bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling of Double Diffusion in Turbulent Mass Transport in Porous Media
Authors: de Lemos Marcelo J. S.
Published: March 2009

This work presents derivations of macroscopic heat and mass transport equations for turbulent flow in permeable structures. Two driving mechanisms are considered to contribute to the overall momentum transport, namely temperature driven and concentration driven mass fluxes. Double-diffusive natural convection mechanism is investigated for the fluid phase in turbulent regime. Equations are presented based on two distinct procedures. The first method considers time averaging of the local instantaneous mass transport equation before the volume average operator is applied. The second methodology employs both averaging operators but in a reverse order. This work is intended to demonstrate that additional transport mechanisms are mathematically derived if temperature, concentration and velocity present simultaneously time fluctuations and spatial deviations within the domain of analysis. A modeled form for the final mass transport equation is presented where turbulent transfer is based on a macroscopic version of the k-ε model.
Development of Microfluidic Flow Sensor in a Polymeric Microchip
Authors: Salgado Juan David , Horiuchi Keisuke , Dutta Prashanta
Published: March 2009

A microfluidic flow sensor has been developed to precisely measure the flow rate in a micro/nanofluidic channel for lab-on-a-chip applications. Mixed electroosmotic and pressure driven microflows are investigated using this sensor. Our microflow sensor consists of two components: fluidic circuit and electronic circuit. The fluidic circuit is embedded into the microfluidic chip, which is formed during the microfabrication sequences. On the other hand, the electronic circuit is a microelectronic chip that works as a logical switch. We have tested the microflow sensor in a hybrid poly di-methyl-siloxane (PDMS)-glass microchip using de-ionized (DI) water. Softlithography techniques are used to form the basic microflow structure on a PDMS layer, and all sensing electrodes are deposited on a glass plate using sputtering technique. In this investigation, the microchannel thickness is varied between 3.5 and 10 microns, and the externally applied electric field is ranged between 100V/mm and 200V/mm. The thickness of the gold electrodes is kept below 100nm, and hence the flow disturbance due to the electrodes is very minimal. Fairly repeatable flow results are obtained for all the channel dimensions and electric fields. Moreover, for a particular electric field strength, there is an appreciable change in the flow velocity with the change of the channel thickness.
Parallel-in-Time Simulation of 2D Laminar Unsteady Flow Around a Square Obstacle
Authors: Trindade J. M. F. , Pereira J. C. F.
Published: March 2009

The present work reports an application of a parallel-in-time algorithm to the solution of the unsteady incompressible form of the Navier-Stokes equations to calculate the vortex shedding flow past a square obstacle in a channel for laminar Reynolds numbers. The parallel in time algorithm is based on the iterative use of coarse global sequential solvers (or integrators) with fine local parallel ones, allowing the time domain decomposition and the propagation of solution jumps on the coarse time-grid. Calculation starts with a sequential solution along the time domain of the problem on a coarse time-grid and is followed by an iterative procedure using the coarse time-grid and a finer one. The temporal evolution on the finer time-grid is calculated in parallel. This iterative procedure provides successive corrections for the problem solution. Some problems may emerge from the use of two temporal grids in this predictor-corrector fashion when solving the Navier-Stokes equations. Among them we have analyzed the influence of the number of processors and the number of iterations required for convergence. Significant computer time saving was achieved when compared with the single processor computing time.
A Study of the Sedimentation of a Sphere Near a Vertical Wall Using Three-Dimensional PIV
Authors: Harrison Graham M. , Tatum Jared A. , Lawson Nicholas J.
Published: March 2009

The sedimentation of a sphere through a fluid is a standard testbed problem in non-Newtonian fluid mechanics. The experimentally determined velocity fields may be compared with numerical predictions obtained using finite element simulations. In this work, the influence of an adjacent wall, in addition to elastic and shear thinning effects, on the velocity field in the fluid surrounding the sphere is studied. Three different test fluids are employed: a Newtonian reference fluid, a constant shear viscosity (elastic) Boger fluid, and a shear thinning elastic fluid. All three fluids have similar zero shear viscosities. For all experiments, the terminal velocity is achieved before measurements begin. Significant differences in both the location and magnitude of the recirculation zones are observed for the different test fluids. In addition, the shape of the wake is qualitatively different for the various fluids.
Stochastic Estimation of the Flow Structure Downstream of a Separating/Reattaching Flow Using Wall-Pressure Array Measurements
Authors: Daoud Mohamed , Naguib Ahmed
Published: March 2009

