• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2874-2879
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• 2020

Due to excess reactivity, fresh nuclear fuel often contains burnable poisons. This research looks at six different burnable poisons and their impacts on reactivity, material attractiveness, and waste management. An MCNP simulation of a PWR fuel pin was performed with a fuel burnup of 60 GWd/MTHM to determine when each burnable poison fuel type would decrease below a k_∞ of 1. For determining the plutonium material attractiveness in each burnable poison fuel type, the plutonium isotopic content of the used fuel was evaluated using Bathke's Figure of Merit formula. For the waste management analysis, the thermal output of each burnable poison fuel type was determined through ORIGEN decay simulations at 100 and 300 years after being discharged from the core. The performance of all six burnable poisons varied over the three criteria considered and no single burnable poison performed best in all three considerations.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1126-1139
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• 2016

In this research, for the first time, a new optimization method, i.e., strength Pareto evolutionary algorithm II (SPEA-II), is developed for the burnable poison placement (BPP) optimization of a nuclear reactor core. In the BPP problem, an optimized placement map of fuel assemblies with burnable poison is searched for a given core loading pattern according to defined objectives. In this work, SPEA-II coupled with a nodal expansion code is used for solving the BPP problem of Kraftwerk Union AG (KWU) pressurized water reactor. Our optimization goal for the BPP is to achieve a greater multiplication factor ($K_{eff}$) for gaining possible longer operation cycles along with more flattening of fuel assembly relative power distribution, considering a safety constraint on the radial power peaking factor. For appraising the proposed methodology, the basic approach, i.e., SPEA, is also developed in order to compare obtained results. In general, results reveal the acceptance performance and high strength of SPEA, particularly its new version, i.e., SPEA-II, in achieving a semioptimized loading pattern for the BPP optimization of KWU pressurized water reactor.

• Nuclear Engineering and Technology
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• 제30권4호
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• pp.342-352
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• 1998

A nuclear design feasibility of soluble boron free(SBF core for the medium-sized(600MWe) PWR was investigated. The result conformed that soluble boron free operation could be performed by using current PWR proven technologies. Westinghouse advanced reactor, AP-600 was chosen as a design prototype. Design modification was applied for the assembly design with burnable poison and control rod absorber material. In order to control excess reactivity, large amount of gadolinia integral burnable poison rods were used and B4C was used as a control rod absorber material. For control of bottom shift axial power shape due to high temperature feedback in SBF core, axial zoning of burnable poison was applied to the fuel assemblies design. The combination of enrichment and rod number zoning for burnable poison could make an excess reactivity swing flat within around 1% and these also led effective control on axial power offset and peak pin power, The safety assessment of the designed core was peformed by the calculation of MTC, FTC and shutdown margin. MTC in designed SBF core was greater around 6 times than one of Ulchin unit 3&4. Utilization of enriched BIO(up to 50w1o) in B4C shutdown control rods provided enough shutdown margin as well as subcriticality at cold refueling condition.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3106-3116
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• 2022

The present work presents analysis results of the core design optimizations for an annular, prismatic High Temperature Gas-cooled Reactor (HTGR) with passive decay-heat removal features. Its thermal power is 100 MW_t and the operating temperature is 850 ℃ (1123 K). The neutronic calculations are done for the core with heterogeneous distribution of fuel and burnable poison particles (BPPs) to flatten the reactivity swing and power peaking factor (PPF) during the reactor operation as well as for control rod (CR) insertion into the core to restrain a small excess reactivity less than 1$. The next step of the study is done for evaluation of core reactivity coefficient of temperature.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.238-247
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• 2020

The Burnable Poison (BP) is very important for all Light Water Reactors in order to hold-down the initial excess reactivity and to control power peaking. The use of BP is even more essential as the excess reactivity increases significantly with a longer operation cycle. In this paper a feasibility study was conducted in order to investigate the benefits of a new combinational BP concept designed for 24-month cycle PWR core. The reference designs in this study are based on the two Korean fuel assemblies; 17 × 17 Westinghouse (WH) design and 16 × 16 Combustion Engineering (CE) design. A modification was done on these two designs to extend their cycle length from 18 months into 24 months. DeCART2D-MASTER code system was used to perform assembly and core calculations for both designs. A preliminary test was conducted in order to choose the best BP suitable for 24-month as a representative for single BP concept. The comparison between the results of two concepts (combinational BP concept and single BP concept) showed that the combinational BP concept can replace the single BP concept with better performance on holding down the initial excess reactivity without violating the design limitations.

