Repository degradation

Pearcy, E. C., Prokryl, J. D., Murphy, W. M. Leslie, B. W. 1994. Alteration of uraninite from the Nopal I deposit, Pena Blanca District, Chihuahua, Mexico, compared to degradation of SNF in the proposed U.S. high level nuclear waste repository at Yucca Mountain, Nevada. Applied Geochemistry, 9, 713—732. 

The third major water resource study involved 76 reservoirs located in 11 midwestem states. These studies determined the occurrence and temporal distribution of herbicides and their degradation products in the outflow from selected reservoirs in the upper Midwest they also explored whether the occurrence of herbicides in the reservoir outflow could be related to drainage-basin characteristics, water and land use, herbicide use, and climate. It was found that reservoirs are repositories for herbicides from midwestem streams and that herbicides and their degradation products were detected more frequently throughout the year in reservoirs than in streams. Reservoirs hold runoff from cropland causing herbicide concentrations to decrease downstream, and they dampen the pulse of herbicides that occur during the spring flush. 

Glaus MA, van Loon LR, Chodura A, Fischer K. 1999. Degradation of cellulosic materials under the alkaline conditions of a cementitious repository for low and intermediate level radioactive waste. Part I. Identification of degradation products. Anal. Chim. Acta 398 111-122. 

Particle settling can represent a significant chemical flux, especially where flocculation or low turbulence promotes the settling process. Sometimes the sediment becomes a long-term repository for the chemical alternatively, a chemical may be degraded within the sediments, or eventually be returned to the water by a variety of remobilization processes. 

House dust may adsorb pollutants released from activities and materials from inside the home or contaminants may be tracked in on particles and fibers from outside. Once adsorbed, contaminants do not degrade or degrade more slowly compared with outdoor environments [89]. Thus, house dust is a sink and repository it collects pesticides Uke a passive sampler. 

Fig. 6 Example of useful visualizations of an HTS campaign on 365,000 compounds of the NIH molecular libraries small molecule repository in an example enzyme assay. The Z-factor for this HTS campaign over all the normalized controls was Z 0.82 and the robust Z-factor for the screened compounds was degraded only slightly to Z -0.8, and the signal-to-background of -24.2 and signal-to-noise of -143.3 indicated an excellent assay and HTS campaign. The (a) frequency distribution of the activities, the (b) 2-D scattergram of activities as a function of plate order, and (c) a 3-D view of the plates and wells against their activities, all indicate a robust close to normally distributed screen, with no serious plate-based artifacts...

Loss of repository stability and waste isolation can occur in two ways as a result of sudden disruptive events and as a result of long-term degradation events. Analysis of the probability, characteristics and consequences of sudden disruptive events such as meteorite impacts and major earthquakes is the province of risk analysis. Such analyses produce estimates of the... 

The other method of analysis of repository safety is concerned with degradation processes that can occur and persist over long time periods. One of the most familiar examples of such degradation is corrosion. On a geologic time scale, an ice age might produce events and processes that lead to long-term degradation. 

Prediction of the consequences of degradation release conventionally involves data and models for three steps of analysis geosphere transport, biosphere transport, and biosphere consequences. I will discuss these and add two others analysis, rather than assumption, of repository degradation, and consideration of the geosphere/biosphere interface and its effect on biosphere consequences. These refinements to safety assessment procedures, when developed and implemented, can be expected to aid validation of results. 

Aside from disruptive events such as meteorite impact, repository degradation can result from natural processes such as ice ages or from phenomena such as waste-geology interactions. 

Chemicals that are released, either by design or accident, into the terrestrial environment come in contact with the soil, and the soil can possibly become a repository for the fugitive chemical. If this happens, the chemical could become an integral part of soil and thus move with the soil during erosion episodes, or the chemical could pass through soil profiles and come in contact with ground water. Of course, the possibility exists that the chemical can be degraded into less harmful byproducts. 

LOUTHAN, M.R., Jr., The potential for microbiologically influenced corrosion in the Savannah River spent fuel storage pools , Proc. NATO Workshop on Microbial Degradation Processes in Radioactive Waste Repositories and in Nuclear Fuel Storage Areas, Budapest, 1996, Kluwer, Dordrecht (1997). 

Van Loon, L.R., Glaus, M.A., 1997. Review of the kinetics of aUcahne degradation of cellulose in view of its relevance for safety assessment of radioactive waste repositories. Journal of Environmental Polymer Degradation 5, 97—109. 

---