Generation of particles and fragments by quasicontinuous wave fiber laser irradiation of stainless steel, alumina, and concrete materials

Hiroyuki Daido,Tomonori Yamada,Shuichi Hasegawa,Hiroyuki Furukawa,Masabumi Miyabe,Chikara Ito,Takuya Shibata

doi:10.2351/7.0000190

Abstract

An experimental characterization is presented on fine particles, droplets, and fragments produced at the interaction region between a 2.7 kW quasicontinuous wave (repetitive pulsed operation with a 10 ms pulse duration) fiber laser and stainless steel, alumina, and heavy concrete samples. In the samples, the recoil pressure induced by vaporization pushes particles and fragments into the ambient atmosphere. In order to preserve a safe working environment, in particular for nuclear decommissioning, special care should be taken to confine and retrieve such particles during laser processing. In the experiments, particle production from the vapor and the molten phase layer in the targeted material was observed with a high-speed camera, with fine particles collected and analyzed using an electron microscope. The observed results were qualitatively interpreted with the help of a simplified one-dimensional hydrodynamic code coupled with a stress computation code. Characterization and classification of the results are expected to provide a useful database that will contribute to the decommissioning of nuclear facilities and other industrial applications.

Highlights

Laser processing techniques such as welding, cutting, cladding, and so forth have been utilized in a variety of industrial fields such as the automotive and heavy industries.[1,2] Decommissioning of nuclear facilities is one attractive application for these techniques.[3,4,5,6] They can be applied to almost any material regardless of their mechanical properties
An experimental characterization is presented on fine particles, droplets, and fragments produced at the interaction region between a 2.7 kW quasicontinuous wave fiber laser and stainless steel, alumina, and heavy concrete samples
An experimental characterization of the fine particles, droplets, and fragments produced at the interaction regions with a highpower laser was presented

Summary

Introduction

Laser processing techniques such as welding, cutting, cladding, and so forth have been utilized in a variety of industrial fields such as the automotive and heavy industries.[1,2] Decommissioning of nuclear facilities is one attractive application for these techniques.[3,4,5,6] They can be applied to almost any material regardless of their mechanical properties. The development of high-power disk and fiber lasers, coupled with improvement in beam delivery, thermal management of the system, and multiple channel output, has further enhanced decommissioning capability by providing scalable power in the multikilowatt regime with higher beam quality, emphasizing their usefulness in such applications. 99% of the radioactivity in decommissioning is associated with the fuel and the reactor vessel, which is removed following permanent shutdown and requires special attention, significantly large infrastructure remains. Deconstruction of these medium- to low-level-contaminated structures requires considerable time and funding, detailed planning, and precise execution. It requires a similar degree of expertise and regulatory control

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Conclusion