1.1 This test method covers the determination of the heavy element atom percent fission in irradiated uranium (U) fuel with initial plutonium (Pu) content from 0 to 50% from isotopic analyses of the fuel before and after irradiation (1,2).

1.2 The test method specifies the computational procedures for handling mass spectrometric analyses. Chemical separation procedures and mass spectrometer operation procedures are specified in Test Method E267.

1.3 The test method is applicable to thermal-reactor U and Pu fuels but does not apply to fuels containing thorium or U before irradiation.

1.4 The determination of burnup from changes in isotopic composition has several requirements that limit its usefulness and accuracy. The most obvious requirement is the availability of a pre-irradiation specimen which truly represents the sample to be analyzed. A second limiting requirement is the availability of correct neutron-spectrum-dependent reactor parameters, especially capture-to-fission ratios for U, Pu, and Pu. Finally, many additional factors implicitly assumed to be negligible in this treatment become significant at high exposures.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.