Petite sismique measurements at the Spent Fuel Test - Climax

Abstract

In May 1984, a petite sismique estimate of the deformation modulus (E) was carried out at the Spent Fuel Test - Climax (SFT-C) at the Nevada Test site. The first part of the experiment was to repeat an earlier suite of measurements that were taken before the spent fuel was emplaced to see if any changes had resulted from heating the rock mass. The results of this measurement indicate a decrease in the modulus. However, these results are suspect in view of the findings in the second part of the experiment, which was designed to minimize the effects due to spurious resonances in the source and geophone locations. These effects were thought to bias the earlier measurements. The measurements indicate that the rock acts as a low-pass filter to the propagating wavefield. Furthermore, it is noted that the blow from a hammer is not a purely impulsive source. Therefore, depending on the type of source used and the distance away from the source, a different peak frequency and, hence, E could be measured for the same rock mass. Unless these effects are somehow factored out of a petite sismique survey, the value of E obtained could be severely biased. 20 figures