[en] Partially failed containers may provide a meaningful barrier to the release of gaseous ¹⁴CO₂. A modeling approach is outlined and sample calculations are provided that show the effect on release due to a limited perforation area, to decreasing temperature, and to partial occlusion of the perforated area by corrosion products. 5 refs., 4 tabs

[en] Partially failed containers may provide a meaningful barrier to the release of gaseous radionuclides. A modeling approach is outlined and sample calculations are provided that show the effects on release due to a limited perforation area, to decreasing temperature, and to the partial occlusion of the perforated area by corrosion products. 8 refs., 2 tabs

[en] Radionuclides breakthrough times as calculated through constant retardation factors obtained in dilute solutions are non-conservative. The constant retardation approach regards the solid as having infinite sorption capacity throughout the solid. However, as the solid becomes locally saturated, such as in the proximity of the waste form-packing materials interface, it will exhibit no retardation properties, and transport will take place as if the radionuclides were locally non-reactive. The magnitude of the effect of finite sorption capacity of the packing materials on radionuclide transport is discussed with reference to high-level waste package performance. An example based on literature sorption data indicates that the breakthrough time may be overpredicted by orders of magnitude using a constant retardation factor as compared to using the entire sorption isotherm to obtain a concentration-dependent retardation factor. 8 references, 3 figures, 3 tables

[en] A temperature dependent expression for the free energy of formation of U₃O₇ from its constitutive elements is obtained utilizing basic thermodynamic data gathered from the literature. Similar expressions for the enthalpy and entropy of formation are also obtained. 11 refs., 6 tabs

[en] After showing the relevance of the semi-infinite medium approximation for describing leaching, all identified, potentially rate-controlling leaching mechanisms are integrated into a mathematical formulation which also incorporates two important system parameters: the specimen surface area-to-solution volume ratio and the leachant renewal frequency. Asymptotic analysis of a linearized version of the model shows that predicted short- and long-term leaching behaviors are physically correct. Surface processes tend to be initially rate-controlling, while at longer times dilution conditions of the leachant determine the rate-determining mechanism. Under dynamic leaching conditions, network dissolution eventually controls the leaching process; whereas, under static conditions bulk diffusion eventually prevails. The nonlinear version of the model was adapted to sodium and silicon leaching from borosilicate glass in deionized water, and fully implemented on computer by using a numerical strategy. The resulting code was named LIX. This more complex version upholds the conclusions reached by the asymptotic analysis. Moreover, when tested against actual PNL 76-68 glass leaching data, LIX shows excellent capabilities in reproducing the experimental evidence, in particular the effects of the surface area-to-solution volume ratio

[en] The concept of final long-lived radwaste storage in facilities built in geological formations involves the development of very deep repositories that ensure safety, i. e. that can withstand malicious or accidental disturbances throughout very long periods of time. This concept was developed after an extended period of review reflection discussion and consideration of other options. This article is intended to provide a vision of the state-of-the-art and a description of the latest breakthroughs and tendencies from the perspective of an integral approach. (Author) 11 refs

[en] We can say that in past decade have been undertaken important changes in the people participation about radioactive waste in the OECD countries, which enable the acceptance of proposed solutions.

[en] Institutions involved in the long-term management of radioactive waste are facing a rapidly evolving environment stemming from the ongoing societal changes. As in many other environmental areas, a demand for higher public participation in the decision making process leads to a need for analysing its implications and reviewing the role of the different stakeholders in order to respond to the new social challenges. This article offers a general overview on the institutions adaptation needs, and trends and, in particular, on the evolving role of the safety regulatory authorities, mainly based on the lessons learnt within the Forum on Stakeholder Confidence (FSC). (Author) 19 refs

[en] Recent studies have indicated that localized corrosion of a relatively small area of a waste container may impair the containment function to such an extent that larger releases may be possible than from the bare waste form. This would take place when a large number of holes coexist on the container while their concentration fields do not interact significantly with each other. After performing a steady state analysis of the release from a hole, it is shown that much fewer independent holes can coexist on a container surface than previously estimated. The calculated radionuclide release from multiple independent holes must be changed accordingly. Previous analyses did not proceed to a correct application of the linear superposition principle. This resulted in unacceptable physical conclusions and undue strain on the performance assessment necessary for a container licensing procedure. The paper also analyzes the steady state release from penetrations of finite length and whose concentration fields interact with one another. The predicted release from these penetrations is lower than the previously calculated release from holes of zero thickness. It is concluded here that the steady-state release from multiple holes on a waste container can not exceed the release from the bare waste form and that multiple perforations need not be a serious liability to container performance. 8 refs., 3 figs., 1 tab

[en] The Brookhaven National Laboratory (BNL) Waste Materials and Environment Modeling (WMEM) Program has been assigned the task of helping the DOE formulate and certify analytical tools needed to support and/or strengthen the Waste Package Licensing strategy. One objective of the WMEM program is to perform qualitative and quantitative analyses of processes related to the internal waste package environment, e.g., temperature, radiolysis effects, presence of moisture, etc. The primary objective of this report is to present the findings of a literature review of work pertinent to predicting intact waste package internal temperatures under spent fuel isolation conditions. Therefore, it is assumed that a repository scale thermal analysis has been conducted and the exterior temperature of the waste package is known. Thus, the problem reduces to one determined by the waste package and its properties. Secondary objectives of this report are to identify key parameters and methodologies for performing the thermal analysis within intact waste containers, and identify sources of uncertainty in these calculations. 37 refs., 6 figs., 2 tabs