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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Nuclear Engineering and Technology
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Journal DOI :
Korean Nuclear Society
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Volume & Issues
Volume 37, Issue 6 - Dec 2005
Volume 37, Issue 5 - Oct 2005
Volume 37, Issue 4 - Aug 2005
Volume 37, Issue 3 - Jun 2005
Volume 37, Issue 2 - Apr 2005
Volume 37, Issue 1 - Feb 2005
Selecting the target year
ORGANIZATIONAL CONTRIBUTIONS TO NUCLEAR POWER PLANT SAFETY
GHOSH S. TINA ; APOSTOLAKIS GEORGE E. ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 207~220
Nuclear power plants (NPP) are complex socio-technological systems that rely on the success of both hardware and human components. Empirical studies of plant operating experience show that human errors are important contributors to accidents and incidents, and that organizational factors play an important role in creating contexts for human errors. Current probabilistic safety assessments (PSA) do not explicitly model the systematic contribution of organizational factors to safety. As some countries, like the United States, are moving towards increased use of risk information in the regulation and operation of nuclear facilities, PSA quality has been identified as an area for improvement. The modeling of human errors, and underlying organizational weaknesses at the root of these errors, are important sources of uncertainty in existing PSAs and areas of on-going research. This paper presents a review of research into the following questions: Is there evidence that organizational factors are important to NPP safety? How do organizations contribute to safety in NPP operations? And how can these organizational contributions be captured more explicitly in PSA? We present a few past incidents that illustrate the potential safety implications of organizational deficiencies, some mechanisms by which organizational factors contribute to NPP risk, and some of the methods proposed in the literature for performing root-cause analyses and including organizational factors in PSA.
TECHNOLOGY-NEUTRAL NUCLEAR POWER PLANT REGULATION: IMPLICATIONS OF A SAFETY GOALS- DRIVEN PERFORMANCE-BASED REGULATION
MODARRES MOHAMMAD ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 221~230
This paper reviews the pivotal phases of the evolution of the current technology-dependent nuclear power safety regulation in the United States. Understanding of this evolution is essential to the development of any future regulatory paradigm, including the technology-neutral regulatory approach that the U.S. Nuclear Regulatory Commission (NRC) has recently embarked on to develop. The paper proposes and examines the implications of a predominately rationalist and best-estimate probabilistic regulatory framework called safety goals-driven performance-based regulation. This framework relies on continuous assessment of performance of a set of time-dependent safety-critical systems, structures and components that assure attainment of a broad set of technology-neutral protective, mitigative, and preventive goals. Finally, the paper discusses the steps needed to develop a corresponding technology-neutral regulatory system from the proposed framework.
ISSUES IN FORMULATING PERFORMANCE-BASED APPROACHES TO REGULATORY OVERSIGHT OF NUCLEAR POWER PLANTS
YOUNGBLOOD R. W. ; KIM I. S. ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 231~244
In recent decades, significant effort has led to risk-informed improvements to regulation. Performance-based approaches also promise significant gains in efficiency (level of safety versus effort). However, significant work remains to be done before performance-based approaches realize their full potential in regulation of nuclear power plants. This paper reviews key concepts related to performance-based regulation, discusses some applications of performance-based approaches, and identifies issues that still need to be addressed. Realistic, experience-based models of licensee performance are still lacking; this makes it difficult to assess the prospective effectiveness of any given regulatory approach, in light of the performance issues that it will actually face. Also, while 'compliance' is an intuitively straightforward concept to apply within a prescriptive implementation, its analog in a performance-based approach remains unclear. An overarching theme of the paper is that formal methods of decision analysis are very helpful in developing appropriate regulatory approaches, especially performance-based ones; this theme is illustrated at several points.
