We have measured the transmittance of 3-kW CO(2) laser light through Ge-coated Ag hollow waveguides. The basic characteristics such as transmissivity, bending loss, and output-beam properties are described. A maximum laser power of 2.6 kW was delivered through a straight hollow waveguide that was 1.7 mm in diameter and 2 m long. Furthermore, 4-m-long waveguides were fabricated by joining two waveguides. Finally, preliminary experiments on welding steel plates were done with the light transmitted through the waveguide. Although the focusing properties of the output beam should be improved for practical laser processing, this type of waveguide is promising for high-power CO(2) laser-light transmission.

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A simple method has been developed for calculating the second order sensitivity coefficient of static and burnup-dependent core performance parameters. The method is applied to a small and a large fast breeder reactors. Changes in core performance parameters due to 10% cross section changes are compared with that predicted by the first and the second order sensitivity analyses. Numerical results reveal that the changes in breeding ratio, reaction rate ratio of the 2s*U capture to the 2ssPu fission rate and burnup reactivity loss due to the 10% change in the 2sgPu fission cross section and/or the 2ssPu v-value show nonlinear behavior, and the second order sensitivity can predict the changes accurately.

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