Transcript Nuclear T/H system experiment

Nuclear Thermal Hydraulic
System Experiment
NUCLEAR AND HYDROGEN SYSTEM LABORATORY, KAIST
2015.05.28
Fukushima accident
• Earth quake  Reactor shut down
• Electricity supply from grid is failed
• Emergency diesel generator is also failed
• Submerged by Tsunami
• Reactor Coolant Pump is turned off
• Thermal energy couldn’t be removed
• Most of safety systems were
dependent on electricity
• Fuel melt / Hydrogen explosion / heat
up of spent fuel pool
Nuclear Safety Systems
Systems that required to remove the decay heat under the postulated accident
ex ) Safety Injection system (Inject water to the primary loop during accient)
After Fukushima, following requirement were added to the safety systems
 System should remove the decay heat even without electricity
 We call this system as “Passive safety system”
 Usually gravity is used for the driving force of passive safety system
Nuclear Power Plant accident
Fuel rods
A number of systems
(Thermal hydraulic systems)
Thermal
Energy
From
Fuel rod
Electric
Energy
(from atomic
decay)
“Decay heat”
Heat should be removed
Safety system
Passive Containment Cooling System
Passive system that removes decay heat by cooling the steam/air in the containment
Decay heat
(Steam)
Decay heat
How can we measure and calculate the performance of this system  Experiment for PCCS
PCCS Test
Purpose
◦ To calculate heat removal capacity and heat transfer coefficient of the condensing tube
◦ Check the effect of the Air/Steam Fraction
◦ Check the effect of the Pressure
PCCS Test Facility
Main test section
◦ Chambers : Heat exchangers
◦ Steam Generator
◦ PCCT and Cooling water pipes
Chamber :
Air/Steam mixture
SG
PCCT
Experiments Procedure
1. Set up test condition
◦
◦
◦
◦
Steam pressure of the steam generator
Angle of the condensing tube (Already Fixed)
Temperature of cooling water (inlet)
Mass flow rate of cooling water
2. Open the valve of SG connected to the chamber
3. Measure or set the properties of system
◦ System pressure and temperature
◦ Outlet temperature of cooling water
4. Calculate heat capacity and heat transfer coefficient
5.Open the venting valve on the chamber for 1 min and close it
◦ Air/Mass Fraction of the System changed ( for next Exp. Case.)
6.Repeat previous steps
Experiments Procedure
Steam generator
◦ 2 ,3 and 4 bar saturated condition (one pressure condition for one group)
Cooling water
◦ Pressure: 1 bar(atmosphere)
What you measure? Or check?
◦ Temperature of cooling water in / out
◦ Mass flow rate
◦ Twall
Channel geometry information
◦ Outer diameter of pipe = 49.1 mm
◦ Inner diameter of pipe = 40 mm
◦ Length of pipe = 0.7 m
Heat transfer rate
and heat transfer coefficient
Heat transfer rate : Amount of heat transferred per time
Single-phase fluid
m
m
Tin
Tout
Q  H eat transfer rate [W ]
Q  m ( h out  hin )  m C p (T out  Tin )
 : D ensity of fluid [kg/m ]
3
** Mass flow rate,
m   V   uA
3
V : V olum etric flow rate [m /s]
u : velocity of fluid [m /s]
2
A : C ross-sectional area of flow channel [m ]
Heat transfer rate
and heat transfer coefficient
Heat transfer coefficient : Amount of heat transferred per time, per area, and per temperature difference
m
m
Tin
Tout
Twall
Q  H eat transfer rate [W ]
Tbulk
h
Q
A (T sat  T w all )
Heat transfer coefficient is affected by
: Geometry / Angle / Materials / Air-mass fraction / Pressure ….
2
[W /m .K ]
Heat transfer rate
and heat transfer coefficient
Heat transfer rate : Amount of heat transferred per time
Single-phase fluid
m
m
Tin
Tout
Q  H eat transfer rate [W ]
 L (  L   G ) gi L G k L
3
h  0.728[
D  L (T sat  T w all )
1/ 4
]
Notes
Your Report Should includes
◦ Clear Conditions for each case
◦ Air / Steam Fraction of each experiments (Through the calculation)
◦ Heat Transfer Coefficient of PCCS for each case and the reason for the difference between each case.