• 에너지공학
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• 제13권4호
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• pp.242-258
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• 2004

한국원자력연구소에서는 기존의 일체형 가연성 독봉과 다른 이중구조로 된 가연성독봉 개념을 제시하였다. 이중구조 가연성독봉(Erbia Duplex BP)은 내부에 Natural U+Gd$_2$O$_3$, 외부에는 Enriched $UO_2$+Er$_2$O$_3$를 배열시킨 구조이다. 이러한 독봉은 장주기 노심에서 기존의 Gadolinia BP과 동일한 반응도제어를 할 수 있을 것이라 예상된다. 이중구조 가연성독봉의 핵적 타당성을 확인하기 위해 24개월 주기용 한국표준형원자로를 비교대상으로 선정하였으며, 기존 연구된 여러 가지 독봉설계안들과 4가지 핵특성에 대하여 비교 분석하였다. 핵특성 평가 결과, 이중구조가연성 독봉은 비교대상보다 무한증배계수, 첨두봉출력인자, 반응도억제가, 감속재온도계수측면에서 모두 유리한 경향을 보였다. 설계변수에 따른 민감도분석을 통해 도출한 최적화된 핵연료집합체를 이용하여 노심적용 타당성을 확인하였다. 주기길이, 첨두출력 및 감속재온도 계수를 비교하였으며 전 노심해석결과 주기길이가 비고대상보다 4-7일 길게 나타났다. 이러한 결과는 등가의 독봉집합체를 설계했음에도 불구하고 노심에 장전되는 우라늄의 양이 서로 달라서 생기는 현상으로 판단된다. 하지만 전체적인 핵특성을 비교해보면 이중구조 가연성독봉을 장전한 노심이 비교대상노심보다 다소 유리하면서도 거의 비슷함을 알 수 있었다. 마지막으로 경제성 평가를 통해 장주기 노심에서의 이중구조 가연성독봉의 제조 가능성 및 적용 타당성이 충분히 확인되었다.

• Nuclear Engineering and Technology
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• 제50권7호
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• pp.1024-1036
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• 2018

In this paper, McCARD code was verified using various models listed in the NUREG/CR-6361 benchmark guide, which provides specifications for single pin-cells, single assemblies, and the whole core classified depending on the nuclear properties and structural characteristics. McCARD code was verified by comparing its results with those of SCALE code for single pin-cell and single assembly benchmark problems. The difference in the multiplication factor obtained through the two codes did not exceed 90 pcm. The benchmark guide treats a total of 173 whole core experiments. The experiments are categorized as simple lattices, separator plates, reflecting walls, reflecting walls and separator plates, burnable absorber fuel rods, water holes, poison rods, and borated moderator. As a result of numerical simulation using McCARD, the mean value of the multiplication factors is 1.00223 and the standard deviation of the multiplication factors is 285 pcm. The difference between the multiplication factors and the experimental value is in the range of -665 pcm to + 1609 pcm. In addition, statistics of results for experiments categorized by reactor shape, additional structure, burnable poison, etc., are detailed in the main text.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2003년도 춘계학술발표대회 요약집
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• pp.57-57
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• 2003

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.224-224
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• 2002

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 추계학술발표회요약집
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• pp.267-267
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• 2002

• 방사성폐기물학회지
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• 제18권4호
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• pp.481-496
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• 2020

After nuclear power plants are permanently shut down and decommissioned, the remaining irradiated metal components such as stainless steel, carbon steel, and Inconel can be used as neutron absorber. This study investigates the possibility of reusing these metal components as neutron absorber materials, that is burnable poison. The absorption cross section of the irradiated metals did not lose their chemical properties and performance even if they were irradiated over 40-50 years in the NPPs. To examine the absorption capability of the waste metals, the lattice calculations of WH 17×17 fuel assembly were analyzed. From the results, Inconel-718 significantly hold-down fuel assembly excess reactivity compared to stainless steel 304 and carbon steel because Inconel-718 contains a small amount of boron nuclide. From the results, a 20wt% impurity of boron in irradiated Inconel-718 enhances the excess reactivity suppression. The application of irradiated Inconel-718 as a burnable absorber for SMR core was investigated. The irradiated Inconel-718 impurity with 20wt% of boron content can maintain and suppress the whole core reactivity. We emphasize that the irradiated metal components can be used as burnable absorber materials to control the reactivity of commercial reactor power and small modular reactors.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2001년도 추계학술발표회요약집
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• pp.258-258
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• 2001

