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[en] Conclusions: Proposed V-1 ALS can cope with 2 x DN 500 DBA. Work on V-1 ALS able to cope with DN 200 DBA and to mitigate DN 500 BDBA will have been finished by April 1994. Further leaktightness improvements are going on on the V-1 HZ boundary during outages with the aim to reduce the existing leak rate by 50%
[en] With the increasing economic pressures being faced and the potential for shortening outage times under the conditions of deregulated electricity markets in the world, licensees are motivated to get an increasing amount of the on-line maintenance (OLM). The benefits of the OLM includes increased system and plant reliability, reduction of plant equipment and system material condition deficiencies that could adversely impact operations, and reduction of work scope during plant refueling outages. NUMARC 93-01 presents OLM and it provides plan for analysis of reactor safety and risk assessment, and it approves selection of out of service (OOS) for single and multiple structure, systems, and components (SSCs) by performing appropriate risk assessment in quantitative and qualitative ways
[en] Controlled islanding is considered to be the last countermeasure to prevent a system-wide blackout in case of cascading failures. It splits the system into self-sustained islands to maintain transient stability at the expense of possible loss of load. Generator coherence identification is critical to controlled islanding scheme as it helps identify the optimal cut-set to maintain the transient stability of the post-islanding systems. This paper presents a novel approach for online generator coherency identification using phasor measurement unit (PMU) data and dynamic time warping (DTW). Results from the coherence identification are used to further cluster non-generator buses using spectral clustering with the objective of minimizing power flow disruptions. The proposed approach is validated and compared to existing methods on the IEEE 39-bus system and WECC 179-bus system, through which its advantages are demonstrated.
[en] We quantify the impact of refinery outages on petroleum product prices. The empirical analysis focuses on wholesale gasoline prices in the US using weekly data collected from January 2002 through September 2008, a period including many refinery outages. We match refinery unit output to specific wholesale gasoline markets, and then estimate panel data regressions to quantify the impact of refinery unit outages on wholesale gasoline prices while controlling for time-specific effects, city-specific effects, fuel-specific effects, refinery concentration, and other factors that could impact the price of refined petroleum products. The estimation results show that refinery outages have a statistically significant positive impact on refined product prices, and that the magnitude of this effect is larger for certain special fuel blends. Policy implications are discussed. (author)
[en] The recent ''station blackout'' (ie loss of on-site and off-site AC power) incidents at the Vogtle PWR in the US and Hinkley Point B AGR in the Uk have led to further public concern about the safety of nuclear power, even though in each case the actual increase in the chance of an accident leading to a release of radioactivity to the environment was negligible. The industry may be wise to invest precautionary measures to reduce the frequency of such incidents and to increase public confidence. (author)
[en] Planned outages at Asea-Atom boiling water reactors in Scandinavia are remarkably short and efficient by world standards, and their duration is getting shorter. The reasons behind this achievement are examined, and the ingredients of a successful outage are described. (author)
[en] This paper investigates the impact of opportunistic maintenance strategy on power equipment maintenance scheduling under economic dependence. The model focuses on power equipment with two types of failures: random failure and deterioration failure. Unlike previous research which didn’t consider opportunistic maintenance between different failures modes, opportunistic maintenance strategy is proposed in this paper. In the opportunistic maintenance strategy, whenever random failure occurs, decision has to be made on whether deterioration failure is preventively maintained based on the degree of equipment deterioration and economic dependence. Firstly, Markov process is used to describe equipment state-space diagram. And then, in order to determine the optimal inspection rate, preventive maintenance threshold and opportunistic maintenance threshold of power equipment, the analytical expressions of inspection cost, maintenance cost, repair cost and outage cost are quantified. Finally, the total cost is minimized to get the optimal maintenance strategy. Case studies demonstrate the feasibility of the proposed model. (paper)
[en] Introducing heterogeneous networks as a solution for increasing capacity and data rate in cellular networks faces several challenges to be addressed by network designers. Among them, interference is an important issue leading to the reduction in coverage probability or equivalently, the increase in outage probability. Hence, development of schemes that increase the coverage probability in networks seems essential. In this paper, a power control algorithm based on Poisson Point Process (PPP) is proposed to increase the coverage probability in networks. PPP has been shown to accurately model real networks. We provide numerical results to show that our proposed power control algorithm converges to an optimal point and increases the coverage probability, compared to previous works that apply constant transmit power for each tier of the network.
[en] With the increasing economic pressures being faced and the potential for shortening outage times under the conditions of deregulated electricity markets in the world, licensees are motivated to get an increasing amount of online maintenance (OLM). OLM means a kind of planned maintenance of nuclear reactor facilities, including structure, systems, and components (SSCs), during power operation. In Korea, a similar situation is made up, so it needs to establish a regulatory framework for OLM. A few years ago, foreign countries' practices related to OLM were surveyed by the Working Group on Inspection Practices (WGIP) of OECD/NEA/CNRA. The survey results and additional new information of countries' status will be helpful to establish our own regulatory framework for OLM, which are analyzed in this paper. From the analysis, some considerable points to be addressed for establishing a regulatory framework for OLM are suggested
[en] The target of the paper is to turn the attention of the specialists into several directions connected with the NPP outage. The first direction is connected with the outage contribution to the NPP safety. The second one is connected with the way of thinking and the approaches used for the analysis and planning of the maintenance activities during the outage. The third one is connected with the knowledge and practice which can be used for scientific basis of the NPP safety during outage. The knowledge and experience in this field can be used in the other branches of the industry, where the requirements to reliability and safety are high