![]() Image adapted from Houtz, Allen and Cooper, Doug "The Ratio Control Architecture" The flow controller then adjusts the controlled feed flow rate so that it matches the set point (3). The ratio relay outputs the calculated controlled feed flow rate which is compared to the actually flow rate of the controlled feed stream. Isopleths of the predicted deposition are useful to identify areas of maximum drift transport in the environs of the gaseous diffusion plant.The wild feed flow rate is received by the ratio relay and then multiplied by the desired mix ratio. Preliminary model estimates of drift deposition are compared to depositionmeasurements. Samples from two depths following rainstorms revealed the absence of vertical or horizontal movement with maximum concentrations of 0.13 ppb at 50 meters from the tower. To determine the potential for movement of drift-derived chromium to surface streams, soil-water samplers (wells) were placed along a distance gradient to Little Bayou Creek. Results suggest that differences in retention are related to chemical properties of the drift rather than physical lodging of the particle residue. Leachate from each one inch throughfall simulant removed 3% of the drift mass from litter compared to 7 to 9% from live foliage. A laboratory study simulating throughfall from 1 to 6 inches of rain suggested that there are more exchange sites associated with litter than live foliage. This hypothesis is contrary to basic assumptions in calculating drift emissions. Results indicate that elemental content in drift water (mineral residue) may not be equivalent to the more » content in the recirculating cooling water of the tower. The site of drift contamination, size characteristics, and elemental content of drift particles were determined using a scanning electron microscope with energy dispersive x-ray analysis capabilities. Chromium concentrations in plant materials (fescue grass) decreased with increasing distance from the cooing tower, ranging from 251 +- 19 ppM at 15 meters to 0.52 +- 0.07 ppM at 1500 meters. The transfer and fate of chromium from cooling tower drift to terrestrial ecosystems were quantified at the Department of Energy's uranium enrichment facility at Paducah, Kentucky. Hopefully, the Chalk Point Program will satisfy this need. At the present time, drift deposition measurements, sufficiently comprehensive for model verifications, are unavailable. ![]() Current programs in which drift characteristics at the tower mouth and drift deposition downwind of the tower are being measured are summarized. ![]() The discrepancies are attributed mainly to different assumptions in the models regarding the initial effective height of the droplets. The predicted maximum drift deposition differs by two orders of magnitude, and the downwind locations of the maximum differ by one order of magnitude. Several drift deposition models are compared using a more » set of standard input conditions. One of the major efforts in our program is to evaluate the assumptions, limitations, and applicabilities of various analytical models for drift deposition prediction. The estimation of salt deposition has relied primarily on predictions from a variety of models, with very few direct measurements. Drift from cooling towers can corrode and damage structures in the immediate vicinity of the towers, cause a public nuisance if located near parking lots or high-density traffic areas, and endanger local vegetation. Congress is looking into the conglomeration of nuclear reactors into energy centers of limited area.
0 Comments
Leave a Reply. |