1. Nuclear Thermal Hydraulic System Experiment
Nuclear and Hydrogen System Laboratory, KAIST

2. 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

3. 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

4. Nuclear Power Plant accident
A number of systems
(Thermal hydraulic systems)
Thermal
Energy
From
Fuel rod
(from atomic decay)
“Decay heat”
Electric
Energy
Fuel rods
Heat should be removed
Safety system

5. 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

6. 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

7. PCCS Test Facility Main test section Chambers : Heat exchangers
Steam Generator
PCCT and Cooling water pipes
Chamber :
Air/Steam mixture SG
PCCT

8. 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

9. 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

10. Heat transfer rate and heat transfer coefficient
Heat transfer rate : Amount of heat transferred per time
Single-phase fluid
** Mass flow rate,

11. Heat transfer rate and heat transfer coefficient
Heat transfer coefficient : Amount of heat transferred per time, per area, and per temperature difference
Twall
Tbulk
Heat transfer coefficient is affected by
: Geometry / Angle / Materials / Air-mass fraction / Pressure ….

12. Heat transfer rate and heat transfer coefficient
Heat transfer rate : Amount of heat transferred per time
Single-phase fluid

13. 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.