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| Fissile material | Fissile material mass mixed with moderating substances having an average hydrogen density less than or equal to H2O (grams) | Fissile material mass mixed with moderating substances having an average hydrogen density greater than H2Oa (grams) |
| 235U (X) | 60 | 38 |
| 233U (Y) | 43 | 27 |
| 239Pu or 241Pu (Z) | 37 | 24 |
| Uranium enrichment in weight percent of 235U not exceeding | Fissile material mass of 235U (X) (grams) |
| 24 | 60 |
| 20 | 63 |
| 15 | 67 |
| 11 | 72 |
| 10 | 76 |
| 9.5 | 78 |
| 9 | 81 |
| 8.5 | 82 |
| 8 | 85 |
| 7.5 | 88 |
| 7 | 90 |
| 6.5 | 93 |
| 6 | 97 |
| 5.5 | 102 |
| 5 | 108 |
| 4.5 | 114 |
| 4 | 120 |
| 3.5 | 132 |
| 3 | 150 |
| 2.5 | 180 |
| 2 | 246 |
| 1.5 | 408 |
| 1.35 | 480 |
| 1 | 1,020 |
| 0.92 | 1,800 |