Enrichment Measurement with the On-Line Enrichment Monitor (OLEM)

The International Atomic Energy Agency (IAEA) has recently deployed advanced On-Line Enrichment Monitors (OLEM) to monitor the enrichment of UF6 gas in centrifuge-type enrichment facilities for safeguard purposes. The OLEM is a culmination of several years of development by the US Support Program and the US Department of Energy, where prototypes were developed and tested, and continue to be tested, in gas centrifuge enrichment facilities. The IAEA developed robust field systems based on the prototypes, incorporating the standard IAEA approaches for physical and data security, and an initial installation of several collection nodes has been performed. The OLEM is an advanced design reducing the challenges associated with previous on-line meters and providing higher measurement precision. The OLEM approach does not use radiation sources and is designed to be installed outside cascade halls, allowing easier access for installation and maintenance. The OLEM uses a gamma-ray spectrometer to measure the 186 keV emissions of 235U and along with pressure and temperature measurements, calculates the 235U concentration of the UF6 gas. The OLEM delivers a high precision measurement capability in an unattended manner, which provides continuous assurance on the enrichment level of the UF6 gas. Depending on the safeguards approach, the OLEM can measure the feed stock going into the cascade hall, and the enriched material (product) and depleted material (tails) coming out of the cascade hall. Knowing the enrichment levels of flows in and out of the cascade hall can support near real time uranium-235 mass balance estimations, when combined with mass or flow measurements. This paper will provide information on the development, initial deployment, and experience gained to date.