tailieunhanh - Nuclear Power System Simulations and Operation Part 5

Tham khảo tài liệu 'nuclear power system simulations and operation part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Development of an Appendix K Version of RELAP5-3D and Associated Deterministic-Realistic Hybrid Methodology for LOCA Licensing Analysis 49 change with and without the prevention algorithm. It can be seen that nucleate boiling heat transfer was successfully prevented by the algorithm which modifies the existing heat transfer logic. Fig. 5. Comparison of measured and calculated temperature changes for film boiling assessment Fig. 6. Comparison of measured and for transition boiling assessment Core flow distribution during blowdown To fulfill the requirement of taking into account cross flow between regions and any flow blockage calculated to occur during blowdown as a result of cladding swelling or rupture the feature of the cross flow junction of the RELAP5-3D would be applied. In cross flow 50 Nuclear Power - System Simulations and Operation junctions the transverse momentum convection terms are neglected. Therefore there is no transport of x-direction momentum due to the flow in the transverse direction. To assess the calculation of core flow distribution under flow partial blockage two EPRI flow blockage tests Tapucu et al. 1984 were adopted in which single-phase liquid and two-phase air water were used for a range of blockages and flow conditions. The comparisons of the calculated channel pressure distribution for the unblocked channel of the two-phase test against measurements is shown in Figure 8. 10 8 T---1---1--1---1--1---1--1---1--1---1---1--1---1--1---1--1---1--F ----------- htmode 1101001 RELAP5-3D K -----------htmode 1101001 RELAP5-3D 6 transition boiling --------------------------------------------1-------------r I I I I I I sat. nucleate boiling I I 4 subcooled nucleate boiling 2 J_I_I_II_II_I_II_I_II_I_II_II_L 0 Time s Fig. 7. Heat transfer mode calculated by the modified RELAP5-3D with w o nucleate boiling lock-out Fig. 8. Comparison of measured and .