Production And Characterization Of A Plutonium-238 Loaded Ceramic Waste Form For The Study Of The Effects Of Alpha Decay
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High level nuclear waste (HLW) that contains sufficient quantities of actinides undergoes various degrees of alpha radiation damage to the matrix material. This damage results from dissipation of energy from both the alpha particle and the recoil nucleus that emitted the alpha particle. The alpha particle, with an approximate energy of 5 MeV and a typical range of 20 ltm, imparts its energy to the surrounding matrix by both electronic excitation and direct elastic collision. The recoiled nucleus, with energies of approximately 85 keV and ranges of only tens of nanometers, disrupts the greatest number of neighboring atoms primarily by elastic collisions. 239 For the alpha decay of pu in a crystalline matrix, the ejected alpha particle may dislocate hundreds of matrix atoms by the end of its track. The recoiled - U nucleus may displace over
1000 local atoms, depending on the atomic density and displacement energy of the material. Over the expected lifetime of a geological repository, HLW forms containing large amounts of actinides would accumulate significant structural damage that may adversely influence the materials performance. To investigate the (x radiation effects on potential waste form materials, accelerated at damage studies are conducted by incorporating a high activity radionuclide such as 238pu (274 times the activity of 1 9Pu) or 244Cm into the material of interest [ 1,2]. Another method is to irradiate the material with heavy ions or He ions [3]. One may also study geological specimens that contain actinides [4]. Alpha-decay studies of crystalline materials or glass materials containing actinide host crystalline phases reveal that the crystalline material may become amorphous due to accumulation of dislocated matrix atoms [5,6]. Amorphization of crystalline phases leads to volume increases that may in turn lead to microcracking. Swelling
and cracking of the material usually have detrimental effects on the performance of the waste form [7]. After prolonged exposure, He or other gas bubbles may develop. However, some crystalline materials, such as PuO 2, U0 2 and ZrO 2 for example, show little damage to the crystalline structure. For the most current review on effects of a-decay damage, see reference 8. Argonne National Laboratory has developed a durable ceramic waste form (CWF) to immobilize alkali, alkaline earth, rare earth and halide fission products and transuranics that accumulate during the electrometallurgical processing of spent nuclear fuel. Accelerated a1193 Mat. Res. Soc. Symp. Proc. Vol. 556 ©1999 Materials Research Society
decay studies have been initiated to study the effects of alpha decay on the ceramic waste form. The electrometallurgical spent fuel treatment process was developed to condition specific types of Department of Energy (DOE) spent nuclear fuel that may not be suitable for direct disposal in a geological repository. The electrometallurgical process uses an electrorefiner containing a eutectic molten salt to desolve the fuel. Currently, Argonne National Laboratory is proc
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