Laser cutting technology capable of remote cutting is being developed to reduce radiation exposure to workers and minimize secondary waste generation when dismantling highly polluted nuclear power plant facilities (reactors, pressurizers, steam generators, coolant pumps, etc.). Laser cutting proceeds in air or water, and at this time, secondary products containing radioactive materials are inevitably generated. In air cutting, dust and aerosol are generated, and in underwater cutting, aerosol, water vapor, dispersed particles (colloid, suspension), sediment (dross, sediment), and radioactive waste liquid are generated. Dispersed particles float in the form of fine particles in water, increasing the turbidity of water as cutting progresses, hindering work, and aerosols contain micrometer-sized particles together with water vapor, which can threaten the safety of workers. Particles dispersed in water and aerosol are within 10% of the mass ratio among secondary products, but the volume they occupy is very large, which can have a significant impact on the environment as well as a burden on treatment capacity. Various characterization methods are being developed to diagnose the generation mechanism and physical and chemical properties of laser cutting secondary products in real time and to secure technologies for collecting and removing dispersed particles and aerosols in water. This study introduces a real-time laser cutting secondary product characteristic evaluation method that can identify the key mechanisms of secondary product generation by analyzing the plasma formation process on laser cutting surface and behavior of aerosol, underwater dispersed particles produced by secondary products, as well as physical and chemical properties in real time with various measurement technologies such as Optical Emission Spectrometer (OES), Particle Size Analyzer (PSA), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM) and Inductively Coupled Plasma Time-of-Flight Mass Spectrometry (ICP-TOF-MS).

The use of natural paint for the application to walls and furnishings is now increasing to improve indoor air quality, thereby the natural paint could be a significant source of biogenic volatile organic compounds (BVOCs) in indoor environments. Recent studies have shown that gas-phase reactions between terpenes and ozone can generate sub-micron size particles and toxic volatile organic compounds such as aldehydes and ketones. In this research, we have studied the formation of particles and secondary organic compounds during the reaction of ozone with terpenes emitted from commercial natural paint. The paint applied onto stainless steel was dried and oxidized in a teflon chamber. Two monoterpenes (α- and β-pinenes) were identified by FTIR and GC/MS. Several tests were performed to evaluate the effects of ozone concentration on particle formation. Increased ozone levels significantly affect the increase of particle number concentration (monitored with SMPS), which results in the increase of particle counts ranging from 8,000 to 70,000 particles/㎤. Gas-phase products such as formaldehyde, acetaldehyde, acetone + acrolein, and propionaldehyde were identified during the terpene/ozone reactions by HPLC. These compounds are potential hazardous chemical compounds having harmful health effects to animals and plants. The results obtained from this study provide an insight on the adverse effect of eco-friendly natural product on indoor air quality (IAQ).

산업부산물인 폐유황의 재황용을 목적으로 개질처리된 유황을 대상으로 콘크리트용 혼화재료로써의 물성검토를 위하여 개질처리된 유황을 콘크리트에 외할 첨가하여 개질유황 첨가별 압축강도 및 내구성능을 평가한 결과를 고찰하였다.