This investigation examines the surface-pressure fluctuations and associated flow structures spatiotemporally in the developing flow downstream of the reattachment point of a fence-with-splitter-plate flow. Simultaneous measurements of the wall-pressure and velocity field were undertaken using a 16-microphone array, extending over the streamwise range 1.67 < x/Xr < 3.33 (where Xr is the mean reattachment length), and X-hotwire sensor at two Reynolds numbers of 8000 and 16000, based on the fence height above the splitter plate. The array data were used to obtain the wavenumber-frequency spectrum of the wall-pressure fluctuation. The results illustrate that Taylor hypothesis of frozen eddies reasonably describes the flow in the investigated zone. This allowed utilization of the time-dependent LSE of the velocity field to estimate the spatial structure of the flow above the microphone array. The results confirm the association of the most-energetic pressure fluctuation with the passage of quasi-periodic vortices.
Unsteady Jets in Crossflow
Authors: Zaman K. B. M. Q.
Published: March 2009

The effect of periodic perturbation on a jet in a cross-flow (JICF) is reviewed. In the first part of the paper, flow visualization results from several past works are discussed. Beginning with a description of the characteristic vortex systems of a JICF it is shown that specific perturbation techniques work by organizing and intensifying specific vortex systems. Oscillatory blowing works primarily through an organization of the shear layer vortices. A mechanical perturbation technique is found to organize the wake vortices. In the second part of the paper, results of an ongoing experiment involving another mechanical perturbation technique are discussed. It involves two tabs at the orifice exit whose asymmetry in placement is reversed periodically. It directly modulates the counter-rotating vortex pair (CVP). Effects of the perturbation for an array of three adjacent orifices are explored. The flowfield data show an improvement in mixing compared to the unperturbed case.
Laboratory Study of Two-Dimensional Flow Components of Bridge Flow
Authors: Parr Alfred D.
Published: March 2009

This paper describes a laboratory set-up that introduces undergraduate fluid mechanics student to the concept of two-dimensional flow at bridges. The experiment involves mostly flow visualization using dye injection. The students are asked to identify angles of attack through the bridge opening, areas of ineffective flow and location with dominant eddies.
Acoustic Emission Measurement of Flow Transition in Cross-Corrugated Channels
Authors: Hessami Mir-Akbar
Published: March 2009

Study of transition from laminar to turbulent flow in a cross-corrugated channel can assist researchers, and designers and manufacturers of cross-corrugated plate heat exchangers with their endeavours to improve the thermal and hydraulic performance of these units. The conventional methods of study of flow transition in a channel involve insertion of a probe into the flow to measure pressure, temperature and/or velocity of the flow. The probe may not only disturb the flow but also it may not be physically possible to place the probe inside the channel under investigation due to its small size. Therefore, in this paper, a non-invasive acoustic emission measurement technique is described, and the results of the flow transition in two cross-corrugated channels are presented. These results are compared with similar experimental data obtained by heat transfer and pressure loss measurements in such channels. Good agreement is reported. The acoustic emission measurement technique being non-intrusive, can be applied to various areas of research where flow disturbance must be avoided.
Quantification of Mixing Performance in Parallel Jets
Authors: Bunderson Nathan E. , Smith Barton L.
Published: March 2009

Experiments of unvented parallel planar jets having variable slot widths and velocities are presented. A flow visualization study shows that, for sufficiently large spacing, the jets “flap” and that this motion is maximized for a matched exit momentum flux condition. The extent of the jet mixing with the ambient fluid is investigated using two-component hot wire anemometry. It is demonstrated that the flapping increases mixing of the jets with the ambient. In addition, it is shown that the mixing increases with distance between the jets and with jet-width ratio.
Matrix Solution Techniques for CFD Applications on Non-Uniform Grids
Authors: Smith Jason
Published: March 2009

In this paper several different matrix solution strategies are applied to a benchmark problem discretized on a series of non-uniform grids. The problem solved is similar to the three-dimensional Poisson pressure problem, the most CPU intensive part of many CFD codes. The primary goal of this study is to determine how sensitive the various schemes are to grid aspect ratio. It is known that most methods, especially those that utilize point iteration, deteriorate when applied to non-uniform grids. It is shown that even though MG methods using point iteration as smoother break down as a stand-alone solver, they still are an effective preconditioning scheme for Krylov subspace methods. In addition, the application of these schemes to fully coupled CFD solvers as well as unstructured grids is discussed.
The Use of Turbulent Inlet Boundary Conditions for the Modelling of High Aspect Ratio Free Jets
Authors: Holdo̸ Arne E. , de With Govert
Published: March 2009

There are many practical situations when jets are emanating from non-axis-symmetric apertures. The complexities associated to the numerical modelling of a high aspect ratio jet is embedded in its physical complexity. Consequently, the numerical modelling does not only require a high mesh resolution, but furthermore it requires a careful construction of the inlet boundary velocity. The present work consists of a series of Large Eddy Simulation (LES) simulations using different inflow boundary conditions. This work is aimed to find suitable inlet boundary conditions which resemble the turbulent features that can be expected near the jet orifice. The turbulent inlet conditions are constructed by means of a variable velocity. The velocity profile is constructed such that the statistical quantities for turbulence are satisfied, this includes a correct turbulent intensity of the velocity signal and an ‘a priori’ selected frequency spectrum. Experimental work of Quinn et al. (5) is used to validate the computational data.
Natural Convection in a Vertical Cavity Partially Filled With Porous Medium: Effect of Aspect Ratio, Darcy and Fluid Rayleigh Numbers
Authors: Anand Sushant , Arora R. C.
Published: March 2009

