scholarly journals Leaching Behavior of Cesium, Strontium, Cobalt, and Europium from Immobilized Cement Matrix

2021 ◽  
Vol 11 (18) ◽  
pp. 8418
Author(s):  
Ja-Young Goo ◽  
Bong-Ju Kim ◽  
Myunggoo Kang ◽  
Jongtae Jeong ◽  
Ho Young Jo ◽  
...  
Keyword(s):  
Portland Cement ◽  
Nuclear Power ◽  
Power Plants ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
The Other ◽  
Cement Matrix ◽  
Leaching Behavior ◽  
Binding Material ◽  
Over Time

Numerous low-level and intermediate-level radioactive wastes are generated from the decommissioning processes of nuclear power plants; these wastes are immobilized to prevent the release of radionuclides under disposal conditions. In this study, we investigated the leaching behavior of Cs, Sr, Co, and Eu, which are common in immobilized decommissioning wastes. Ordinary Portland cement (OPC) was used as an immobilization agent. During the test, leaching of the nuclides occurred in the order of Cs, Sr, Co, and Eu and decreased over time. The results showed that 41.4% of the total Cs leached over 90 days, although the other elements leached in quantities less than 1.5%. CaCO3 was precipitated by the release of cementitious materials, indicating carbonation of the leachate. The leachability indexes in all cases exceeded the acceptable criteria (>6). The results of the present study suggest that OPC can be effectively used as a binding material to immobilize nuclides (Cs, Sr, Co, and Eu) contained in decommissioning wastes.

Mineralogical Aspects of Durable Geocement Matrix Formation - Role of Alkali

2014 ◽  
Vol 1004-1005 ◽  
pp. 1523-1530 ◽  
Author(s):  
Pavlо Krivenko ◽  
Hai Lin Cao ◽  
Lu Qian Weng ◽  
Еlena Kаvalerova
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Ceramic Matrix ◽  
Cementitious Materials ◽  
Cement Matrix ◽  
New Materials ◽  
New Class ◽  
High Durability ◽  
Alkali Activated

Less than half a century ago just an idea of presence of free alkalis in a ceramic matrix was considered by ordinary Portland cement people as an absurd one and this was a basic postulate accepted in chemistry of cements. In 1957 a scientist from Ukraine (USSR) Viktor Glukhovsky put forward an assumption which was taken as a base for development and bringing into practice of construction a principally new class of cementitious materials which first appeared in the field under a name of alkaline (now also known under a general name of alkali-activated) cementitious materials. A validity of these ideas was confirmed by more than 50 years of evolutional development and vast experience collected on practical use of new materials in different applications. The paper covers theoretical views on role played by alkali in the formation of an alkali-activated cement matrix with high durability. Examples of compositional build-up of the alkali-activated cementitious materials vs. quantity of added alkali and type of aluminosilicate component are reported together with results of 50-year experience obtained from observation of concrete structures made from these cements.

scholarly journals A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3467
Author(s):  
Ankit Kothari ◽  
Karin Habermehl-Cwirzen ◽  
Hans Hedlund ◽  
Andrzej Cwirzen
Keyword(s):  
Carbon Dioxide ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Cementitious Materials ◽  
Cold Climate ◽  
Supplementary Cementitious Materials ◽  
Short Exposure ◽  
Chemical Admixtures ◽  
Composite Cements ◽  
Alkali Activated

Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

A trial construction of high durability railway viaducts with local aggregates

2019 ◽  
Author(s):  
Kotaro Kawamura ◽  
Joe Takemura ◽  
Shigenobu Iguchi ◽  
Tsutomu Yoshida ◽  
Masashi Kobayashi
Keyword(s):  
Fly Ash ◽  
Side Effects ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
The Other ◽  
Strength Concrete ◽  
High Durability ◽  
Sound Barrier ◽  
Early Strength ◽  
Structural Measure

<p>We are carrying out a construction project of new railroad viaducts. These new railroad viaducts are constructing using about 110,000 m<span>3</span> volume concrete. In this construction place, it is difficult for us to get low ASR-reactive aggregates and it is expected to be supplied with snowmelt water on the viaducts in winter. Then we tested ASR-reactive these local aggregates and found an effective mixed ratio of fly-ash is 20% of cement. On the other hand, various side effects were also expected by using fly-ash. For example, initial cracking due to contraction, early strength concrete, bleeding, etc. Therefore, we repeated various tests and examined and carried out a method that could ensure the same construction method and quality as when using ordinary Portland cement, even with fly-ash. Also, we adopted a structure that is unlikely to be affected by rainwater as a structural measure. For example, the entire adoption of a ramen type viaduct that has eliminated bearings, adoption of FRP sound barrier, etc. Then we made it possible to build highly durable railway viaducts by these various measures of materials and structures.</p>

The power of empowering team leadership over time: A multi-wave longitudinal study in nuclear power plants

2021 ◽  
Vol 133 ◽  
pp. 105015
Author(s):  
Mario Martínez-Córcoles ◽  
Inés Tomás ◽  
Francisco J. Gracia ◽  
José M. Peiró
Keyword(s):  
Longitudinal Study ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Team Leadership ◽  
Over Time

An overview of research activities on cementitious materials for radioactive waste management

2012 ◽  
Vol 1475 ◽  
Author(s):  
Zoran Drace ◽  
Irena Mele ◽  
Michael I. Ojovan ◽  
R. O. Abdel Rahman
Keyword(s):  
Radioactive Waste ◽  
Waste Management ◽  
Nuclear Power ◽  
Power Plants ◽  
Management Practices ◽  
Fuel Cycle ◽  
Large Body ◽  
Cementitious Materials ◽  
Radioactive Waste Management ◽  
Research Activities

