Streptomyces thermocyaneoviolaceus의 Xylanase 생산조건 및 Xylooligo당의 생산

주길재,박희동,최준호,이인구,이오석,권달호 慶北大學校農業科學技術硏究所 1998 慶北大農學誌 Vol.16 No.-

농산폐자원으로부터 기능성물질인 xylooligo당을 생산하기 위해서 내열성 균주인 S.thermocyaneoviolaceus가 생산하는 xylanase의 생산최적조건을 검토한 결과 0.8% 밀기울, 0.06% yeast extract, 0.06% bactopeptone, 0.05% MgSO₄·7H₂O, 0.005% FeSO₄·7H₂O, 0.05% KH₂PO₄및 0.2% K₂HPO₄를 함유한 배지(pH7.0)에서 50℃, 24시간 배양시 최고효소활성(2.47 unit/ml)의 배양상징액을 얻을 수 있었다. 효소의 최적반응조건은 pH5.5, 65℃였다. 또한 pH안정성을 조사한 결과 pH4.5∼9.5사이에서 4℃에서 12시간후에도 80% 이상의 효소활성을 유지하였고, 열 안정성은 60℃에서 1시간 처리후 94%이상의 효소활성을 유지하는 내열성이 있는 효소였다. 생산된 xylanase birchwood xylan 반응생성물을 TLC 및 HPLC로 확인해 본 결과, pH가 낮을수록(pH 5.0∼6.0) xylobiose와 xylotriose및 소량의 xylose의 양이 증가하였고, pH가 높을수록 (pH8.0∼9.0) X₄이상의 각종 xylooligo당의 양이 상대적으로 증가하였다. 또한 24 시간후에는 xylan의 상대량이 25% 이하로 감소하면서 주분해산물로 xylobiose가 생산되었으며 xylotriose와 xylose 및 X₄이상의 각종 xylooligo당이 생산되었다. A thermotolerant bacterium, Streptomyces thermocyaneoviolaceus which produced xylan-degrading enzymes, utilized excellently xylan of wheat bran by producing the enzymes in comparison with that of birchwood or oat spelts. Optimal enzyme production was achieved in WB medium containing 0.8% wheat bran, 0.06% yeast extract, 0.06% bactopeptone, 0.05% MgSO₄·7H₂O, 0.05% FeSO₄·7H₂O, 0.05% KH₂PO₄ and, 0.2% K₂HPO₄(pH 7.0) at 50℃ for 24 hrs. The optimal pH and temperature for the hydrolysis of xylan were pH 5.5 and 65℃, respectively. The enzyme activity was retained more than 80% at the range from pH 4.5 to pH 9.5 at 4℃ for 12 hrs and 94% on the heat-treatment at 65℃ for 1 hr. Xylobiose, xylotriose, xylose, and other xylooligosaccharides were produced as end products from hydrolysis of birchwood xylan by the xylanase of S. thermocyaneoviolceus.

소수성 촉매를 이용한 수소동위원소 교환 반응 측정을 위한 순환 반응기

최희주,이한수,안도희,강희석,김광락 한국공업화학회 2002 응용화학 Vol.6 No.2

The catalytic rate constants of hydrophobic catalysts developed for the removal of tritium mainly generated in the pressurized heavy water reactors should be measured. A recycle reactor was designed and built for characterzing the long-term behavior of the catalyst performance at the various temperatures and gas velocities.The catalytic rate constants were measured at the apparent gas velocity of 0.5 m/s and the temperature of 60℃. The initial catalytic constant was 8.44×10^-4mol/g.sec. This value is much greater than that considered in the design of Wolsong Tritium Removal Facility.