• Nuclear Engineering and Technology
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• 제47권5호
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• pp.559-566
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• 2015

The thermalehydraulic characteristics for the CANadian Deuterium Uranium Flexible (CANFLEX)-burnable poison (BP) fuel channel, which is loaded with a BP at the center ring based on the CANFLEX-RU (recycled uranium) fuel channel, are evaluated and compared with that of standard 37-element and CANFLEX-NU (natural uranium) fuel channels. The distributions of fuel temperature and critical channel power for the CANFLEX-BP fuel channel are calculated using the NUclear Heat Transport CIRcuit Thermohydraulics Analysis Code (NUCIRC) code for various creep rate and burnup. CANFLEX-BP fuel channel has been revealed to have a lower fuel temperature compared with that of a standard 37-element fuel channel, especially for high power channels. The critical channel power of CANFLEX-BP fuel channel has increased by about 10%, relative to that of a standard 37-element fuel channel for 380 channels in a core, and has higher value relative to that of the CANFLEX-NU fuel channel except the channels in the outer core. This study has shown that the use of a BP is feasible to enhance the thermal performance by the axial heat flux distribution, as well as the improvement of the reactor physical safety characteristics, and thus the reactor safety can be improved by the use of BP in a CANDU reactor.

• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1729-1737
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• 2019

This paper presents neutronics design of VVER-1000 fuel assembly using burnable poison particles (BPPs) for controlling excess reactivity and pin-wise power distribution. The advantage of using BPPs is that the thermal conductivity of BPP-dispersed fuel pin could be improved. Numerical calculations have been conducted for optimizing the BPP parameters using the MVP code and the JENDL-3.3 data library. The results show that by using $Gd_2O_3$ particles with the diameter of $60{\mu}m$ and the packing fraction of 5%, the burnup reactivity curve and pin-wise power distribution are obtained approximately that of the reference design. To minimize power peaking factor (PPF), total BP amount has been distributed in a larger number of fuel rods. Optimization has been conducted for the number of BPP-dispersed rods, their distribution, BPP diameter and packing fraction. Two models of assembly consisting of 18 BPP-dispersed rods have been selected. The diameter of $300{\mu}m$ and the packing fraction of 3.33% were determined so that the burnup reactivity curve is approximate that of the reference one, while the PPF can be decreased from 1.167 to 1.105 and 1.113, respectively. Application of BPPs for compensating the reduction of soluble boron content to 50% and 0% is also investigated.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1526-1533
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• 2022

Small modular reactors have garnered considerable attention in the recent years. Plate fuel elements exhibit a good application prospect in small modular pressurized water reactors for marine applications. Further, improved economic benefits can be achieved by extending the core lifetime of small modular reactors. However, it is necessary to realize a large initial residual reactivity for achieving a relatively long burnup depth finally. Thus, the selection of a suitable burnable poison (BP) is a crucial factor that should be considered in the design of small modular reactors. In this study, some candidate BPs are selected to realize the effective control of reactivity. The results show that ²³¹Pa₂O₃, ²⁴⁰Pu₂O₃, ¹⁶⁷Er₂O₃, PACS-J, and PACS-L are ideal candidates of BP, and since the characteristics of BP can increase the final burnup depth of assembly, the economic benefits are gained. Additionally, an optimal combination scheme of BPs is established. Specifically, it is proved that through a reasonable combination of BPs, a low reactivity fluctuation during the lifetime can be achieved, leading to a large final burnup depth.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.59-64
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• 1996

Feasibility of soluble boron free operation for the medium-sized commercial reactors was investigated. Westinghouse advanced reactor, AP-600 was chosen as a design prototype. Design modification was applied for the assembly design with gadolinia burnable poison-high Gd enrichment and axial poison zoning. CASMO and NECTA-C code system checked axial offset and peaking factors as fuels burned up. A core with complex axial burnable poison zoning satisfied design goals - small excess reactivity for 18 month cycle. Therefore, critical bank positioning for three control rod banks was sought with ease. A.O. value and Fq value were kept within the safety limit.

• Nuclear Engineering and Technology
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• 제20권1호
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• pp.19-26
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• 1988

저누출 장전 모형은 새 연료를 안에서부터 넣는 in-out 형태를 취하여 격납 용기의 fluence를 줄이고 중성자 경제성을 높이고자 하는 것으로, 이 경우에는 노심내의 전체적인 중성자 경제성은 좋아지지만 노심 중앙부에서의 새연료의 과다 반응도 때문에 안전성 여유를 줄이게 되므로 많은 수의 가연성 독붕봉을 사용하여 첨두 인자를 조절해야만 한다. 본 논문에서는 가연성 독붕봉 연소에 따른 출력 변화를 섭동으로 취급하며, 이를 출력감도 계수(Power Sensitivity Coefficient)로 표시한다. 최적화된 가연성 독붕봉의 분포를 구하기 인하여 알고 있는 주기말상태로부터, 노심 내의 출력과 과다 반응도를 제어하면서 주기초로 추적해 나가는 역연소법(Reverse Depletion Method)의 도입에 대한 타당성을 출력 민감도 계수개념과 선형 계획법을 이용하여 원자력 7호기 제1주기에 응용하여 검증했으며, 가연성 독붕봉의 추정량과 실제량과의 차이는 최대 4.5%의 오차를 보였다.