Mufa Hossen | Korea University (original) (raw)

Papers by Mufa Hossen

Research paper thumbnail of Scaling Analysis to Design an Air-Water Loop Seal Clearing SET Facility Using MARS-KS Code

Loop seal clearing (LSC) is one of the most important phenomena in a small break or medium break ... more Loop seal clearing (LSC) is one of the most important phenomena in a small break or medium break loss of coolant accident in a pressurized water reactor (PWR). The loop seal formation (LSF) is closely related to the depression of liquid level of core while LSC reduce the depression of liquid level of core. A typical PWR has Ushaped crossover pipes which connect the steam generator outlet plenum to the reactor coolant pump and water in this pipe is called loop seal. Steam venting through the break in a cold leg small break loss of coolant accident (SBLOCA) is achieved only after the water in at least one of the crossover legs is blown out to either the break or reactor vessel [1]. During a SBLOCA in a Westinghouse type PWR, the core liquid level is depressed temporarily before steam clears liquid out of the primary loop seals [2]. The LSC in SBLOCA is an important phenomenon that governs the whole thermal–hydraulic behavior of the primary system. In a physical sense, sustaining of a ...

Research paper thumbnail of Mechanism of loop seal clearance occurring at U-shaped pipe with air-water two-phase flow

Nuclear Engineering and Design, 2020

Main purposes of the LOCAL (LOop seal Clearance separate effect test of ATLAS) facility are to in... more Main purposes of the LOCAL (LOop seal Clearance separate effect test of ATLAS) facility are to investigate the effect of cross-over leg (COL) diameter at the loop seal clearance (LSC), to evaluate the two-phase flow regime through high speed visualization, and to suggest the mechanistic models for the LSC prediction at Small Break-Loss of Coolant Accident (SB-LOCA) in Light Water Reactors (LWRs). In this paper, we introduce a key mechanism of the onset of the LSC occurring at U-shaped COL with air-water two-phase flow condition. The onset of LSC is coupled with the flow regime transition at vertical upward and horizontal section of COL. Slug flow with single Taylor bubble results in decrease of pressure difference at vertical upward section and causes rapid flow regime transition at horizontal section from the stratified to the slug. The critical velocity of gas leading to flow regime transition at horizontal section can explain the onset of LSC and high speed visualization can provide the clear understanding of LSC phenomena at the local point of view.

Research paper thumbnail of Construction schedule delay risk assessment by using combined AHP-RII methodology for an international NPP project

Nuclear Engineering and Technology, 2015

Research paper thumbnail of Derivation of New Non-Dimensional Parameter for Air-Water Counter Current Flow Limitation in Vertical Pipe

Counter current flow limitation (CCFL) is one of the most important phenomenon in the safety anal... more Counter current flow limitation (CCFL) is one of the most important phenomenon in the safety analysis of a pressurized water reactor (PWR). The CCFL phenomenon can occurs in the hot-leg and intermediated leg of a PWR during a small break of loss of coolant accident (SBLOCA). In the counter-current two-phase flow in vertical tube, gas flows upwards through the center of the tube and liquid film flows downward. A shear stress is set up at the interface which retards the liquid film to flow downward. In a given liquid flow rate, there is a certain gas flow rate at which very large waves appears on the interface, the flow becomes chaotic, the gas pressure drop increases significantly and the upward flow of gas limits the downward flow of liquid at the top of the tube which is called CCFL or flooding [1]. The most widely used correlations for CCFL are Wallis type [1] and Kutateladze form [2]. The Wallis type correlation can be expressed as equation (1) while the Kutateladzee form can be ...

Research paper thumbnail of Analysis of LSC phenomena of ATLAS cold leg SBLOCA tests using MARS-KS code

Journal of Nuclear Science and Technology, 2018

Loop seal clearing (LSC) is an important phenomenon for the safety of a pressurized water reactor... more Loop seal clearing (LSC) is an important phenomenon for the safety of a pressurized water reactor (PWR) during a small-break loss-of-coolant accident (SBLOCA). The investigation on an LSC phenomenon of 4″, 6″, and 8.5″ break cold leg SBLOCAs simulated by Advanced thermal-hydraulic Test Loop for Accident Simulation (ATLAS) is performed using a Multidimensional Analysis of Reactor Safety-KINS Standard (MARS-KS) code. The LSC triggers earlier for larger break sizes during tests and calculations. LSCs occur during the simultaneous sudden decrease of steam condensation rate and the sudden increase of the break volumetric flow rate while the core volumetric flow rate increases slowly in calculation. The five phases of an SBLOCA transient are blowdown, pressure plateau, LSC, boil-off, and core-recovery phase, which can be identified by observing the volumetric flow rate and the time-dependent pressure variation. Loop seal refilling (LSR) occurs due to the trivial steam flow rate to the crossover leg inlet in calculation. The sensitivity analysis shows that the combination of countercurrent flow limitation (CCFL) model option for hot leg and steam generator (SG) inlet (Kutateladze, c = 1.36, m = 1), crossover legs (Kutateladze, c = 1, m = 1), and SG U-tubes (Wallis, c = 1, m = 1) provide good prediction of the LSC phenomenon and thermal-hydraulics behaviors in an SBLOCA transient by MARS-KS code calculation.

