• Nuclear Engineering and Technology
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• v.39 no.4
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• pp.257-272
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• 2007

Supercritical water-cooled reactors (SCWRs) are recognized as a Generation IV reactor concept. The Super LWR is a pressure-vessel type thermal spectrum SCWR with downward-flow water rods and is currently under study at the University of Tokyo. This paper reviews Super LWR safety. The fundamental requirement for the Super LWR, which has a once-through coolant cycle, is the core coolant flow rate rather than the coolant inventory. Key safety characteristics of the Super LWR inhere in the design features and have been identified through a series of safety analyses. Although loss-of-flow is the most important abnormality, fuel rod heat-up is mitigated by the "heat sink" and "water source" effects of the water rods. Response of the reactor power against pressurization events is mild due to a small change in the average coolant density and flow stagnation of the once-through coolant cycle. These mild responses against transients and also reactivity feedbacks provide good inherent safety against anticipated-transient-without-scram (ATWS) events without alternative actions. Initiation of an automatic depressurization system provides effective heat removal from the fuel rods. An "in-vessel accumulator" effect of the reactor vessel top dome enhances the fuel rod cooling. This effect enlarges the safety margin for large LOCA.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.47-58
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• 2019

The paper presents the results of a multi-criteria comparative evaluation of 12 feasible Russian nuclear energy deployment scenarios with thermal and fast reactors in a closed nuclear fuel cycle. The comparative evaluation was performed based on 6 performance indicators and 5 different MCDA methods (Simple Scoring Model, MAVT / MAUT, AHP, TOPSIS, PROMETHEE) in accordance with the recommendations elaborated by the IAEA/INPRO section. It is shown that the use of different MCDA methods to compare the nuclear energy deployment scenarios, despite some differences in the rankings, leads to well-coordinated and similar results. Taking into account the uncertainties in the weights within a multi-attribute model, it was possible to rank the scenarios in the absence of information regarding the relative importance of performance indicators and determine the preference probability for a certain nuclear energy deployment scenario. Based on the results of the uncertainty/sensitivity analysis and additional analysis of alternatives as well as the whole set of graphical and attribute data, it was possible to identify the most promising nuclear energy deployment scenario under the assumptions made.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4062-4071
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• 2022

Long-term aluminum (Al) corrosion tests were designed to investigate the condition that would generate severe Al corrosion and precipitation. Buffer agents of sodium tetraborate (NaTB), trisodium phosphate (TSP) and sodium hydroxide (NaOH) were adopted. The insulation materials, fiberglass and calcium silicate (Ca-sil), were examined to explore their effects on Al corrosion. The results show that significant precipitates were formed in both NaTB/TSP-buffered solutions at high pH. The precipitates formed in NaTB solution raise more concerns on chemical effects in GSI-191. A passivation layer formed on the surfaces of coupon in solution with the presence of insulations could effectively mitigate Al corrosion. The Fe-enriched intermetallic particles (IPs) embedded in coupon appeared to serve as seeds to readily induce precipitation via providing extra area for heterogeneous Al hydroxide precipitation. X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses indicate that the precipitates are mainly boehmite (γ-AlOOH) and no direct evidence confirms the presence of sodium aluminum silicate or calcium phosphate.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.358-366
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• 2023

Due to the International Maritime Organization's (IMO) environmental regulations on NOx and SOx, LNG-fueled eco-friendly ships are gaining attention worldwide, and various eco-friendly ships are being proposed and demanded for conversion to eco-friendly ships in Korea, as the eco-friendly ship law has recently been enforced. In this study, the initial basic design was performed to convert an existing Marine Gas Oil (MGO) fueled ship into an LNG-DF propulsion ship, targeting medium-sized ship, to select the fuel tank capacity and main dimensions and appropriate fuel ratio between the two fuels. In particular, Sustainable basic design method considering environmental impact were proposed by performing a Life Cycle Assessment (LCA) throughout the design process, and various design options were compared and analyzed to meet different design conditions by applying them.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.855-865
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• 2024

