The International Atomic Energy Agency (IAEA) has deployed the On-Line Enrichment Monitor (OLEM) to measure the 235U enrichment of UF6 gas flowing in header pipes in gaseous centrifuge enrichment plants. A next generation prototype OLEM has been developed to alleviate a challenge with accounting for deposits on the interior of the pipe. Deposits have the same radiometric signature as the UF6 gas and are indistinguishable in the current OLEM. The current analysis approach estimates the deposit contribution by extrapolation of radiation detector response as a function of the UF6 gas process, typically a two-step analysis process. Using a modified dual-collimator approach with an array of cadmium-zinc-telluride (CZT) detectors, a next generation OLEM prototype has been built and performance demonstrated in a lab environment. The system provides real-time measurement of the UF6 gas and deposits separately, potentially increasing precision and reducing analysis time. This next-generation OLEM also is smaller, with about half the size and weight of the current OLEM. This paper will provide an overview of the prototype design and the results of measurements in the lab.