ASTM-C1769:2015 Edition

1.1 A sample of spent nuclear fuel is analyzed to determine the quantity and atomic ratios of uranium and plutonium isotopes, neodymium isotopes, and selected gamma-emitting nuclides (¹³⁷Cs, ¹³⁴Cs, ¹⁵⁴Eu, ¹⁰⁶Ru, and ²⁴¹Am). Fuel burnup is calculated from the ¹⁴⁸Nd-to-fuel ratio as described in this method, which uses an effective ¹⁴⁸Nd fission yield calculated from the fission yields of ¹⁴⁸Nd for each of the fissioning isotopes weighted according to their contribution to fission as obtained from this method. The burnup value determined in this way requires that values be assumed for certain reactor-dependent properties called for in the calculations (1, 2).2

1.2 Error associated with the calculated burnup values is discussed in the context of contributions from random and potential systematic error sources associated with the measurements and from uncertainty in the assumed reactor-dependent variables. Uncertainties from the needed assumptions are shown to be larger than uncertainties from the isotopic measurements, with the largest effect arising from the value of the fast fission factor. Using this factor will provide the most consistent burnup value between calculated changes in heavy element isotopic composition.

1.3 This standard practice contains explanatory notes that are not part of the mandatory portion of the standard.

1.4 The values stated in SI units are to be regarded as the standard. Mathematical equivalents are given in parentheses.

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.