To analyze the radioactivity of 3H and 14C in miscellaneous radioactive wastes generated from nuclear power plants, a wet digestion method using sulfuric acid is currently used. However, sulfuric acid is classified as a special management material, and there is no disposal method for contaminated radioactive waste. Therefore, research on a thermal decomposition method that can analyze the DAW radioactive waste samples without using sulfuric acid is necessary. In this study, we will cover the final sample amount, sample injection method, and prevention of organic ignition to meet the minimum detection limit requirements of the analysis equipment. Through this research, optimal conditions for the thermal decomposition method for analyzing the radioactivity of 3H and 14C in DAW radioactive wastes generated from nuclear power plants can be derived.

Boric acid-containing B-10 is used in a nuclear reactor as a coolant and absorbs thermal neutrons generated during nuclear fission in the primary circuit. Boron-containing coolant water waste is generated from maintenance, floor drain, decontamination, and reactor letdown flows. There are two options for aqueous solution waste of boric acid. One is recycling and discharge through filtration, ion exchange, and reverse osmosis. The other is immobilization after evaporation and crystallization processes. The dry powder of boric acid waste liquid can be immobilized by cement, polymer, etc. Before the mid-1990s, concentrated boric acid waste was solidified with a cement matrix. To overcome the disadvantage of low waste loading of cement waste form, a method of solidifying with paraffin was adopted. However, paraffin solids were insufficient to be disposed of as final waste. Paraffin is a kind of soft solidified material and has low compressive strength and poor leaching resistance. As a result, it was decided as an unsuitable form for disposal. In KOREA, paraffin waste form was adopted for boric acid waste treatment in the 1990s. A large amount of paraffin waste forms about 20,000 drums (200 l drum) were generated to treat boric acid waste and were stored in nuclear power sites without disposal. In this study, we want to obtain high-purity boric acid waste by oxidizing and decomposing solid paraffin waste form through a boric acid catalytic reaction. In this reaction, paraffin is separated in the form of various by-products, which can then be treated through a liquid waste treatment device or an exhaust gas treatment device. The proper temperature for sample decomposition during the catalytic reaction was set through TGA analysis. Compositions of by-products and residues generated at each stage of the reaction could be analyzed to determine the state during the reaction. Finally, the boric acid waste powder was perfectly separated from paraffin waste form with disposable products through this pyrolysis process.

Lotus-type porous nickel with cylindrical pores was fabricated by unidirectional solidification under an Ar gas atmosphere using the thermal decomposition method of the compounds such as sodium hydroxide, calcium hydroxide, calcium carbonate, and titanium hydride. The decomposed gas does form the pores in liquid nickel, and then, the pores become the cylindrical pores during unidirectional solidification. The decomposed particles from the compounds do play a rule on nucleation sites of the pores. The behavior of pore growth was controlled by atmosphere pressure, which can be explained by Boyle's law. The porosity and pore size decreased with increasing Ar gas pressure when the pores contain hydrogen gas decomposed from calcium and sodium hydroxide and titanium hydride, ; however it they did not change when the pores contain containing carbon dioxide decomposed from calcium carbonate. These results indicate that nickel does not have the solubility of carbon dioxide. Lotus-type porous metals can be easily fabricated by the thermal decomposition method, which is superior to the conventional fabrication method used to pressurized gas atmospheres.

YIG 전구체 분말은 요소의 열분해반응을 이용한 균일침전법에 의해서 질산염으로부터 제조하였다. 침전은 철이온이 먼저 침전한 후 이트륨이온이 침전하는 과정으로 이루어졌다. YGI전구체 분말은 철산화물과 비정질로 구성되어 있으며 그 분말의 대략적인 화학식은 2.5Fe2O3.Y3(OH)9-2x(CO3)x.nH2O로 되어있다. YIG 전구체 분말의 열분해과정은 dehydration, 철산화물의 recrystallization, yttrium carbonate 및 yttrium oxide의 형성과 고상반응등 여러단계로 구성되어 있다. 열처리온도가 증가함에 따라 Y2O3와 Fe2O3의 고상반응에 의해 YFeO3 intermediate을 경유해서 YIG상이 형성됨을 확인하였다. 단일상의 YIG는 1200˚C에서 6시간 공기중에서 소성함에 의해서 얻을 수 있었다.

The Stockholm Convention, which was adopted in Sweden in 2001 to protect human health and the environment, includes regulations for Persistent Organic Pollutant Rotors such as toxic and bioaccumulatives. Currently, there are 28 types of materials. This prohibits and limits the production, use, and manufacture of products. Korea is a member of the Convention, and it is necessary to prepare management and treatment plans to address the POP trends. Thus, we experimentally investigate whether the environmentally stable incineration is achieved when the sample is thermally treated using the Lab-scale (1 kg/hr). The target samples is pesticides in liquid phase and solid phase. In this study, organic chlorinated pesticides and their thermal characteristics were analyzed. We calculated the theoretical air volume based on the element analysis results. Because the interior of the reactor is small, more than 10 times of the air ratio was injected. The retention time was set to at least 4 seconds using a margin. The incineration temperature was 850℃ and 1100℃. Thus, we experimentally investigated whether the environmentally stable incineration was achieved when the sample was thermally treated using the Lab-scale (1 kg/hr). We analyzed five types of exhaust gas; the 02 concentration was high, but the CO amount decreased. Complete combustion is difficult because of the small size of the furnace due to the nature of Lab-scale. The organic chlorine-containing pesticide had an average decomposition rate of 99.9935%. Considering the decomposition rates of organic chlorine-containing pesticide in this study, the incineration treatment at over 2 ton/hour, which is typical for a conventional incinerator, is possible. Considering the occurrence of dioxins and unintentional persistent organic pollutants, it can operate at more than 1,100℃.