Numerical investigation of natural convection in a rectangular cavity partially filled with fluid-saturated porous medium has been carried out. Rayleigh number (104 to 107) and Darcy Number (10−1 to 10−10), Aspect Ratio (0.75, 1.0, and 1.25) are considered parameters. The governing equations have been solved numerically by SIMPLEC, a finite volume method on staggered grid arrangement. Power-law scheme has been used to approximate convective and diffusive fluxes. The results obtained are presented for the streamlines, isotherms and variation of Nusselt number at the walls. For values of Darcy Number above 10−4, a convective regime has been found to exist in which flow is nearly independent of Darcy Number, while at low values (below 10−6) the conduction dominated region occurs in the porous medium. Increase in Aspect Ratio increases intensity of circulation while maintaining the symmetry with respect to diagonals. Increase in aspect ratio increases the region of uniform temperature which covers most of the porous region.
Droplet-Resolved Dilute Spray Evaporation Model
Authors: Johnson Samuel B. , Lewis Sonny J. , Delplanque Jean-Pierre
Published: March 2009

A numerical model that enables the simulation of polydispersed spray behavior while allowing the resolution of droplet-scale features is described. This Lagrangian model is based on a sectional approach and captures the effect of polydispersity, droplet initial speed and direction. It is designed for flexibility in that it can be used for a variety of droplet-based processes. The model performance is illustrated using two basic configurations: spray combustion and water mist fire suppression. The spray combustion case shows how the droplet-scale resolution can be critical since phase equilibrium is controlled by droplet surface temperature, which cannot be adequately captured using a lump-parameter model. The water mist case allows a demonstration of the basic features of the spray model such as the ability to characterize the ability of smaller droplets to get close enough to a fire or a hot surface.
Aeroacoustic Study of Tonal Noise Generated by Axial Flow Fans
Authors: Belamri T. , Wang G.
Published: March 2009

SPLNoise is an aeroacoustic program developed to predict tonal noise generated by low speed axial fans. It is based on a generalization of the acoustic analogy of Lowson. The main input to the program are the radial thrust and torque distribution along the blade. This radial distribution is obtained from a CFD calculation. An automatic link to CFX commercial CFD code was made. Noise testing was performed in the anechoic and reverberant room at the Trane Company. Comparison between predicted noise levels and experimental data is very satisfactory.
Odyssey of the Enhanced Boiling Surface
Authors: Webb Ralph L.
Published: March 2009

This paper traces the evolution of enhanced boiling surfaces. Early work was highly empirical and done in industrial research. The 1968 Milton patent described the first porous coated surface, and the 1971 Webb patent described a “structured” tube surface geometry. The first fundamental understanding of the “pore-and-tunnel” geometry was published by Nakayama in 1980. Webb and Chien’s flow visualization allowed observation of the evaporation in the sub-surface tunnels. They also performed an experimental parametric study that defines the effect of pore diameter and pitch on the boiling performance. The progression of work on analytical boiling models is also reviewed.
Vitrified Waste Corrosion Rates From Field Experiment and Reactive Transport Modeling
Authors: Bacon Diana H. , Ojovan Michael I. , McGrail B. Peter , Ojovan Natalie V. , Startsceva Irene V.
Published: March 2009