고리 및 영광 논토양에 대한 ^137Cs의 모의 사고 침적시 토양-벼 전이계수

최용호,임광묵,박효국,최희주,이한수 대한방사선 방어학회 2002 방사선방어학회지 Vol.27 No.4

고리 및 영광 원전 반경 5km 내 11곳의 논토양을 원상대로 재배상자에 채취하여 실험 온실로 운반한 후 벼의 이식 전과 생육중에 ^137Cs을 담수의 표면에 처리하였다. 이식전 처리시 ^137Cs의 토양-작물체 전이계수(m²kg^-1-dry plant)는 토양에 따라 8배 정도의 변이를 보였고 평균은 지역간 차이가 거의 없이 쌀알의 경우 1.1 x 10^-4 , 볏짚의 경우 2.7 x 10^-4 이었다. 분얼초기 처리와 수잉기 처리시 전이계수는 이식전 처리에 비해 대체로 2∼3 배 및 15∼30 배 정도 높았다. 토양 유기물 함량과 전이계수 간에는 정의 상관이 있었다. 본 실험결과에 입각하여 우리나라 논에 대한 일회성 사고침적시 적용할 수 있는 ^137Cs 전이계수의 대표치를 침적시기별로 제안하였다. Undisturbed soil blocks were taken into culture boxes from 11 paddy fields within 5 km radii of Kori and Yonggwang NPPs and carried to a greenhouse where ^137Cs was applied to the surface of standing water before rice transplanting and during its growth. Transfer factors (m²kg^-1-dry plant) of ^137Cs applied before transplanting varied with soils by a factor of about 8. The mean was 1.1 x 10^-4 for hulled rice seeds and 2.7 x 10^-4 for straw without significant regional differences. The ^137Cs applications at the early tillering stage and booting stage resulted in, on the whole, 2∼3 and 15∼30 times, respectively, higher transfer factors than the application before transplanting. A positive correlation was found between soil organic matter and transfer factor. Generic values of transfer factors were proposed for an acute accidental deposition of ^137Cs onto Korean paddy fields in different times of the year.

회귀분석(regression analysis)을 이용한 개인별 혈중알콜농도의 감소율 계산

홍성욱,권미아,최혜진,박용훈,인상환,김동우,정주연,우상희,박혜성 內務部 國立科學搜査硏究所 2002 國立 科學 搜査 硏究所 年報 Vol.34 No.-

상용 소수성 백금촉매의 제조비용 절감

안도희,백승우,강희석,최희주,정흥석 한국공업화학회 2003 응용화학 Vol.7 No.2

Wolsong Tritium Removal Facility(WTRF) is being constructed at Wolsong Nuclear Power Plant for reduction of the radiation hazards from tritium. The Liqiud Phase Catalytic Exchange (LPCE) process developed by KAERI and KEPRI was selected for the transfer process in WTRF. Approximately 2,000 litres of the hydrophobic platinum catalyst will be charged in the LPCE column. It was estimated that more than half of material cost for the catalyst preparation arised from H₂PtCl-(6) as a platinum precursor and high purity hydrogen gas as a reducing agent. In order to reduce material costs for the catalyst preparation, various catalysts were prepared and characterized using three kinds of H-(2)PtCl-(6) and two kinds of high purity hydrogen gas. It appears from the experiment that characteristics of the catalyst does not depend on both a kind of H₂PtCl_(6) and purity of hydrogen in the experimental conditions.

Characterization of Hydrophobic Catalysts for Hydrogen Isotope Exchange Using a Recycle Reactor

Heui-Joo Choi,Hansoo Lee,Kwang-Rag Kim,Do-Hee Ahn 한국공업화학회 2002 Journal of Industrial and Engineering Chemistry Vol.8 No.6

Modeling of the Environmental Behavior of Tritium Around the Nuclear Power Plants

Choi, Heui-Joo,Lee, Hansoo,Kang, Hee Suk,Choi, Yong Ho,Lee, Chang Woo 한국원자력학회 2002 Nuclear Engineering and Technology Vol.34 No.3

Comparison of Engineered Barriers for Alternative Disposal Concepts for CANDU Spent Nuclear Fuels in Korea

Heui-Joo Choi,Jong Youl Lee,Dong-Keun Cho 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