UNCERTAINTY AND SENSITIVITY STUDIES WITH THE PROBABILISTIC ACCIDENT CONSEQUENCE ASSESSMENT CODE OSCAAR
HOMMA TOSHIMITSU ; TOMITA KENICHI ; HATO SHINJI ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 245~258
This paper addresses two types of uncertainty: stochastic uncertainty and subjective uncertainty in probabilistic accident consequence assessments. The off-site consequence assessment code OSCAAR has been applied to uncertainty and sensitivity analyses on the individual risks of early fatality and latent cancer fatality in the population outside the plant boundary due to a severe accident. A new stratified meteorological sampling scheme was successfully implemented into the trajectory model for atmospheric dispersion and the statistical variability of the probability distributions of the consequence was examined. A total of 65 uncertain input parameters was considered and 128 runs of OSCAAR with 144 meteorological sequences were performed in the parameter uncertainty analysis. The study provided the range of uncertainty for the expected values of individual risks of early and latent cancer fatality close to the site. In the sensitivity analyses, the correlation/regression measures were useful for identifying those input parameters whose uncertainty makes an important contribution to the overall uncertainty for the consequence. This could provide valuable insights into areas for further research aiming at reducing the uncertainties.
THE APPLICATION OF PSA TECHNIQUES TO THE VITAL AREA IDENTIFICATION OF NUCLEAR POWER PLANTS
HA JAEJOO ; JUNG WOO SIK ; PARK CHANG-KUE ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 259~264
This paper presents a vital area identification (VAI) method based on the current fault tree analysis (FTA) and probabilistic safety assessment (PSA) techniques for the physical protection of nuclear power plants. A structured framework of a top event prevention set analysis (TEPA) application to the VAI of nuclear power plants is also delineated. One of the important processes for physical protection in a nuclear power plant is VAI that is a process for identifying areas containing nuclear materials, structures, systems or components (SSCs) to be protected from sabotage, which could directly or indirectly lead to core damage and unacceptable radiological consequences. A software VIP (Vital area Identification Package based on the PSA method) is being developed by KAERI for the VAI of nuclear power plants. Furthermore, the KAERI fault tree solver FTREX (Fault Tree Reliability Evaluation eXpert) is specialized for the VIP to generate the candidates of the vital areas. FTREX can generate numerous MCSs for a huge fault tree with the lowest truncation limit and all possible prevention sets.
GOTHIC-3D APPLICABILITY TO HYDROGEN COMBUSTION ANALYSIS
LEE JUNG-JAE ; LEE JIN-YONG ; PARK GOON-CHERL ; LEE BYUNG-CHUL ; YOO HOJONG ; KIM HYEONG-TAEK ; OH SEUNG-JONG ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 265~272
Severe accidents in nuclear power plants can cause hydrogen-generating chemical reactions, which create the danger of hydrogen combustion and thus threaten containment integrity. For containment analyses, a three-dimensional mechanistic code, GOTHIC-3D has been applied near source compartments to predict whether or not highly reactive gas mixtures can form during an accident with the hydrogen mitigation system working. To assess the code applicability to hydrogen combustion analysis, this paper presents the numerical calculation results of GOTHIC-3D for various hydrogen combustion experiments, including FLAME, LSVCTF, and SNU-2D. In this study, a technical base for the modeling oflarge- and small-scale facilities was introduced through sensitivity studies on cell size and bum modeling parameters. Use of a turbulent bum option of the eddy dissipation concept enabled scale-free applications. Lowering the bum parameter values for the flame thickness and the bum temperature limit resulted in a larger flame velocity. When applied to hydrogen combustion analysis, this study revealed that the GOTHIC-3D code is generally able to predict the combustion phenomena with its default bum modeling parameters for large-scale facilities. However, the code needs further modifications of its bum modeling parameters to be applied to either small-scale facilities or extremely fast transients.
