• Nuclear Engineering and Technology
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• v.25 no.2
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• pp.193-203
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• 1993

A new heuristic method for loading pattern search has been developed to overcome short-comings of the algorithmic approach. To reduce the size of vast solution space, general shuffling rules, a regionwise shuffling method, and a pattern grouping method were introduced. The entropy theory was applied to classify possible loading patterns into groups with similarity between them. The pattern search program was implemented with use of the PROLOG language. A two-group nodal code MEDIUM-2D was used for analysis of power distribution in the core. The above mentioned methodology has been tested to show effectiveness in reducing of solution space down to a few hundred pattern groups. Burnable poison rods were then arranged in each pattern group in accordance with burnable poison distribution rules, which led to further reduction of the solution space to several scores of acceptable pattern groups. The method of maximizing cycle length(MCL) and minimizing power-peaking factor(MPF) were applied to search for specific useful loading patterns from the acceptable pattern groups. Thus, several specific loading patterns that have low power-peaking factor and large cycle length were successfully searched from the selected pattern groups.

• Korean Journal of Optics and Photonics
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• v.5 no.1
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• pp.84-89
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• 1994

A tunable pulsed dye laser was operated in a single longitudinal mode by injection locking with a cw ring dye laser. A doubled Nd:YAG laser was used as the pumping source. Phase sensitive detection technique was applied to maintain the required match between the master laser frequency and the slave resonator cavity length. The fluctuation of the center frequency of the pulsed laser was < 10 MHz, and the pulse duration (FWHM) was 6 ns. The linewidth measured by scanning confocal interferometer was 130 MHz. When pumped by 50 mJ of the doubled Nd:YAG laser, the output energy of the pulsed dye laser was 2 mJ and the peak power was 330 kW. 30 kW.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.63-66
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• 2004

본 논문에서는 채널간간섭 자기소거를 위한 부대역 부호화기법에 따른 직교 주파수분할다중화의 첨두전력대 평균전력비가 분석된다. 인접부대역에 대척신호를 할당하는 기존 상관부호화의 경우 전송신호열에서 형상성분이 발생되며, 이로 인하여 직교 주파수분할다중화 시스템의 첨두전력 대 평균전력비가 최대 3dB 가량 증가됨을 이론적$\cdot$실험적으로 검증한다. 그리고 이와 같은 형상성분을 제거할 수 있는 새로운 부대역 부호화기법이 제시된다. 여기서는 인접부대역에 할당되는 신호쌍의 위상차가 신호사상기의 출력에 따라 변화된다. 그 결과, 새로운 부대역 부호화기법이 적용된 시스템은 기존의 시스템보다 $2\~3dB$ 적은 첨두전력 대 평균전력비를 가지는 것을 확인할 수 있다.

• Korean Journal of Optics and Photonics
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• v.27 no.3
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• pp.95-100
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• 2016

High-power quasi-continuous-wave (qcw) operation in Yb-doped double-clad fiber lasers with near-diffraction-limited quality of the output beam is reported. Based on numerical simulation, we built a simple, all-fiberized Yb fiber laser, and a fiber-based master-oscillator power amplifier (MOPA). Both laser systems have successfully produced qcw output with average power greater than 150 W at 1080 nm and 10 ms pulse duration at 10 Hz repetition rate, corresponding to a peak power greater than 1.5 kW for 205 W of pump power at 976 nm. Laser performance, including beam quality and slope efficiency, was characterized in both configurations. Prospects for power scaling and applications are discussed.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.411-416
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• 1996

최근 웨스팅하우스사가 SECY-83-472에 근거하여 개발한 최적평가방법론인 WCOBRA/TRAC UPI EM을 이용하여 Appendix K, Superbounded, Nominal 계산을 고리 1호기에 대하여 수행하였다. 15%증기발생기 관막음율, 출력 첨두 계수 2.35, 최대 선형 열출력 15.588kw/ft을 사용하여 계산한 결과 Appendix K 최대 피복재 온도는 1941℉로서 KAERI/Siemens가 RTSR 작성시 수행한 해석에 비하여 운전여유도가 증가한 것으로 나타났으며, 그 결과가 SECY 방법론에 합당함을 확인하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.17-22
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• 1995

