Analysis of parallel channel instabilities in the CANDU supercritical water reactor

Numerical analysis of parallel-channel density wave instabilities in a supercritical water reactor

“…Because of the several related research works on the supercritical fluids (SCFs) conducted in the recent past [1][2][3][4][5][6][7][8][9][10][11][12][13][14] in addition to the decades together related research experience [15][16][17][18][19][20] and based on those findings, it is reasonable to believe that the development of a SCWR is one of the viable options to implement the generation IV nuclear reactor in practice and make it operational in the near future, provided the remaining uncertainties associated with a new possible technology are addressed adequately. The TH stability and the related safety of the SCWR are one of the important identified areas which have received a considerable importance among the concerned scientific community.…”

“…The related research works, in spite of the varied nature of those, more or less agree that a SCWR, in its relevant operating conditions, might undergo DWOs, a dynamic instability, which gets originated purely due to the nonlinear interactions of the TH parameters and might get influenced with the neutronic parameters as well. The TH models, which have been used for the prediction of DWOs, can be based on linear perturbation and frequency-domain approaches [1-3, 5, 8, 21, 22], or based on nonlinear time-domain solution methodologies [5,[9][10][11][12][13][14]. Although the fact that the MSBs predicted from these two categories of models occasionally differed in quantitative agreements, the related studies with these models did predict the possibility of DWOs in an SCW system considering a single channel, subjected to the highest reactor power, as a representative of the complete reactor core.…”

“…In the aforementioned works on parallel-channel DWIs, mostly out-of-phase DWOs in a two-channel SCW system were analyzed. Ignoring the impact of neutronic coupling and including 2-3 channels in the numerical model, parallel-channel analysis of DWOs predicted the possibility of in-phase and out-of-phase modes of instabilities in the operating regime of a typical pressure tube (PT) SCWR [12] and quantified the effect of spatial reactor power variation in its respective MSBs. As per as the concept of the pressure vessel (PV) SCWR design and the related TH stability issues are concerned, the numerical investigations [33][34][35], which were based on a single-channel analysis, reported the possibility of DWOs in its relevant operating regime.…”

Numerical Instability Study of Supercritical Water Flowing Upward in Two Heated Parallel Channels

“…Dutta et al (2015) modified a 1-D nonlinear thermal-hydraulic code (THRUST) to make it available for stability analyses of parallel channels in CANDU SCWR. Both in-phase and out-of-phase Density Wave Oscillations were studied and the results showed that the CANDU SCWR had a larger stable zone for the in-phase mode than the out-of-phase mode, and that for both instability modes, increasing the asymmetric level of power input would make the CANDU SCWR more unstable.…”

Nuclear coupled thermal hydraulic analysis of fast transient depressurization in supercritical channels

“…The TH model, THRUST, which was earlier used to analyze the TH behavior of various supercritical pressure water systems (Dutta et al, 2015a(Dutta et al, , 2015b(Dutta et al, , 2015c is at present integrated with the neutron point kinetic (NPK) solver (Sanchez, 1989) using temperature and density reactivity feedback coefficients to account for the time-dependent reactor power. The model THRUST solves the nonlinearly coupled mass, momentum in axial direction and energy conservation equations along with the thermodynamic equation of state in the time domain using a characteristic-based, fully implicit finite difference method.…”