NDA MEASUREMENT OF THE ENRICHMENT OF URANIUM IN THE PRODUCT HEADER PIPES IN THE CASCADE AREA.

The gamma rays measurements on product header pipes inside the cascade areas in a gas centrifuge enrichment plant have been performed with a high resolution Ge detector. The purpose of present works is to investigate whether the NDA measurement can verify the declared enrichment level or not. The uranium deposit can be estimated from the difference in count rate of 185.7 keV gamma rays between with and without uranium gas in the product pipes. It was found that the amounts of deposit were less than those of gas phase uranium. 185.7 keV, 84.2 keV and 63.3 keV gamma rays intensities were measured to determine the enrichment. The obtained results of the count rate of 185.7 keV gamma rays were almost constant over several months. This means that the gas pressure is stable and the increasing rate of the uranium deposit is small enough. The measurement time required was at most 10 minutes. So we can conclude that the measurement of 185.7 keV gamma rays intensity gives quick indication of the no production of uranium higher than declared enrichment under the condition that the pressure of UFfi gas is constant. The measurement of the 84.2 keV and 63.3 keV gamma rays intensity would also be effective measures in determining tne enrichment of UF6 gas.