Calcine dissolution studies were performed in FY-94,95 in order to extend the knowledge of dissolution and to obtain information necessary for scale-up design and operation. Experiments reported in this document were performed with non-radioactive and actual calcines to generate qualitative data regarding: (a) calcine dissolution rates, (b) undissolved solids settling characteristics, (c) undissolved solids heel formation, and (d) chemical treatments for undissolved solids heel dissolution. The goal of this work was to achieve complete calcine dissolution, or to determine conditions that would result in the maximum calcine dissolution. Small scale laboratory experiments (test-tube dissolutions) and a bench scale dissolver set-up were used in the effort. Results from this work show the bulk of the undissolved solids to settle at a rate of >9 inches per second when the baseline dissolution parameters are used. Baseline dissolution parameters were 100 grams of calcine being dissolved in 1 L of 5 M HNO{sub 3} at > 90 C while the solution is being vigorously and constantly mixed. This work also verified that dissolution is most complete when performed with aggressive mixing. Sequential dissolutions performed with non-radioactive and actual calcine indicate that little undissolved solids heel build-up is expected, and this small heel can …

The authors have been developing a novel threshold Cherenkov detector, consisting of a gas radiator followed by a UV photosensitive wire chamber using CsI photocathodes. The photo-detector lies directly in the particle path and is thus required to have single photo-electron sensitivity and yet to be insensitive to the passage of a charged particle. In addition, the detector should be made of low mass material to minimize the effect of multiple scatterings. The proposed threshold Cherenkov counters are called Hadron Blind Detectors (HBDs) because they are blind to low energy hadrons which have lower speed {beta} for given momentum p than that of electrons. HBDs can be used in colliders, especially heavy ion hadron colliders (RHIC, LHC), which have huge {number_sign} of hadrons produced per event, to select electrons by being blind to low-momentum hadrons. The authors have studied two different methods to build HBDs described as follows: (1) windowless configuration; (2) thin window configuration. The authors describe herewith their recent experimental results on HBD research obtained with CsI photo-cathodes and HBD prototype beam testing in 1995.