Economic feasibility of strontium-90 fueled heaters for use in cold regions

This study was conducted to conceptually design and obtain cost estimates for various radioisotope fueled heating systems for use in potential cold regions applications, and to determine the economic feasibility of radioisotope fueled heaters by comparing them to fuel oil systems. The applications have been identified and grouped, according to thermal output: (1) 1 kWt septic tank heaters, well-head heaters, heaters to assist operation of sewage lagoons, and (2) 7 or 12 kWt potable water system heaters. Potentially economic locations for these heaters are in remote Alaskan communities of 50 to 200 residents, where fuel oil prices and reliability requirements are high. Two basic conceptual heat designs were considered: a heat source and radiation shielding with no external heat transfer equipment, and a heat source and radiation shielding with external heat transfer equipment. Costs for both conceptual designs were estimated for heater sizes of 1 kWt, 7 kWt, and 12 kWt. The major costs were for the heat source and equipment. Radioisotope heaters were found to be much more expensive than fuel oil systems. The radioisotope fuel costs contribute 50 percent or more to the overall cost. Thus, an effective method to make a substantial reduction in radioisotope system cost would be to lower the Sr price from 10 cents/curie. It was concluded that radioisotope heaters will not be economically competitive with fuel oil systems unless one or more of the following situations occur: the price of strontium-90 is reduced below 10 cents/curie; fuel oil prices increase significantly; or for a particular application, the reliability or adaptability of a fuel oil system is unacceptable and a radioisotope system is satisfactory

Dose and risk assessment for intrusion into mixed waste disposal sites

Sites previously used for disposal of radioactive and hazardous chemical materials have resulted in situations that pose a potential threat to humans from inadvertent intrusion. An example generic scenario analysis was developed to demonstrate the evaluation of potential exposure to either cleanup workers or members of the public who intrude into buried waste containing both radioactive and hazardous chemical contaminants. The example scenarios consist of a collection of exposure routes (or pathways) with specific modeling assumptions for well-drilling and for excavation to construct buildings. These scenarios are used to describe conceptually some potential patterns of activity by non-protected human beings during intrusion into mixed-waste disposal sites. The dose from exposure to radioactive materials is calculated using the GENII software system and converted to risk by using factors from ICRP Publication 60. The hazard assessment for nonradioactive materials is performed using recent guidelines from the US Environmental Protection Agency (EPA). The example results are in the form of cancer risk for carcinogens and radiation exposure

The comparison of element partitioning in two types of thermal treatment facilities and the effects on potential radiation dose

The US Department of Energy (DOE) is performing a technical analysis to support the potential development of risk-based, numerical radiological control criteria (RCC) for mixed waste from DOE operations. As part of the technical analysis, potential future radiation doses are being calculated for workers at thermal treatment facilities and members of the public residing near such facilities. This study compared two types of thermal treatment systems: a conventional combustion chamber with excess air, represented by a rotary kiln with afterburner, and an oxygen-deficient pyrolysis unit, represented by a plasma arc furnace. The purpose of the first part of this study is to estimate the partitioning for significant radionuclides and elements in the two types of thermal treatment systems. Excess-air systems are generally found to produce heavy-metal chlorides, oxides, and sulfates; plasma-arc systems tend to produce more volatile free metals. This difference causes a change in source term dominance from halide volatility to free metal volatility. Chemical thermodynamic methodology is used to estimate partitioning in the two treatment systems. The second part of the study examines how the potential radiation dose to workers handling residue materials is affected by partitioning of radionuclides at the different types of facilities

Inventory Data Package for Hanford Assessments

This document presents the basis for a compilation of inventory for radioactive contaminants of interest by year for all potentially impactive waste sites on the Hanford Site for which inventory data exist in records or could be reasonably estimated. This document also includes discussions of the historical, current, and reasonably foreseeable (1944 to 2070) future radioactive waste and waste sites; the inventories of radionuclides that may have a potential for environmental impacts; a description of the method(s) for estimating inventories where records are inadequate; a description of the screening method(s) used to select those sites and contaminants that might make a substantial contribution to impacts; a listing of the remedial actions and their completion dates for waste sites; and tables showing the best estimate inventories available for Hanford assessments

The role of Allee effect in modelling post resection recurrence of glioblastoma

Resection of the bulk of a tumour often cannot eliminate all cancer cells, due to their infiltration into the surrounding healthy tissue. This may lead to recurrence of the tumour at a later time. We use a reaction-diffusion equation based model of tumour growth to investigate how the invasion front is delayed by resection, and how this depends on the density and behaviour of the remaining cancer cells. We show that the delay time is highly sensitive to qualitative details of the proliferation dynamics of the cancer cell population. The typically assumed logistic type proliferation leads to unrealistic results, predicting immediate recurrence. We find that in glioblastoma cell cultures the cell proliferation rate is an increasing function of the density at small cell densities. Our analysis suggests that cooperative behaviour of cancer cells, analogous to the Allee effect in ecology, can play a critical role in determining the time until tumour recurrence