• 한국항행학회논문지
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• 제23권6호
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• pp.554-560
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• 2019

원전에서 각종 전자카드는 시간에 경과함에 따라 열화가 되므로 이에 대한 대책이 필요하다. 이 열화 카드들 중에서 노외중성자감시시스템의 카드들은 방사선원의 레벨에서 발생되는 중성자속을 총 원자로출력의 200%까지 연속적으로 감시하게 되는데, 원자로출력이 낮을 때의 경우와 높을 때의 경우의 출력감시신호처리 방법이 달라야 한다. 원자로 출력이 낮을 때는 대수적으로 발생되는 펄스신호를 선형적으로 계수하여 신호처처리를 해야 되지만, 원자로 출력이 커지게 되면 통계이론에 의한 방법으로 처리해야 정확한 값을 얻을 수 있기 때문이다. 이때 전자카드가 열화되는 것이 문제가 된다. 따라서, 본 연구에서는 저출력일 때와 고출력일 때의 신호처리 방법을 달리하여 일정한 기준에 의한 원자로의 출력레벨에서 이를 저출력에서 고출력으로 전환하기 위한 열화 입력선택회로를 개발하였다. 개발된 선택회로의 신뢰성을 확인하기 위하여 원전에서 사용되는 실제의 데이터값을 적용하여 테스트하였으며, 그 결과를 분석하여 선택회로의 정당성을 입증하였다.

• 대한전자공학회논문지
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• 제13권5호
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• pp.17-23
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• 1976

고속열중성자로에서 정상 운전중인 원자로를 운전정지하였다가 재가동할 때 가장 문제가 되는 것은 핵분열 생성물인 Xe135의 독소작용이다. 이것은 Xe135가 원자로 출력에 영향을 주는 열중성자에 대한 흡수단면적이 크고 그의 반감기가 길기 때문이다. 그러므로 원자로의 일시적 운전정지가 요구될 때 이의 재가시에는 반듯이 이 독소를 능과할 수 있는 충분한 초과반응도를 가해 주던지, Xe135가 붕괴되어 그의 농도가 줄어든 이후에야 원자로의 재가동이 가능하게 된다. 위와 같은 문제는 사실상 원자로 운전시 안전성 뿐만 아니라 경제성에도 큰 영향을 주고 있다. 본 논문에서는 이 점을 고려하여 Pontoyagin의 최대원리를 이용하여 운전정지를 최적화시키므로서 언제든지 원자로를 전출력으로 재가동할 수 있도록 운전정지 방법을 개선하였다. 그러나 제어과정에서나 그 이후에도 X, 농도는 제어된 허용치를 넘지 않고 최소시간 이내에 모든 제어를 끝내도록 하였다. The buildup of fission product, i.e. Xe-135 poisoning, is a prime factor in restarting a nuclear reactor from the shutdown, which was under normal operation in the high flux thermal reactor, It is caused by the high absorption crosssection of Xe-135 to thermal neutrons and its long half life, from which the thermal power is affected. It is then possible to restart a nuclear reactor after the sufficient excess reactivity to override this poisoning must be inserted, or its concentration is decreased sufficiently when its temporary shutdown is required. As ratter of fact, these have an important influence not only on reactor safety but also on economic aspect in operation. Considering these points in this study, the shutdown process was cptimized using the Pontryagin's maximum principle so that the shutdown mirth[d was improved as to restart the reactor to its fulpower at any time, but the xenon concentration did not excess the constrained allowable value during and after shutdown, at the same time all the control actions were completed within minimum time from beginning of the shutdown.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.109-110
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• 2005

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.1015-1021
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• 2016

Structures, systems, and components (SSCs) important to safety of nuclear facilities shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions. Although SSC classification guidelines for nuclear power plants have been well established and applied, those for research reactors have been only recently established by the International Atomic Energy Agency (IAEA). Korea has operated a pool-type research reactor (the High Flux Advanced Neutron Application Reactor) and has recently exported another pool-type reactor (Jordan Research and Training Reactor), which is being built in Jordan. Korea also has a plan to build one more pool-type reactor, the Kijang Research Reactor, in Kijang, Busan. The safety classification of SSCs for pool-type research reactors is proposed in this paper based on the IAEA methodology. The proposal recommends that the SSCs of pool-type research reactors be categorized and classified on basis of their safety functions and safety significance. Because the SSCs in pool-type research reactors are not the pressure-retaining components, codes and standards for design of the SSCs following the safety classification can be selected in a graded approach.

