• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3543-3548
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• 2023

Shutdown chemistry evolution is performed in nuclear power plants at each refueling outage (RFO) to establish safe conditions to open system and minimize inventory of corrosion products in the reactor coolant system (RCS). After hydrogen peroxide is added to RCS during shutdown chemistry evolution, corrosion products are released and are removed by filters and ion exchange resins in the chemical volume control system (CVCS). Shutdown chemistry evolution including RCS clean-up time to remove released corrosion products impacts the critical path schedule during RFOs. The estimation of clean-up time prior to RFO can provide more reliable actions for RCS clean-up operations and transients to operators during shutdown chemistry. Electric Power Research Institute (EPRI) shutdown calculator (SDC) enables to provide clean-up time by Co-58 peak activity through operational data from nuclear power plants (NPPs). In this study, we have investigated the results of EPRI SDC by shutdown chemistry data of Co-58 activity using NPP data from previous cycles and modeled the estimated clean-up time by EPRI SDC using average Co-58 activity of the NPP. We selected two RFO data from the NPP to evaluate EPRI SDC results using the purification time to reach to 1.3 mCi/cc of Co-58 after hydrogen peroxide addition. Comparing two RFO data, the similar purification time between actual and computed data by EPRI SDC, 0.92 and 1.74 h respectively, was observed with the deviation of 3.7-7.2%. As the modeling the estimated clean-up time, we calculated average Co-58 peak concentration for normal cycles after cycle 10 and applied two-sigma (2σ, 95.4%) for predicted Co-58 peak concentration as upper and lower values compared to the average data. For the verification of modeling, shutdown chemistry data for RFO 17 was used. Predicted RCS clean-up time with lower and upper values was between 21.05 and 27.58 h, and clean-up time for RFO 17 was 24.75 h, within the predicted time band. Therefore, our calculated modeling band was validated. This approach can be identified that the advantage of the modeling for clean-up time with SDC is that the primary prediction of shutdown chemistry plans can be performed more reliably during shutdown chemistry. This research can contribute to improving the efficiency and safety of shutdown chemistry evolution in nuclear power plants.

• 대한의용생체공학회:의공학회지
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• 제19권6호
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• pp.617-622
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• 1998

신냉매인 R-404A를 사용하여 저온특성이 우수한 한냉물리치료기를 개발하였다. 임상평가를 통해서 침온도계를 슬관절 강 내 및 둔부근육 내에 삽입하여 직접 근육온도를 측정하였고, 적외선체열촬영기를 이용하여 표피온도를 객관적으로 측정하였다. 슬관절 부위에 대한 5분 동안의 한냉물리치료에 따른 표피 및 관절강 내 온도변화를 측정한 결과, 표피는 23.3${\pm}4.7^{circ}C$, 관절강 내는 4.1${\pm}1.0^{circ}C$의 온도저하를 보였으며 2~3시간이 경과한 후에도 한냉치료효과가 지속됨을 알 수 있었다. 냉기치료 후 둔부근육에서 측정된 최저온도는 2, 4, 6cm 깊이에서 각각 35.1${\pm}$0.7, 36.2${\pm}$0.4, 36.9${\pm}0.3^{circ}C$였고, 이에 도달하기까지의 시간은 각각 20${\pm}$3.0, 25${\pm}$4.5, 45${\pm}$8.5분이었다. 치료 후 2시간이 경과한 뒤의 온도는 근육의 2, 4, 6cm 깊이에서 각각 36.2${\pm}$0.5, 36.6${\pm}$0.3, 36.9${\pm}0.3^{circ}C$였고, 치료 전에 비해 유의한 온도 차이가 있었다. 또한 5분간 한냉을 가하는 동안 피부 및 근육 내에서 온도의 증가, 즉 반응성 혈관확장은 관찰되지 않았다. 본 연구를 통해서 개발된 한냉물리치료기는 근육의 연축 혹은 강직, 물리적 외상, 화상, 동통의 감소, 관절염 등에 효과적으로 사용되리라 생각된다.

