Term
ATWS
Describe the purpose of ATWS. |
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Definition
-10 CFR rule to create a redundant system to RPS.
-Limits RPV pressure to <1500psig.
-Fuel energy deposition to <280cal/gram and clad oxidation <17% by vol.
-Containment press <56psig and suppression pool temp <170F. |
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Term
ATWS
Describe the effects on the recirc pumps with an ATWS signal. |
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Definition
| -Both pumps tripped by tripping the field breaker upon receipt of an ATWS signal. |
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Term
ATWS
Describe the SCRAM air header depressurization. |
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Definition
| -Air is bled off by energizing either of the two alternate rod insertion valves (25-30secs). |
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Term
ATWS
Describe the effects on the main turbine/feed pumps on ATWS signal. |
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Definition
-ATWS trips main turbine and all Rx feed pumps.
-These also trip at +48" for Rx HI/HI water level. |
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Term
ATWS
Describe the ATWS logic. |
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Definition
-2 out of 2 taken once.
-A and C for system A.
-B and D for system B. |
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Term
ATWS
Describe the power supplies to the ATWS channels and ARI SCRAM valves. |
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Definition
-Channel A: Y-70 and D-11.
-Channel B: Y-80 and D-21.
-ARI scram valves: D-11 and D-21. |
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Term
ATWS
Describe the automatic initiation setpoints for ATWS. |
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Definition
-Rx pressure of 1135psig.
-RPV low-low level -47" with 7.3sec.
-Manual initiation at C-05 (must arm). |
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Term
ATWS
Describe the effects of a loss of 125VDC on ATWS. |
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Definition
| Cant depressurize solenoid valves and may not be able to trip recirc field brkrs. |
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Term
ATWS
Describe the effects of a loss of Y-70/80 on ATWS. |
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Definition
| Parallel 125VDC power supply will take over, therefore, there are no effects. |
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Term
ATWS
Describe the effects of a loss of instrument air on ATWS. |
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Definition
| Less than 60 psi the control rods will drift in. |
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