• Nuclear Engineering and Technology
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• 제35권5호
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• pp.497-505
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• 2003

This paper describes a computational approach to the quantification of primary damage under irradiation and demonstrates the effect of neutron energy spectra on the formation of the displacement cascade. The development of displacement cascades in ${\alpha}-Iron$ has been simulated using the MOLDY code - a molecular dynamics code for simulating radiation damage. The primary knock-on atom energy, key input to the MOLDY code, was determined from the SPECTER code calculation on two neutron spectra. The two neutron spectra include; (i) neutron spectrum in the instrumented irradiation capsule of the high-flux advanced neutron application reactor (HANARO), and (ii) neutron spectrum at the inner surface of the reactor pressure vessel steel for the Younggwang nuclear power plant No.5 (YG 5). Minor differences in the normalized neutron spectra between the two spectra produce similar values of PKA energy, which are 4.7 keV for HANARO and 5.3 keV for YG 5. This similarity implies that primary damage to the components of the commercial nuclear reactors should be well simulated by irradiation in the HANARO. Moreover, the application of the MD calculations corroborates this statement by comparing cascades simulation results.

• Nuclear Engineering and Technology
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• 제46권3호
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• pp.423-430
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• 2014

An in-pile performance test of HANA claddings was conducted at up to 67 GWD/MTU in the Halden research reactor in Norway over a 6.5 year period. Four types of HANA claddings (HANA-3, HANA-4, HANA-5, and HANA-6) and a reference Zircaloy-4 cladding were used for the in-pile test. The evaluation parameters of the HANA claddings were the corrosion behavior, dimensional changes, hydrogen uptake, and tensile strength after the claddings were tested under the simulated operation conditions of a Korean commercial reactor. The oxide thickness ranged from 15 to 37 mm at a high flux region in the test rods, and all HANA claddings showed corrosion resistance superior to the Zircaloy-4 cladding. The creep-down rate of all HANA claddings was lower than that of the Zircaloy-4 cladding. In addition, the hydrogen content of the HANA claddings ranged from 54 to 96 wppm at the high heat flux region of the test rods, whereas the hydrogen content of the Zircaloy-4 cladding was 119 wppm. The tensile strength of the HANA and Zircaloy-4 claddings was similarly increased when compared to the un-irradiated claddings owing to the radiation-induced hardening.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.344-350
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• 2021

As the High Flux Advanced Neutron Application Reactor (HANARO) has been recently required to support new R&D relevant to future nuclear systems requiring a much higher neutron fluence, the development of irradiation capsule technology for long-term irradiation testing was performed in three steps (3, 5, 10 dpa). At first, several design improvements of a standard capsule were suggested based on a failure analysis of the capsule and successfully applied for irradiation testing at HANARO at up to eight reactor operation cycles equivalent to 3 dpa. Based on a schematic stress analysis of the vulnerable parts of the previous capsule, an optimized design of the capsule was made for 5 dpa irradiation. The newly designed capsule was safely out-pile tested up to 450 days, which was equivalent to 5 dpa irradiation in the reactor. The test results were submitted to the Reactor Safety Review Committee of HANARO and irradiation testing for 5 dpa was approved. The capsule was also successfully out-pile tested to evaluate the possibility of irradiation testing for 10 dpa. For a higher neutron fluence exceeding 10 dpa, new capsule technologies, including a new capsule that has a different bottom design and neutron flux boosting capsule, were also suggested.

