A Transport Code for Radiocolloid Migration: With an Assessment of an Actual Low-Level Waste Site

AbstractRecently, there is increased concern that radiocolloids may act as a rapid transport mechanism for the release of radionuclides from high-level waste repositories. The role of colloids is, however, controversial because the necessary data and assessment methodology have been limited. To quantitatively assess the role of colloids, the TRACR3D transport code has been enhanced by the addition of the population balance equations. The code was tested against the experimental laboratory column data of Avogadro et al. Next a low-level radioactive waste site was investigated to explore whether colloid migration could account for the unusually rapid transport of plutonium and americium observed. The nature and modeling of radiocolloids are discussed along with site simulation results from the TRACR3D code.

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Treatment and Disposal of the Radioactive Graphite Waste

18th International Conference on Nuclear Engineering: Volume 1 ◽

10.1115/icone18-29985 ◽

2010 ◽

Cited By ~ 1

Author(s):

Lifang Tian ◽

Mingfen Wen ◽

Jing Chen

Keyword(s):

Radioactive Waste ◽

Radioactive Contamination ◽

Carbon Material ◽

Advanced Technology ◽

High Level Waste ◽

Graphite Material ◽

Low Level ◽

Radioactive Graphite ◽

High Level ◽

Low Level Radioactive Waste

A large number of nuclear reactors with graphite as moderator and reflector material are facing to be decommissioned now or later, and the radioactive graphite waste is a large part of the involved wastes. In addition, high temperature gas-cooled reactors being developed rapidly use a large quantity of graphite material (up to 95%) in the nuclear fuel elements, besides graphite material as their moderator and reflector material in the reactor cores. Therefore, it is very critical to manage these graphite wastes from the decommissioned and being decommissioned reactors. The part with low-level radioactive contamination that could not be reused now, may be disposed of as solid waste to reduce its volume, and the possibility of its being retrieved and reused in the future with advanced technology should be considered. The other graphite waste with high-level radioactive contamination requires much more consideration. Due to several factors, such as its large quantity, a lack of available disposal sites and public acceptance, it may not be disposed of directly in the repository any more. An option may be the transformation of the high-level radioactive graphite waste into low-level radioactive waste through physical and chemical processes. The current technologies involve, e.g., thermal treatment to release 36Cl, capture of the 14C from the gases of incineration of carbon material and decomposition of carbon dioxide into solid carbon. After these treatments the carbon material might be decontaminated and separated as low-level radioactive waste and a small amount of residual high-level waste could be disposed of ultimately. In order to achieve a sustainable development of graphite material, the maximum utility and the minimal disposal of radioactive graphite should be considered in the management of radioactive graphite waste. It is urgent to explore new technologies for decontaminating and recycling radioactive graphite.

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Triggering of transient LES relaxations in ferrets: role of sympathetic pathways and effects of baclofen

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.2000.279.1.g157 ◽

2000 ◽

Vol 279 (1) ◽

pp. G157-G162 ◽

Cited By ~ 22

Author(s):

Esther Staunton ◽

Scott D. Smid ◽

John Dent ◽

L. Ashley Blackshaw

Keyword(s):

Gastroesophageal Reflux ◽

Lower Esophageal Sphincter ◽

Glucose Infusion ◽

Gastric Distention ◽

Low Level ◽

Before And After ◽

Esophageal Sphincter ◽

Splanchnic Mechanoreceptors ◽

High Level

Activation of gastric vagal mechanoreceptors by distention is thought to be the trigger for transient lower esophageal sphincter relaxations (TLESR), which lead to gastroesophageal reflux. The contribution of higher-threshold gastric splanchnic mechanoreceptors is uninvestigated. GABABreceptor agonists, including baclofen, potently reduce triggering of TLESR by low-level gastric distention. We aimed to determine first whether this effect of baclofen is maintained at high-level distention and second the role of splanchnic pathways in triggering TLESR. Micromanometric/pH studies in conscious ferrets showed that intragastric glucose infusion (25 ml) increased triggering of TLESR and reflux. Both were significantly reduced by baclofen (7 μmol/kg ip) ( P < 0.05). When 40 ml of air was added to the glucose infusion, more TLESR occurred than with glucose alone ( P < 0.01). These were also reduced by baclofen ( P < 0.001). TLESR after glucose/air infusion were assessed before and after splanchnectomy (2–4, 9–11, and 23–25 days), which revealed no change. Baclofen inhibits TLESR after both low- and high-level gastric distention. Splanchnic pathways do not contribute to increased triggering of TLESR by high-level gastric distention.

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Spent Fuel as a Waste Form - Data Needs to Allow Long Term Performance Assessment Under Repository Disposal Conditions.

