This study presents a Kalman filter-based framework to establish a real-time in situ monitoring system for groundwater contamination based on in situ measurable water quality variables, such as specific conductance (SC) and pH. First, this framework uses principal component analysis (PCA) to identify correlations between the contaminant concentrations of interest and in situ measurable variables. It then applies the Kalman filter to estimate contaminant concentrations continuously and in real-time by coupling data-driven concentration-decay models with the previously identified data correlations. We demonstrate our approach with historical groundwater data from the Savannah River Site F-Area: We use SC and pH data to estimate tritium and uranium concentrations over time. Results show that the developed method can estimate these contaminant concentrations based on in situ measurable variables. The estimates remain reliable with less frequent or no direct measurements of the contaminant concentrations, while capturing the dynamics of short- and long-term contaminant concentration changes. In addition, we show that data mining, such as PCA, is useful to understand correlations in groundwater data and to design long-term monitoring systems. The developed in situ monitoring methodology is expected to improve long-term groundwater monitoring by continuously confirming the contaminant plume's stability and by providing an early warning system for unexpected changes in the plume's migration.

The next generation of nuclear reactors will expose materials to conditions that, in some cases, are even more extreme than those in current fission reactors, inevitably leading to new materials science challenges. Radiation-induced damage and corrosion are two key phenomena that must be understood both independently and synergistically, but their interactions are often convoluted. In the light water reactor community, a tremendous amount of work has been done to illuminate irradiation-corrosion effects, and similar efforts are under way for heavy liquid metal and molten salt environments. While certain effects, such as radiolysis and irradiation-assisted stress corrosion cracking, are reasonably well established, the basic science of how irradiation-induced defects in the base material and the corrosion layer influence the corrosion process still presents many unanswered questions. In this review, we summarize the work that has been done to understand these coupled extremes, highlight the complex nature of this problem, and identify key knowledge gaps. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

A N attractive method of accelerating very high energy particles is the arrangement in cascade, as shown in Fig. 1, of several electrostatic generators whose charging current is provided by the decay of alpha particle emitting radioactive elements. Perhaps the most suitable element is gaPo 210 which emits alpha particles of 5.3-Mev energy while decaying to stable 8 2Pb 206 . When the polonium is surrounded by an isolated metal shield, the emitted alpha particles will continue to reach the shield until it is charged to a potential equal to one-half the maximum kinetic energy of the alpha particles expressed in electron volts.For a current of 25 /*a and 2 Mev per stage, two conditions must be satisfied. If one-half of the emitted alpha particles is collected by the shield about 1 g of Po is required per stage. The second requirement restricts the loss of energy of the alpha particles in the polonium source to about 1 Mev so that the thickness of the active material on the inner sphere should not exceed about 4X10~5 cm. FIG. 1. Schematic drawing of electrostatic generator with several stages in cascade.ERS 11 AND 12 JUNE 1 AND 15, 1946 Thus the radius of the inner sphere must be bigger than 15 cm. The cost of commercially available polonium prohibits the construction of such a device. However, it appears possible that polonium can be produced from bismuth in reasonable quantities by the following reaction : l 83 Bi 209 -hwW 83 Bi 210 + 7

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