• 한국환경과학회지
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• 제15권10호
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• pp.945-949
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• 2006

For a membrane bio-reactor, it is possible to fillet and separate activated sludge and effluent by head loss of centimeters, if non-woven fabric material is used as titration media. However, if non-woven fabric material is used to thicken high-concentration sludge, excessive sludge attachment causes the rapid decrease of flux. Mesh with fore sizes of $100{\mu}m,\;150{\mu}m,\;and\;200{\mu}m$ allows for easy separation of attached sludge. This study examined the possibility of mesh as filtration media. Existing close-flow filtration process, which requires maintaining sludge movement, makes It difficult to obtain high thickening rate. With a view of complementing this weakness, this study has made an experimental examination on how high-concentration sludge (about 3,000mg/L to 10,000mg/L) will be filtered and thickened when mesh module is submersed in the bio-reactor. Effluent flowed from the bottom of the bio-reactor by head loss of 65cm. In case of pore size of $100{\mu}m$, SS showed high recovery of 80% to 96%; therefore, it has been decided that mesh can be used as filtration media. Filtration lasted for more than 9 hours, until sludge with 9,000mg/L in MLSS concentration was thickened 9 times as dense. In the range from 3,610mg/L to 9,060mg/L in MLSS concentration, it was possible to obtain effluent with less than 2mg/L in MLSS concentration within 10 minutes.

• KSBB Journal
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• 제6권3호
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• pp.309-319
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• 1991

효소를 이용하여 대구피 젤라틴 가수분해물을 연속적으로 생산하기 위해 한외여과막 반응기에서의 젤라틴 가수분해 최적 공정조건 및 한외여과막 반응기를 장시간 작동하였을 때의 효소활성 저하원인을 규명하였다. 효소농도가 0.4mg/ml까지 증가함에 따라 기절의 전환율은 증가하였으나 기질의 경우는 농도가 증가함에 따라 전환율이 감소하였다. 유량(Flux)이 클수록 전환율은 감소되었으며 잔류시간이 길수록 전환율을 증가하였다. 한외여과막 반응기 장치의 작동시 가질의 전환율은 반응시간 1시간 부근에서 최대 전환율을 나타내었으며 시간당(8시간 작동) 평균 전환율 감소는 2.1%였다. 한외여과막을 통한 효소 누출은 반응시간 10~60분 범위에서 최대였으며 6시간 이후에는 거의 누출되지 않았다. 전체 효소량 중 누출량은 $50^{\circ}C$에서 16%인데 비해 $35^{\circ}C$에서는 12%였다. 그러나 효소 누출과 기질 전환율 사이에 명백한 상호관계는 나타나지 않았다. 막에 의한 효소의 활성저하는 작동시간 120분까지 나타났으며, 이때 초기속도의 36%가 저하하였다. 연속식(CSTMR)에서 $K_m$ 값은 회분식의 그것보다 20배 큰 반면 $K_2$ 10.5배 낮았다. 최적 가수분해조건은(기질농도 10%, $50^{\circ}C$, pH 8.0, 유량 7.31ml/min, 잔류시간 82분, S / E = 50w / w) 하에서의 생산량은 효소 mg당 가수분해물이 285mg으로 회분식 44.8mg에 비해 6배 이상이었다.

• 한국압력기기공학회 논문집
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• 제12권1호
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• pp.93-100
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• 2016

Since the sodium-cooled fast reactor is operated in a hostile environment due to the use of liquid sodium as its coolant, advanced techniques for in-service inspection are required to periodically verify the integrity of the reactor. This paper presents the development of in-service inspection techniques for Proto-type Generation IV Sodium-cooled Fast Reactor. First, the 10 m long plate-type ultrasonic waveguide sensor has been developed for in-service inspection of reactor internals, and its feasibility was verified through several under-water and under-sodium experiments. Second, the combined inspection system for in-service inspection of ferromagnetic steam generator tubes has been developed. The remote field eddy current testing and magnetic flux leakage testing can be conducted simultaneously by using the developed inspection system, and the detectability was demonstrated through several damage detection experiments. Finally, the electro-magnetic acoustic transducer which can withstand high temperature and be installable in the remote operated vehicle has been developed for in-service inspection of the reactor vessel, and its detectability was investigated through damage detection experiments.