Development of laser decontamination. 4. Test of beam transmission by fibers and the most suitable condition

In this work, the characteristics of laser beam transmission by optical fibers and decontamination speed by the most suitable condition and improvement of the characteristics of secondary products are experimented for apply laser decontamination technique to radioactive wastes treatment and decommissioning of nuclear fuel facilities. The results are as follows. (1) Beam transmission: For Q switch pulse YAG laser, beam transmission by optical fibers were examined. Transmission energy increase in proportion to diameter of fiber. The maximum transmission energy of optical fiber was 61 mJ, which was not damaged. The transmission energy of bundle fiber was more plenty than the energy of single fibers at same numbers. It is able to apply bundle fiber to transmission system of Q switch pulse YAG laser beam. (2) Improvement of decontamination speed: Imitation contaminants were removed perfectly on the condition that, the irradiation frequency was 2 times, move speed of test piece was 3.0 mm/sec, beam diameter was 1.2 mm, repetition speed was 10 Hz. At this time, the number of beam shots were more 4 in the unit area. The case of fluence is constant, the number of beam shots were increased by spread of beam diameter in the unit area. (3) Measurement of secondary products: Particle diameters of more than 50% secondary products by Q switch pulse YAG laser were less than 0. 1 μm. Particle diameters of more than 50% secondary products by normal pulse YAG laser were from 0.1 μm to 1 μm. (author)