• 대한소아치과학회지
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• 제25권2호
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• pp.400-420
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• 1998

We already know that it is very difficult to obtain an "isolated field" for direct bonding during the surgical exposure of unerupted teeth. The aim of this in-vitro study is to simulate the clinical situation of forced eruption and to evaluate the tensile strengths of preligatured button with several types of contamination which can happen during the surgical exposure of unerupted teeth. Four orthodontic direct bonding systems were used. ($Ortho-One^{TM}$, $Rely-a-Bond^{(R)}$, $Ortho-Two^{TM}$, Phase $II^{(R)}$) Each material was divided into four groups(n=20) : Group 1. (Control, no contamination), Group 2. (Rinse etching agent with saline instead of water), Group 3. (Blood contamination of etched surface for 30 seconds), Group 4. (Blood contamination of primed surface for 30 seconds) 320 bovine anterior permanent teeth were divided into the above mentioned 16 groups. Enamel surface was flattened and ground under water coolant. Pre-ligatured buttons were prepared to the same form. (Cut 0.25 ligature wire 10 cm in length. Twist the ligature wire 30 times clockwise. Mark the wire 15mm and 35mm points from button. Make a loop sticking two points together and twist the loop 6 times counterclockwise.) The bonded specimens were stored at $37^{\circ}C$ saline solution for 3 days. Then the tensile strength of each sample was measured with Instron universal testing machine, crosshead speed of 0.5mm/min. The following results were obtained: 1. As compared to control groups (Group 1) of each material, Rely-a-Bond had a significantly lower mean tensile strengths than other material. (p<0.01) 2. In Group 2. of Ortho-One and Rely-a-Bond, the mean tensile strengths decreased about 7.7% and 11.1%, respectively with statistical significances. (p<0.05) 3. In Group 2. of Ortho-Two and Phase II, the mean tensile strengths did not decrease. 4. In Group 3. of Ortho-One, Rely-a-Bond, Ortho-Two, and Phase II, the mean tensile strengths decreased about 60.8%, 56.1%, 60.2%, and 46.0%, respectively with statistical significances. (p<0.01) 5. In Group 4. of Ortho-One and Rely-a-Bond, the mean tensile strengths did not decrease. 6. In Group 4. of Ortho-Two and Phase II, the mean tensile strengths were decreased about 20.95% and 22.28%, respectively with statistical significances. (p<0.01) There were formations of a hump shaped mass from bonding resin under blood contamination which disturbed direct bonding procedure. According to Reynolds, the proper bond strength for clinical manipulation should be at least 45N or about 4.5Kg.F. According to these results, it can be concluded that Ortho-One could be used during surgical exposure of unerupted teeth. In any case, blood contamination of the etched surface should be avoided, but the blood contamination of primed surface of Ortho-One may not decrease bond strength. Just 'blowing-out' is enough to remove blood from primed surface of Ortho-One. You can verify the clean surface of the primer of Ortho-One after blowing out the blood contamination.

• Nuclear Engineering and Technology
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• 제39권5호
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• pp.603-616
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• 2007

Roy Huddle, having invented the coated particle in Harwell 1957, stated in the early 1970s that we know now everything about particles and coatings and should be going over to deal with other problems. This was on the occasion of the Dragon fuel performance information meeting London 1973: How wrong a genius be! It took until 1978 that really good particles were made in Germany, then during the Japanese HTTR production in the 1990s and finally the Chinese 2000-2001 campaign for HTR-10. Here, we present a review of history and present status. Today, good fuel is measured by different standards from the seventies: where $9*10^{-4}$ initial free heavy metal fraction was typical for early AVR carbide fuel and $3*10^{-4}$ initial free heavy metal fraction was acceptable for oxide fuel in THTR, we insist on values more than an order of magnitude below this value today. Half a percent of particle failure at the end-of-irradiation, another ancient standard, is not even acceptable today, even for the most severe accidents. While legislation and licensing has not changed, one of the reasons we insist on these improvements is the preference for passive systems rather than active controls of earlier times. After renewed HTGR interest, we are reporting about the start of new or reactivated coated particle work in several parts of the world, considering the aspects of designs/ traditional and new materials, manufacturing technologies/ quality control quality assurance, irradiation and accident performance, modeling and performance predictions, and fuel cycle aspects and spent fuel treatment. In very general terms, the coated particle should be strong, reliable, retentive, and affordable. These properties have to be quantified and will be eventually optimized for a specific application system. Results obtained so far indicate that the same particle can be used for steam cycle applications with $700-750^{\circ}C$ helium coolant gas exit, for gas turbine applications at $850-900^{\circ}C$ and for process heat/hydrogen generation applications with $950^{\circ}C$ outlet temperatures. There is a clear set of standards for modem high quality fuel in terms of low levels of heavy metal contamination, manufacture-induced particle defects during fuel body and fuel element making, irradiation/accident induced particle failures and limits on fission product release from intact particles. While gas-cooled reactor design is still open-ended with blocks for the prismatic and spherical fuel elements for the pebble-bed design, there is near worldwide agreement on high quality fuel: a $500{\mu}m$ diameter $UO_2$ kernel of 10% enrichment is surrounded by a $100{\mu}m$ thick sacrificial buffer layer to be followed by a dense inner pyrocarbon layer, a high quality silicon carbide layer of $35{\mu}m$ thickness and theoretical density and another outer pyrocarbon layer. Good performance has been demonstrated both under operational and under accident conditions, i.e. to 10% FIMA and maximum $1600^{\circ}C$ afterwards. And it is the wide-ranging demonstration experience that makes this particle superior. Recommendations are made for further work: 1. Generation of data for presently manufactured materials, e.g. SiC strength and strength distribution, PyC creep and shrinkage and many more material data sets. 2. Renewed start of irradiation and accident testing of modem coated particle fuel. 3. Analysis of existing and newly created data with a view to demonstrate satisfactory performance at burnups beyond 10% FIMA and complete fission product retention even in accidents that go beyond $1600^{\circ}C$ for a short period of time. This work should proceed at both national and international level.

