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What is the CRD system condition if Pressure Indicator between CRD suction filters and CRD pumps indicates 10" Hg Vacuum for 5 seconds?
CRD suction filter bypass, AO-3-20, will be open (opens at 8" Hg Vacuum). The running CRD pump will still be running.
Note: There is NO time limit associated with this
The CRD suction filter high dP alarm is received indicating the filters are clogged. What automatic system function occurs to prevent a trip of the CRD pump?
At 8" Hg Vacuum, the CRD suction filter bypass valve, AO 3-20, opens to bypass the filters.
The pressure indicator at the suction of the running CRD pump reads 15" Hg Vacuum and steady. What is the condition of the system 5 seconds later?
The running CRD pump has tripped (12" Hg Vacuum for 2 seconds). The CRD suction filter bypass valve is open.
What are the CRD pump auto-starts?
There are no auto-starts for the CRD pumps.
Which Scram time is faster, a Scram initiated with an RPV pressure of 800 psig, or a Scram initiated with an RPV pressure of 400 psig?
The Scram from 400 psig is faster.
Per Fig 10 in B.01.02-06, a Scram from 800 psig takes 2.75 seconds and a Scram from 400 psig takes 2.6 seconds. The curve shows the longest Scram time occurs from approx. 650 psig.
Which Scram time is faster, a Scram initiated from 1000 psig, or a Scram initiated from 800 psig?
The 1000 psig Scram is faster.
The 800 psig Scram takes longer than the 1000 psig Scram. Refer to Fig 10 in the B.01.02-06.
What is the expected condition of the Scram Pilot Valves (SV-117/118) following a Scram?
The Scram Pilot Valves are de-energized, which vents off the Scram Air Header.
What is the expected condition of the SDV vent and drain valves following a Scram?
The SDV vent and drain valve solenoid valves de-energize which allow the SDV vent and drain valves to close.
What is the failure position of the CRD flow control valves, CV 3-19A/B, on loss of Y20?
On loss of Instrument Air?
CRD flow control valves fail CLOSED on loss of Y20 or on loss of air.
What is the power supply to the CRD flow control valves?
Y20 and Instrument Air
Following a Scram, what is the expected position of the in-service CRD flow control valve? Why?
The CRD flow control valve will be CLOSED.
System flow will be going to the accumulators and the flow element is located before the tap-off for the charging header. The flow element senses high flow and closes the flow control valves.
What is the Scram Discharge Volume Scram setpoint?
What is the power supply to the flow element circuit?
On a loss of Y30, what is the expected condition of the CRD flow control valves? Why?
Y30 is the power supply to the flow element circuit. Loss of Y30 shows as a loss of flow. This causes the flow control valves to open.
What is the Safety-Related functional design bases requirement of the CRD/CRH system?
CRD/CRH is required to rapidly insert withdrawn control rods into the core (Scram) in response to automatic signals from RPS (Reactor Protection System).
Where is the normal CRDH suction aligned? Why?
From the condensate system, after the cond demins. This provides high quality filtered water with low O2 content.
What is the CRD pump min flow protection flowrate? Where does it discharge?
Approx. 20 gpm.
Discharges to the CSTs.
What is the normal flowrate to the Recirc pump seals?
3 gpm per Recirc pump.
What is the normal charging header pressure?
Approx. 1500 psig.
What is the normal drive water header pressure?
Approx. 265 psig greater than RPV pressure.
What is the normal cooling header flowrate? What is the normal cooling flow per drive?
Approx. 48 gpm cooling header flow.
With 121 drives, this is approx. 0.4 gpm per drive.
Which speed control valves (in the four valve manifold) open to insert a rod?
The odd ones open to insert.
- SV-123 aligns drive water to the bottom of the piston.
- SV-121 aligns top of piston to the exhaust header.
Which speed control valves (in the four valve manifold) open to withdraw a rod?
The even ones open to withdraw.
- SV-122 aligns drive water to the top of the piston.
- SV-120 aligns bottom of piston to the exhaust header.
What is the drive speed as adjusted by the speed control valves?
Approx. 3 inches per second.
48 seconds +/- 9.6 seconds total.
What valves are used to hydraulically isolate a drive? In what order are the valves operated?
CRD-101 and CRD-102 isolate the CRD.
When isolating, close CRD-101 then CRD-102.
Are the Scram pilot valves (SV-117/118) Energize-to-Open, or De-energize-to-Open?
SV-117 and SV-118 are De-energize-to-Open.
They are in series and must both open to cause Scram valves CV-126 and CV-127 to open.
What happens at a volume of 38 gallons in the scram discharge volume?
At 38 gallons, a rod block is inserted.
What is the scram discharge volume rod block setpoint?
What is the scram discharge volume alarm setpoint?
On a failure of RMCS, what methods are available to move rods?
Given a failure of RMCS, a Scram is the only remaining method of moving rods.
On receipt of a CRD accumulator annunciator, the outplant operator states that the local light stays lit when pushed. What is the accumulator condition causing the alarm?
If the light stays lit, low N2 pressure is the cause of the alarm.