The Hanford Site in southeastern Washington State has been used extensively by the U.S. Department of Energy (DOE) to produce nuclear materials for the U.S. strategic defense arsenal. A large inventory of radioactive and mixed waste has accumulated in 177 buried single- and double-shell tanks. Liquid waste recovered from the tanks will be pre-treated to separate the low activity fraction from the high-level and transuranic wastes. The low-activity waste (LAW) will be immobilized in glass and placed in a near-surface disposal system on the Hanford Site. Vitrifying the LAW will generate over 160,000 m3 of glass. Before the immobilized low-activity waste (ILAW) can be disposed, DOE must approve a performance assessment (PA), which is a document that describes the long-term impacts of the disposal facility on public health and environmental resources. A sound scientific basis for determining the long-term release rates of radionuclides from LAW glasses must be developed if the PA is to be accepted by regulators and stakeholders. To conduct this calculation, Pacific Northwest National Laboratory (PNNL) used a methodology in which the waste form release rate was calculated by modeling the basic physical and chemical processes that are known to control dissolution behavior using a reactive transport code, STORM [1]. This methodology was used instead of empirical extrapolations from laboratory “leaching” experiments commonly used in other PA or in the phenomenological approach of SIA “Radon” [2]. This methodology is preferred because the dissolution rate, and hence radionuclide release rate, from silicate glasses is not a static variable—a constant that can be derived independently of other variables in the system. Glass dissolution rate is a function of three variables (neglecting glass composition itself): temperature, pH, and composition of the fluid contacting the glass. SIA Radon has been running a field experiment for over 12 years to evaluate the behavior of a high sodium glass buried in a loamy soil. The radioactive waste glass (K-26) made from actual intermediate-level waste from the Kursk (RBMK) reactor was manufactured and placed in a shallow trench. The waste stream was 86 mass% NaNO3, very similar to the salt content expected for Hanford LAW. The final glass composition had a Na2O content of roughly 16 mass%, making it very relevant to the glass formulations being considered at Hanford. A joint US DOE-SIA Radon project was devised to validate the modeling approach used for the ILAW PA by modeling glass corrosion in the subsurface experimental facility [3]. This paper gives an estimate of glass corrosion and ion exchange rates for K-26 waste glass based on field measurements.
Ductile Cast Iron for Transportation Cask Bodies
Authors: Warnke E. P. , Steinwarz W. , Sowa W. , Hu¨ggenberg R.
Published: March 2009

Casks for transportation and storage are necessary for the handling of spent fuel elements and other radioactive waste. These casks must provide sufficient shielding against nuclear radiation, safe confinement even under severe hypothetical mechanical and thermal accident conditions and assurance of the subcriticality of the content under these conditions. Since more than 20 years ductile cast iron is established as a well qualified and proven material for the fabrication of the cask body of the CASTOR and MOSAIK type casks.
Comparative Testing of New Sorbents for LRW Purification
Authors: Ilin Vadim A. , Karlin Yury V. , Dmitriev Sergey A. , Belyanina Natalya G. , Makeeva Vera Eu.
Published: March 2009

Sorption of radionuclides from various liquid radioactive wastes (LRW) is almost a traditional method, which is usually applied while developing technologies for LRW purification. There are a great number of sorbents of different kind and sorption properties, but research in developing new types of sorbents with high functional properties is still in actual state. Especially it is very important for LRW purifying technologies, which apply sorption-membrane scheme of purification. This paper is devoted to the comparative testing of new sorbents (biosorbent, fitosorbent, modified natural zeolite, and synthetic sorbent on the base of barium sulfate and some others). The aim of this testing is to determine the main properties of new sorbents and to compare them with some well-known and industrially applied ones, for example, ion exchange resins, natural zeolites and some others. All the experiments were conducted with applying real LRW and namely, radioactive evaporation bottoms from Physical Energy Institute of Obninsk town (Kaluga region) and radioactive aqueous solution from near-surface solid radioactive waste (SRW) repository drainage system of Zagorsk (Sergiev Posad town of Moscow region) branch of Moscow SIA “Radon”. Distribution coefficients of some α-, β-, γ- radionuclides at sorption in static and dynamic conditions were obtained for studied sorbents. Conclusions and some recommendations on applying the studied sorbents have been done.
Reduction of False Positives in the Identification of Nuclides in Environmental Samples
Authors: Haywood Susan E.
Published: March 2009

Gamma-ray spectra containing peaks that are too close in energy for deconvolution to be done accurately are best analyzed by a library-based method. However, a library-based analysis done with a large library may result an unacceptable number of false positives being reported. A normal working library suitable for analyzing environmental samples containing unknown materials may have over 1000 peaks, many of which are too close for deconvolution to be done accurately. A program has been written that uses a library-based analysis method that reduces the reporting of false positives, while retaining the ability to identify isotopes accurately from a large range of possibilities. In addition, the peak area calculation has been improved by allowing the energy calibration to be a free parameter in the fit of individual multiplets. This peak area improvement can result in a change of activity of several percent for some nuclides. In some cases, shifting the multiplet position can reduce false positives by identifying a peak in the multiplet as an unknown rather than associating it with a nuclide. One spectrum showed a marked peak activity improvement when the calibration was allowed to shift even though the the average error in the original calibration was 0.08%. Results obtained from a study on the identification of uranium decay products are presented.
Safety and Sustainability Implications of Long Term Storage of Radioactive Waste
Authors: Rowat John
Published: March 2009

