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Implications of Air Ingress Induced by Density-Difference Driven Stratified Flow. ICAPP 2008.

DE2008933177

Publication Date	2008
Personal Author	Kim, E. S.; Schultz, R.; Oh, C.; Petti, D.; Liou, C. P.
Page Count	11
Abstract	One of the design basis accidents for the Next Generation Nuclear Plant (NGNP), a high temperature gas-cooled reactor, is air ingress subsequent to a pipe break. Following a postulated double-ended guillotine break in the hot duct, and the subsequent depressurization to nearly reactor cavity pressure levels, air present in the reactor cavity will enter the reactor vessel via density-gradient-driven-stratified flow. Because of the significantly higher molecular weight and lower initial temperature of the reactor cavity air-helium mixture, in contrast to the helium in the reactor vessel, the air-helium mixture in the cavity always has a larger density than the helium discharging from the reactor vessel through the break into the reactor cavity. In the later stages of the helium blowdown, the momentum of the helium flow decreases sufficiently for the heavier cavity air-helium mixture to intrude into the reactor vessel lower plenum through the lower portion of the break. Once it has entered, the heavier gas will pool at the bottom of the lower plenum. From there it will move upwards into the core via diffusion and density-gradient effects that stem from heating the air-helium mixture and from the pressure differences between the reactor cavity and the reactor vessel.
Keywords	Air flow Gas cooled reactors Blowdown Depressurization Reactor accidents Diffusion Graphite Heating Helium Mixtures Molecular weight Oxidation Reactor vessels Validation
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Idaho National Laboratory, Idaho Falls, ID.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200826

Implications of Air Ingress Induced by Density-Difference Driven Stratified Flow. ICAPP 2008.

Implications of Air Ingress Induced by Density-Difference Driven Stratified Flow. ICAPP 2008.
DE2008933177

Publication Date	2008
Personal Author	Kim, E. S.; Schultz, R.; Oh, C.; Petti, D.; Liou, C. P.
Page Count	11
Abstract	One of the design basis accidents for the Next Generation Nuclear Plant (NGNP), a high temperature gas-cooled reactor, is air ingress subsequent to a pipe break. Following a postulated double-ended guillotine break in the hot duct, and the subsequent depressurization to nearly reactor cavity pressure levels, air present in the reactor cavity will enter the reactor vessel via density-gradient-driven-stratified flow. Because of the significantly higher molecular weight and lower initial temperature of the reactor cavity air-helium mixture, in contrast to the helium in the reactor vessel, the air-helium mixture in the cavity always has a larger density than the helium discharging from the reactor vessel through the break into the reactor cavity. In the later stages of the helium blowdown, the momentum of the helium flow decreases sufficiently for the heavier cavity air-helium mixture to intrude into the reactor vessel lower plenum through the lower portion of the break. Once it has entered, the heavier gas will pool at the bottom of the lower plenum. From there it will move upwards into the core via diffusion and density-gradient effects that stem from heating the air-helium mixture and from the pressure differences between the reactor cavity and the reactor vessel.
Keywords	Air flow Gas cooled reactors Blowdown Depressurization Reactor accidents Diffusion Graphite Heating Helium Mixtures Molecular weight Oxidation Reactor vessels Validation
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Idaho National Laboratory, Idaho Falls, ID.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200826