Horizontal cable trays fire in a well‐confined and mechanically ventilated enclosure using a two‐zone model

International audienceElectrical cable trays are used in large quantities in nuclear power plants (NPPs) and are one of the main potential sources of fire. A malfunction of electrical equipment due to thermal stress for instance may lead to the loss of important safety functions of the NPPs. The investigation of such fires in a confined and mechanically ventilated enclosure has been scarce up to now and has been investigated in the nuclear industry. In the scope of the OECD PRISME-2 project, the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) conducted more than a dozen of fire tests involving horizontal electrical cable trays burning either in open atmosphere under a calorimetric hood or inside mechanically ventilated compartments to investigate this topic. Calorimetric hood experiments in open atmosphere highlighted that the halogenated flame retardant cable tests had shorter ignition time, faster fire growth rate and higher peak of Heat Release Rate (HRR), compared with the mineral flame retardant cables tested. The influence of the enclosure on the fire behavior depends on the temperature of the surrounding gas of the cables, as well as on the oxygen content at the level of cables. The enclosure strongly impacts the pyrolysis of the fuel, decreasing the mass loss rate and the HRR of the fuel, affecting the fire duration. For tests performed at low ventilation level, combustion of unburned gases occurred due to a high production of pyrolysed gas in excess. A semi-empirical model of horizontal cable trays fires in a well-confined enclosure was developed. This model is partly based on the approach used in FLASH-CAT and on experimental findings from the IRSN cables fire tests. It was implemented in the two-zone model SYLVIA. The major features of the compartment fire experiments, such as characteristic HRR and fire duration, could then be reproduced with acceptable error, except for combustion of unburned gases, occurring in the upper part of the fire compartment. The development of such a semi-empirical model is a common practice in fire safety engineering concerned with complex solid fuels

Nonlinear Optics

This chapter provides a brief introduction into the basic nonlinear-optical phenomena and discusses some of the most significant recent advances and breakthroughs in nonlinear optics, as well as novel applications of nonlinear-optical processes and devices. Nonlinear optics is the area of optics that studies the interaction of light with matter in the regime where the response of the material system to the applied electromagnetic field is nonlinear in the amplitude of this field. At low light intensities, typical of non-laser sources, the properties of materials remain independent of the intensity of illumination. The superposition principle holds true in this regime, and light waves can pass through materials or be reflected from boundaries and interfaces without interacting with each other. Laser sources, on the other hand, can provide sufficiently high light intensities to modify the optical properties of materials. Light waves can then interact with each other, exchanging momentum and energy, and the superposition principle is no longer valid. This interaction of light waves can result in the generation of optical fields at new frequencies, including optical harmonics of incident radiation or sum- or difference-frequency signals