Utilization of SCC Technology for Large Placements in New Nuclear Construction: A Study On SCC Stability and Constructability

This paper discusses the use of Self Consolidating Concrete (SCC), in a large scale placement during new nuclear plant construction. SCC has provided cost and labor savings and construction process improvements. Use of SCC has been effective in schedule acceleration by reducing placement durations and early curing termination with rapid strength gain. Self-consolidating properties were particularly of value at placements of poor access as internal vibrators were not effective and large surface area made form vibrators ineffective beyond the perimeter. This paper provides a discussion of technical challenges encountered in development of a properly functioning SCC mixture, and testing performed to overcome these challenges. The paper discusses the engineering considerations and laboratory and field trials preparing for a 3950 cubic meter placement for the basemat of a nuclear plant. The placement was anticipated to take 35 hours at 110 m3/hour batch plant output. Overview of mix design specifications and mix development is provided. The mixture satisfied the laboratory test parameters including SCC tests; stability and column segregation. However, the mixture had to undergo rounds of constructability testing beyond laboratory development prior to the large placement. The placement was completed successfully in 35 hours over multiple shifts.

Harmonic Source Identification in Power Distribution System and Meter Placement using Network Impedance Approach

The growing use of non-linear loads in the electrical systems has made harmonics a serious problem. Harmonic disturbance leads to degradation of power quality by deforming the current or voltage waveforms, thus, necessitating the effective techniques for harmonics detection. The purpose of this study is to propose a method for a single harmonic source identification in power distribution system by implementing a network impedance technique, and optimize the meters allocation by optimum meter placement algorithm (OMPA). The main advantage of this technique is that it results in enhanced accuracy with minimum vulnerability towards deviations in the measurements. Moreover, it minimizes the number of nodes for meter allocations, thereby resulting in economic advantages. To validate the results and effectiveness of the proposed methodology, a standard IEEE 13-Bus industrial network is designed using ETAP software and the algorithm is developed in MATLAB software. The validation of proposed algorithm OMPA is done by comparing its results with Monte Carlo Algorithm (MCA) technique. The results show that without any deviation in the network impedances, OMPA gives 89% accuracy as compared to 75% accuracy of MC. With the deviations in the harmonic impedances, the accuracy of both algorithms is decreased. For the deviation value ꝺ = 1-13 in the harmonic impedances, the overall accuracy of OMPA stays at 75%, while that of MCA drops down to 56%. The developed algorithm OMPA is not only better in performance in harmonics identification with minimum number of meters, but also shows more resistance to the variations in the harmonic impedances as compared to MCA.