Investigation of the core neutronics analysis conditions for evaluation of burn-up nuclear characteristics of the next-generation fast reactors

Takino, Kazuo; Oki, Shigeo

JAEA-Data/Code 2023-003, 26 Pages, 2023/05

JAEA-Data-Code-2023-003.pdf:1.66MB

Since next-generation fast reactors aim to achieve a higher core discharge burn-up than conventional reactors do, core neutronics design methods must be refined. Therefore, a suitable analysis condition is required for the analysis of burn-up nuclear characteristics to accomplish sufficient estimation accuracy while maintaining a low computational cost. We investigated the effect of the analysis conditions on the accuracy of estimation of the burn-up nuclear characteristics of next-generation fast reactors in terms of neutron energy groups, neutron transport theory, and spatial mesh. This study treated the following burn-up nuclear characteristics: criticality, burn-up reactivity, control rod worth, breeding ratio, assembly-wise power distribution, maximum linear heat rate, sodium void reactivity, and Doppler coefficient for the equilibrium operation cycle. As a result, it was found that the following conditions were the most suitable: 18-energy-group structure, 6 spatial meshes per assembly with diffusion approximation. Additionally, these conditions should apply to correction factors for energy group structure, spatial mesh and transport effects.

An Investigation on the control rod homogenization method for next-generation fast reactor cores

Takino, Kazuo; Sugino, Kazuteru; Oki, Shigeo

Annals of Nuclear Energy, 162, p.108454_1 - 108454_7, 2021/11

https://doi.org/10.1016/j.anucene.2021.108454

Numerical investigations on the coolability and the re-criticality of a debris bed with the density-stratified configuration

Li, C.-Y.; Uchibori, Akihiro; Takata, Takashi; Pellegrini, M.*; Erkan, N.*; Okamoto, Koji*

Dai-25-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2021/07

The capability of stable cooling and avoiding re-criticality on the debris bed are the main issues for achieving IVR (In-Vessel Retention). In the actual situation, the debris bed is composed of mixed-density debris particles. Hence, when these mixed-density debris particles were launched to re-distribute, the debris bed would possibly form a density-stratified distribution. For the proper evaluation of this scenario, the multi-physics model of CFD-DEM-Monte-Carlo based neutronics is established to investigate the coolability and re-criticality on the heterogeneous density-stratified debris bed with considering the particle relocation. The CFD-DEM model has been verified by utilizing water injection experiments on the mixed-density particle bed in the first portion of this research. In the second portion, the coupled system of the CFD-DEM-Monte-Carlo based neutronics model is applied to reactor cases. Afterward, the debris particles' movement, debris particles' and coolant's temperature, and the k-eff eigenvalue are successfully tracked. Ultimately, the relocation and stratification effects on debris bed's coolability and re-criticality had been quantitatively confirmed.

Distance for fragmentation of a simulated molten-core material discharged into a sodium pool

Matsuba, Kenichi; Isozaki, Mikio; Kamiyama, Kenji; Tobita, Yoshiharu

Journal of Nuclear Science and Technology, 53(5), p.707 - 712, 2016/05

https://doi.org/10.1080/00223131.2015.1113897

In order to develop an evaluation method of the distance for fragmentation of molten core material discharged into the sodium plenum, a sodium experiment with visual observation was conducted using an X-ray imaging system. In the current experiments, 0.9 kg of molten aluminum (initial temperature: around 1473 K) was discharged into a sodium pool (initial temperature: 673 K) through a nozzle (inner diameter: 20 mm). Based on the experimental results, the distance for fragmentation of the liquid column was estimated to be 100 mm in the experiments. Through the sodium experiment, useful knowledge was obtained for the future development of an evaluation method of the distance for fragmentation of molten core material. As a next step, sodium experiments using higher-density molten materials will be conducted to enrich the experimental knowledge. Besides, a new semi-empirical correlation will be developed to evaluate more appropriately the distance for fragmentation under CDA conditions.

Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool

Matsuba, Kenichi; Kamiyama, Kenji; Toyooka, Junichi; Tobita, Yoshiharu; Zuev, V. A.*; Kolodeshnikov, A. A.*; Vasilyev, Y. S.*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

To develop a method for evaluating the distance for fragmentation of molten core material discharged into sodium, the particle size distribution of alumina debris obtained in the FR tests was analyzed. The mass median diameters of solidified alumina particles were around 0.4 mm, which are comparable to particle sizes predicted by hydrodynamic instability theories such as Kelvin-Helmholtz instability. However, even though hydrodynamic instability theories predict that particle size decreases with an increase of Weber number, such the dependence of particle size on We was not observed in the FR tests. It can be interpreted that the tendency of measured mass median diameters (i.e., non-dependence on Weber number) suggests that before hydrodynamic instabilities sufficiently grow to induce fragmentation, thermal phenomena such as local coolant vaporization and resultant vapor expansion accelerate fragmentation.

Review of actinide nitride properties with focus on safety aspects

Albiol, T.*; Arai, Yasuo

JAERI-Review 2001-040, 50 Pages, 2001/12

JAERI-Review-2001-040.pdf:3.08MB

no abstracts in English

Application of a hexagonal element scheme in the finite element method to three-dimensional diffusion problem of fast reactors

;

Journal of Nuclear Science and Technology, 20(11), p.951 - 960, 1983/00

https://doi.org/10.3327/jnst.20.951

no abstracts in English

Estimation of multiple control rod worth with strong interaction effect in large fast reactors

Journal of Nuclear Science and Technology, 13(9), p.517 - 520, 1976/09

https://doi.org/10.3327/jnst.13.517

no abstracts in English

Development of a new temperature sensor of which insulation resistance is measurable online

Kondo, Yuki; Takaya, Shigeru; Yada, Hiroki; Hashidate, Ryuta

no journal, , 

In sodium-cooled fast reactors, a large number of temperature sensors are used for temperature monitoring and heater control of sodium-containing equipment. In the conventional insulation resistance measurement method for temperature sensors, preparation work such as stopping the temperature measurement function and separating from the electric board is required, and the workload also increases with increasing the number of target equipment, which has become a problem from the viewpoint of inspection period. In this study, we have developed a new temperature sensor of which insulation resistance is measurable online, and evaluated the performance by experiments.