Commercial deployment of nuclear microreactors presents an opportunity for the industry to rethink its approach to manufacturing, siting, operation and maintenance, and fuel cycle management as certain principles used in grid-scale nuclear projects are not applicable to a decentralized microreactor economy. The success of this nascent industry is dependent on its ability to reduce infrastructure, logistical, regulatory and lifecycle costs. A utility-like 'Central Facility' that consolidates the services required and responsibilities borne by vendors into one or a few centralized locations will be necessary to support the deployment of a fleet of microreactors. This paper discusses the requirements for a Central Facility, its implications on the cost structures of owners and suppliers of microreactors, and the impact of the facility for the broader microreactor industry. In addition, this paper discusses the pre-requisites for eligibility as well as the opportunities for a Central Facility host site. While there are many suitable locations for such a capability across the U.S., this paper considers a facility co-located with the Vogtle Nuclear Power Plant and Savannah River Sites to illustrate how a Central Facility can leverage the existing infrastructure and stimulate a local ecosystem.

• Nuclear Engineering and Technology
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• v.52 no.3
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• pp.499-507
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• 2020

Research reactors for radioisotope production, fuel and material testing and research activities are designed, constructed and operated based on the society's needs. In this study, neutronic and thermal hydraulic design of a high neutron flux research reactor core for radioisotope production is presented. Main parameters including core excess reactivity, reactivity variations, power and flux distribution during the cycle, axial and radial power peaking factors (PPF), Pu₂₃₉ production and minimum DNBR are calculated by nuclear deterministic codes. Core calculations performed by deterministic codes are validated with Monte Carlo code. Comparison of the neutronic parameters obtained from deterministic and Monte Carlo codes indicates good agreement. Finally, subchannel analysis performed for the hot channel to evaluate the maximum fuel and clad temperatures. The results show that the average thermal neutron flux at the beginning of cycle (BOC) is 1.0811 × 10¹⁴ n/㎠-s and at the end of cycle (EOC) is 1.229 × 10¹⁴ n/㎠-s. Total Plutonium (Pu₂₃₉) production at the EOC evaluated to be 0.9487 Kg with 83.64% grade when LEU (UO₂ with 3.7% enrichment) used as fuel. This designed reactor which uses LEU fuel and has high neutron flux and low plutonium production could be used for peaceful nuclear activities based on nuclear non-proliferation treaty concepts.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.4
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• pp.271-282
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• 2015

External cost is cost imposed on a third party when producing or consuming a good or service. Since the 1990s, the external costs of nuclear powered electricity production have been studied. Costs are a very important factor in policy decision and the external cost is considered for cost comparison on electricity production. As for nuclear fuel cycle, a chosen technology will determine the external cost. However, there has been little research on this issue. For this study, methods for external cost on nuclear power production have been surveyed and analyzed to develop an approach for evaluating external cost on nuclear fuel cycles. Before the Fukushima accident, external cost research had focused on damage costs during normal operation of a fuel cycle. However, accident cost becomes a major concern after the accident. Various considerations for external cost including accident cost have been used to different studies, and different methods have been applied corresponding to the considerations. In this study, the results of the evaluation were compared and analyzed to identify methodological applicability to the external cost estimation with nuclear fuel cycles.

• Nuclear Engineering and Technology
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• v.54 no.9
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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.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.369-376
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• 2018

The ability to recover the nearly limitless supply of uranium contained within the world's oceans would provide supply security to uranium based fuel cycles. Therefore, in addition to U.S. national laboratories conducting R&D on a system capable of harvesting seawater uranium, a number of collaborative university partners have developed alternative technologies to complement the national laboratory scheme. This works summarizes the systems analysis of such novel uranium recovery technologies along with their potential impacts on seawater uranium recovery. While implementation of some recent developments can reduce the cost of seawater uranium by up to 30%, other researchers have sought to address a weakness while maintaining cost competitiveness.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.1
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• pp.79-88
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• 1983

A prediction of emission concentrations was made by calculating chemical equilibrium on the basis of an indicated pressure diagram in spark ignition engine using methanol as a fuel. A prediction according to Otto cycle was also made and for carbon dioxide, carbon monoxide and nitric oxide, emission test was performed using a conventional SI engine that was modified a little considering fuel characteristics. An investigation was made for those three cases-results from an indicated pressure diagram, Otto cycle and emission test. A good agreement between the measured values and the predicted ones existed for carbon dioxide and carbon monoxide, but not for nitric oxide. And good results existed for the other emission concentrations.