Glass/Ceramic Interactions in the Can-in-Canister Configuration for Disposal of Excess Weapons Plutonium
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EXPERIMENTAL METHODS Because the purpose of this test is to determine if the chemical changes in water that has reacted with HLW glass alters the corrosion rate of the ceramic or release and transport of Pu and the neutron absorbers, a "sandwich" configuration, as illustrated in Figure 1, was selected. To match the approximate volumes of glass and ceramic in a can-in-canister configuration, 85% of the volume was allocated for glass (42.5% in the top and bottom beds) and 15% with ceramic. Details on the glass and ceramic materials used are given in the Materials section. Details on the PUF system are discussed next.
Glass
Ceramic
Figure 1. Schematic of PUF Interaction Test
PUF System The PUF system has been discussed in detail elsewhere [3,4], but is briefly described here. The basic test apparatus consists of a column packed with particles of the test material or materials of a known size and density, and a computer data acquisition and control system. The column is fabricated from a chemically inert material (polyetheretherketone) so that dissolution reactions are not influenced by interaction with the column. A porous titanium plate with nominal pore size of 0.2 iAm is sealed in the bottom of the column to ensure an adequate pressure differential for the conductance of fluid while operating under unsaturated conditions [5]. When water saturated, the porous plate allows water but not air to flow through it, as long as the applied pressure differential does not exceed the air entry relief pressure, or "bubble pressure," of the plate. A computer control system logs test data to disk from several thermocouples, pressure sensors, inline sensors for effluent pH and conductivity, and column weight from an electronic balance to accurately track water mass balance and saturation level. The column is also fitted
with a "PUF port," which is an electronically actuated valve that periodically vents the column gases at an interval specified by the operator. The purpose of column venting is to prevent reduction in the partial pressure of important gases, especially 02 and CO 2 that are participants in a variety of homogeneous and heterogeneous chemical reactions. Materials The ceramic used in this test (CPSF5) was produced at Lawrence Livermore National Laboratory and shipped to PNNL. The target composition (see Table 1) was 80 mass% zirconolite with 15 mass% Ba-hollandite and 5 mass% Table 1. Target Comrutile, 16 mass% PuO2 , and doped approximately equimolar with Gd. position for CPSF5 Mass% The simulated HLW glass used in the PUF experiment was received Oxide 17.91 from the Savannah River Technology Center (SRTC) labeled WP-14. ZrO, 40.85 Staff at SRTC transmitted a chemical analysis of the glass, which is TiO 2
given in Table 2.
Crushed glass and ceramic were prepared following the procedure detailed by the American Society for Testing and Materials [6]. The materials were ball milled and sieved to separate the 850 to 212 Atm (-20+70 mesh) size fraction. The crushed and sieved material was then
346
CaO GaO A120 3
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