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

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?

Cold Shutdown process PRZ. Temp. (F) Time(Sec) 5 10 15 20 25 30 5 10 15 20 25 30 181.130 181.131 181.132 181.133 181.134 181.135 181.136 181.137 181.138 181.139 181.140 PRZ. Temp. (F) Time(Sec) Cold Shutdown process

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

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 ℃ http://www.atomic.or.kr/atomica/ ≦ 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

UPRZ Analysis PRZ. Temp. (F) Time(Sec) 5 10 15 20 25 30 181.130 5 10 15 20 25 30 181.130 181.131 181.132 181.133 181.134 181.135 181.136 181.137 181.138 181.139 181.140 PRZ. Temp. (F) Time(Sec)

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

Steam Enthalpy and Flow Analysis 5 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 2600000 2620000 2640000 2660000 2680000 2700000 2720000 2740000 2760000 2780000 2800000 Steam Enthalpy Time (Sec)

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 2700000.

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.

Malfunction G-43, G-44 PRZ. Temp. (F) Time(Sec) 5 10 15 20 25 30 5 10 15 20 25 30 181.130 181.131 181.132 181.133 181.134 181.135 181.136 181.137 181.138 181.139 181.140 PRZ. Temp. (F) Time(Sec) Malfunction G-43, G-44

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)

HV 201 (RHR Suction valve)

RHR heat exchanger leak (#43) WRHRCVC UCTMT 34.60023 34.60026 34.60028 34.6003 34.60032 34.60033 Considerable Point In the steady-state, HV201 valve is closed. The position of RHR system is outside of containment.

Loss of RHR Pump (#44) Considerable Point WRHRCVC UCTMT 34.60023 34.60026 34.60028 34.6003 34.60032 34.60033 Considerable Point In the steady-state, HV201 valve is closed. The position of RHR system is outside of containment.

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.

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.

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.

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!!!