THE IMPROVEMENT OF NUCLEAR SAFETY REGULATION: AMERICAN, EUROPEAN, JAPANESE, AND SOUTH KOREAN EXPERIENCES
CHO BYUNG-SUN ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 273~278
Key concepts in South Korean nuclear safety regulation are safety and risk. Nuclear regulation in South Korea has required reactor designs and safeguards that reduce the risk of a major accident to less than one in a million reactor-years-a risk supposedly low enough to be acceptable. To date, in South Korean nuclear safety regulation has involved the establishment of many technical standards to enable administration enforcement. In scientific lawsuits in which the legal issue is the validity of specialized technical standards that are used for judge whether a particular nuclear power plant is to be licensed, the concept of uncertainty law is often raised with regard to what extent the examination and judgment by the judicial power affects a discretion made by the administrative office. In other words, the safety standards for nuclear power plants has been adapted as a form of the scientific technical standards widely under the idea of uncertainty law. Thus, the improvement of nuclear safety regulation in South Korea seems to depend on the rational lawmaking and a reasonable, judicial examination of the scientific standards on nuclear safety.
RESEARCH ON LASER-ACCELERATED PROTON GENERATION AT KAERI
PARK SEONG HEE ; LEE KITAE ; CHA YOUNG HO ; JEONG YOUNG UK ; BAIK SUNG HOON ; YOO BYUNG DUK ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 279~286
A prototype of a relativistic proton generation system, based on laser-induced plasma interaction, has been designed and fabricated. The system is composed of three major parts: a fs TW laser; a target chamber, including targets and controls; and a diagnostic system for charged particles and lasers. An Offner-type pulse stretcher for chirped pulse amplification (CPA) and eight pass pre-amplifier are installed. The main amplifier will be integrated with a new pumping laser. The design values of the laser at the first stage are 1 TW in power and 50 fs in pulse duration. We expect to generate protons with their maximum energy of approximately 3 MeV and the flux of at least
per pulse using a 10
m Al target. A prototype target chamber with eight 8-inch flanges, including target mounts, has been designed and fabricated. For laser diagnostics, an adaptive optics based on the Shack-Hartmann type, beam monitoring, and alignment system are all under development. For a charged particle, CR-39 detectors, a Thomson parabola spectrometer, and Si charged-particle detectors will be used for the density profile and energy spectrum. In this paper, we present the preliminary design for laser-induced proton generation. We also present plans for future work, as well as theoretical simulations.
ON THE CREEP PROPERTY OF URANIUM DIOXIDE
RHEE YOUNG WOO ; KANG KI WON ; KIM KEON SIK ; YANG JAE HO ; KIM JONG HEON ; SONG KUN WOO ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 287~292
]The effects of silica-based additives have been investigated to improve the creep property of a
pellet. The additive composition,
(SCC), was selected according to the dihedral angle and the distribution of the second phase. It was observed that the creep rate of the
was slower than that of the pure
. However, the creep rate of the
was about 3_48 times faster than that of the pure
, depending on the applied stress in the lower stress range. In the case of the
, the creep rate decreased in comparison with that of the
. The observed enhancement in the creep rate might depend on a balance between the positive role of the viscous intergranular phase and the negative roles of the additives and the grain growth.
AB INITIO CALCULATIONS OF STRONGLY CORRELATED ELECTRONS: ANTIFERROMAGNETIC GROUND STATE OF
YUN YOUNSUK ; KIM HANCHUL ; KIM HEEMOON ; PARK KWANGHEON ;
Nuclear Engineering and Technology, volume 37, issue 3, 2005, Pages 293~298
We have performed the density functional theory calculations of
using the spin-polarized generalized gradient approximation (SP-GGA) and the SP-GGA+U approach. The SP-GGA+U approach correctly predicts the insulating electronic structure with antiferromagnetic ordering, but the SP-GGA calculations predict metallic behavior. The cohesive properties obtained from the SP-GGA+U calculations are in good agreement with the available experimental results and previous calculations. The spin-polarized local density of states shows that the antiferromagnetic ordering of
is governed by 5f orbitals of uranium ion. Our calculations demonstrate that the strong correlation of U 5f electrons should be taken into account for a reliable description of