As temporary storage facilities for spent nuclear fuel (SNF) are becoming saturated, there is a growing interest in finding solutions for treating SNF, which is recognized as an urgent task. Although direct disposal is a common method for handling SNF, it results in the entire fuel assembly being classified as high-level waste, which increases the burden of disposal. Therefore, it is necessary to develop SNF treatment technologies that can minimize the disposal burden while improving long-term storage safety, and this requires continuous efforts from a national policy perspective. In this context, this study focused on reducing the volume of high-level waste from light water reactor fuel by separating uranium, which represents the majority of SNF. We confirmed the chlorination characteristics of uranium (U), rare earth (RE), and strontium (Sr) oxides with ammonium chloride (NH4Cl) in previous study. Therefore, we prepared U-RE-SrOx simulated fuel by pelletizing each elements which was sintered at high temperature. The sintered fuel was again powdered by heating under air environment. The powdered fuel was reacted with NH4Cl to selectively chlorinate the RE and Sr elements for the separation. We will share and discuss the detailed results of our study.

Interests in molten salt reactor (MSR) using a fast spectrum (FS) have been increased not only for having a high power density but for burning the high-level waste generated from nuclear power plants. For developing the FS-MSR technologies, chloride-based fuels are considered due to the advantage of higher solubility of actinides and lanthanides over fluoride-based salts. Despite significant progress in development of MSR technology, the manufacturing technology for production of the fuel is still insufficiently understood. One of the option to prepare the MSR fuel is to use products from pyroprocessing where oxide form of spent nuclear fuel is reduced into metal form and useful elements can be collected via electrochemical methods in molten salt system at high temperature. In order to chlorinate the products into chloride form, previous study used NH4Cl to chlorinate U metal into UCl3 in an airtight reactor. It was found that the U metal was completely chlorinated into chloride forms; however, impurities generated by the reaction of NH4Cl and reactor wall were found in the product. Therefore, in this work, the air tight reactor was re-deigned to avoid the reaction of reactor wall by insertion of Al2O3 crucible inside of the reactor. In addition, the reactor size was increased to produce UCl3 over 100 g. Using the newly designed reactor, U metal chlorination experiments using NH4Cl chlorinating agent were performed to confirm the optimal experimental conditions. The detailed results will be further discussed.

Thermodynamically, TRUOx, REOx, and SrOx can be chlorinated using ammonium chloride (NH4Cl) as a chlorinating agent, whereas uranium oxides (U3O8 and UO2) remain in the oxide form. In the preliminary experiments of this study, U3O8 and CeO2 are reacted separately with NH4Cl at 623 K in a sealed reactor. CeO2 is highly reactive with NH4Cl and becomes chlorinated into CeCl3. The chlorination yield ranges from 96% to 100%. By contrast, U3O8 remains as UO2 even after chlorination. We produced U/REOx- and U/SrOx-simulated fuels to understand the chlorination characteristics of the oxide compounds. Each simulated fuel is chlorinated with NH4Cl, and the products are dissolved in LiCl-KCl salt to separate the oxide compounds from the chloride salt. The oxide compounds precipitate at the bottom. The precipitate and salt phases are sampled and analyzed via X-ray diffraction, scanning electron microscope-energy dispersive spectroscopy, and inductively coupled plasma-optical emission spectroscopy. The analysis results indicate that REOx and SrOx can be easily chlorinated from the simulated fuels; however, only a few of U oxide phases is chlorinated, particularly from the U/SrOx-simulated fuels.

Boron nitride nanotubes (BNNTs) are receiving great attention because of their unusual material properties, such as high thermal conductivity, mechanical strength, and electrical resistance. However, high-throughput and highefficiency synthesis of BNNTs has been hindered due to the high boiling point of boron (~ 4000℃) and weak interaction between boron and nitrogen. Although, hydrogen-catalyzed plasma synthesis has shown potential for scalable synthesis of BNNTs, the direct use of H2 gas as a precursor material is not strongly recommended, as it is extremely flammable. In the present study, BNNTs have been synthesized using radio-frequency inductively coupled thermal plasma (RF-ITP) catalyzed by solid-state ammonium chloride (NH4Cl), a safe catalyst materials for BNNT synthesis. Similar to BNNTs synthesized from h-BN (hexagonal boron nitride) + H2, successful fabrication of BNNTs synthesized from h-BN+NH4Cl is confirmed by their sheet-like properties, FE-SEM images, and XRD analysis. In addition, improved dispersion properties in aqueous solution are found in BNNTs synthesized from h-BN +NH4Cl.

