Year
2008
Abstract
Currently, the IAEA verifies the 235U material balance at enrichment facilities using destructive analysis (DA). Although very accurate, this procedure involves long delivery periods and is very costly and cumbersome as it requires the shipment of UF6 samples to the IAEA Safeguards Analytical Laboratory at Seibersdorf, Austria. An experimental Tunable Diode Laser Spectroscopy (TDLS) measurement system dedicated to determination of enrichment in UF6 gas was recently proven to be capable of achieving levels of accuracy comparable to DA. The UF6 TDLS operates by measuring the absorption caused by UF6 gas in a measurement cell in the spectral region of 1290-1296 ?m-1 to determine the linear convolution of the 235UF6 and 238UF6 concentrations fitting the observed absorption. Unlike many other molecules, the UF6 absorption spectrum has a wide range and no absorption peak ratio technique can be used. The absorption measurement needs to be absolute and thus requires extreme levels of stability, in particular in the control of the laser temperature. The TDLS technology can be embedded in a transportable instrument (UF6 Laser System: UFLS) and left resident at a facility so that inspectors are able to perform in situ analyses. Scientific work continues at the General Physics and Kurchatov Institutes in Moscow in an effort to improve the performance, safety and ease of operation of the UFLS. Improved lasers with larger wavelength ranges and better temperature stability will be integrated into the existing experimental set up. Further development work is underway to optimize the design of the gas handling line and measurement cell to minimize the memory effect, thus reducing/decreasing the time between measurements and simplifying cleaning operations. The design modifications will also improve the compactness of the optical path and reduce possible external interference emanating for example from the presence of humidity or temperature fluctuations. Once the technology has matured sufficiently, the manufacturing of UFLS will be undertaken to industrial standards with the aim of installing UFLS at enrichment plants under IAEA safeguards by 2010