- "Water puts the fire out"
- (If the light goes out, then it is due to water level)
On receipt of a CRD accumulator annunciator, the outplant operator states that the local light goes out when pushed. What is the accumulator condition causing the alarm?
If the light goes out, high water level is the cause of the alarm.
- "Water puts the fire out"
- (If the light goes out, then it is due to water level)
What is the expected drive water flowrate when inserting one rod?
Approx. 4 gpm
What is the expected drive water flowrate when withdrawing one rod?
Approx. 2 gpm
What is a possible cause of a single rod drifting IN?
Inlet or outlet scram valve leaking by.
What is a possible cause of a single rod drifting OUT?
Failure of the collet mechanism to latch.
What is the expected response in both Charging water header and Drive water header pressures if the in-service CRD flow control valve (CV 3-19A/B) failed OPEN?
- Charging water taps off before the valve and would therefore lower.
- Drive water taps off after the valve and would therefore rise.
What is the expected response in both Charging water header and Drive water header pressures if the in-service CRD flow control valve (CV 3-19A/B) failed CLOSED?
- Charging water taps off before the valve and would therefore rise.
- Drive water taps off after the valve and would therefore lower.
What mode(s) is/are Tech Spec 3.1.5 (Control Rod Scram Accumulators) applicable?
Modes 1 and 2
What is the 20 minute Tech Spec in 3.1.5 (Control Rod Scram Accumulators)? What is the required action?
B. Two or more control rod scram accumulators inoperable with reactor steam dome pressure => 900 psig.
- Restore charging water header pressure to => 940 psig.
- (Other actions exist, but are 1 hour or greater)
What cools the CRD pump speed increaser and thrust bearing?
How long is the time delay associated with the CRD pump trip on a suction pressure of 12" Hg Vacuum?
What automatic system response, if any, occurs to protect the CRD post filters?
The post filters are the filters after the CRD pumps and do not have any automatic features.
Per the B.01.03-05 Operating Requirement: "Pump Bypass Flow SHALL be reduced if the suction filter dP alarm point (10 in. Hg) can NOT be cleared by Normal Operating Procedures"
What valve should be operated to reduce this flow?
This is talking about CRD-169 in the pump bypass line back to the CSTs
What is the alarm setpoint for the CRD post filters? Are there any automatic system actions for these filters?
No automatic actions
If fewer than 80 HCUs are in service, what is the required flowpath lineup to ensure cooling water dP and exhaust dP do not cause inadvertent rod motion?
With fewer than 80 HCUs in service, the CRD-RWCU lineup must be available to maintain required flows/pressures via CRD-30.
What is the 1 hour steady state CRD pump motor current limit? What is the maximum allowed CRD pump motor current?
- No more than 34 amps for 1 hour.
- Never more than 39 amps.
Why is it important to close CRD-101 before closing CRD-102/112 when isolating an HCU?
A reactor Scram will result in damage to the CRD if it should occur while the accumulator is available.
What is the risk with isolating the CRD pump (CRD-3-1 or CRD-3-2) while it is running?
The CRD pumps have a min flow line (approx. 20 gpm). However, the min flow line is undersized and continued operation of the pump with its discharge isolation valve closed is harmful to the pump.
What effect, if any, does adjusting CRD drive water flow or temperature have on core reactivity?
Approximately 1 MWth
The outplant operator makes an adjustment to CRD pump bypass flow by throttling open CRD-169. What must they check per the precautions? What do they do if the condition is outside of band?
The operator MUST verify the discharge header pressure is between 1485 and 1500 psig.
If outside of 1485 to 1500 psig, the operator should adjust the CRD pump discharge valve (CRD-3-1 or CRD-3-2) as required.
If 45 HCUs are isolated, what additional lineup must exist for the CRD system? Why?
An additional flowpath must be provided using RWCU.
Isolating multiple HCUs causes higher than normal cooling and exhaust header pressures. These higher pressures can cause inadvertent rod motion.
#11 CRD pump is running while at normal 100% power operation. A bus 15 lockout occurs. What is the condition of the CRD system? What action(s) should you take to correct the condition?
#11 CRD pump is powered off bus 15. There are no auto-start features for CRD pumps. Thus, there is no CRD pump running.
The operator should start #12 CRD pump, if available. Otherwise, the operator should Scram the reactor on receipt of the second accumulator low pressure alarm.
What is the CRD pump bypass flow limit during normal power operations? Why?
If HPCI initiated, a CRD pump trip could occur on low suction pressure if flow is higher than 30 gpm.
Annunciator 5-B-22 (Scram Pilot Header Hi/Lo Pressure) is received in the Control Room. If pressure is low (< 60 psig) how could the plant respond if operators are unable to restore Scram Pilot Header air pressure?
CRDs may begin to drift into the core as scram air header pressure lowers and CRD scram vavles open.
What are the Scram Pilot Header High/Low Pressure setpoints? (5-B-22)
- High = 75 psig
- Low = 60 psig
Following a Scram, actions are taken to address the initiating issue, and the Scram is now reset. The panel operator notes annunciator 5-B-17 (Charging Water Low Pressure) came in when the Scram was reset. Why would it be in?
This alarm may come in immediately on resetting a Scram due to the large demand for flow for CRD accumulator charging.