As part of a validation study of burnup calculations of BWR cores, lattice physics analyses were performed on the measured burnups and the isotopic inventories of U, Pu, and Nd isotopes of eight samples taken from 9Â9-9 BWR fuel assemblies of three and five cycles of irradiations. Burnup calculations in assembly geometry were carried out with a neutronics code system, SRAC, and a Monte Carlo burnup calculation method, MVP-BURN, based on a nuclear data library, JENDL-3.3. The measured burnups were determined based on the Nd-148 method, where the fission yield of 148 Nd, energy release per fission, and correction factors for neutron captures by 147 Nd and 148 Nd were analytically obtained by averaging with burnups. The C/Es of the sample burnups are 0.96 to 1.07 for both analysis methods. By modifying the power histories to adjust the calculated burnups to the measurements of the samples, burnup calculations were performed again and the isotope inventories were compared with the measurements. The C/Es of the inventories are 1.00 to 1.09 for 235 U, 0.91 to 1.04 for 239 Pu, 0.96 to 1.07 for 240 Pu, and 0.90 to 1.02 for 241 Pu for the six samples excluding those of a corner fuel rod.
The Na‐P1‐type zeolite having a high cation‐exchange capacity (CEC) was obtained using the waste coal fly ash from thermal power stations and a 2M NaOH solution at 100°C. The Na‐P1‐type zeolite was formed with the reaction time of 6 h at 100°C, and its CEC value increased with an increase in the reaction time. The addition of a suitable amount of NaAlO2 to the fly ash was also effective for improving the CEC value. A new composite material consisting of the Na‐P1‐type zeolite and magnetite was synthesized from the fly ash and iron chlorides because the magnetic collection was possible using this composite material after radioactive Cs+ ion adsorption. The existence of nanosized magnetites in the polycrystalline zeolite (several micrometers) was confirmed by TEM observations. The CEC and magnetic property of these composite materials were characterized.
As part of an international experimental program REBUS, core physics experiments have been implemented on a UO 2 core, which consists of 3.3 and 4.0 wt% UO 2 fuel rods in a square pitch of 1.26 cm, and two partial MOX cores, which replace 7 Â 7 UO 2 fuel rods in the center of the UO 2 core by fuel bundles made of fresh BR3 MOX fuel or irradiated BR3 MOX fuel with an average burnup of 20 GWd/t. Burnup calculations of the BR3 MOX fuel were performed using a general-purpose neutronic calculation code SRAC, and core calculations of the three critical cores were carried out using SRAC, a transport calculation code THREEDANT, and a continuous-energy Monte Carlo code MVP. The measured inventories of major U and Pu isotopes on a sample taken from the BR3 MOX fuel agree with the results of the burnup calculations within 3% deviation. The k eff 's of the three cores are from 0.985 to 1.002. The measured burnup reactivity of the irradiated BR3 MOX fuel was well reproduced by the three types of core calculations. The influence of the accuracy of the inventory calculations on burnup reactivity was studied by comparing between the calculated and measured inventories. The result indicates that the biases in the inventory and reactivity calculations compensate each other, and it makes the total biases of the burnup reactivity small.
Analysis of measured isotopic compositions of four high-burnup BWR MOX fuel samples was performed by using a general-purpose neutronic calculation code SRAC and a continuous-energy Monte Carlo burnup code MVP-BURN. The initial Pu fissile content of the samples was 5.52 wt%, and the burnups ranged from 50 to 80 GWd/t. It is confirmed that a geometrical model including the effect of UO 2 assemblies adjacent to the MOX assembly is necessary in the burnup calculations to obtain accurate calculated isotopic compositions. The calculated results of MVP-BURN with JENDL-3.3 taking such effect into account show more accurate results for major actinides (U, Pu, and Am isotopes) and most fission products than those of infinite assembly calculations. The paper also shows the results calculated using SRAC with JENDL-3.3, ENDF/B-VII, and JEFF-3.1.
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