A pulsed four‐level solid‐state laser (Nd3+ : yttrium‐aluminum‐garnet) was developed to determine concentration profiles of the fission product cesium in multilayered spherical coated‐particle fuel. In addition, the system can be used for the simulation of cracked coatings by radial borings. The laser system with a Fabry‐Perot‐type resonator fulfills the requirements of small pulse width, absence of higher modes, and consistency of pulse energy. Control and timing is maintained with a ’’Qswitch’’ and a ’’Brewster polarisator’’. Single‐bore holes are ? 10 &mgr;m in diameter, and hole depths range up to 200 &mgr;m. The evaporated radioactive material is sampled with an efficiency ≳ 95% on a glass plate which is used for &ggr; and &bgr; counting. The formation of ’’deep’’ holes is theoretically explained by a self‐channeling mechanism and briefly discussed. Techniques used for radial‐distribution measurements for the fission product137Cs in different irradiated coated particles are presented. Radially bored particles simulating cracked coatings are heat treated and fractional releases are measured.