지하수나 폐수 등에 포함된 독성을 가진 음이온류나 양이온류 등의 유독물질을 경제적으로 처리하는데 탁월한 분리기능을 가진 것으로 알려진 전기투석공정에 사용하기 위해 음이온 교환 복합막을 제조하여 그 전기화학적인 특성을 조사하였다. 다양한 조성의 vinylbenzylchloride (VBC)와 divinylbenzene (DVB) 그리고 α,α-azobis(isobutyronitrile) (AIBN)으로 이루어진 단량체 용액에 다공성 지지체인 poly(ethylene) (PE)을 함침한 후 열중합 가교시켜 poly(VBC-DVB)/PE 복합막을 생성한 다음 trimethylamine(TMA)과 acetone을 이용해 음이온 교환기(-N + (CH3)3)를 함유하는 복합막을 제조하였다. 음이온 교환막 제조시 VBC/DVB의 비율과 TMA/Acetone의 비율에 따른 막의 함수율, 이온교환용량(IEC) 및 전기저항을 조사하였다. 그 결과 제조된 막들은 사용된 PE지지체의 얇은 막두께에 기인하여 아스톰사의 상용화 음이온 교환막(AMX)보다 높은 IEC와 낮은 전기저항 및 낮은 함수율 등을 나타내는 것을 확인할 수 있었다. 본 실험에서 제조된 복합막은 저렴한 제조비용과 우수한 전기화학적 특성으로 정수 및 폐수처리를 위한 전기투석공정에 충분히 적용될 수 있음을 알 수 있었다.

꼬막, 참굴, 바윗굴 및 가리비 등 폐기되는 몇 종의 패각류를 이용하여 칼슘 보강용 식품 첨가제의 원료로써 사용 할 수 있는 고순도의 탄산칼슘을 제조하고자 하였다. 꼬막 패각을 900℃에서 5시간 회화한 회화분의 칼슘 함량이 64.9%로 가장 높게 나타났으며, 가리비 62.5%, 참굴 62.4%, 바윗굴 61.5% 순이었다. 백색도는 가리비 패각 회화분의 경우 81.6-85.8로서 패각류 중 가장 높았다. 꼬막 패각 회화분(Ca 39.92%)에 ammonium chloride process(ACP)와 ammonium nitrate process(ANP)법을 적용하여 제조한 CaCO₃의 Ca 함량은 40.03-40.04%로 높아졌고, ANP법에 의해 제조한 pH조정 시료의 경우가 40.04%로서 가장 높았으며, 이 방법들에 의해 불순물이 거의 대부분 제거되는 것으로 나타났다. ACP법과 ANP법에 의해 제조한 CaCO₃의 백색도는 101.0-101.5로 매우 우수하였으며, 칼슘보강용 식품첨가제로서 사용될 가능성이 충분하다고 판단된다.

New functional surfactant, N,N-dimethyl-N-dodecyl-N-(2-methyl benzimidazoyl) ammonium chloride(DDBAC) having benzimidazole(BI) functional group have been synthesized and the critical micellar concentration of DDBAC measured by surface tentiometry and electric conductivity method was 8.9×10-4M. Micellar effects in DDBAC functional surfactant solution on the hydrolysis of p-nitrophenylacetate(p-NPA), p-nitrophenylpropionate(p-NPP) and p-nitrophenylvalerate(p-NPV) were observed with change of various pH (Tris-buffer). The pseudo first rate constants of hydrolysis of p-NPA, p-NPP and p-NPV in optimum concentration of DDBAC solution increase to about 160, 280 and 600 times, respectively, as compared with those of aqueous solution at pH 8.00(Tris-buffer). It is considered that benzimidazole functional moiety accelerates the reaction rates of hydrolysis because they act as nucleophile or general base. In optimum concentration of DDBAC solution, the rate constants of hydrolysis of p-NPP and p-NPV increase to about 1.5 and 3.0 times, respectively, as compared with that of p-NPA. It means that the more the carbon numbers of alkyl group of substrates, the larger the binding constants between DDBAC micelle and substrates are. To know the hydrolysis mechanism of p-NPCE(p-NPA, p-NPP and p-NPV), the deuterium kinetic isotope effects were measured in D2O solutions. Consequently the pseudo first order rate constant ratios in H2O and D2O solution, kH2O/kD2O, were about 2.8～3.0 range. It means that the mechanism of hydrolysis were proceeded by nucleophile and general base attack in approximately same value.