Liquid−liquid solvent extraction process consists of dispersion of one phase into another in the form of fine drops and allowing the solute of interest to migrate from one phase into the other. Subsequently, it is essential to separate the two phases for further processing. In this regard, it is critical to continuously monitor the interface of two liquid phases as entrainment of one phase with another will lead to severe issues in downstream equipment and processes to follow. In this regard, an ultrasonic (UT) based online interface tracking device is developed which can detect the top layer of liquid−liquid interface (30% TBP/DD and water containing trace amounts of uranium) as well as estimate its dispersion thickness. This has been achieved using a single minimally invasive sensor. A novel signal-processing algorithm is developed to denoise and extract meaningful parameters for this estimation from the reflected and highly scattered/attenuated UT signal. The paper reports development of a mathematical model of the algorithm, experimental setup, and validation of the proposed system in a batch gravity settler.

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Redundancy is essential for achieving fault tolerance and higher dependability attributes. Redundancy by means of replication of identical units is widely used and under the assumption of random failures, it proves to be beneficial also. But common cause failures (CCFs) are threat to such redundancy schemes. With the increasing use of computerbased/electronic programmable systems in critical applications, CCFs are becoming major contributors to systems failures. The paper briefly reviews the phenomena of CCFs, its potential sources, triggering mechanisms, propagation and defence measures. It also reviews CCF models and comments on their limitations. A reactor protection system (RPS) is one of the safety critical systems in a nuclear power plant (NPP). A computer based RPS of a new NPP is taken for CCF case study. The system design is analyzed for its capability in preventing/reducing potential sources, triggering mechanisms and barriers against propagation of CCFs. The paper compares the CCF defence mechanisms employed in the new RPS along with two other recent RPSs of two reputed NPPs -AP1000 and Areva.