd increases with an increase in the Ca/Si ratio.


2013 ◽  
Vol 1518 ◽  
pp. 179-184
Author(s):  
Christina Greis Dahlberg ◽  
Patrik Sellin ◽  
Mireia Grivé ◽  
Lara Duro ◽  
Kastriot Spahiu

ABSTRACTIf groundwater enters a damaged canister and comes in contact with the spent fuel, radionuclides are released into the water in the void inside the canister when fuel dissolves. Solubility limits restrict the amount of radioelements that may migrate with the water flowing from the canister. In this study the impact of variability in groundwater chemistry compositions and the impact of uncertainties in thermodynamic data on solubility limits for Np, Pb, Pu, Ra, Se, Th, U and Zr were looked into. The solubility limits for all the studied radioelements seemed to be more sensitive to uncertainties in thermodynamic data than to differences in groundwater chemistry. The sole exception was radium, where variability in water composition has a somewhat larger impact. Radium is also the most safety critical element in the safety assessment SR-Site and groundwater compositions are expected to vary during the assessment period of one million years.


Author(s):  
Laurent Guillier ◽  
Sandra Martin-Latil ◽  
Estelle Chaix ◽  
Anne Thébault ◽  
Nicole Pavio ◽  
...  

AbstractTemperature and relative humidity are major factors determining virus inactivation in the environment. This article reviews inactivation data of coronaviruses on surfaces and in liquids from published studies and develops secondary models to predict coronaviruses inactivation as a function of temperature and relative humidity. A total of 102 D-values (time to obtain a log10 reduction of virus infectivity), including values for SARS-CoV-2, were collected from 26 published studies. The values obtained from the different coronaviruses and studies were found to be generally consistent. Five different models were fitted to the global dataset of D-values. The most appropriate model considered temperature and relative humidity. A spreadsheet predicting the inactivation of coronaviruses and the associated uncertainty is presented and can be used to predict virus inactivation for untested temperatures, time points or new coronavirus strains.ImportanceThe prediction of the persistence of SARS-CoV-2 on fomites is essential to investigate the importance of contact transmission. This study collects available information on inactivation kinetics of coronaviruses in both solid and liquid fomites and creates a mathematical model for the impact of temperature and relative humidity on virus persistence. The predictions of the model can support more robust decision-making and could be useful in various public health contexts. Having a calculator for the natural clearance of SARS-CoV-2 depending on temperature and relative humidity could be a valuable operational tool for public authorities.


2020 ◽  
Vol 11 ◽  
pp. 310-322
Author(s):  
Felix M Badaczewski ◽  
Marc O Loeh ◽  
Torben Pfaff ◽  
Dirk Wallacher ◽  
Daniel Clemens ◽  
...  

This study is dedicated to link the nanoscale pore space of carbon materials, prepared by hard-templating of meso-macroporous SiO2 monoliths, to the corresponding nanoscale polyaromatic microstructure using two different carbon precursors wthat generally exhibit markedly different carbonization properties, i.e., a graphitizable pitch and a non-graphitizable resin. The micro- and mesoporosity of these monolithic carbon materials was studied by the sorption behavior of a relatively large organic molecule (p-xylene) in comparison to typical gas adsorbates (Ar). In addition, to obtain a detailed view on the nanopore space small-angle neutron scattering (SANS) combined with in situ physisorption was applied, using deuterated p-xylene (DPX) as a contrast-matching agent in the neutron scattering process. The impact of the carbon precursor on the structural order on an atomic scale in terms of size and disorder of the carbon microstructure, on the nanopore structure, and on the template process is analyzed by special evaluation approaches for SANS and wide-angle X-ray scattering (WAXS). The WAXS analysis shows that the pitch-based monolithic material exhibits a more ordered microstructure consisting of larger graphene stacks and similar graphene layer sizes compared to the monolithic resin. Another major finding is the discrepancy in the accessible micro/mesoporosity between Ar and deuterated p-xylene that found for the two different carbon precursors, pitch and resin, which can be regarded as representative carbon precursors in general. These differences essentially indicate that physisorption using probe gases such as Ar or N2 can provide misleading parameters if to be used to appraise the accessibility of the nanoscale pore space.


