Tank 29H Saltcake Core and Supernate Sample Analysis

MARTINO, CHRISTOPHERJ

Savannah River Site (S.C.)

关键词: Aluminium;    Waste Retrieval;    Interstitials;    Filtration;    Hydroxides;   

DOI  :  10.2172/825575
RP-ID  :  WSRC-TR-2004-00130-Rev 0
RP-ID  :  AC09-96SR18500
RP-ID  :  825575

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report provides the final results of analyses of the saltcake core sample and a separate supernate sample from Tank 29H. The supernate sample was markedly different from the drained interstitial liquid. The Tank 29H supernate had a reduction in 238Pu upon filtering through a 0.45-micron filter. Approximately 25 per cent of the U is in suspension in the supernate and can be removed by filtration. As expected, the radionuclides Cs-137 and Tc-99 are entirely soluble and the actinides are largely insoluble, in the interstitial liquid, within experimental error. It is not known how representative this saltcake sample is for the entire tank. There is considerably more liquid present in this sample than in most other tank samples examined thus far. The history of the tank indicates that some of the saltcake in the top layer likely dissolved by the addition of low ionic strength solutions over the past few years. Also, the sample was collected at the bottom of a 7-foot well that was mined into the saltcake with water. These water additions could have dissolved the sodium nitrate in the top layer, and left behind a layer containing the remaining salts, including those of aluminum, although it is not possible to confirm this with this sample. Conversely, if this high aluminum composition is similar throughout the tank, more interstitial liquid may be released upon draining, and more will be retained by the remaining saltcake. The draining characteristics of a high aluminum composition waste are also expected to be different from those of sodium nitrate, although the impact is not known. The high concentration of aluminum species led to precipitation of aluminum hydroxide during a draining/dissolution test using deionized water. If this occurs during tank retrieval, it has significant impacts for tank waste retrieval schedules. This phenomenon would likely manifest as slow dissolution and percolation rates, depending on the volume of the high aluminum region, and the method of water addition.