235 U/238 U isotopic ratio measurements in reference materials by using the high resolution inductively coupled plasma mass spectrometry

Uranium isotopic ratio analyses with nuclear concern is usually done by dedicated mass spectrometers, mainly those based on thermal ionization source (TIMS). In this work, a mass spectrometer using a inductively coupled plasma as a source of ions with a Nier-Johnson reverse geometry analyzer (High Resolution Inductively Couple Plasma Mass Spectrometer, Finnigan MAT Element, Bremen, Germany) was used in order to an analyze uranium compound and determine the isotopic ratios of the isotopes 235 U and 238 U. The NBS 500 certificate material (National Institute for Standards and Technology, NIST, former National Bureau of Standards, NBS) was analyzed along ten days to obtain more consistent data. The results showed good agreement with the certificate and with TIMS results, Results for NBS 200 and 030 are also presented for discrete days. (author)