Radiation Damage of a Glass-Bonded Zeolite Waste Form Using Ion Irradiation
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layer within the TEM disk, making the damage difficult to discern. As an alternative to the lead irradiation, a sample was irradiated with 1 MeV krypton. EXPERIMENT Materials The glass-bonded zeolite waste form was formed in a multistep process [12]. Zeolite 5A (composition in table 1) was combined with the surrogate salts listed in table 2. The salt-occluded zeolites were then mixed with P57 glass (composition in table 1) and the waste form produced in a hot isostatic press.
Zeolite 5A P57 Glass
Table Si 13.1 19.2
I: Zeolite and Glass Compositions (at %) Na K Al B Ca ---3.9 5.0 ---13.8 0.3 6.2 ---10.5 2.5
0 64.2 61.2
Cl ------
Table II: Surrogate Salt Composition (at%) Ce Pr Nd Sm I Cs Ba La Rb Sr Y Cl Li K Na Br 50.5 26.5 19 3.1 0.002 0.034 0.081 0.042 0.010 0.178 0.064 0.057 0.109 0.054 0.181 0.028 Sample Preparation To prepare TEM samples, a bulk sample was taken from the waste form using a 1 cm diameter core drill. One-half nmm slices were taken from the core drilled cylinder with a slow speed wafering saw; oil was used as the cutting lubricant. From the 0.5 mm thick wafers, 3 mm diameter disks were cored. An ultrasonic core drill was used with SiC and water as the cutting slurry. The 3 mm disks were mechanically polished on both sides to 0.08 mm thick; water was the grinding lubricant. A dimple was ground into the center of one side to a depth of -0.07 mm using a 15 mm diameter grinding wheel. The final step was to ion mill (Gatan PIPS) at 50 with 3 keV Ar ions at room temperature. A JEOL 2010 TEM operated at 200 keV was used to for the microscopy. Irradiations Ion irradiations were performed using the IVEM-Tandem User Facility at Argonne National Laboratory. Samples were irradiated using 100 keV lead ions to a fluence of 101 Pb+/cm 2 (peak displacement of 51 dpa, rate of 1.3x1012 Pb+/cm 2s). A sample was irradiated with 1 MeV krypton ions to 10" Kr /cm 2 (peak displacement of 0.11 dpa, rate of 8.2x 10"2 Kr /cm's). Samples were irradiated with 30 keV helium to a maximum fluence of 2x10' He/cm (peak displacement of 0.80 dpa, rate of 1.1xl012 He÷/cm 2s). The peak displacement quoted here is the maximum dpa within a TEM foil thickness, however, for Kr and He the displacement rate is nearly uniform over the sample thickness. Irradiations were stopped at intermediate doses to determine the response to fluence. All irradiations were performed at room temperature. Doses were calculated using TRIM97 assuming a displacement energy of 25 eV. If the displacement energies were 35 eV, the calculated displacements are: 0.21 dpa (1016 He+/cm 2 ), 37 dpa (106 Pb+/cm 2 ), and 0.07 dpa (10" Krt/cm2). For TRIM calculations, the composition of zeolite 5A was used as the composition. RESULTS Unirradiated Characterization: The unirradiated material has three distinct major phases: an amorphous glass phase, a crystalline phase resulting from salt-occluded zeolite, and a crystalline lanthanide bearing phase. To a lesser extent, alumina and potassium chloride phases have been found. Microsomite, sodium chloride, and lithium alu
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