1. Compact Nuclear Simulation Analysis
Nuclear Reactor Experiments
Compact Nuclear Simulation Analysis
TEAM Ⅱ

2. I N D E X Cold Shutdown process Malfunction G-43, 44
Definition of Cold Shutdown
UPRZ Analysis
Steam Enthalpy and Flow Analysis
Malfunction G-43, 44
Residual Heat Removal(RHR)
RHR heat exchanger leak (#43)
Loss of RHR Pump (#44)
Another Situation?

3. Cold Shutdown process PRZ. Temp. (F) Time(Sec) 5 10 15 20 25 305 10 15 20 25 30
PRZ. Temp. (F)
Time(Sec)
Cold Shutdown process

4. Definition of Cold Shutdown
Introduction
define 'Cold Shutdown'
look into some factors in that state and analyze them.
Pressurizer Temperature, Steam Enthalpy, Steam Flow
deal with some problems under two mal-functions. : G43 / G44

5. The definition of 'Cold shutdown'
Criteria for deciding "Cold shutdown"
the primary coolant system average temperature
sub-criticality with a shutdown margin
Definition from some conferences
CNS Manual   88 ∓ 3 ℃
≦ 90 ℃   ∆k/k ≦ 1%
≦ 60 ℃   ∆k/k ≦ 5%
UCN 3 & 4 FSAR
≦ 210 ℉(98.9℃) not suggested the exact value
Our definition
Cold -> quite low, compared to at full power – 343.4℃ or hot shutdown – 171∓3℃
shutdown

6. UPRZ Analysis PRZ. Temp. (F) Time(Sec) 5 10 15 20 25 30 181.1305 10 15 20 25 30
PRZ. Temp. (F)
Time(Sec)

7. Assumption Axis Analysis CNS has no error.
Pressurized Temp. = Core Hot-leg Temp.
Axis
Horizontal axis : Time(Second)
Vertical axis : Pressurized Temperature(F)
(181F = 83C)
Analysis
Residual heat supplied for a moment.
Temperature dropped by convection current.
Small Temp. deviation since short detection time

8. Steam Enthalpy and Flow Analysis5 10 15 20 25 30
-0.10
-0.05
0.00
0.05
0.10
Steam Flow
Time (Sec) 5 10 15 20 25 30
Steam Enthalpy
Time (Sec)

9. Assumption and Axis Analysis CNS has no errors.
Steam = Steam between steam generator and turbine in the main steam system
Horizontal axis : Time(sec) Vertical axis : Steam Flow and Steam Enthalpy, respectively But we can't find out any scale from given graphs.
Analysis
As time goes by (up to 28 sec.),
Steam Flow is zero
Steam Enthalpy is kept constant at the value of

10. Conclusion and Discussion
Steam is not generated by the steam generator.
Steam gets stuck between the steam generator and the turbine. So there is no steam flow and leftover steam has constant enthalpy 
From these results, we can assume
the steam isolation valve of the main steam system is closed
the turbine is stopped in the secondary loop during the cold shutdown. 
And heat loss through the pipe wall is not considered in the CNS operation.

11. Malfunction G-43, G-44 PRZ. Temp. (F) Time(Sec) 5 10 15 20 25 305 10 15 20 25 30
PRZ. Temp. (F)
Time(Sec)
Malfunction G-43, G-44

12. Residual Heat Removal (RHR)
The Residual Heat Removal (RHR) system
functions to remove heat from the core and reactor coolant system during plant cooldown and refueling operations
supplies initial reactor coolant system circulation and purification during a plant startup.
serves as part of the Emergency Core Cooling System (ECCS)

13. HV 201 (RHR Suction valve)

14. RHR heat exchanger leak (#43)
WRHRCVC
UCTMT
Considerable Point
In the steady-state, HV201 valve is closed.
The position of RHR system is outside of containment.

15. Loss of RHR Pump (#44) Considerable Point
WRHRCVC
UCTMT
Considerable Point
In the steady-state, HV201 valve is closed.
The position of RHR system is outside of containment.

16. Analysis
RHR suction valve, HV 201 must meet the condition that RCS pressure be less than 26.9 kg/cm2. Therefore RHR pump does not operate during the 100% of power.  so, WRHRCVC Flow=0 is natural as the graph shows.
RHR system is outside of containment, therefore when RHR leakage happen, the containment temperature does not change.
And change of containment temperature in the graph is under the order of 10-3 and this order of change is not important. It is reasonable that unstability of the CNS code may  cause this small change. We can neglect the change of temperature.

17. Another Situation? If the reactor is in the state of refueling
In #43,  RHR suction valve, HV 201 is open and RHR is functioning normally.
The leakage of RHR is critical. The water level of reactor will decrease and the amount of water decrease and failing of removing residual heat will cause increase of temperature of reactor.
In #44, RHR must remove residual heat, but loss of the pump bring about failure of transfering heat to heat exchanger in RHR system, so this may cause increasing of containment temperature.

18. Entrance of RHR system, suction valve HV 201 will closed automatically when RCS system pressure increased to 52 kg/cm2
Endurance condition of RHR system is under 350F and 650 psia. therefore, if HV201 valve open in steady-state, RHR loop will destroyed by pressure and temperature.
And, we can decide abnormality of reactor not by change of containment temperature but by change of containment pressure.

19. Thank you!!! Jang Dong Ju Lim Hee Jae Yun Won Ho Ha Jeong Heon
Ham Sun Sik
Yu Mong Jin
Jeong Seong Hun
Jeon Seong Sik
Thank you!!!