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Takano, Kazuya; Maruyama, Shuhei; Hazama, Taira; Usami, Shin

Proceedings of Reactor Physics Paving the Way Towards More Efficient Systems (PHYSOR 2018) (USB Flash Drive), p.1725 - 1735, 2018/04

Irradiation dependence of the core excess reactivity was investigated for the Monju system startup tests at zero-power carried out in 2010. The excess reactivity basically decreases with the decay of Pu in zero-power operation. However, the excess reactivity little changed in the two month period of the startup tests, which suggests a positive reactivity insertion during the period. The investigated irradiation dependence shows that the positive reactivity increases with reactor operation and mostly saturates by the fission-dose attained during the Monju zero-power operation in a month (10 fissions/cm). The saturated positive reactivity is equivalent to approximately 47% of the initially accumulated self-irradiation damage recovery assuming the defects were recovered by the fission-fragment irradiation in the reactor operation.

Tada, Kenichi

Proceedings of Reactor Physics Paving the Way Towards More Efficient Systems (PHYSOR 2018) (USB Flash Drive), p.2929 - 2939, 2018/04

JAEA develops a new nuclear data processing system FRENDY. We investigated all processing methods and we focused on the probability table generation using the ladder method which is adopted in the PURR module in NJOY. To improve the probability table generation, the more sophisticated method was introduced in the calculation methods of the Chi-Squared random numbers and the complex error function. We also investigated the appropriate ladder number. To investigate the impact of the difference of the complex error function calculation method, the K values of the benchmark experiments with the probability tables by the both methods were compared. The calculation results indicated that the appropriate ladder number is 100 and the difference of the calculation methods of the Chi-Squared random numbers and the complex error function has no significant impact on the neutronics calculation.