In situ determination of rheological properties and void fraction in Hanford Waste Tank 241-SY-101

Abstract

Portions of this AbstractThis report presents the results of the operation of the void fraction instrument (VFI) and ball rheometer in Hanford Tank 241-SY-103. The two instruments were deployed through risers 17C and 22A in July and August 1995 to gather data on the gas content and rheology of the waste. The results indicate that the nonconvective sludge layer contains up to 12% void and an apparent viscosity of 104 to 105 CP with a yield strength less than 210 Pa. The convective layer measured zero void and had no measurable yield strength. Its average viscosity was about 45 cP, and the density was less than 1.5 g/cc. The average void fraction was 0.047 f 0.015 at riser 17C and 0.091 f 0.015 at riser 22A. The stored gas volume based on these void fraction measurements is 2 13 f 42 m3 at 1 atmosphere.... lll SummaryHanford waste Tank 241-SY-103 is filled to about two-thirds capacity, and the current waste level is about 6.9 m. The waste consists of a relatively thin, incomplete crust layer floating on a convective layer about 3.6 m thick with a 3.3-m nonconvective sludge layer on the bottom. This tank has experienced gas release events (GREs) at irregular intervals of roughly three months since its last fill in 1988. Though these events are much smaller than those of its neighbor, Tank 241-SY-101, there is a need to obtain measurements of the void fraction profile and waste rheology in order to estimate the stored gas volume and the amount that could potentially be released.The ball rheometer was deployed July 14 and August 8, 1995, and the void fraction instrument (VFI) on July 19 and August 18, 1995, to supply this information. Each instrument was deployed in risers 17C and 22A, which are located in the southeast and northwest quadrants at 8.5 m and 6.1 m from tank center, respectively. Because riser 17C is not vertical, the ball rheometer cable rubbed on the riser lip, requiring a load cell of relatively low resolution.The rheological properties of the convective layer were uniform and characterized by a low viscosity (about 45 cP), no yield strength (e 2 Pa), zero void fraction, and a density of about 1 . 5 gkc. The nonconvective sludge layer had a yield strength of less then 2 1 0 Pa and an apparent viscosity of 104 to 105 cP. The rheology of the sludge varied widely with depth and was very sensitive to shear history, more so in riser 22A than 17C. The ball rheometer was not able to penetrate a heavier heel layer, about 120 cm thick, on the tank bottom.The data also revealed much different void fractions in the nonconvective layers in each riser. The local void ranged up to 12.5% in the lower portion of the sludge layer. The average void fraction at 17C was 0.047 k 0.015; it was 0.091 4 0.015 at riser 22A. This difference may be attributed to differences in GRE history at the two locations. The waste in the vicinity of 17C may have participated in more of the recent rollover events, while the waste around riser 22A may have remained relatively undisturbed. Assuming approximately equal portions of the tank a...

An Approach to Understanding Cohesive Slurry Settling, Mobilization, and Hydrogen Gas Retention in Pulsed Jet Mixed Vessels

“…The ball-rheometer data are not considered in this summary because the measurements were limited to regions of the sediments with a shear strength less than 900 Pa (the ball would be supported by sediment with a shear strength ≥ 900 Pa;. The ball-rheometer was unable to be deployed to the tank bottom in each of the six listed waste tanks; in AN-103, the ball was supported at greater than half of the sediment depth Stewart et al 1995). Thus, to represent a sediment over its entire depth, the ball rheometer data can be biased low.…”

“…The yield stress of the settled layer, as measured with the ball rheometer in riser 4A (renumbered to riser 006), approximately 10 days after the mixer pump was directed at that location, was about 10 Pa at 24 inches above the tank bottom and 30 Pa at 6 inches (Stewart et al 1995). The ball apparently did not reach the tank bottom, indicating that it was fully supported by the waste, which thus has a shear strength of at least 900 Pa ).…”

In situ rheology and gas volume in Hanford double-shell waste tanks

“…They have performed as designed in all tests and had no significant problems. The initial testing program in SY-101 and SY-103 is documented in Stewart et al (1995), Brewster et al (1995), and Shepard et al (1995).…”

“…The Ball Rheometer System Design Description, WHC-SD-WM-SDD-043, discusses in detail all design information and references all other design documents pertaining to the ball rheometer (also see Stewart et al 1995). The ball rheometer system, shown in Figure 1.1, consists of a71-N (16 Ib), 9.12-cm-diameter tungsten alloy ball tethered to a steel cable that is wound onto a spool or drum: The cable runs through a guide that distributes the line across the width of the spool, so only a single layer of cable is needed on the spool.…”

“…This remote temperature measurement is adequate because the void calculation is very insensitive to errors in waste temperature. A temperature error of 5°C would change the measurement by about 0.25% void (see Stewart et al 1995 for detailed error analysis).…”