Basalt temperature effects

The groundwater transport of radionuclides through waterbearing interbed layers in the Columbia River basalt formation will be controlled by reactions of the radionuclides with groundwater and interbed solids. These interactions must be understood to predict possible migration of radionuclides from a proposed radioactive waste repository in basalt. Precipitation and sorption on interbed solids are the principle reactions that retard radionuclide movement in the interbeds. The objective of the work described herein was to determine the sorption and desorption behavior of radionuclides important to safety assessment of a high-level radioactive waste repository in Columbia River basalt. The effects of groundwater composition, redox potential, radionuclide concentration, and temperature on these reactions were determined. 

Results of the leaching experiments at 25°C are more difficult to interpret. Basalt ground water is not the most effective leaching agent nor is shale the least effective. It appears that at the lower temperature fluoride plays a minor role and other, less obvious, factors predominate. Some of the differences could result from kinetic effects. This is a continuing study with further sampling scheduled at still longer time periods, so it is possible that later results will help clarify the 25°C data. 

Response of Natural Coals to Metamorphism. The Martinsburg slate and its anthraxolite have clearly been subjected to low grade metamorphism. Presuming a low temperature origin such as suggested in the preceding section, at least part of the anthraxolite rank increase must be caused by this metamorphism. In order to evaluate this contribution to rank increase, it is useful to examine known cases of metamorphism of natural coals. MacFarlane (25) studied the thermal effects of intruded olivine basalt sills on Yampa coals (Colorado). He carried out parallel laboratory studies in which unaltered... 

Acoustic insulation on the valve body and at least the first five pipe diameters downstream is an effective method of noise treatment to half the loss given in point 1. Note here, however, that the quality of insulation is very important. Although having no particular preference, the author has had reasonably satisfactory results with Refrasil insulation, a high temperature thermal and acoustic insulation made from basalt, glass fibre and silica which reduced... 

Applications. In the following paragraphs, the conditions (temperature, time, water/rock mass ratio, surface area) and the results on closed system oxygen consumption and redox conditions of the basalt-water experiments are compared to expected conditions in the open system backfill and near-field environment of an NWRB. Crushing of basalt for pneumatically emplaced backfill could result in a substantial fraction of finegrained basalt with a variety of active surface sites for reaction similar to the crushed basalt used in the experiments. The effects of crushing on rates of mineral-fluid reactions are well documented (10,26). 

With the addition of bentonite to a crushed basalt backfill, aqueous diffusion would be the most effective mass transfer process (31). Aagaard and Helgeson (32) state that at temperatures <200°C, aqueous diffusion rates are orders of magnitude greater than rates of silicate hydrolysis even in acid solutions. Therefore, the dissolution rate of backfill phases and the overall mass transfer process could be controlled by reactions at the mineral-fluid interface. As stated earlier, dissolution of basalt phases in the sampling autoclave experiments may also be controlled by interface reactions. 

The shock experiments with synthetic basaltic eucrite at room temperature reveal a similar pressure-dependent sequence of characteristic shock features in pyroxene and plagioclase to those seen in samples recovered from previous experiments (see, e.g., ]9,10]). Also, tliere is no change in the sequence of progressive shock effects at elevated initial temperatures. Amorphization of plagioclase... 

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