Low-level Radioactive Waste Storage Research Articles

Evaluation of Thermal Hydraulics Characteristics of Natural Cooling Low Level Radioactive Waste Storage System

It is necessary to design a low level radioactive waste storage system so that the decay heat of radioactive waste does not breach the structural safety limit. Currently, this waste storage system is designed as a natural cooling system, which continuously cools the radioactive waste without an active device. It consists simply of a storage pit for radioactive waste and air inlet and outlet ducts. The radioactive waste is cooled by natural convective air flow, which is generated by the buoyancy of heated air due to the decay heat of radioactive waste. It is important to clarify the flow characteristics in the systems in order to evaluate the cooling performance. The air mass flow rate through the system is determined by the balance between the natural convective flow force and pressure loss within the system. Therefore, the pressure drop and flow pattern in the waste storage pit are important flow characteristics. In this study, the pressure drop and air temperature distribution, greatly influenced by the flow pattern in the pit, were measured using a 1/5 scale model and compared with the results obtained from CFD. Flow network analysis, which is a simple model that simulates the flow by nodes and junctions, was conducted and its validity was confirmed by experimental results and CFD.

Radiation streaming and skyshine evaluation for a proposed low-level radioactive waste assured isolation facility.

Texas is investigating the idea of building a long term waste storage facility, also known as an Assured Isolation Facility. This is an above-ground, retrievable low-level radioactive waste storage facility. A preliminary, scoping-level analysis has been extended to consider more complex scenarios of radiation streaming and skyshine by using MCNP to model the facility in greater detail. Using bounding source term assumptions, the radiation doses and dose rates are found to exceed applicable limits by an order of magnitude. By altering the facility design to fill in the hollow cores of the prefabricated concrete slabs used in the roof over the "high-gamma" rooms where the waste with greatest gamma radiation intensity is stored, dose rates outside the facility decrease by an order of magnitude. With the modified design, the annual dose at the site fenceline is less than the 1 mSv annual limit for exposure of the public. Within the site perimeter, modifying the roof results in an order of magnitude drop in the dose rate for personnel outside the facility and on the facility roof, as well as a significant drop inside the facility. Radiation streaming inside the facility can be lowered almost two orders of magnitude by placing operational restrictions to keep at least two rows of waste containers in front of the high-gamma room to cut down on the size of the path for streaming.

Stratigraphic correlation of oligocene marginal marine and fluvial deposits across the middle and lower coastal plain, South Carolina

The age and stratigraphic relationship of the Upland Unit, which crops out at the Savannah River Site near Barnwell, South Carolina has been the focus of many recent investigations. The geological interpretation of the Upland Unit is particularly significant since it serves as the upper confining unit used in the storage of lowlevel radioactive wastes at the Savannah River Site. The age and regional extent of the unit is also important in providing an accurate geological map of the upper coastal plain. The age of the Upland Unit has been in dispute because it lacks datable material. Extensive coring and seismic studies have been conducted to investigate the occurrence and regional distribution of this stratigraphic unit. Lithologically, the Upland Unit consists of poorly sorted, clayey to silty, medium- to coarse-grained sands and gravels of fluvial origin. Similar quartz gravel deposits have been reported from the Chandler Bridge Formation near Charleston, South Carolina. These ‘Upland-like’ gravels are the oldest gravels of Tertiary age reported in the lower coastal plain. The Chandler Bridge Formation is interpreted as a downdip marginal marine facies of an extensive fluvial drainage system which once extended from the upper to the lower coastal plain of South Carolina. Where present, the Chandler Bridge Formation is overlain by nodular phosphate deposits of the Edisto Formation (late Oligocene to early Miocene), and underlain by the Ashley Formation of late Oligocene age. Pollen and dinoflagellate analyses conducted on sediment samples also confirm a late Chattian age for the Chandler Bridge Formation. Consequently, if quartz clasts in the Chandler Bridge Formation represent fluvial transport of Upland Unit gravels from the upper coastal plain which seems likely, then the age of the Upland Unit can be no younger than late Oligocene. Lithologic and stratigraphic analyses suggest that the Upland Unit and the Chandler Bridge Formation are correlative and represent a sequence of fluvial and marginal marine deposits of late Oligocene age. The depositional history of these formational units provides additional information concerning the geological evolution of the middle and lower coastal plain of South Carolina.