열출력 108㎿$_{t}$급의 소형 원자로를 설계하였다. 설계 제한 조건으로 2년의 재장전 주기, 무붕산 노심, 저 출력 밀도를 채택하였고, 핵연료 집합체의 설계는 울진 304호기의 사양을 그대로 사용하였다. 노심 출력 준위 제어는 제어봉만으로 가능하도록 하였다. CASMO-3와 KINS-3를 통해 설계된 노심의 주기 길이 만족 여부 확인, 첨두 계수, 감속재 온도 계수, 출력 계수 등을 계산하였다. 설계 결과, 한국 표준 원전 핵연료집합체 사양으로 저출력 밀도의 소형인자로를 무붕산 운전으로 가정하여 설계 가능함을 알 수 있었으며, 감속재 온도 계수가 음의 안전성을 갖고 있으며, 가연성 독봉의 축방향 Zoning이 필요하며, 기존 상용로의 경우 보다 독봉을 많이 사용되어야 하며, 제어봉이 서양 장기판처럼 배치될 정도로 많이 사용되어야 함을 알았다.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.316-317
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• 2000

펄스형 $CO_2$레이저는 적외선 영역인 10.6 $mu extrm{m}$ 파장의 매우 안정된 고출력 펄스를 방출시킬 수 있으므로 산업용, 군사용, 의료용, 각종 물리.화학의 기초 연구용 등의 광범위한 응용 분야에서 각광을 받고 있다. 특히 금속의 정밀절단, 심용접에서는 수 십 Hz로부터 수 kHz의 펄스 출력이 필요하다. 펄스방식은 Normal Pulse와 Super Pulse로 크게 나눌 수 있다. Normal Pulse의 경우에는 Pulse의 파고치가 연속파의 파고치와 동일하기 때문에 펄스시의 평균 출력은 연속파의 경우보다 낮다. Super Pulse의 경우에는 Pulse 파고치를 연속파의 파고치보다 훨씬 높게 할 수 있으므로 평균 출력은 낮지만 첨두 출력이 높아서 유리 등 세라믹 재료의 가공에 널리 사용된다$^{(1)}$ (중략)

• Korean Journal of Optics and Photonics
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• v.6 no.1
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• pp.21-25
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• 1995

Q-switched Waveguide $CO_{2}$ laser using polygon mirror were constructed and their output characteristics were measured. Waveguide was made of the beryllium oxide tube of inner diameter of 2 mm, outer diameter of 20 mm, and length of 200 mm. A flat ZnSe output coupler of 80% reflectivity was placed on the 9 mm distance from the end of the waveguide. Convex lens was used to reduce the coupling loss between the polygon mirror and the waveguide. The polygon mirror was located behind of convex lens. With this condition, continuous output of the laser were measured as 1.2 W. In the Q-switched mode. pulse width 120 ns were measured with rotational speed 7,559 RPM. and peak power of up to 250 W. 250 W.

• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.389-400
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• 1994

The predictability of KAERI version of RELAP5/MOD3 on reflood peak cladding temperature during large break loss-of-coolant accident is assessed against 18 test runs in FLECHT SEASET test data. The associated uncertainty is statistically quantified. The selected test runs include a gravity feed test and several forced feed tests with wide range of the parameters such as flooding rate, system pressure, initial clad temperature, rod bundle power. The results show that the code under-predicts the peak cladding temperature by 7.56 K on average. The upper limit of the associated uncertainty at 95% confidence level is evaluated to be about 99 K, It including the bias due to the under-prediction.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.81-92
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• 1996

This study is to compare the weldability of Zircaloy-4 end cap of nuclear fuel pin using by GTA and Nd :YAG LB. The welding parameters which affect bead width and penetration depth have been investigated. The effect of joint geometry of end cap for GTAW and LBW has been studied and optimum conditions of Zircaloy-4 endcap welding have been found. Microstructures and microhardness of GTA and LB welded zones have been also compared.