It is expected that around 576,000 bundles of CANDU spent nuclear fuels (SNF) will be generated from the four CANDU reactors located at the Wolsong site. The authors designed and proposed a reference disposal concept based on the KBS-3 type and KURT geological data in 2022. In addition, we have reviewed the literatures and selected four alternative disposal methods to develop the higherefficiency disposal concept than the reference concept since 2021. As known well, the most important safety functions of the geological disposal are containment and isolation, and the secondary function is retardation. A disposal canister covers the former, and buffer may do the latter. In this study, we design the engineered barrier systems for the four alternative concepts: (1) mined deep borehole matrix, (2) sub-seabed disposal, (3) deep borehole disposal, and (4) multi-level dispoal. Assuming total 10,000 tU of CANDU SNF, four different kinds of unit disposal module consisting of disposal canisters and compacted bentonite buffers are designed based on the technique currently available. Two alternative concepts, sub-seabed disposal and multi-level disposal, share the same unit module design with the reference concept in 2022. For all the alternative concepts, we assume that the density of the compacted buffer is 1.6 g/cm3. For the mined deep borehole matrix disposal, we introduce a disposal canister slightly modified from the Canadian NWMO canister with a capacity of 48 bundles. The thickness of a copper layer is changed to be 10 mm considering the long-term corrosion resistance. The buffer thickness around a disposal canister is 20 cm, and the diameter of a borehole is 100 cm. Two different kinds of buffer blocks are proposed for the easy handling of them. For the deep borehole disposal, a SiC-stainless steel canister is designed, and 63 bundles of CANDU SNF is emplaced in the canister. We expect that the SiC ceramic canister shows very excellent corrosion resistance and has a high thermal conductivity under the geological conditions. The deep borehole will be plugged with four layered sealing materials consisting of granite blocks, compacted bentonite, SiC ceramic, and concrete plugs.

Some Notes on the KBS-3V Disposal Concepts for Spent Nuclear Fuels in Korea

Heui-Joo Choi,Jong Youl Lee,Won-Il Ko,Yung-Zun Cho 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.1

Around 40 years ago, in the mid-1980s, Swedish government approved the KBS-3 method for the direct disposal of spent nuclear fuels (SNF) in Sweden. Since then, this method has become a reference for many countries including Korea, Republic of. The main ideas of the KBS-3 method are to locate SNF at 500 m below the ground surface using a copper disposal canister and a bentonite buffer. In 2016, our government announced the National Plan (NP 2016) regarding the final management of high-level waste (HLW) in Korea. In 2019, new committee were organized to review the NP 2016, and they submitted the final recommendations to the government in 2021. Finally, the government announced the 2nd National Plan in December, 2021. So far, KAERI has developed the technologies related to the final management of SNF in two directions. One follows ‘direct disposal’ based on the KBS-3 concept, and the other ‘recycling’ based on ‘pyroprocessing-and-SFR’ (PYRO-SFR). Even though Posiva and SKB obtained the construction permits with the KBS-3 method in Finland and Sweden, respectively, there are still several technical obstacles to applying directly to our situations. Some examples are as follows: high burnup, huge amounts of SNF, and high geothermal gradient in Korean peninsula. In this work, we try to illustrate some limits of the KBS-3 method. Within our country, currently, the most probable disposal option is the KBS-3 type geological disposal, but no one knows what the best option will be in 20 or 30 years if those kinds of drawbacks are considered. That is, we compare the effects of the drawbacks using our geological data and characteristics of spent fuels. Last year, we reviewed alternative disposal concepts focusing on the direct disposal of SNF and compared the pros and cons of them in order to enhance the disposal efficiency. We selected four candidate concepts. They were multi-level disposal, deep borehole disposal, sub-seabed disposal and mined deep borehole matrix. As mentioned before, KAERI has developed a pyroprocessing technology based on the SFR to reuse fissile radionuclides in SNF. Even though we can consume some fissile nuclides such as 239Pu and 241Pu using PYRO-SFR cycle, there still remain many long-lived radionuclides such as 129I and 135Cs waiting for the final disposal. The authors review and propose several concepts for the future final management of the long-lived radionuclides.

Development of repository concept for the high-level wastes

Heui-Joo Choi,Jong Youl Lee,Jongwon Choi,Pil Soo Hahn 한국방사성폐기물학회 2004 한국방사성폐기물학회 학술논문요약집 Vol.2 No.2