Barnwell reopens for low-level radioactive waste storage

Barnwell reopens for low-level radioactive waste storage

Reply

Department of Anesthesiology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510.In Reply:--I am grateful to Smith for providing members of the anesthesiology research community with a timely reminder of how those of us involved in biomedical research must strive to educate the public about that complicated process. There are several points raised by Smith to which I would like to respond, in the order in which they are raised in his letter.Smith infers that I consider market forces to be evil. That is not the case. Unlike Smith, who appears to attribute an inherent good to market forces, I simply view them as one of many forces with which we interact. Most reasonable individuals, when approaching the edge of a cliff, will exercise caution. Although the force of gravity assists them in maintaining a firm footing, should they lose their balance, that same force of gravity may draw them over the edge to an uncertain fate. It is the result of the application of the force, rather than the force itself, that should lead to a judgment of value. Appropriate application of market forces will continue to strengthen academic settings. Misapplication will destroy them.Smith recognizes the importance of both basic and applied research but does not seem to be aware of the symbiotic relationship that exists between taxpayer-supported and private, investor-supported research. Federal and state grants and nonprofit organizations fund much of the basic science research aimed at a better understanding of natural phenomena. Small biotechnology companies, in recent years, have grown from those academic settings and, in turn, sold or licensed their discoveries to larger companies. The large companies, with resources necessary to undertake long-term product development, acquire this knowledge base and work to bring a new product to market. It is this model of symbiosis, not as described by Smith as parasitism, that has contributed to profound advances in medical care. The for-profit companies continue to rely heavily on the knowledge base developed through public support of basic research.Smith asks whether citizens of the United States should be asked to pay for research "if the aim of the research is purely knowledge acquisition. . . ." The following question was asked in polls taken in 1985, 1988, and 1990: Do you agree or disagree with the following: "Even if it brings no immediate benefits, scientific research which advances the frontiers of knowledge is necessary and should be supported by the Federal Government." More than 80% of the respondents in each of the years agreed that basic research should be supported by the government.* Smith asked an important question, one that has been asked before. We in the research community cannot assume, however, that the public will continue to support federal funding of basic research. It has been suggested that a proposed federal tax cut could result in a 30% reduction in funds for the National Institutes of Health.**In recent years, the research community has been called on to educate the public about the process of science. We must explain the value of animal models in biomedical research. We must inform our neighbors about the importance of radioactive materials in both clinical and research endeavors so that they may make reasoned decisions about storage of low-level radioactive waste. We must educate the public about the long-term value of investing in basic biomedical research. Had an effective polio vaccine not been developed it has been suggested that current annual costs for that disease would be $30 billion.My colleagues in the research community may ask why, at a time of increased competition for potentially shrinking research dollars, we should take on these additional responsibilities. My answer is simple: We cannot expect Big Bird or Barney to do it all.J. G. Collins, Ph.D.; Department of Anesthesiology; Yale University School of Medicine; 333 Cedar Street; New Haven, Connecticut 06510.*National Science Board: Science and Engineering Indicators 1991. Washington, D.C., U.S. Government Printing Office (NSB 91-1), p 12.**Marshall E: Nobelists make a pica for NIH budget. Science 267:1415, 1995.(Accepted for publication March 28, 1995.)

Iterative approach to groundwater flow modeling of the Martinsville Alternative Site, under consideration for low-level radioactive waste storage in Clark County, Illinois, U.S.A. : Beard, T C; Perry, C J; Fox, T C; Naymik, T G; Shanahan, P Environ Geol Water Sci V18, N3, Nov–Dec 1991, P195–207

Iterative approach to groundwater flow modeling of the Martinsville Alternative Site, under consideration for low-level radioactive waste storage in Clark County, Illinois, U.S.A. : Beard, T C; Perry, C J; Fox, T C; Naymik, T G; Shanahan, P Environ Geol Water Sci V18, N3, Nov–Dec 1991, P195–207

Iterative approach to groundwater flow modeling of the Martinsville Alternative Site, under consideration for low-level radioactive waste storage in Clark County, Illinois, U.S.A.

The regulatory requirements for characterization of the Martinsville Alternative Site (MAS) were fulfilled by applying an iterative approach to the groundwater flow modeling of the site and surrounding area. The approach consisted of field data collection and development of an initial conceptual model. The numerical model was then constructed to be consistent with the data and conceptual model. Next, the calibration results were evaluated statistically, and visually by a groundwater modeling review committee, to determine if the model accurately represented groundwater flow at the site. Initial results failed acceptance criteria because the values of numerical model input parameters had to be varied beyond observed data ranges to calibrate the results, and therefore the model was inconsistent with the initial conceptual model. This led to additional field data collection in areas where the numerical model deviated most from field-determined data. The new data provided sufficient information to revise the conceptual model and calibrate the numerical model successfully. Model calibration was followed by validation. Validation of the numerical model provided additional assurance that the model correctly simulated the observed system. No additional data were found to be necessary during validation of the MAS numerical model. The iterative approach proved to be successful for calibrating and validating this groundwater flow model and should be implemented from the onset of characterization planning in other applications.