The stabilization techniques are highly required for damaged nuclear fuel to strengthen safety in terms of transportation, storage, and disposal. This technique includes recovering fuel materials from spent fuel, fabrication of stabilized pellets, and fabrication of fuel rods. Thus, it is important to identify the leaching behavior of the stabilized pellets to verify their stability in humid environments which are similar to storage conditions. In this study, we introduce various leaching experiment methods to evaluate the leaching behavior of the stabilized pellets, and determine the most suitable leaching test methods for the pellets. Also, we establish the leaching test conditions with various factors that can affect the dissolution and leaching behavior of the stabilized pellets. Accordingly, we prepare the simulated high- (55 GWd/tU) and low- (35 GWd/tU) burnup nuclear fuel (SIMFUEL) and pure UO2 pellets sintered at 1,550°C and 1,700°C, respectively. Each pellet is placed in a vessel and filled with DI water and perform the leaching test at three different temperature to verify the leaching mechanism at different temperature range. Based on the standard leaching test method (ASTM C1308-21), the test solution is removed from the pellet after specific time intervals and replaced in the fresh water, and the vessel is placed back into the controlled-temperature ovens. The test solutions are analyzed by using ICP-MS.

Thermoelectric materials and devices are energy-harvesting devices that can effectively recycle waste heat into electricity. Thermoelectric power generation is widely used in factories, engines, and even in human bodies as they continuously generate heat. However, thermoelectric elements exhibit poor performance and low energy efficiency; research is being conducted to find new materials or improve the thermoelectric performance of existing materials, that is, by ensuring a high figure-of-merit (zT) value. For increasing zT, higher σ (electrical conductivity) and S (Seebeck coefficient) and a lower к (thermal conductivity) are required. Here, interface engineering by atomic layer deposition (ALD) is used to increase zT of n-type BiTeSe (BTS) thermoelectric powders. ALD of the BTS powders is performed in a rotary-type ALD reactor, and 40 to 100 ALD cycles of ZnO thin films are conducted at 100oC. The physical and chemical properties and thermoelectric performance of the ALD-coated BTS powders and pellets are characterized. It is revealed that electrical conductivity and thermal conductivity are decoupled, and thus, zT of ALD-coated BTS pellets is increased by more than 60% compared to that of the uncoated BTS pellets. This result can be utilized in a novel method for improving the thermoelectric efficiency in materials processing.

Irradiated uranium dioxide in damaged used fuel could oxidize during transportation, interim storage or disposal, resulting that the fuel pellet fragments are reduced to a grain-sized powder that can easily escaped from the damaged rod. It has been reported that oxidized spent fuel (i.e. U4O9+x) that was in contact with water could increase the dissolution rate by making the grain boundaries more accessible to the water. Therefore, the damaged used fuel requires stabilization technology including nuclear material recovery, pellet manufacturing process, and stabilization fuel rod manufacturing that can secure safety in terms of permanent disposal. In this study, we prepared pure UO2 and SIMFUEL pellets that are a mixture of UO2 and surrogated metallic oxides for fission products equivalent to a burn-up of 35 GWd/tU and 55 GWd/tU as the stabilized spent fuel. The UO2 and fission products powders were milled and pressed into pellets at 250 MPa and sintered at 1,550°C and 1,700°C for 6 hours in an atmosphere of 4%H2-Ar. The prepared UO2 and SIMFUEL pellets were placed in PTFE Teflon vessels and filled with deionized water to identify the leaching behavior by a long-term leaching experiment under the similar condition to a repository for the safe disposal.

최근 탄소 중립 정책에 따른 신재생에너지 활용을 위한 노력이 가속화되고 있다. 이를 위하여 본 연구에서는 바이오매스 작물 중 하나인 케나프 (Hibiscus cannabinus L.)를 연료화하기 위하여, 미이용 목재 자원과 폐목재 자원을 혼합하여 고형연료인 펠릿을 제조하고 품질을 분석하였다. 품질을 평가하기 위해 목재 펠릿, 비목재 펠릿과 Bio-SRF의 품질기준을 통해 성형한 펠릿의 품질을 파악하였다. 케나프 펠릿의 경우 겉보기밀도, 발열량 등에서는 목재 펠릿 품질기준을 만족하였으나 회분의 함량이 기준을 초과하였다. 이를 보완하기 위해 목재 자원인 폐목재를 혼합하여 제조한 펠릿의 특성을 조사한 결과, 질소 및 겉보기밀도, 회분, 발열량 등에서 오히려 품질을 저하시키는 경향을 보이는 것으로 나타났다. 한편, 미이용 목재를 혼합하여 성형된 펠릿의 품질을 조사한 결과, 겉보기밀도, 함수율, 질소, 황, 발열량의 조건에서 대부분 목재 펠릿의 품질기준을 만족하였다. 다만 회분함량의 경우 비목재 펠릿 및 Bio-SRF의 15% 이하 기준을 만족하고 있지만, 목재 펠릿의 최저 기준인 B등급 2.0% 이하 기준의 경우 만족하는 경우와 만족하지 못하는 경우가 발생하였다. 함수율 15%(w.b.)에서 케나프와 미이용 목재의 혼합비가 2:8인 경우와 함수율 20%(w.b.)에서 케나프와 미이용 목재의 혼합비가 6:4 및 2:8인 경우에 기준을 만족하였고, 그 이외에는 기준을 만족하지 못하였다. 특히, 케나프만을 사용하거나 폐목을 섞은 경우는 모두 기준을 만족하지 못하므로, 목재 펠릿의 기준을 만족하는 연료 이용을 위해서는 케나프와 미이용 목재 자원을 혼합 활용하는 것이 바람직할 것으로 판단된다.