MRS Proceedings ◽

10.1557/proc-84-87 ◽

1986 ◽

Vol 84 ◽

Author(s):

V. M. Oversby

Keyword(s):

Performance Assessment ◽

Waste Form ◽

High Level Waste ◽

Detailed Knowledge ◽

Spent Fuel ◽

Expected Performance ◽

High Level ◽

Term Performance ◽

Physical And Chemical ◽

Waste Repositories

AbstractPerformance assessment calculations are required for high level waste repositories for a period of 10,000 years under NRC and EPA regulations. In addition, the Siting Guidelines (IOCFR960) require a comparison of sites following site characterization and prior to final site selection to be made over a 100,000 year period. In order to perform the required calculations, a detailed knowledge of the physical and chemical processes that affect waste form performance will be needed for each site. While bounding calculations might be sufficient to show compliance with the requirements of IOCFR60 and 40CFRI91, the site comparison for 100,000 years will need to be based on expected performance under site specific conditions. The only case where detailed knowledge of waste form characteristics in the repository would not be needed would be where radionuclide travel times to the accessible environment can be shown to exceed 100,000 years. This paper will review the factors that affect the release of radionuclides from spemt fuel under repository conditions, summarize our present state of knowledge, and suggest areas where more work is needed in order to support the performance assessment calculations.

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Getting the Spirit of Office Technologies! Does the Internal Organization Environment Support or Constrain?

Human Factors in Information Systems ◽

10.4018/978-1-931777-10-0.ch015 ◽

2011 ◽

pp. 194-210

Author(s):

Huub J.M. Ruel

Keyword(s):

Technology Implementation ◽

Information Technologies ◽

Organizational Environment ◽

Adaptive Structuration Theory ◽

Low Level ◽

Adaptive Structuration ◽

Work Autonomy ◽

High Level ◽

The Relationship

The relationship between Advanced Information Technologies (AIT) and organization is complex. Several theories and approaches try to get grip on this complex relationship. Adaptive Structuration Theory (AST) (DeSanctis and Poole, 1994) is one of them. It introduces the concept of spirit of AIT as an important determinant of AIT appropriation. AIT with a clear, coherent spirit will lead to a high level of AIT appropriation. But what about the role of the internal organizational environment? Does this constrain or support the role of the AIT’s spirit regarding AIT appropriation? This paper presents a study that aims to find an answer to this question. Three hypotheses were formulated and tested in four offices where employees used office technologies. Results confirm that a clear spirit is positively related to the level of appropriation as distinguished by DeSanctis and Poole (1994) and Poole and DeSanctis (1990). The results also make clear that this relationship is more positive among users who experienced a low level of change in the internal organizational environment along with the office technology implementation than among users who experienced a high level of change. Furthermore, the relationship is more positive among users with a low level of work autonomy than among users with a high level of work autonomy. This is not fully in line with our expectations. However, we think an explanation is available. We suppose that the answer lies in the office technology development process. All office technologies in this study’s offices were probably developed without anticipating the changes that office technology implementations might bring about in the internal organizational environment and with the aim to build systems that “reconfirm” the current “restrictive” work procedures. This study’s results once again indicate that office technology and other organizational components are interrelated.

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Assessment of Redox Conditions in the Near Field of Nuclear Waste Repositories: Application to the Swiss high-level and intermediate level waste disposal concept

MRS Proceedings ◽

10.1557/proc-807-539 ◽

2003 ◽

Vol 807 ◽

Cited By ~ 2

Author(s):

Paul Wersin ◽

Lawrence H. Johnson ◽

Bernhard Schwyn

Keyword(s):

Solid Phase ◽

Near Field ◽

Intermediate Level ◽

Redox Conditions ◽

High Level Waste ◽

Redox Potentials ◽

Spent Fuel ◽

Reducing Conditions ◽

High Level ◽

Waste Repositories

ABSTRACTRedox conditions were assessed for a spent fuel and high-level waste (SF/HLW) and an intermediate-level waste (ILW) repository. For both cases our analysis indicates permanently reducing conditions after a relatively short oxic period. The canister-bentonite near field in the HLW case displays a high redox buffering capacity because of expected high activity of dissolved and surface-bound Fe(II). This is contrary to the cementitious near field in the ILW case where concentrations of dissolved reduced species are low and redox reactions occur primarily via solid phase transformation processes.For the bentonite-canister near field, redox potentials of about -100 to -300 mV (SHE) are estimated, which is supported by recent kinetic data on U, Tc and Se interaction with reduced iron systems. For the cementitious near field, redox potentials of about -200 to -800 mV are estimated, which reflects the large uncertainties related to this alkaline environment.

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