ASTM C1769-15
为测定选定同位素以及评估燃料燃耗的废核燃料分析的标准实施规程

Standard Practice for Analysis of Spent Nuclear Fuel to Determine Selected Isotopes and Estimate Fuel Burnup

标准号

ASTM C1769-15

发布

2015年

发布单位

美国材料与试验协会

当前最新

ASTM C1769-15

 

 

引用标准

ASTM C1625 ASTM C859 ASTM D1193 ASTM E244

适用范围

5.1 This standard practice defines a measure of heavy element atom percent fission from which the output of heat during irradiation can be estimated.

5.2 This standard practice is restricted in use to samples where accurate pre-irradiation U and Pu isotopic analysis is available. This data should be available from the fuel manufacture.

5.3 The contribution of ²³⁸U fast fission is not subject to measurement from isotopic analysis. For reactors in which the majority of fissions are caused by thermal neutrons, the contribution may be estimated from the fast fission factors, ε, found in each reactor design document.

5.4 In post-irradiation isotopic analysis, take extreme care to avoid environmental uranium contamination of the sample. This is simplified by using sample sizes in which the amount of each uranium isotope is more than 1000 times the levels observed in a blank carried through the complete chemistry and mass spectrometry procedure employed.

5.5 Take care to make sure that both the pre-irradiation and the post-irradiation samples analyzed are representative. In the pre-irradiation fuel, the ²³⁵U and ²³⁶U atom ratio content may vary from lot to lot. ²³⁶U is not found in naturally uranium in measurable quantity (<2 ppm of a u basis) but forms during irradiation and increases with each successive pass through the fuel cycle. In the post-irradiation examination of a large fuel element, the atom percent fission normally varies radially and axially. Radial and axial profiles of atom percent fission can be determined by analyzing samples obtained from along the radius or axis of the fuel element. An average value of atom percent fission can be obtained by totally dissolving the fuel to be averaged, and then mixing and analyzing an aliquot of the resultant solution.

5.6 The burnup of an irradiated nuclear fuel can be determined from the amount of a fission product formed during irradiation. Among the fission products, ¹⁴⁸Nd has the following properties to recommend it as an ideal burnup indicator: (1) It is not volatile. (2) It does not migrate in solid fuels below their recrystallization temperature. (3) It has no volatile precursors. (4) It is nonradioactive and requires no decay corrections. (5) It has a low destruction cross section. (6) Formation of ¹⁴⁸Nd from adjacent mass chains can be corrected for. (7) It has adequate emission characteristics for mass analysis. (8) Its fission yield is nearly equivalent for ²³⁵U and ²³⁹Pu. (9) Its fission yield is essentially independent......

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