• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1211-1218
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• 2017

Monte Carlo neutron transport codes generally use the method of successive generations to converge the fission source distribution to-and then maintain it at-the fundamental mode. Recently, a phenomenon called "clustering" has been noted, which produces fission distributions that are very far from the fundamental mode. In this study, a mathematical model of clustering in Monte Carlo has been developed. The model draws on previous work for continuous-time birth-death processes, as well as methods from the field of population genetics.

• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1326-1338
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• 2017

The continuous energy Monte Carlo neutron transport code, MC21, was coupled to the CTF subchannel thermal-hydraulics code using a combination of Consortium for Advanced Simulation of Light Water Reactors (CASL) tools and in-house Python scripts. An MC21/CTF solution for VERA Core Physics Benchmark Progression Problem 6 demonstrated good agreement with MC21/COBRA-IE and VERA solutions. The MC21/CTF solution for VERA Core Physics Benchmark Progression Problem 7, Watts Bar Unit 1 at beginning of cycle hot full power equilibrium xenon conditions, is the first published coupled Monte Carlo neutronics/subchannel T-H solution for this problem. MC21/CTF predicted a critical boron concentration of 854.5 ppm, yielding a critical eigenvalue of $0.99994{\pm}6.8E-6$ (95% confidence interval). Excellent agreement with a VERA solution of Problem 7 was also demonstrated for integral and local power and temperature parameters.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4335-4349
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• 2023

Nuclear marine propulsion has been emerging as a next generation carbon-free power source, for which proper passive residual heat removal systems (PRHRSs) are needed for long-term safety. In particular, the characteristics of unlimited operation time and compact design are crucial in maritime applications due to the difficulties of safety aids and limited space. Accordingly, a compact and long-term-operable PRHRS has been proposed with the key design concept of using both air cooling and seawater cooling in tandem. To confirm its feasibility, this study conducted system design and a transient analysis in an accident scenario. Design results indicate that seawater cooling can considerably reduce the overall system size, and thus the compact and long-term-operable PRHRS can be realized. Regarding the transient analysis, the Multi-dimensional Analysis of Reactor Safety (MARS-KS) code was used to analyze the system behavior under a station blackout condition. Results show that the proposed design can satisfy the design requirements with a sufficient margin: the coolant temperature reached the safe shutdown condition within 36 h, and the maximum cooling rate did not exceed 40 ℃/h. Lastly, it was assessed that both air cooling and seawater cooling are necessary for achieving long-term operation and compact design.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.4
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• pp.418-425
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• 2021

Submarines are weapons systems that have been proven to be useful in battle since World War I and have continued to improve the efficiency of propulsion systems in order to be used efficiently on the battlefield. In particular, countries that unable to utilize nuclear propulsion systems make efforts to increase the efficiency of Air Independent Propulsion systems, and typical examples are fuel cells, Stirling engines and MESMA. It is also expected that the development of new propulsion systems such as hydrogen-reformer fuel cells, metal-air fuel cell and direct combustion propulsion systems will continue, so the characteristics of these will be examined and the performance based on the published data be checked in this thesis.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1354-1359
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• 2014

A survey is carried out for the future energy sources to be used for ship's propulsion and ship's machinery and operations. 44 global experts from Korea, America, Norway, Denmark, Japan and German who are currently working in the shipyard and offshore fields participated at the survey. Quantitative predications on the market shares of various energy sources, such as oil, LNG, fuel cell, wind energy, solar energy and nuclear energy are made. MPI (market prediction index) is considered as a quantitative index for easy comparison between future's energy sources used for ship's propulsion and operations. It is expected that the MPI of LNG becomes twofold in 2020 against 'before 2016'. It could be also said that hydrogen based fuel cell is expected to increase rapidly for the coming years unless a new alternative energy appears.