Storage and disposal of radioactive waste are complementary rather than competing activities, and both are required for the safe management of wastes. Storage has been carried out safely within the past few decades, and there is a high degree of confidence that it can be continued safely for limited periods of time. However, as the amounts of radioactive waste in surface storage have increased, concern has grown over the sustainability of storage in the long term and the associated safety and security implications. In response to these concerns, the IAEA has prepared a position paper [1] that is intended for general readership. This presentation will provide a summary of the position paper, and a discussion of some safety issues for further consideration. A key theme is the contrast of the safety and sustainability implications of long term storage with those of early disposal. A number of factors are examined from different points of view, factors such as safety and security, need of maintenance, institutional control and information transfer, community attitudes and availability of funding. The timing and duration of the process of moving from storage to disposal, which are influenced by factors such as the long timeframes required to implement disposal and changing public attitudes, will also be discussed. The position paper focuses on the storage of three main types of waste: high level waste from the reprocessing of nuclear fuel, spent nuclear fuel that is regarded as waste and long-lived intermediate level radioactive waste. Long term storage of mining and milling waste, and other large volumes of waste from processes involving the use of naturally occurring radioactive materials are not discussed. Specialist meetings were held last year by the IAEA on the sustainability and safety of long-term storage to establish and discuss the issues where a broad consensus exists, and to investigate areas where issues remain unresolved. Within the technical community, it is widely agreed that perpetual storage is not considered to be either feasible or acceptable because of the impossibility of assuring active control over the time periods for which these wastes remain potentially hazardous. For high-level and long-lived radioactive waste, the consensus of the waste management experts is that disposal in deep underground engineered facilities — geological disposal — is the best option that is currently available, or likely to be available in the foreseeable future.
Cementitious Systems for Encapsualation of Intermediate Level Waste
Authors: Sharp J. H. , Hill J. , Milestone N. B. , Miller E. W.
Published: March 2009

Encapsulation in cement is the favoured method in the UK for disposal of intermediate and low level radioactive wastes. It is usual to use composite cement systems incorporating blast furnace slag (BFS) or pulverised fuel ash (PFA) as these offer several advantages over Portland cement, notably a lower heat of hydration. The use of these mineral additions utilises a waste product which would itself need a disposal route and, because of the decreased amount of Portland cement used, provides a reduction in cost and energy consumption. Cementitious systems have many attributes which make them suitable for encapsulation and immobilisation, including: • Inexpensive and readily available; • Assist immobilisation of radionuclides by: a) acting as a diffusion barrier, b) providing sorption and reaction sites, c) maintaining a high pH which in turn decreases radionuclide solubility; • Provide radiation shielding which is not degraded by the radiation; • Controllable permeation and diffusion characteristics over a wide range via selection of constituents and components. Where physical adsorption is a significant factor for immobilisation, the calcium silicate hydrate gel (C-S-H) formed on hydration of a Portland cement is advantageous as it has a high surface area and large micropore volume. Composite cements based on blast furnace slag will produce a higher proportion of C-S-H than ordinary Portland cement increasing the sorption capacity, and reducing the capillary porosity so that the diffusion resistance is increased. Intermediate level waste covers a wide range of materials, for example, metals and ion exchangers, each with differing chemical properties. It is, therefore, necessary to access the ability of the cementitious system to immobilise different wastes and to characterise the products formed. It is also necessary that alternative encapsulant materials be considered for immobilising wastes not suited to the composite cements already being used. The techniques employed to do this include x-ray diffraction (XRD), to identify standard and non-standard hydration products, isothermal conduction calorimetry (ICC) and scanning electron microscopy (SEM).
A Finite Element Computer Model for the Application of Electrokinetics to Contaminated Land
Authors: Kwong Simon , Paulley Alan , Bond Alex
Published: March 2009

The computer code TRAFFIC incorporating three-dimensional (3-D) electrokinetic capabilities, coupled flow, transport and chemical speciation, using a finite element approach has been used to replicate published laboratory scale experiments [1, 2]. Two test cases have been presented using TRAFFIC with chemical speciation options and the Euler-Lagrangian transport formulation. The first of these (Case A with graphite anode) provided useful insights into the capabilities of the code to simulate realistic and complex problems, while the second (Case B with iron anode) closely reproduced the experimental results. It was also shown that the Euler-Lagrangian transport scheme was much better in coping with the steep chemical gradients, whereas the standard Euler scheme is less stable. Given the good results of these test cases, it is concluded that the code has been verified and partially validated.
Characterization of Plutonium Contaminated Soils From the Nevada Test Site for Remediation Method Selection
Authors: Torrao Guilhermina , Carlino Robert , Hoeffner Steve L. , Navratil James D.
Published: March 2009

