Alpha-Decay Radiation Damage Study of a Glass-Bonded Sodalite Ceramicwaste form
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ALPHA-DECAY RADIATION DAMAGE STUDY OF A GLASS-BONDED SODALITE CERAMIC WASTE FORM S. M. Frank, T. L. Barber, T. DiSanto, K. M. Goff, S. G. Johnson, J-F Jue, M. Noy, T. P. O’Holleran and W. Sinkler* Argonne National Laboratory-West, PO Box 2528, Idaho Falls, ID, 83403-2528 *Current Address: UOP, Des Plaines, IL 60017 ABSTRACT Effects of alpha decay on the ceramic waste form used to immobilize fission products and actinides accumulated from electrometallurgical treatment of Department of Energy metallic spent nuclear fuel is being studied. This involved the preparation of a surrogate ceramic waste form containing two-weight percent plutonium-238 and monitoring changes to the waste form resulting from alpha-decay damage. The phase assembly of the ceramic waste form consists of glass-bonded sodalite with small quantities of nepheline, halite and plutonium dioxide. The waste form has been monitored for three years and has acquired an internal alpha-decay dose of 1x 1018 disintegrations per gram of material. Methods used to monitor the material include: density determination, chemical durability measured by immersion testing, microscopy and powder xray diffraction. The investigation has, to date, found little alteration to the waste form due to alpha-decay damage. X-ray diffraction analysis has detected a unit cell volume increase of 0.7 percent of the plutonium dioxide phase. Furthermore, bubbles and/or voids have been observed by transmission electron microscopy in the sodalite and glass phase. The origin of these defects is unclear and under investigation. INTRODUCTION Electrometallurgical treatment of spent, metallic nuclear fuel, at Argonne National Laboratory in Idaho, produces a relatively pure uranium product and two high-level waste forms [1]. These durable waste forms are termed the metallic and ceramic waste forms [2]. The ceramic waste form (CWF) contains alkali, alkaline earth, rare earth and halide fission products and small quantities of uranium and transuranic elements (< 1 weight percent). To investigate the effects of alpha decay on the CWF, surrogate waste form material was produced containing approximately 2 weight percent plutonium-238. The high specific activity of 238Pu ‘accelerates’ the damage to the host material such that the current 238Pu alpha-decay dose of 1 x 1018 alphadecays/gram of material, obtained after 3 years, corresponds to an equivalent 239Pu decay exposure time of 1000 years. Incorporation of high-activity radionuclides is but one method applied to the study of radiation damage to materials. Please see Ewing et al. [3] for a review on this topic. This multiyear study of alpha-decay damage involves periodic measurement of the 238Puloaded CWF to determine changes to the materials chemical durability, physical characteristics and microstructure [4,5]. Chemical durability is determined by the product consistency test (PCT), macroscopic volume changes measured by density analysis, phase composition and individual phase volume change measured by x-ray diffraction (XRD), and microscopic ana
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