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April 2003, GIF SCWR Mtg. at Madison. Safety analysis of supercritical-pressure light-water cooled reactor with water rods. Yoshiaki Oka. SCLWR-H plant system. Flow rate low Level 1 Reactor scram Level 2 AFS Level 3 MSIV/ADS/LPCI system Pressure low Level 1 Reactor scram
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April 2003, GIF SCWR Mtg. at Madison Safety analysis of supercritical-pressure light-water cooled reactor with water rods Yoshiaki Oka
Flow rate low Level 1Reactor scram Level 2AFS Level 3MSIV/ADS/LPCI system Pressure low Level 1Reactor scram Level 2MSIV/ADS/LPCI system Pressure high Level 1Reactor scram Level 2SRV AFS: auxiliary feedwater system MSIV: main steam isolation valve ADS: automatic depressurization system LPCI: low pressure core injection system
Capacity: RCIC(AFS) TD1 unit: 4%/unit AFSTD2 units: 4%/unit ADS 8 units: 20%/unit at 25MPa LPCIMD 3 units: 150kg/s/unit at 1.0MPa Configuration: TD- RCIC LPCI/RHR TD-AFS TD-AFS LPCI/RHR LPCI/RHR RCIC: reactor core isolation cooling system RHR: residual heat removal system
Total loss of feedwater accident PCT: peak cladding temperature
Loss of load without turbine bypass transient PCT: peak cladding temperature
Durations of high cladding temperature PCT: Peak Cladding Temperature
MSL ADS MSIV Break ADS line MFL LPCI Result – 100% hot leg break (blowdown)
Break Result – 100% Cold leg break (blowdown)
Depressurization cools the core effectively T = 0 sec : Scram, T = 1 sec : ADS Core power does not exceed 100%. Cladding temperature does not exceed that of normal operation.
T = 0 sec : ADS, T = 0.55 sec : Scram Core power increases to 160% before scram. But cladding temperature does not exceed that of normal operation because core flow rate is higher.
Summary of the results • Total loss of flow accident: maximum cladding temperature stays low, 833C (margins to the limit 1260C) • Overpressurization transient without turbine bypass shows 50% power rise and Tc reaches 727C, (margins to the limit 800C ) • Duration of high cladding temperature is short less than 5 sec. Potential for improvement of fuel integrity criteria at transients. • Hot leg break LOCA gives rise to reactivity insertion. But Tc reaches only 550C. Core flow is induced by depressurization due to the once-through coolant cycle. • Cold leg break LOCA, Tc reaches 930C, (margins to the limit 1260C) • Depressurization cools the core effectively