Plutonium (239/240Pu) contamination in soils is an environmental concern at many U.S. Department of Energy (DOE) sites. Remediation actions have been attempted using different technologies, and clean-up plans have been implemented at several sites, such as the Nevada Test Site (NTS). During the 1950’s and early 1960’s, nuclear weapons testing at and near the NTS resulted in soil contaminated with plutonium particles. Clean-up efforts are continuing using conventional remediation techniques. However, the DOE desires to obtain technologies that can further reduce risks, reduce clean-up costs, and reduce the volume of contaminated soil for disposal. Low levels of plutonium contamination are distributed somewhat uniformly throughout the NTS soils and, as a result, it is difficult to obtain volume reductions above 70%. The subject of this research was to characterize the plutonium-contaminated soil from the Tonopah Test Range (TTR) north of the NTS. In order to select remediation methods, it is important to gain a better understanding of how plutonium is bound to the contaminated soil; thus, size separation, magnetic separation, and the sequential extraction (SE) methods were used for this purpose. The SE method consisted of targeting five operationally defined geochemical phases: ion exchangeable, bound to carbonates, bound to iron and manganese oxides (reducible), bound to organic matter, and resistant. Radiometric measurements were used to determine plutonium in each of these defined phases in the soil. Selected stable elements were also determined, to compare the operation of the SE method to other investigators. The SE experiments were performed with two types of samples: soil without heat treatment and soil with heat treatment. The MF treatment was used to destroy the organic content in the soil so as to further evaluate the SE procedure. Particle size analysis indicated that approximately 37% of the TTR soil by weight was larger than 300 micrometers and this fraction contained little plutonium, < 100 pCi/g. Thus, size separation may be useful as part of a remediation process. Magnetic separation tests showed that the magnetic fraction of the TTR soils is very small, and the non-magnetic fraction still contained the majority of the plutonium. Thus, a magnetic separation step in a treatment process would not be useful. Following SE, analysis results of the stable elements agreed with reported values. The SE results also indicated an association of plutonium with the organic and resistant defined phases. The main change in 239/240Pu distribution following heat treatment was an increase of plutonium recovery in the reducible phase. The SE results showed that fairly aggressive chemical treatment would be required if leaching were part of a remediation process.
Long-Term Stewardship and Risk Management Strategies for Inactive Nuclear Test Sites in the United States
Authors: Shafer D. S. , Chapman J. B. , Hassan A. E. , Pohll G. , Pohlmann K. F. , Young M. H.
Published: March 2009

Characterizing and managing groundwater contamination associated with the 828 underground nuclear tests conducted at the Nevada Test Site are among the most challenging environmental remediation issues faced by the U.S. Department of Energy. Although significant long-term stewardship and risk management issues are associated with underground nuclear tests on the Nevada Test Site, of possible equal concern are a smaller number of underground nuclear tests conducted by the United States, 12 total, at eight sites located off the Nevada Test Site. In comparison to the Nevada Test Site, the U.S. Department of Energy has minimal institutional controls at these “offsite test areas” (Offsites) to serve as risk barriers. The corrective action and closure strategy under development for the Central Nevada Test Area and proposed recommendations [1] concerning long-term stewardship for this and the other Offsites illustrate long-term stewardship and risk management strategies applicable to underground nuclear test areas in the United States. The groundwater flow and transport model for the Central Nevada Test Area, site of the 1968 Faultless underground nuclear test, is the first model accepted by a U.S. state regulator (the Nevada Division of Environmental Protection) for an underground nuclear test area. Recommendations for the Central Nevada Test Area and other Offsites include developing decision support models to evaluate the impacts of future changes of land and water uses on previous decisions involving groundwater-use restrictions. Particularly for the Offsites in arid states such as Nevada, New Mexico, and Colorado, it is difficult to envision all future demands on subsurface resources. Rather than trying to maintain complex flow and transport models to evaluate future resource-use scenarios, decision support models coupled with original contaminant flow and transport models could be used as scoping tools to evaluate the sensitivity of previously established resource-use boundaries. This evaluation will determine if the previously established boundaries are still adequate for proposed new land and resource uses or if additional data collection or modeling will be necessary to make technically sound decisions. In addition, previously developed Data Decision Analyses, used to quantitatively evaluate the costs and benefits of different data collection activities conducted during the site characterization phase, could be maintained as a long-term stewardship tool to identify new data collection efforts, if necessary as indicated by a decision support model.
A Framework for Assessing the Cost and Financing Uncertainties of the Belgian High Level-Waste Repository
Authors: Kunsch P. L.
Published: March 2009

This paper presents the general approach presently developed by ONDRAF/NIRAS/NERAS, the Belgian radioactive waste management agency for dealing with the economic and financial uncertainties of the High-level-Waste (HLW) repository project in clay. This project will be for many more years the object of R&D studies. Many uncertainties thus still exist regarding the final design, the eventual costs, and the realisation schedule. Recommendations from the Electric Power Research Institute (EPRI) are available for computing contingency factors to be applied on top of the basic costs delivered by project engineers. We show in this paper that fuzzy logic is a natural way to use the recommendations of EPRI. Fuzzy logic is a mathematical technique for representing unprecise or relatively vague judgments made by experts, like: ‘this project is preliminary’, ‘this concept is insufficiently mature’, etc. This approach is considered in many fields as being well-suited for coping with uncertainties implied by such judgments. In the present case, distinction is made between uncertainties related to policy, project, technology, and realisation schedule. The paper details the sequence of basic steps used by the agency to produce as a final product the per-unit tariff of the different waste categories. Expert judgments are interpreted by the fuzzy-logic technique to derive EPRI-like contingency factors for each project task, as well as a fuzzy operating schedule within a given political scenario. Conclusions are given on how this approach can be validated and set into practice.
Winfrith: Life After Decommissioning — Nuclear Site to Science and Technology Park
Authors: Neal Alan
Published: March 2009

