Granitic bedrock

The effects of acid rain are particularly severe in areas where the bedrock is granite or other materials incapable of neutralizing H+ ions. As the concentration of acid builds up in a lake, aquatic life, from algae to brook trout, dies. The end product is a crystal-clear, totally sterile lake. 

Except for large scale accidental releases (e.g. nuclear explosions or catastrophic accidents at nuclear plants), water will be the main transport medium of plutonium to man. Therefore the size and location of plutonium sources, its pathways to man and its behaviour in natural waters are essential knowledge required for the evaluation of its ecological impact. That information, combined with radiological health standards, allows an assessment of the overall risk to the public from plutonium e.g. from a waste repository for spent unreprocessed reactor fuel elements in deep granite bedrock (8, 9). ... 

Table II summarizes analytical data for dissolved inorganic matter in a number of natural water sources (J3, 9, J 9, 20, 21). Because of the interaction of rainwater with soil and surface minerals, waters in lakes, rivers and shallow wells (<50m) are quite different and vary considerably from one location to another. Nevertheless, the table gives a useful picture of how the composition of natural water changes in the sequence rain ->- surface water deep bedrock water in a granitic environment. Changes with depth may be considerable as illustrated by the Stripa mine studies (22) and other recent surveys (23). Typical changes are an increase in pH and decrease in total carbonate (coupled), a decrease in 02 and Eh (coupled), and an increase in dissolved inorganic constituents. The total salt concentration can vary by a factor of 10-100 with depth in the same borehole as a consequence of the presence of strata with relict sea water. Pockets with such water seem to be common in Scandinavian granite at >100 m depth.

In 1976 the Swedish government stipulated that no new nuclear reactors should be charged until it had been shown how the radioactive waste products could be taken care of in an "absolutely safe manner" (8). Consequently, the nuclear power industry (through their joint Nuclear Fuel Supply Co, SKBF) embarked on a program referred to as the Nuclear Fuel Safety (KBS) Project (8). In one of the schemes (9) a repository for spent nuclear fuel elements in envisaged at a depth of 500 m in granitic bedrock. The repository will ultimately contain 6000 tonnes of uranium and 45 tonnes of plutonium. The spent fuel elements will be stored in copper cylinders (0.8 m in diameter and 4.7 m in length) with a wall thickness of 200 mm the void will be filled with lead. 

A general conclusion from the review of the distribution of plutonium between different compartments of the ecosystem was that the enrichment of plutonium from water to food was fairly well compensated for by man s metabolic discrimination against plutonium. Therefore, under the conditions described above, it may be concluded that plutonium from a nuclear waste repository in deep granite bedrock is not likely to reach man in concentrations exceeding permissible levels. However, considering the uncertainties in the input equilibrium constants, the site-specific Kd-values and the very approximate transport equation, the effects of the decay products, etc. — as well as the crude assumptions in the above example — extensive research efforts are needed before the safety of a nuclear waste repository can be scientifically proven. 

Rydberg, J. "Groundwater Chemistry of a Nuclear Waste Repository in Granite Bedrock" UCRL-53155 Lawrence Livermore Lab. Livermore, 1981. 

Reg soils are closely associated with desertic regions. They have developed on stable surfaces where coarse, gravelly desert alluvium is exposed, and are characterized by a well-developed desert pavement and exhibit some well-defined soil horizons. They occur mostly on depositional surfaces where stones and gravels have been deposited since Neogene times. The surfaces commonly consist of stony, unconsolidated sedimentary deposits in which limestone, dolomite, chalk, flint and marl predominate, together with some fines (silt and clay). Sandstone and granite debris have also been reported to contribute to Reg formation. Less frequently, they form on sedimentary bedrock (Fig. 1.5). 

Age column is given in years, rock column is portion of rock used in a foundation, fireplace or wall in square feet, height of ceiling in ieet. Area is in square feet. Blanks in furnace column indicate no use of furnace, tightness A is average, T is tight, D is drafty, as stated by the homeowner, soil column shows soil from granite bedrock in a foundation, fireplace or wall. Water column is radon concentration in pCi/1. 

Comparison of water composition of four lakes influenced by different bedrocks in their catchments. Drainage areas of Lake Zota and Lake Cristallina contain only gneiss and granitic gneiss that of Lake Piccolo Naret contains small amounts of calcareous schist that of Lake Val Sabbia exhibits a higher proportion of schist. 

For both alternatives a storage in granitic bedrock at a depth of 500 m is considered. This is well below the groundwater table. The waste canisters will be placed in vertical holes in horizontal tunnels and both holes and tunnels will be filled with a backfill material (c.f. Figure 1). 

In this paper some of the chemical aspects of such a waste storage in granitic bedrock are discussed 2-T). 

Groundwater composition in granitic bedrock at great depth and the artificial standard waters used... 

Rennerfelt, J., "Composition of Groundwater at Great Depth in Granitic Bedrock", KBS TR 36, 1977... 

Allard, B., Kipatsi, H. and Torstenfelt, B., "Technetium Reduction and Sorption in Granitic Bedrock", subm. to Radiochem. Radioanal. Lett. 

Some experimental drilling programs underway in Sweden, including a well some 5000 meters in granite bedrock, may shed further light on Gold s hypothesis. 

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