Systems Exam 3 - Residual Heat Removal

Question 1

What are the RHR boration requirements?

Answer 1

→RHR boron concentration is greater than OR equal to RCS boron concentration
OR
→Both RHR and RCS boron concentrations are greater than 2400 ppm
OR
→RHR boron concentration is greater than required cold shutdown boron concentration AND at least one RCP (1 or 4 preferred) is operating.

Question 2

In solid plant operation, stopping an RHR pump will cause pressure to….

Answer 2

INCREASE

The loss of RHR Pump discharge pressure will cause PCV-131 (if in AUTO) to close and raise pressure.

Question 3

What interlocks are associated to MANUALLY open 8812, RWST to RHR pump suction valve?

Other info about 8812s?

Answer 3

8811, Containment Sump to RHR Pump Suction Valve must be closed

→normally open when in standby
→powered from uEB3-1 (Tr A) and uEB4-1 (Tr B)

Question 4

What interlocks are associated to manually open 8811, Containment Sump to RHR Pump Suction Valve?

Other info about 8811s?

Answer 4

Interlocks:
→8812 closed - RWST to RHR Pump Suction
→8701 or 8702 closed - Loop Suction Isolation Valves must be closed

Other Info:
→auto open on Lo-Lo RWST level 33% with SI signal (both blue lights on panel)
→relief valve lifts at 475 psig
→powered by uEB3-2 (Tr A) and eEB4-2 (Tr B)

Question 5

What interlocks are associated with 8701 and 8702 Loops 1 & 4 Suction Isolation Valves?

Answer 5

→u-8811A/B closed - Containment Sump to RHR Pump Suction Isolation Valve
→u-8812A/B closed - RWST to RHR Pump Suction Valve
→u-8804A/B closed - RHR Pump to CCP/SIP Suction Valve
→RCS pressure from u-PT-405/403 must be <364 psig
→interlocks bypassed if opening from Remote Shutdown Panel

Question 6

What interlocks are associated to MANUALLY open 8804A/B?

Answer 6

→u-8701A/B OR u-8702A/B closed - one of the RHR Pump Hot Leg Recirc Valves
→u-8814A&B OR u-8813 closed - SIP 1 & 2 Miniflow Valves (8814s) OR the SIP Miniflow Return Valve (8813)
→u-8511A OR u-8512B closed - CCP 1 Alternate Miniflow Isolation Valve
→u-8511B OR u-8512A closed - CCP 2 Alternate Miniflow Isolation Valve

Question 7

What are the RHR Pump auto starts?
What will trip a running RHR Pump?

Answer 7

→auto starts on Safety Injection with SIS (at 10 sec)
→trips on undervoltage or overcurrent (instantaneous or delayed)

Question 8

RHR Valve Interlocks

Answer 8

Question 9

TS 3.9.5 RHR High Water Level (Mode 6)

Answer 9

One RHR loop shall be OPERABLE and in operation in MODE 6 with the water level ≥ 23 feet above the top of the reactor vessel.

Question 10

TS 3.9.6 RHR Low Water Level (Mode 6)

Answer 10

Two RHR loops shall be OPERABLE and one RHR loop shall be in operation in MODE 6 with the water level < 23 feet above the top of the reactor vessel flange

Question 11

Which conditions, per TS 3.5.2 and SOP-102, will cause dual train inoperability?

Answer 11

→Closing either train cross connect valve u-8716A or -B in MODE 1, 2 or 3 will render both trains of RHR INOPERABLE.
→Closing either cold leg injection valve u-8809A or -B in MODE 1, 2 or 3 will render both trains of RHR INOPERABLE.

OR

→Opening hot leg injection valve u-8840
→Opening RHRP discharge to RWST isolation valve u-8717 (alarms on SSII if not closed)

Question 12

Containment Sump to RHR Suction Valves u-8811A/B open automatically when…

Answer 12

the RWST reaches its LO-LO alarm at 33% level and RHR swap over permissive (blue light) in, indicating SI signal is present.

Question 13

When is RHR put into service?

Answer 13

→put in service <350°F and <350 psig (per IPO-005)
→suction piping limited to <350°F and <400 psig
→RCS pressure from u-PT-405/403 must be <364 psig before valves can be opened

Question 14

Per SOP-102, during ECCS operation if CCW is not available the effected RHR train can only be used for injection phase, if temperature of fluid to be pumped is…

Answer 14

→ >120°F then recirculation mode is not possible (EOS-1.3 Bases)
→ >150°F fluid then CCW must be supplied to the mechanical seals (SOP-102 Notes).

Question 15

Power Supplies for Hot Leg Suction Valves (u-8701A/8702A and 8701B/8702B)

Answer 15

→8701A/B are A Train Electrical
→8702A/B are B Train Electrical
→Mechanical A for A, B for B

Question 16

During a LOCA RHR pumps are stopped if pressure is…

Answer 16

→ >shut off head and increasing
→if pressure decreases to <325 psig (425 psig adverse) the pumps need to be restarted

Question 17

RHR System Letdown Control Valve u-HCV-128

Answer 17

→fails closed on loss of air or power
→full open on RHR letdown operation w/pressure controlled by PCV-131

Question 18

Tech Specs

3.4.6 RCS Loops - Mode 4
3.4.7 RCS Loops - Mode 5, Loops Filled
3.4.8 RCS Loops - Mode 5, Loops Not Filled

Answer 18

Question 19

Tech Spec 3.4.12 requirements for LTOP

Answer 19

→2 RHR suction reliefs (lift @ 450 psig ± 3%), or
→2 PORVs, or
→1 of each
→0 SI pumps capable of injecting
→2 charging pumps capable of injecting
→0 accumulators capable of injecting

If these requirements are not met, then the RCS must be depressurized and a 2.98 sq in vent path must be made in the RCS pressure boundary.