UKAEA’s Winfrith site was built in the late 1950’s to undertake research and development into electricity generation from nuclear power. Pioneering scientific and technical work was carried out which resulted in a better understanding of nuclear issues, particularly nuclear safety. At its peak, Winfrith employed 2000 staff and at one time had nine operational nuclear reactors. The most noticeable landmark being the Steam Generating heavy Water Reactor (SGHWR) which, when in operation, provided the National Grid with enough electricity for a small town. In the early 1990’s the UK Government wound down its programme of nuclear R&D, and work started on restoring the environment of the Winfrith site by the progressive removal of the nuclear facilities. Winfrith has always been considered to be one of three key sites in Dorset for development of quality employment, and the site management, with the support of the DTI, decided to undertake a programme of environmental restoration that retained appropriate buildings and infrastructure systems that could be put to alternative long term use. To date, successes have been achieved in both the decommissioning work and also the establishment of tenants. All the fuel has been removed from the nuclear reactors and five reactors have been completely dismantled. Decontamination of other facilities has been completed. A notable example of this work is the return of a fuel fabrication building to a green field site. Another example was the decommissioning of a building that contained gloveboxes, and laboratories equipped with high efficiency filtered ventilation systems. This building was decommissioned, the area of land containing it delicensed, and the building leased to non-nuclear tenants. This thorough, painstaking process involved the use of recently developed industry techniques and required close working with the Nuclear Installations Inspectorate (NII). The tenant base is growing and at the end of 2002 there are 40 different companies resident on site with employee numbers ranging from 1 to several hundreds with a total of ∼ 1000 staff. In addition, the UKAEA programme employs ∼ 500 as staff and contractors. The larger tenants include QinetiQ and DSTL (both from the former Defence Evaluation and Research Agency), the Natural Environment Research Council’s Centre for Ecology and Hydrology, and RWE Nukem. The progressive decommissioning work continues and as UKAEA retreats across the site, from east to west, the non-nuclear research and development businesses move in. The range of work established at Winfrith provides a focus for its further development as a scientific and technical centre of excellence. Facilities have been created in partnership with the local council for small and start-up businesses, while strong links are being encouraged with universities that have an interest in areas such as environmental research. Together they will form a vital part of the commercial community, stimulating growth through technical interaction and innovation.
Approaches for Addressing MARSSIM Complications
Authors: Johnson R. L. , Durham L. A. , Miller D. S.
Published: March 2009

The Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) was developed as a multi-agency framework for supporting radioactive site closure in the United States. MARSSIM provides a coherent, technically defensible process for establishing that exposed surfaces (soil or structure) satisfy site cleanup requirements. Site cleanup requirements are assumed to be dose or risk-derived. Unfortunately, many sites have complications that challenge a direct application of MARSSIM. Example complications include decision documents requirements that are not MARSSIM-friendly, the potential for subsurface contamination, and incomplete characterization information. These types of complications are typically the rule, rather than the exception, for sites undergoing radiologically-driven remediation and closure. This paper discusses approaches used to circumvent MARSSIM-related closure issues, while still providing a technically defensible closure protocol that is consistent with the spirit of MARSSIM and acceptable to the regulatory and broader stakeholder community.
The Bandsaw: A Highly Sophisticated Dismantling Technique for the Karlsruhe Multi Purpose Research Reactor
Authors: Leffrang U. , Stanke D. , Prechtl E. , Suessdorf W.
Published: March 2009

For the dry dismantling and segmentation of dedicated components within the reactor pressure vessel (RPV) of the Karlsruhe Multi Purpose Research Reactor (MZFR) a bandsaw has been applied. The general decommissioning concept for the MZFR as well as constructional details of the bandsaw itself and the experience gained so far during the segmentation of the RPV closure head and the upper spacer are given with the present paper.
Special Radiometric Investigations at BNFL Sellafield and at the UKAEA Dounreay
Authors: Thornley D. J. , Chesterman A. S. , Clark P. A. , Gunn R. D. , McCrindle K. B. , Sampson S. , Lacey D.
Published: March 2009