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hui Zhang ◽  
Ninghao Hou ◽  
Jianhua Zhang ◽  
Xuyi Li ◽  
Yan Huang

One goal for large-scale deployment of connected and autonomous vehicles is to achieve the traffic safety benefit since connected and autonomous vehicles (CAVs) could reduce the collision risk by enhancing the driver’s situation perception ability. Previous studies have analyzed the safety impact of CAVs involved in traffic, but only few studies examined the safety benefits brought by CAVs when approaching high-collision-risk road segments such as the freeway crash hotspots. This study chooses one freeway crash hotspot in Wuhan, China, as an instance and attempts to estimate the safety benefits for differential penetration rates (PRs) of CAVs using the surrogate safety assessment model (SSAM). First, the freeway crash hotspot is identified with kernel density estimation and simulated by VISSIM. Then, the intelligent driver model (IDM) and Wiedemann 99 (a car-following model) are adopted and calibrated to control the driving behaviors of CAVs and human-driven vehicles (HVs) in this study, respectively. The impact that rather CAVs are constrained with or without managed lanes on traffic safety is also discussed, and the PR of CAVs is set from 10% to 90%. The results of this study show that when the PR of CAVs is lower than 50%, there is no significant improvement on the safety measures such as conflicts, acceleration, and velocity difference, which are extracted from the vehicle trajectory data using SSAM. When the penetration rate is over 70%, the experiment results demonstrate that the traffic flow passing the freeway hotspot is with fewer conflicts, smaller acceleration, and smaller velocity difference in the scenario where CAVs are constrained with managed lane compared with the scenario without managed lane control. The safety benefit that CAVs bring needs to be discussed. The lane management of CAVs will also lead to distinct safety impact.


Author(s):  
Neil F. Harman ◽  
Guy S. Anderson ◽  
John N. Lillington ◽  
Russ V. Booler

Much of the attention on small modular reactors (SMRs) has to date been focused on the technology or novel applications, however, this paper tries to set out some thoughts on some of the other issues, or “externalities” within which any SMR proposal must be brought to market. The Paper outlines the UK regulatory regime highlighting differences from that in the US. Regulation in the UK is based on Safety Assessment Principles rather than a prescriptive set of requirements; the amenability of such a regime to assessing novel reactor designs and applications is discussed in general terms. The Paper summarizes the licensing arrangement for nuclear facilities used by the UK nuclear regulator. It goes on to summarize the recent Generic Design Assessment (GDA) programme for new build in the UK in which Serco has been heavily involved. The Safety Assessment Principles reach further than just into the technicalities of engineering design. Two particular areas of interest are picked out: the availability of qualified and experienced personnel and the impact on plant as a result of grid and transmission system issues. With regard to the first of these, in the early days of nuclear power, the UK considered many different reactor designs including gas cooled reactors, fast reactors, heavy water reactors, high temperature reactors and later a small reactor design — the SIR (Safe Integral Reactor) — although this was never built; these are briefly described highlighting any similarities to current proposed small reactor designs and concepts and discussing any lessons that could be learned. Staff in Serco have been involved with all these developments as well as undertaking research in Generation IV concepts. To begin to address the impact on the plant from its interface with the external electricity grid system, the Paper discusses the energy market in the UK (one of the most deregulated), the state of the nuclear industry, the current political landscape as far as nuclear power is concerned, and the prospects for deploying small modular reactors in the UK. It then considers the implications of the European Union’s challenge to decarbonize electricity supply by 2050. Finally, the Paper considers other pertinent issues associated with small reactor concepts and the Safety Assessment Principles. It discusses some of the issues around inspection, given that many of the small reactor concepts are based on underground reactors. Given the smaller size of SMRs, the opportunities for association with novel non-power generating applications are greater than for conventional plant. Some differences associated with these proposals, compared to traditional nuclear power generation, are examined. The paper then also discusses the advantages and disadvantages, as far as safety is concerned, of a farm of small modular reactors compared with a single large reactor.


Author(s):  
Gandhi Jabakuma ◽  
W. Mercy

The drug back reaction measurement is the most important part of the drug safety assessment. In the early days, the measurement is made by trailing the impact after the course of many examples. In the pharmaceutical industries, the most interesting research topic is adverse drug detection which rules the world. In the 21century , the data available in the medical field gave an important development in motivating of an adverse event. Recently, many people put forward the statistical data and also the mining methods which are largely implemented to detect the drug adverse event. In the following paper, we explain more methods explained by expert&rsquo;s researchers in the dynamic domain of data.


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