Table 1.
Top part: chain fission yield (per 100 fissions) for mass series that show less than 7.5% difference between 235U and 239Pu (thermal spectrum fissions), and less than 30% when including 241Pu (thermal spectrum fissions) and 238U (fast spectrum fissions). Bottom part: same values for the other Nd isotopes used as burnup indicators at SCK CEN. Source of numerical data: [34].
| Atomic | 235U thermal | 239Pu thermal | 241Pu thermal | 238U fission | Difference | Max difference | Comment |
|---|---|---|---|---|---|---|---|
| mass series | spectrum | spectrum | spectrum | spectrum | 235U-239Pu | w.r.t. 235U | |
| 98 | 5.7903 | 5.830892 | 5.035685 | 5.944993 | 1% | 16% | (a) |
| 99 | 6.109164 | 6.211806 | 5.961885 | 6.168192 | 2% | 4% | (a) |
| 133 | 6.699915 | 7.016466 | 6.72919 | 6.762707 | 5% | 5% | (b) |
| 134 | 7.872644 | 7.676881 | 7.917365 | 7.609406 | 3% | 4% | (b), (c) |
| 137 | 6.188944 | 6.613842 | 6.650911 | 6.052506 | 7% | 9% | (d) |
| 148 | 1.673660 | 1.642120 | 1.932103 | 2.112485 | 2% | 26% | |
| 143 | 5.956198 | 4.413261 | 4.577993 | 4.622060 | 30% | 32% | |
| 144 | 5.499964 | 3.739785 | 4.227384 | 4.547939 | 38% | 39% | |
| 143+144 | 11.45616 | 8.153046 | 8.805377 | 9.169999 | 34% | 35% | |
| 145 | 3.933647 | 2.986310 | 3.262911 | 3.808983 | 27% | 27% | |
| 146 | 2.997113 | 2.458146 | 2.766456 | 3.445628 | 20% | 34% | |
| 145+146 | 6.93076 | 5.444456 | 6.029367 | 7.254611 | 24% | 28% | |
| 150 | 0.653325 | 0.967459 | 1.209439 | 1.273456 | 39% | 60% | (e) |
(a) 98Mo or 99Tc are difficult to dissolve; (b) the monoisotopic natural abundance of 133Cs means that suitable Cs isotopic reference materials are hardly available, without which the calibrated isotopic ratio measurements (having the low uncertainties characteristic of IDMS) are not possible determine with a low uncertainty, it has also a non-negligible cross-section and forms 134Cs upon neutron capture; (c) the decay chain along the mass series 134 is blocked by 134Xe that escapes upon sample preparation and dissolution; (d) 137Cs migration and in-pile decay should be properly accounted for; (e) mass 150 has a low fission yield.
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