Determination of conditions for reloading the solid blanket module of a hybrid fusion-fission reactor with uranium and thorium source materials

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发表日期：

2025年9月29日

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I. V. Danilov,
I. A. Larionov,
A. Yu. Leshukov,
A. V. Lopatkin,
I. B. Lukasevich,
V. S. Nazarov,
A. V. Razmerov,
M. N. Sviridenko,
Yu. S. Strebkov,
A. G. Sysoev

摘要

Background

Dry cooling of the solid blanket designed by the NIKIET JSC for a tokamak fusion-fission hybrid reactor can significantly facilitate design and technological implementation of the shutdown mode. However, this requires a calculated confirmation of (non)exceedance for the safe operation limits of the blanket with dry cooling in the shutdown mode.

Aim

To determine the safe conditions for reloading the source material blanket of a hybrid fusion-fission reactor in a shutdown mode.

Materials and methods

The considered solid blanket options include uranium and thorium source materials, as well as heavy and light water coolant under the most conservative conditions. The blanket is simulated as a subcritical system irradiated with 14.1 MeV fusion neutrons. The calculations are performed using the MCU-BR software with the MDBBR50 nuclear database. Studies of dry cooling conditions in the shutdown mode include the calculation of decay heat and analysis of its behavior, as well as thermophysical simulation of dry cooling for the blanket module based on calculated neutron-physical characteristics.

Results

The power of a thorium blanket during the irradiation period is 4–5 times less than of uranium one. However, the difference in decay heat between the two blankets is insignificant due to the considerable contribution of ²³⁹Np and ²³³Pa nuclides, taking into account the rapid decline in the contribution of ²³⁹Np and long-term influence of ²³³Pa contribution. Neutron-physical calculations show the decay heat of all considered blanket options comparable during 10 to 100 days of cooling. During dry cooling in the shutdown mode, the maximum temperature values of the source material in the solid blanket module and its most important structures quickly (in ~2 h) reach and then significantly exceed the operating limits requiring forced coolant circulation.

Conclusion

Dry cooling during reloading of the solid blanket in a hybrid fusion-fission reactor with both uranium and thorium source materials is demonstrated unacceptable due to the rapid increase in the temperature of the source material and structure to a maximum level significantly exceeding the limits of safe operation. Taking into account the obtained results, systems for reloading operations will be developed at the next design stages.