Research paper thumbnail of Concept Selection of NPP Construction Delay Risk Assessment Methodology Using Systems Engineering Approach

Journal of the Korea Society of Systems Engineering, 2015

Research paper thumbnail of Scaling Analysis to Design an Air-Water Loop Seal Clearing SET Facility Using MARS-KS Code

Loop seal clearing (LSC) is one of the most important phenomena in a small break or medium break ... more Loop seal clearing (LSC) is one of the most important phenomena in a small break or medium break loss of coolant accident in a pressurized water reactor (PWR). The loop seal formation (LSF) is closely related to the depression of liquid level of core while LSC reduce the depression of liquid level of core. A typical PWR has Ushaped crossover pipes which connect the steam generator outlet plenum to the reactor coolant pump and water in this pipe is called loop seal. Steam venting through the break in a cold leg small break loss of coolant accident (SBLOCA) is achieved only after the water in at least one of the crossover legs is blown out to either the break or reactor vessel [1]. During a SBLOCA in a Westinghouse type PWR, the core liquid level is depressed temporarily before steam clears liquid out of the primary loop seals [2]. The LSC in SBLOCA is an important phenomenon that governs the whole thermal–hydraulic behavior of the primary system. In a physical sense, sustaining of a ...

Research paper thumbnail of Mechanism of loop seal clearance occurring at U-shaped pipe with air-water two-phase flow

Nuclear Engineering and Design, 2020

Main purposes of the LOCAL (LOop seal Clearance separate effect test of ATLAS) facility are to in... more Main purposes of the LOCAL (LOop seal Clearance separate effect test of ATLAS) facility are to investigate the effect of cross-over leg (COL) diameter at the loop seal clearance (LSC), to evaluate the two-phase flow regime through high speed visualization, and to suggest the mechanistic models for the LSC prediction at Small Break-Loss of Coolant Accident (SB-LOCA) in Light Water Reactors (LWRs). In this paper, we introduce a key mechanism of the onset of the LSC occurring at U-shaped COL with air-water two-phase flow condition. The onset of LSC is coupled with the flow regime transition at vertical upward and horizontal section of COL. Slug flow with single Taylor bubble results in decrease of pressure difference at vertical upward section and causes rapid flow regime transition at horizontal section from the stratified to the slug. The critical velocity of gas leading to flow regime transition at horizontal section can explain the onset of LSC and high speed visualization can provide the clear understanding of LSC phenomena at the local point of view.

Research paper thumbnail of Construction schedule delay risk assessment by using combined AHP-RII methodology for an international NPP project

Nuclear Engineering and Technology, 2015

Research paper thumbnail of Derivation of New Non-Dimensional Parameter for Air-Water Counter Current Flow Limitation in Vertical Pipe

Counter current flow limitation (CCFL) is one of the most important phenomenon in the safety anal... more Counter current flow limitation (CCFL) is one of the most important phenomenon in the safety analysis of a pressurized water reactor (PWR). The CCFL phenomenon can occurs in the hot-leg and intermediated leg of a PWR during a small break of loss of coolant accident (SBLOCA). In the counter-current two-phase flow in vertical tube, gas flows upwards through the center of the tube and liquid film flows downward. A shear stress is set up at the interface which retards the liquid film to flow downward. In a given liquid flow rate, there is a certain gas flow rate at which very large waves appears on the interface, the flow becomes chaotic, the gas pressure drop increases significantly and the upward flow of gas limits the downward flow of liquid at the top of the tube which is called CCFL or flooding [1]. The most widely used correlations for CCFL are Wallis type [1] and Kutateladze form [2]. The Wallis type correlation can be expressed as equation (1) while the Kutateladzee form can be ...

Research paper thumbnail of Analysis of LSC phenomena of ATLAS cold leg SBLOCA tests using MARS-KS code

Journal of Nuclear Science and Technology, 2018

Loop seal clearing (LSC) is an important phenomenon for the safety of a pressurized water reactor... more Loop seal clearing (LSC) is an important phenomenon for the safety of a pressurized water reactor (PWR) during a small-break loss-of-coolant accident (SBLOCA). The investigation on an LSC phenomenon of 4″, 6″, and 8.5″ break cold leg SBLOCAs simulated by Advanced thermal-hydraulic Test Loop for Accident Simulation (ATLAS) is performed using a Multidimensional Analysis of Reactor Safety-KINS Standard (MARS-KS) code. The LSC triggers earlier for larger break sizes during tests and calculations. LSCs occur during the simultaneous sudden decrease of steam condensation rate and the sudden increase of the break volumetric flow rate while the core volumetric flow rate increases slowly in calculation. The five phases of an SBLOCA transient are blowdown, pressure plateau, LSC, boil-off, and core-recovery phase, which can be identified by observing the volumetric flow rate and the time-dependent pressure variation. Loop seal refilling (LSR) occurs due to the trivial steam flow rate to the crossover leg inlet in calculation. The sensitivity analysis shows that the combination of countercurrent flow limitation (CCFL) model option for hot leg and steam generator (SG) inlet (Kutateladze, c = 1.36, m = 1), crossover legs (Kutateladze, c = 1, m = 1), and SG U-tubes (Wallis, c = 1, m = 1) provide good prediction of the LSC phenomenon and thermal-hydraulics behaviors in an SBLOCA transient by MARS-KS code calculation.

Research paper thumbnail of Concept Selection of NPP Construction Delay Risk Assessment Methodology Using Systems Engineering Approach

Journal of the Korea Society of Systems Engineering, 2015