• 한국진공학회지
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• 제18권4호
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• pp.318-330
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• 2009

본 한국원자력연구원에서는 국제열핵융합실험로(ITER)의 일차벽을 개발하기 위해 그라파이트 히터를 이용한 고열부하 시험시설 KoHLT-1(Korea Heat Load Test facility-1)을 구축하였으며, 현재 정상적으로 가동되고 있다. KoHLT-1의 주목적은 Be-CuCrZr-SS의 이종 금속이 HIP 방법에 의해 접합된 ITER 일차벽 mockup의 접합 건전성을 확인하는데 있다. KoHLT-1은 판형 그라파이트 히터, 냉각 jacket이 부착된 상자형 시험용기, 직류 전원, 냉각계통, He 기체 공급계통과 각종 진단계통으로 구성되어 있으며, 이 모든 시설은 Be 처리가 가능한 특수 정화계통이 설치된 실험실에 설치되었다. 그라파이트 히터는 두개의 시험 대상물 사이에 설치되며, 시험대상물과의 거리는 $2{\sim}3\;mm$이다. 시험 대상물의 크기와 요구되는 열유속에 따라 여러 가지의 그라파이트 히터를 설계, 제작하였으며, 전기 저항은 고온 운전 중에 $0.2{\sim}0.5{\Omega}$이 되도록 하였다. 히터는 100V/400 A의 직류전원에 연결되어 있으며, PC와 multi function module로 구성된 전류 조정계통에 의해 미리 프로그램되어 있는 패턴으로 전류를 자동 조절하게 된다. 두 시험대상물에 인가되는 열유속은 calorimetry법에 의해 냉각수의 입, 출구 온도와 유량을 측정하여 얻게 된다. 여러 가지 형태의 ITER 일차벽 Be mockups에 대해 고열부하 시험을 수행하였으며, 시험을 통하여 KoHLT-1 고열부하 시험 시설의 성능이 확인되었고, 24시간 이상의 연속 운전에 있어서도 그 신뢰성이 입증되었다.

• 화훼연구
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• 제19권4호
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• pp.187-191
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• 2011

지온상승억제 효과는 차광망(50%) + 냉각수순환 평균 $18.8^{\circ}C$(최고 $23^{\circ}C$)가 가장 좋았으며, 차광망(50%) + 지하수순환 $23.2^{\circ}C(28.5^{\circ}C)$, 차광도포제(30%)와 차광망(50%)이 각각 $24^{\circ}C$(최고 $30^{\circ}C$) 순으로 나타났다. 고온기 근권냉각수 순환 효과가 가장 큰 모데나 품종은 절화장이 95.9 cm, 생체중이 67.0 g으로 가장 좋게 나타났다. 처리별 수량증가는 차광망(50%)처리에 비해 차광망(50%) + 냉각수순환이 121%로 가장 많았고, 차광망(50%) +지하수순환, 차광도포제(30%)는 각각 59%와 65% 증가하였다. 하우스내부 야간온도를 $8^{\circ}C$로 관리하였을 때 근권온수 순환이 평균 $18^{\circ}C$ 유지하여 무처리에 비해 약 $8^{\circ}C$ 정도 지온상승효과가 있는 것으로 나타났다. 동절기 지하부 온수순환처리에 의한 알스트로메리아 생육은 아스펜, 모데나, 샤넬 품종에서 절화장, 생체중 등 생육이 가장 좋았으며, 보르도 품종은 절화장이 다소 작게 나타났다. 근권온수 순환처리가 생육을 증가시킨 결과로 아스펜 등 4품종 모두에서 꽃목길이, 꽃목경경, 꽃수 및 꽃무게 등 절화품질 또한 증가하였다. 생산량 또한 크게 증가하여 모데나 품종에서 38% 이상으로 가장 높았고, 아스펜, 보르도, 샤넬 순이었다.