Nucleate boiling detected by neutron noise monitoring at doel 2

Defloor, J.; Baeyens, R.

doi:10.1016/0149-1970(88)90075-3

“…24) The ''steaming'' rate is also a key quantity when attempting to predict PWR axial offset anomalies (AOAs), the axial offset being a measure of the unpredicted deviation in the core axial power distribution during operation. e.g., 25,26) This phenomenon is intimately linked to boiling-induced ''crud'' deposits on the fuel rod cladding, thus allowing boron to accumulate in the porous material. 27,28) This can be compound-ed with core flow maldistribution due to significant increases in flow resistance caused by surface fouling.…”

Section: Introductionmentioning

confidence: 99%

“…27,28) This can be compound-ed with core flow maldistribution due to significant increases in flow resistance caused by surface fouling. 25,29) While the AOA phenomenon does not represent a direct safety concern, it can entail reactor power constrains and derating to maintain the required shutdown margin, with the consequence of economic penalty. 30) The need for research on the impact of subcooled boiling and heat transfer on clad corrosion and deposition has been well recognized.…”

Section: Introductionmentioning

confidence: 99%

A Separate-Effect-Based New Appraisal of Convective Boiling and its Suppression

Aounallah¹

2008

Journal of Nuclear Science and Technology

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The development of convective boiling heat transfer correlations and analytical models has been based almost exclusively on the knowledge of global heat transfer coefficients, while the predictive capabilities of the correlation constituting components (typically additive convection and boiling) have remained usually elusive. This becomes important when, for example, developing a mechanistic subcooled void model based on wall heat flux partitioning, or when applying a correlation beyond its developmental range. In the latter case, the preponderance of the individual heat transfer mechanisms, through the phenomenon of boiling suppression, can become significantly different, thus leading to uncharted uncertainty extrapolations. An examination of existing experimental data, obtained under fixed hydrodynamic conditions, has allowed the isolation of the boiling heat transfer contribution over a broad range of thermodynamic qualities (0 to 0.8) and mass fluxes (1,100 to 3,900 kg/(m 2 Ás)) for water at 7.2 MPa. Boiling suppression has been quantified, thus providing valuable new insights on the basic functional relationships of boiling in convective flows. This work has allowed a new interpretation and representation of the standard flow ''boiling map'' (Collier's) to be developed. The convection enhancement and boiling suppression components (F and S) of the well-known Chen's correlation-an important constitutive relationship implemented in several best-estimate (realistic) thermal-hydraulics codes-have been individually determined, showing the pitfall of splitting the correlation for mechanistic boiling heat transfer modelling, and the important role of compensating errors in uncertainty extrapolation. An initial attempt to formulate a new correlation, based for the first time on segregated heat transfer components, is also included.

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“…e.g., 25,26) This phenomenon is intimately linked to boiling-induced ''crud'' deposits on the fuel rod cladding, thus allowing boron to accumulate in the porous material. 27,28) This can be compounded with core flow maldistribution due to significant increases in flow resistance caused by surface fouling.…”

Section: Introductionmentioning

confidence: 99%

“…27,28) This can be compounded with core flow maldistribution due to significant increases in flow resistance caused by surface fouling. 25,29) While the AOA phenomenon does not represent a direct safety concern, it can entail reactor power constrains and derating to maintain the required shutdown margin, with the consequence of economic penalty. 30) The need for research on the impact of subcooled boiling and heat transfer on clad corrosion and deposition has been well recognized.…”

Section: Introductionmentioning

confidence: 99%

A Separate-Effect-Based New Appraisal of Convective Boiling and its Suppression

Aounallah

¹

2008

J. Nucl. Sci. Technol.

2

0

View full text Add to dashboard Cite

The development of convective boiling heat transfer correlations and analytical models has been based almost exclusively on the knowledge of global heat transfer coefficients, while the predictive capabilities of the correlation constituting components (typically additive convection and boiling) have remained usually elusive. This becomes important when, for example, developing a mechanistic subcooled void model based on wall heat flux partitioning, or when applying a correlation beyond its developmental range. In the latter case, the preponderance of the individual heat transfer mechanisms, through the phenomenon of boiling suppression, can become significantly different, thus leading to uncharted uncertainty extrapolations. An examination of existing experimental data, obtained under fixed hydrodynamic conditions, has allowed the isolation of the boiling heat transfer contribution over a broad range of thermodynamic qualities (0 to 0.8) and mass fluxes (1,100 to 3,900 kg/(m 2 Ás)) for water at 7.2 MPa. Boiling suppression has been quantified, thus providing valuable new insights on the basic functional relationships of boiling in convective flows. This work has allowed a new interpretation and representation of the standard flow ''boiling map'' (Collier's) to be developed. The convection enhancement and boiling suppression components (F and S) of the well-known Chen's correlation-an important constitutive relationship implemented in several best-estimate (realistic) thermal-hydraulics codes-have been individually determined, showing the pitfall of splitting the correlation for mechanistic boiling heat transfer modelling, and the important role of compensating errors in uncertainty extrapolation. An initial attempt to formulate a new correlation, based for the first time on segregated heat transfer components, is also included.

show abstract