Dry head end process is developing for pyro-processing at KAERI (Korea Atomic Energy Research Institute). Dry processes, which include disassembly, mechanical decladding, vol-oxidation, blending, compaction, and sintering shall be performed in advance as the head-end process of pyroprocessing. An important goal of the head-end process is the fabrication of a proper feed material for the subsequent electrolytic reduction process. In the vol-oxidation process, the pellet type-SFs are pulverized by an oxidation under an air-blowing condition, and some volatile fission products are removed from the produced powders by using an air flow. After blending, the U3O8 powders are moved to a compactor of compaction process to obtain U3O8 porous pellets. In the fine powders removal system connected with compactor, for the improved performance of oxide reduction process coupled to dry head-end process, the removal/recovery system for fine powders potentially attached to the surface of oxide reduction raw material was developed and applied to the removal of fine powders from green pellets fabricated in dry head-end process. The removal efficiency of fine powders was also verified using porous U3O8 pellets in the fine powders removal system.

Feasibility is investigated for reduction of chromium ore by Si sludge with mixed silicothermic and carbothermic reaction. The reduction behavior of chromium ore using Si sludge is investigated precisely to determine the effects of carbon addition, reaction time, and reaction temperature. The pellets are dropped into the furnace after temperature stabilized. As the amount of C addition increases, the amounts of CO and CO2 gas generation increase. After the dropping of the pellets, the pellets are heated and the reaction starts at about 1,573 K or higher. The pellets maintain their shape until 10 min after the drop, and then melted. As the holding time increased, the size of the reduced metal particles increased. The chromium ore is rapidly reduced by the Si sludge, and the slag penetrated into the chromium ore and reduction progressed inside. As the reduction temperature increased, the reaction initiation time is shortened and the reaction fraction of the reduction reaction increased. As the reaction temperature increased, agglomeration of reduced ferrochrome metal is promoted.

The aim of this research is to evaluate the impact of various process conditions on the physical properties and digestibility of extruded fish feed at different barrel temperatures (120, 130, and 140oC) and moisture contents (35, 40, and 45%). The expansion ratio decreased with increasing the moisture content. The hardness was negatively correlated with the expansion ratio. The bulk density decreased by increasing moisture content. The water holding capacity increased by increasing the moisture content and barrel temperature. Soaking time significantly (p<0.05) affected water stability and the best water stability was observed in all samples soaked for 1 h, but water stability was also stable at 2 h and 3 h. There was a significant increase in the protein digestibility of extruded fish feed, compared to that of the raw material.

본 연구에서는 수입되는 바이오매스를 대체하고 증가하는 국내 RPS의무비율을 보다 효과적으로 대응하기 위해 우드펠릿으로 사용가능한 국내 산림바이오매스 부존자원을 파악하기 위하여 선행연구 방법과 매년 추가로 성장하는 임목생장률을 기준으로 미이용 산림바이오매스의 양을 산정하였다. 그 결과, 임목가공 중 발생하는 부산물 중 20%를 우드펠릿 원료로 사용한다고 가정했을 경우 두 가지 추정 방법으로 도출된 평균값을 기준으로 우드펠릿 생산 가능량을 예측 하였다. 그 결과 미이용 부산물은 2016년 199만 톤, 2020년 228만 톤, 2030년 308만 톤이 발생되고 원목가공 과정에서 발생되는 임목부 산물(피죽, 톱밥 등) 중 20%가 우드펠릿 원료로 활용될 경우 2016년 258만 톤/년, 2020년 295만 톤/ 년 2030년 398만 톤/년의 원재료가 추가되어 미이용 부산물과 원목가공 과정 중 발생되는 부산물로 생산 가능한 우드펠릿 양은 2016년에 274만 톤/년, 2020년 314만 톤/년 2030년 423만 톤/년의 우드펠릿이 생산 가능하다는 결과를 도출 하였다.

