Nondestructive determination of U-235 content of fuel elements

The need of specific and accurate determination of the 235U content of nuclear materials has required the testing and introduction of nondestructive gamma spectrometry for 235U determination in fuel elements. The method is based on measuring spectra of fuel elements and the respective standard using a spectrometer with a semiconductor Ge(Li) or a scintillation NaI(Tl) detector. The 235U content was determined in fuel elements with a nominal content of 2; 3; 4.4; and 80 wt.% 235U. Also studied was the possibility of determining the 238U content for computing fuel enrichment. The applicability of the method for routine in-service use is discussed. (author)