# Table 4 Change in weighted isotopic composition from removal of 1 kg of U-235 or Pu-239

Reactor Change in weighted isotopic composition for removal of 1 kg from mass inventory of Relative change in U-235+Pu-239+Pu-241 mass (%)
U-235 Pu-239
NRU 0.0393 0.0523 3.84
Molten salt reactor (MSR) 0.00962 0.0127 0.911
High temperature gas reactor (HTGR) 0.00609 0.00802 0.570
1. The change in weighted isotopic composition is compared against the corresponding relative change in total sum of U-235, Pu-239, and Pu-241 fissile mass inventories. The MSR and HTGR cases are computed after 1 year of burn-up; the NRU case is computed from data during the 2016/09 to 2016/10 time period