Wood pellets are used by Biomass-solid refuse fuel (Bio-SRF) has been imported from many East-Asia countries especially,Vietnam in Korea. Wood pellets are made through grind and high-pressure process shows different physical characterizationlike high methyl bromide (MB) absorption unlike other wood materials. Furthermore, detected pests in wood pellets havesimilarity with detected pests in stored grain. In this study, we analyzed susceptibility on pupa and adult stages of redflour beetle, Tribolium castaneum in wood pellets against mixture of MB and phosphine (PH3). Mixture treatment ofMB and PH3 was more effective than single MB treatment compare with control. Pupal stage showed more tolerant thanadult stage on each fumigant and 100% mortality was determined at 27 mg/L of MB only at 20°C. However, PH3 increasedMB toxicity on pupae that 100% mortality was observed at 100:1 ratio of MB (5 mg/L) and PH3 (0.05 mg/L) at 20°C.Based on this study, mixture treatment of different type of fumigant will be applied to control of quarantine pests.

The number of pest detection in wooden pellets has increased since wooden pellets as biomass-solid refuse fuel (Bio-SRF) was allowed an import in Korea. In this study, we analyzed an insecticidal effect on pupal and adult stages of red flour beetle (Tribolium castaneum) and maize weevil (Sitophilus zeamais) in wooden pellets using two fumigants, methyl bromide (MB) and phosphine (PH3), for establishing a guideline on fumigation. MB and PH3 both showed a dose-dependent manner in insect mortality after fumigation under 60% filing rate (FR) of wooded pellets in desiccator. In MB fumigation to T. castaneum, adults and pupae showed 100% mortality at 128 mg/L and 161 mg/L in 10°C at 24 h post treatment and pupae showed 100, 74, and 8% mortality against 99 mg/L of MB in 20, 40, and 40% FR, respectively. In PH3 fumigation, S. zeamais adults showed 92% mortality to 4 mg/L, meanwhile T. castaneum adults showed 100% mortality at 120 h post treatment.

본 연구의 목적은 활성탄의 CO2 흡착능을 향상시키기 위하여 화학적 전처리 방법을 개발하는 것이다. 다양한 방법과 이론이 존재하지만 이번 연구에서는 아미노화와 분해를 비교하여 흡착능을 비교하기로 하였다. 본 연구에서는 4가지 유형의 활성탄 입자를 원료 물질과 크기에 따라 준비하였고, 수산화칼륨으로 전처리하여 열처리 및 아민화과정을 거 친 후, CO2 흡착능을 비교 평가하였다. 실험결과, 단순 열처리과정만 적용할 때는 600℃ 가 가장 우수하였고, 800℃에서 아민화시킨 시료가 1.4 mmol/g의 가장 좋은 흡착능을 보 였다. 400～600℃에서 아민화를 시킨 시료는 처리온도와 비례하는 선택도를 보여주었다. 분해시간 또한 흡착능과 정비례하는 관계가 나타났다.

본 연구는 고온미생물인 Bacillus coagulans를 이용하여 발효시킨 탈피대두박(fermented soybean meal; FS)을 어분대체 단백질원으로서 10%, 20% 및 30% 수준별로 첨가한 배합사료를 급여하여 넙치의 성장 및 육질에 미치는 영향을 비교 조사하였다. 사육실험은 평균체중 123 g의 넙치를 원형수조에 50마리씩 실험구별로 3반복으로 수용하면서, 대조 배합사료(control)와 실험배합사료(FS10, FS20, FS30)를 8주간 사육하였다. 수분과 조단백질 함량은 대조 배합사료를 공급한 넙치의 등근육과 실험 배합사료를 공급한 넙치의 등근육에서 유의적한 차이를 보이지 않았으나, 조지방 함량은 실험배합사료 FS20, FS30을 공급한 넙치 등근육에서 유의적으로 높은 값을 나타내었다. 18:2n-6의 함량은 실험배합사료 FS10, FS20, FS30을 공급한 넙치 등근육에서 대조 배합사료를 공급한 넙치 등근육보다 유의적으로 높게 나타났다. 모든 시험구에서 넙치 등근육의 유리아미노산 중 taurine, leucine, alanine, lysine이 공통적으로 높은 함량을 나타내었고, 공급한 사료에 따라 넙치 등근육의 유리아미노산에는 유의적인 차이는 없었다. 핵산관련물질 중 AMP의 함량은, FS20 및 FS30을 공급한 넙치 등근육에서 대조 배합사료를 공급한 것보다 유의적으로 높은 함량을 나타내었다. 이상의 결과로부터, 본 실험 사료조성으로 넙치 치어를 사육하였을 때 어분대체 단백질원으로서 발효대두박을 어분 단백질 함량기준으로 30%까지 대체 가능할 것으로 생각되었다.

In order to investigate a nitriding process of spent oxide fuel and the subsequent change in thermal properties after nitriding, simulated spent fuel powder was converted into a nitride pellet with simulated fission product elements through a carbothermic reduction process. Nitriding rate of simulated spent fuel was decreased with increasing of the amount of fission products. Contents of Ba and Sr in simulated spent fuel were decreased after the carbothermic reduction process. The thermal conductivity of the nitride pellet was decreased by an addition of fission product element but was higher than that of the oxide fuel containing fission product elements.