Question 20

LTOP is required when any CL temperature is…
(Tech Spec 3.4.12)

Answer 20

≤ 320°F

Question 21

When LTOP is required by Tech Spec 3.4.12, the following is also required to ensure no heat transients beyond LTOP capability occur:

Answer 21

1. render all SIPs and one charging pump incapable of injection
2. close and deactivate SI accumulator discharge valves
3. preclude the start of RCPs if secondary water temperature is > 50°F above primary

Question 22

Per Tech Spec 3.4.12, LTOP applies Mode 4, 5, and 6 (when RV head on), but does not apply when all RCS CL temperatures > 320°F and all of the following are met:

Answer 22

1. at least 1 RCP operating
2. PZR level ≤ 92%
3. Plant heatup rate is limited to 60°F per hour

Note: LTOP will still arm ≤350°F

Question 23

Tech Spec 3.5.2 ECCS - Operating

Answer 23

Two ECCS trains shall be operable (Modes 1-3)
→ECCS trains are CCPs, SIPs, RHRPs and piping
→SI Accumulators and RWST not considered part of the LCO
→all ECCS subsystems credited for LOCA

Note: operation in Mode 3 with ECCS pumps made incapable of injecting per LTOP (LCO 3.4.12) is allowed for up to 4 hrs or until temp of all 4 cold legs >375° F, whichever comes first.

Question 24

Tech Spec 3.5.3 ECCS - Shutdown

Answer 24

One ECCS train shall be operable (Mode 4)
→an operable train is CCP and RHR (doesn’t include SIP) capable of taking suction from RWST and swapping to sump
→an RHR train is operable when aligned for shutdown cooling if capable of being manually realigned to ECCS
→if RHR subsystem inoperable, take action to restore immediately
→if CCP subsystem inoperable, restore within 1 hr

Question 25

What happens if we get a blackout while we are in Cold Leg or Hot Leg Recirc?

Answer 25

→RHR pumps trip and do not sequence back on with the BOS →RHR Pumps have Operator Lockout →CCPs and SIPs lose their suction source (SIPs also trip on BO and don't restart) →must turn off CCPs to prevent damage →would have to manually restart RHRPs after BOS OL times out, and then restart CCPs

Question 26

With the RWST level at empty (<9%), _____________________ should not be operated with suction coming from the RWST.

Answer 26

RHRPs, SIPs, and CCPs

Question 27

RHR Miniflow Valves u-FCV-610 & 611

Answer 27

→500 gpm minimum →outlet of RHR HX to suction of RHR Pump →FT on pump discharge →opens at 746 gpm →closes at 1402 →powered from uEB1-1 (610) and uEB4-1 (611)

Question 28

RHR HX Flow Control Valves u-HCV-606 & 607

Answer 28

→full open in standby →fail open on loss of air or power uPC1/uPC4

Question 29

RHR HX Bypass Valves u-FCV-618 & 619

Answer 29

→controls total system flow to 3950 gpm →normally closed when in standby; maintained in manual and closed with 0% demand →fail closed on loss of air or power →powered through uPC1 and uPC4 with backup from uC1 (from process control cabinet 05/06)

Question 30

RHR Shutdown Cooling Mode Flowpath

Answer 30

→suction from hot legs 1 & 4 →through 8701 & 8702 →through RHR HX (cooled by CCW) →back to train related cold legs (Tr A = CL 1 & 2, Tr B = CL 3 & 4) →PCV-131 in CVCS used to control RCS pressure when shutdown

Question 31

ECCS Cold Leg Injection Flowpath

Answer 31

→pumps auto start on SIS (at 10 sec) →suction from RWST through 8812s →3800 gpm through each pump with RCS <200 psig →through RHR HX (cooled by CCW) →both trains inject to all 4 cold legs →cross connect valves (8716s) between CLs 1&2 and CLs 3&4 normally open so that one pump can supply all 4 cold legs

Question 32

ECCS Cold Leg Recirculation Flowpath

Answer 32

→RWST drops to Lo-Lo 33% →suction swaps to containment recirc sump →suctions to CCPs and SIPs tap off between RHR HX outlet and FCV →still injects to all 4 cold legs

Question 33

Which hot legs does RHR inject to during hot leg recirc? Why?

Answer 33

→hot legs 2 & 3 →suction for shutdown cooling is off of hot legs 1 & 4, so it can't also inject into those legs

Question 34

RHR Design Basis

Answer 34

→bring plant from 350° F to 140° F in 24 hrs →single train able to remove residual heat once Rx has been shut down for 150 hrs →low head ECCS injection