ABSTRACTAn overview is given on research activities on cementitious materials for radioactive waste management systems based on the IAEA Coordinated Research Project (CRP) held in 2007-2010. It has been joined by 26 research organizations from 22 countries which shared their research and practical activities on use of cementitious materials for various barrier purposes. The CRP has initially formulated the research topics considered within four specific streams: A) Conventional cementitious systems; B) Novel cementitious materials and technologies; C) Testing and waste acceptance criteria; and D) Modelling long term behaviour.The CRP has analysed both barrier functions and interactions envisaged between various components with focus on predisposal stage of waste management. Cementation processes have achieved a high degree of acceptance and many processes are now regarded as technically mature. A large body of information is currently available on proven waste conditioning technologies although novel approaches are continuing to be devised.Most of the existing technologies have been developed for conditioning of large amounts of operational radioactive waste from nuclear power plants and other nuclear fuel cycle facilities. However new waste streams including those resulting from legacy and decommissioning activities required improved material performance and technologies.The most important outcome of CRP was the exchange of information and research co-operation between different institutions and has contributed towards general enhancement of safety by improving waste management practices and their efficiency. The paper presents the most important results and trends revealed by CRP participants. The research contributions of participating organizations will be published as country contributions in a forthcoming IAEA technical publication.

Structural Integrity for the RPV of French NPP during the LRA

2016 ◽  
Vol 853 ◽  
pp. 453-457
Author(s):  
Ming Ya Chen ◽  
Wei Wei Yu ◽  
Jin Hua Shi ◽  
Rong Shan Wang ◽  
Lv Feng ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Structural Integrity ◽  
The Other ◽  
Light Water Reactor ◽  
Original Design ◽  
Light Water ◽  
Pressurized Thermal Shock ◽  
The Usa ◽  
Reactor Pressure

Most of the French Nuclear Power Plants (NPPs) are currently embarking upon efforts to renew their operating license, while the pressurized thermal shock (PTS) events and environmentally assisted fatigue (EAF) pose potentially significant challenges to the structural integrity of the reactor pressure vessel (RPV) which has the potential to be NPP life-limiting conditions. In the assessment of the PTS events, the deterministic fracture mechanics (DFM) is still used as the basic mechanics in most countries except for the USA. While the maximum nil-ductility-transition temperature (RTNDT) is about 80°C for 54 French RPVs after 40 years operation, the maximum allowable RTNDT is only about 70 oC and 80 oC for the typical PTS events in the IAEA and NEA reports, respectively. On the other hand, the effects of light water reactor (LWR) environmental (other than moderate environment in the code) were not considered in the original design, while the effects of LWR environmental are needed to be considered in the LRA according to the USA regulations. In this paper, the challenges of the PTS and EAF are discussed, and some suggestions are also given for the LRA

scholarly journals Catalytic activity of Pd-Ni in the oxidation of hydrogen for the safety of nuclear power plant

2016 ◽  
Vol 18 (1) ◽  
pp. 15-18
Author(s):  
Dariusz Łomot ◽  
Zbigniew Karpiński
Keyword(s):  
Bimetallic Catalysts ◽  
Nuclear Power ◽  
Power Plants ◽  
Hydrogen Oxidation ◽  
Precious Metals ◽  
Oxidation Of Hydrogen ◽  
Different Temperatures ◽  
Flowing System ◽  
Over Time ◽  
Excellent Stability

Abstract Pd-Ni/Al2O3 systems were investigated in the reaction of hydrogen oxidation in terms of their possible application as catalysts used in passive autocatalytic recombiners (PARs) used in nuclear power plants. Testing experiments were carried out in a flowing system at different temperatures and humidity of the reaction mixture. The bimetallic catalysts exhibited higher response to the increase of temperature and higher resistance to inhibit water than the monometallic palladium catalyst. They showed excellent stability during a few tens of hours, similarly, like their monometallic counterpart. Our bimetallic catalysts of hydrogen oxidation can be used as cheaper alternatives to catalysts based on the precious metals in the hydrogen oxidation without loss of their activity over time.

Natural Radioactivity in the Principal Constituents of French River Ecosystems

1988 ◽  
Vol 24 (1-4) ◽  
pp. 143-147 ◽  
Author(s):  
B. Descamps ◽  
L. Foulquier
Keyword(s):  
Natural Radioactivity ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
The Other ◽  
Whole Body ◽  
Counting Period ◽  
Small Stream ◽  
Zone Ii ◽  
Mining Complex

Abstract The study is based on data covering the water, sediments, plants and fish sampled over a 20-year period at 15 stations along French rivers. Three geographic zones were investigated: one containing a uranium mining complex (Zone 1), another including five major rivers along which nuclear power plants are sited (Zone II) and a third unaffected by nuclear activities (Zone III). Natural radioactivity basically involves 238U, 226Ra and 210Pb in the uranium series, 232Th from the thorium series, 40K and 7Be. The natural radioactivity in Zone II is not different from Zone III, and is thus unaffected by waste discharges from nuclear power plants. The most abundant radionuclide is 40K, while the other nuclides are often found in trace amounts near the detection threshold of the analysis method used (Ge gamma spectrometry with a 15-hour counting period). The 226Ra and 238U concentrations observed in Zone I are at least an order of magnitude higher than in the other two zones due to authorised waste discharges from the Lodève mining complex, but only a small stream is affected. The measured 226Ra concentrations would result in an annual whole body committed dose equivalent attributable to a 200 g weekly fish consumption from this stream of 4.4 x 10-5 Sv.y-1, or 0.86% of the maximum permissible dose (5 mSv).

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