• Nuclear Engineering and Technology
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• 제31권4호
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• pp.391-400
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• 1999

A conceptual core design of the 1,300MWe KNGR (Korean Next Generation Reactor) without using soluble boron for reactivity control was developed to determine whether it is technically feasible to implement SBF (Soluble Boron Free) operation. Based on the borated KNGR core design, the fuel assembly and control rod configuration were modified for extensive use of burnable poison rods and control rods. A new fuel rod, in which Pu-238 had been substituted for a small amount of U-238 in fuel composition, was introduced to assist the reactivity control by burnable poison rods. Since Pu-238 has a considerably large thermal neutron capture cross section, the new fuel assembly showed good reactivity suppression capability throughout the entire cycle turnup, especially at BOC (Beginning of Cycle). Moreover, relatively uniform control of power distribution was possible since the new fuel assemblies were loaded throughout the core. In this study, core excess reactivity was limited to 2.0 %$\delta$$\rho$ for the minimal use of control rods. The analysis results of the SBF KNGR core showed that axial power distribution control can be achieved by using the simplest zoning scheme of the fuel assembly Furthermore, the sufficient shutdown margin and the stability against axial xenon oscillations were secured in this SBF core. It is, therefore, concluded that a SBF operation is technically feasible for a large sized LWR (Light Water Reactor).

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2002년도 추계 학술발표회 논문집
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• pp.71-79
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• 2002

이중구조 가연성독봉(Duplex BP)의 성능을 평가하기 위해 한국표준형발전소 24개월 주기를 기준으로 16개 Gadolinia 독봉이 장전된 핵연료집합체에 대해 핵적 평가를 수행하였다. 16개 Gd 독봉이 장전된 핵연료집합체와 동일한 반응도 억제가를 갖는 Duplex 독봉집합체를 설계하기 위해 내심에 Natural U-12wt%Gd$_2$O$_3$, 외심에는 4.95wt%$UO_2$-2w/oEr$_2$O$_3$을 넣어 이중 성형한 24개의 이중구조 가연성독봉이 장전된 핵연료집합체를 설계하였다. 또한 같은 방법으로 140개의 Erbia 독봉이 장전된 등가핵연료집합체를 설계하였다. 핵설계 특성평가를 위해 연소도에 따른 무한증배계수, 반응도억제가, 첨두봉출력 그리고 냉각재 온도재수에 대한 변화에 대해서 비교하였다. Duplex 독봉은 Gadolinia 독봉에 비해 k-inf의 2차 첨두현상을 완화시켜 반응도 제어면에서 유리한 것으로 나타났다. 그러나, 다량의 Erbia 독봉을 전체적으로 골고루 장전한 핵연료집합체보다는 Duplex BP를 장전한 핵연료집합체가 노심내 반응도 제어면에서 유리하지 못한 것으로 나타났다.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3516-3525
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• 2022

The high capture cross-section (𝜎_c) of Gadolinium (Gd-155 and Gd-157) causes reactivity penalty and swing at the initial stage of fuel burnup in Pressurized Water Reactor (PWR). The present study is concerned with the feasibility of the combination of mixed burnable poison with both low and high 𝜎_c as an approach to minimize these effects. Two considered reference designs are fuel assemblies with 24 IBA rods of Gd₂O₃ and Er₂O₃ respectively. Models comprise nuclear fuel with a homogeneous mixture of Er₂O₃, AmO₂, SmO₂, and HfO₂ with Gd₂O₃ as well as the coating of PaO₂ and ZrB₂ on the Gd₂O₃ pellet's outer surface. The infinite multiplication factor was determined and reactivity was calculated considering 3% neutron leakage rate. All models except Er₂O₃ and SmO₂ showed expected results namely higher values of these parameters than the reference design of Gd₂O₃ at the early burnup period. The highest value was found for the model of PaO₂ and Gd₂O₃ followed by ZrB₂ and HfO₂. The cycle burnup, discharge burnup, and cycle length for three batch refueling were calculated using Linear Reactivity Model (LRM). The pin power distribution, energy-dependent neutron flux and Fuel Temperature Coefficient (FTC) were also studied. An optimization of model 1 was carried out to investigate effects of different isotopic compositions of Gd₂O₃ and absorber coating thickness.