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The Office of Civilian Radioactive Waste Management (OCRWM) of the U.S. Department of Energy {DO£) has a mission to provide for the permanent disposal of radioactive wastes in deep geologic repositories. The OCRWM is currently developing a performance assessment strategy for demonstrating compliance with the safety and performance criteria developed by the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Environmental Protection Agency (EPA). Because of the long time (more than 10,000 years) involved, the OCRWM performance assessment strategy necessarily relies upon computerized models of the geologic repository system and its components.

Aluminum reduction pots at the Pittsburgh ReductionCompany's (Alcoa's) plant i n 1889. Adapted from a photograph, courtesy of Alcoa. DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any WUIUI~~, expnsrcd or implkd, or assumes any kgal liability or nsponribi#tr for the accuracy, c o f n~, or uwfulmss of any information, apparlbs, produd, or process dirdortd, or rtprtsents that its use wwM not infdnge privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government of any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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SUMMARYThe lead-iron-phosphate (Pb-Fe-P) glass developed at Oak Ridge National Laboratory was evaluated for its potential as an improvement over the current reference nuclear waste form, borosilicate (B-Si) glass. The evaluation was conducted as part of the Second Generation HLW Technology Subtask of the Nuclear Waste Treatment Program at Pacific Northwest Laboratory. The purpose of this work was to investigate possible alternatives to B-Si glass as secondgeneration waste forms. While vitreous Pb-Fe-P glass appears to have substantially better chemical durability than B-Si glass, severe crystallization or devitrification leading to deteriorated chemical durability would result if this glass were poured into large canisters as is the procedure with B-Si glass. Cesium leach rates from this crystallized material are orders of magnitude greater than those from B-Si glass. Therefore, to realize the potential performance advantages of the Pb-Fe-P material in a nuclear waste form, the processing method would have to cool the material rapidly to retain its vitreous structure.; i i CONTENTS