Elemental analysis of as-built concrete and aluminum for the National Ignition Facility and their effect upon residual dose rates

GDMS measurements provide final material compositions, which are compared to expected values. Finally, the calculations are repeated with the measured compositions and the residual dose rates are compared to the expected levels. 3-D neutronics calculations have been performed using the TART98 Monte Carlo transport code. Activation calculations have been completed with the ACAB activation code and the FENDL/A-2.0 activation cross section library. These codes have been benchmarked against experiment as well as against other codes. Activation calculations assume that the annual yield is produced in sixty equally spaced shots of 20 MJ yield each. To account for build-up on long-lived radionuclides, 30 years of operation is assumed. GDMS is a relatively new technique for elemental analysis. It is a rapid, direct method that provides quantitative results. Samples are exposed to an argon plasma (+1 kV). Sputtering occurs and atoms diffuse into a self-sustaining negative glow, where they are ionized. These ions are accelerated to 8 kV and pass into magnetic sectors where they are mass analyzed