Radiometric specialist measurements are required for a variety of activities at Sellafield such as support to operational plants, building management, waste management and decommissioning. Measurements are performed using mainly standard components in a novel configuration or using standard products for a non standard application. They are required, for example, to characterise radioactive material which may be outside the normal operating envelope of installed monitoring systems, provide radiometric characterization to aid plant operations, characterise the neutron moderating / absorption properties of materal and vessels, identify the source and characteristics of blockages which may occur in plant vessels and pipes etc. Examples of recent projects have included: • Special investigations of residue material from fuel manufacturing operations, using a combination of Total Neutron Counting, Neutron Coincidence Counting and High Resolution Gamma Spectrometry. • Dose rate measurements and surveys in environments up to 100 Sv/hr in various locations at the Sellafield reprocessing plants. Applications include in-cell measurements and underwater measurements in fuel ponds. • Neutron transmission measurements to verify the presence of absorbing material in plant vessels. • HRGS gamma surveys to identify and quantify a wide variety of radionuclides in waste handling and decommissioing operations. This paper provides insight into BNFL Instrument’s Special Investigation work and will provide examples of interesting projects which have been successfully carried out recently at Sellafield and Dounreay.
Developments in UK Regulation of Nuclear Wastes
Authors: Newstead Stuart , Bacon Mick , Cochrane Jim
Published: March 2009

The UK has a significant nuclear legacy arising from Government funded work going back to the 1940s. Government is proposing radical changes to current arrangements to tackle this legacy, clean-up nuclear sites and develop its policy for managing solid radioactive waste. As part of these developments the Nuclear Installations Inspectorate of the Health & Safety Executive, the Scottish Environment Protection Agency and the Environment Agency are putting in place joint working arrangements to improve the regulation of intermediate level radioactive wastes (ILW). The aim is to ensure that ILW is managed in a sustainable way taking into account long-term environmental considerations. These arrangements provide for improved regulatory oversight of (i) proposals from nuclear site licensees to condition ILW, and (ii) the work by Nirex to develop further its phased disposal concept (PDC). The regulators will scrutinise: • ILW conditioning proposals: This involves assessing site waste management plans, waste management options (e.g. BPEO assessments), conceptual designs and functional specifications for waste conditioning plants, detailed designs, construction, commissioning and operation of the plants, and the state of waste packages. • Nirex’s on-going work: This involves examining Nirex’s PDC, its application to ILW conditioning proposals and associated Letters of Comfort/Letters of Advice (LoC/LoA) and the possible future development of an environmental safety case for an eventual repository. A description is given of the regulators’ process associated with these new arrangements.
The Evolving Process of Plutonium Contaminated Equipment D&D
Authors: Nichols David K.
Published: March 2009

The Department of Energy’s Environmental Management (EM) cleanup and closure mission involves unique management, regulatory, technical and administrative challenges, which differ from typical operating situations or other environmental cleanups. As the country’s first large nuclear cleanup and closure site, Rocky Flats Environmental Technology Site (RFETS) managers were faced with first-of-a-kind issues that required bold and innovative approaches to undertake and accelerate the closure effort. This was the case nearly two years ago when the project was challenged with the task of dismantling hundreds of gloveboxes from former nuclear production buildings.
The Nature of Contamination of the Area in the Nearest Vicinity of Chornobyl NPP Destroyed Unit
Authors: Panasyuk M. I. , Skorbun A. D. , Ronchar V. V. , Zhydkov A. V.
Published: March 2009

A territory around the destroyed by the 1986 accident 4-th unit of Chornobyl NPP has been contaminated severely by radioactive materials pollution from the damaged unit. During the stage of accident consequences mitigation, the radioactive materials in a form of fragments of building constructions, fuel elements, graphite cladding, and upper layer of soil have been collected and buried. Around the destroyed Unit 4 the “Shelter” have been erected, and the decontaminated territory was covered by such anthropogenic soils as a pure crushed stone, sand and poured concrete. Special investigation indicates, however, that those soil turned out to be contaminated as well, and the main amount of the whole activity is concentrated in the so called active layer of the soil, which is located close to the pre-accident earth surface level. Given report is devoted to a possible mechanism of the soils contamination and radionuclide distributions in soils by way of laboratory analysis of cores of wells, which were drilled in the local zone, and gamma logging data analysis as well. The performed sampling analysis of soils, which belongs to the Shelter object industrial site show that radioactive contamination of anthropogenic soils of the active layer is mainly originates from active impurities (fine dispersed fuel particles) being distributed in a uniform way in the soil volume. The industrial site territory is covered by a concrete of a noticeable specific activity. That concrete during construction of “Shelter” flowed out through chinks in the casing and spread over the surrounding site. The concrete leached small fuel particles and carried those particles away from obstruction in mechanical way. This turned out an effective and power enough mechanism to contaminate the industrial site by radionuclides already just after an active stage of the accident. It seems to be perspective to introduce a technology for reprocessing of industrial site soils by way of flotation. That will permit to concentrate the considerable part of an activity and so to reduce sharply the volume of high-active radwastes, which must be buried.