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ILOT > Control Rod Drive Mechanism and Hydraulics - 1.0 > Flashcards

Control Rod Drive Mechanism and Hydraulics - 1.0 Flashcards

1
Q

Describe the construction of the Control Rods

A

Primarily Boron, some have halfnium.

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2
Q

What is the purpose of the Velocity Limiter?

A

Limits drop to 5 ft/sec to mitigate the consequence of a rod drop accident.

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3
Q

What is the purpose of the Couple with a Spud Connection?

A

Can be uncoupled either below vessel or from fuel bridge.

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4
Q

What is the purpose of the Valve Disk?

A

Provides a path for cooling water from the drive up into the reactor when the rod is fully withdrawn and sitting on the bottom of the control rod guide tube. Also allows for scramming of the control rod using reactor pressure alone (without accumulator pressure).

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5
Q

What are the 5 cylinders the drive consists of?

A
  1. Outer Cylinder - Outer surface of the assembly.
  2. Inner cylinder - Forms passage for the collet fingers.
  3. Index Tube - The only movable tube. Notched every 6 inches to hold rod in position.
  4. Piston Tube - Connects pistons to/from withdraw line.
  5. Indicator Tube - Houses the reed switches.
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6
Q

Describe the layout of the reed switches.

A

53 total, one every 3 inches for position (00-48). 4 remaining switches provide full in, full out, over travel in, and over travel out.

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7
Q

What is the purpose of the Collet Fingers?

A

Holds the index tube in position.

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8
Q

What is purpose of the Piston Tube Buffer Holes and Belville Washers?

A

They work in conjunction to slow rod travel and reduce impact on a scram. During a scram, the drive piston sequentially covers the buffer holes, thus restricting flow, allowing pressure to increase and reduce the insert rate during the last 10% of travel.

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9
Q

What are the interlocks and actuations regarding the Scram Dump Volume?

A
  1. CRD SCRAM DISCH VOL NOT DRAINED - 15.3% (5 GAL)
  2. ROD OUT MOTION BLOCK - 65% (25GAL)
  3. CRD SCRAM DISCH VOL WTR LVL HI - 91.1% (35GAL) AND REACTOR SCRAM.
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10
Q

When is a rod considered operable?

A

S - Scram times are in spec.
C - Coupled
R - RPIS
A - Acc. pressure >940#
M - Movable

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11
Q

What are the CRD Suction sources?

A
  1. Cond. reject (normal).
  2. CST
  3. Cond. Xfer system.
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12
Q

Describe the operation of the CRD pump min flow valve.

A

Manually operated and returns to CST.

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13
Q

Describe the operation of the SDV vents and drains.

A
  1. They are normally open and close on scram.
  2. The O/B vent and drain valves close at least 5 seconds after I/B valves close.
  3. Both SDV drain to south RB sump.
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14
Q

Describe the operation of the SRI switches.

A
  1. There are two switches per rod and the positions are Norm/Test/SRI.
  2. Half scram for that rod if one switch is taken out of normal.
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15
Q

What are the conditions required to remove CRDH from service?

A
  1. MSS locked in S/D OR All rods full in.
  2. Recirc pumps are not running and do not require seal purge.
  3. Condensate M/U is capable of making up to the vessel.
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16
Q

What cools the CRD pump thrust bearing and gear box oil cooler and why?

A

RACS. Minimize time without cooling water to prevent Graphitar Seal Damage.

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17
Q

How is a rod coupling check performed?

A

Continuous withdraw on a full out rod and verify:
- No rod overtravel alarm
- Red Full Out light on Full Core Display
- RPIS indicates Pos. 48
- Proper NI response

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18
Q

Describe the operation of F-002A(B) (Flow Control Valves).

A

-Maintains 60-70 GPM
-Closes down to a minimum amount during a scram (mechanically gagged @ 15GPM). It closes since flow is sensed upstream of the charging header. Closing the valve allows the system to recharge the accumulators.

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19
Q

Describe the operation of the Stabilizing valves.

A

Cycle on rod motion to maintain constant flow through the PCV’s and FCV’s. Flow through the stab valves is normally 6 gpm. Withdraw set passes 2 gpm and insert set passes 4 gpm.

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20
Q

What occurs when both CRD pumps trip?

A

Accumulator presser lowers because piston moves up. Rods will scram with accumulator pressure, then reactor pressure.

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21
Q

What are the alternate methods of rod insertion?

A
  1. EO-302 - Remove RPS ckt fuses.
  2. EO-306 - Vent scram air header.
  3. EO-303 - ARI Test Switches (individual rod scrams)
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22
Q

What is the Suction Filter high D/P alarm setpoint?

A

9 psid

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23
Q

What is the Drive Water filter high D/P alarm setpoint?

A

20 psid

24
Q

What is the Accumulator Low Pressure alarm setpoint?

A

1000 psig

25
Q

What is the Accumulator High level alarm setpoint?

A

37 mL

26
Q

When can the scram discharge volume scram be bypassed and why?

A

Can be bypassed if MSS is in S/D or Refuel and this allows the reset of RPS
-This allows resetting the scram to drain the SDV.
-It also inserts a rod block.

27
Q

What system energizes the ARI valves and what are the actuation setpoints?

A

Energized by RRCS on Level 2 (-38”) OR 1071 psig RPV pressure.

28
Q

Number of control rods.

A

185

29
Q

Power supplies for the CRD pumps.

A

1AP207-10B430
2BP207-10B440

  • Powered via 1E breaker and Non-1E breaker on 10B437 (10B448).
  • 1E breaker LOCA load shed (can be O/R and opened from 10C650)
30
Q

CRD pump channels.

A

C & D

31
Q

CRD Pump flow rate

A

98 GPM

32
Q

CRD Pump trips.

A
  1. Suction pressure <25 HgA (2sec TD)
  2. LOCA level 1 (-129”, 1.68#)
33
Q

When does CRD pump runout occur.

A

200GPM
1083#

34
Q

Where does makeup water enter the reactor building?

A

Water enters the Reactor Building through isolation valve HV-4005 (located in Core Spray Pump Room “B” at the 70 ft elevation above the room cooler) and is delivered to the CRD pump suction filters.

35
Q

What do the Pressure Equalizing valves do?

A

2 valves, open at 75 and 85 psid. cross connect the cooling water header to the exhaust header to maintain the exhaust header near reactor pressure at all times

36
Q

What systems power/actuates the Backup scram valves?

A

Need both channels of RPS to actuate. Energizes with DC power to open. Also trips HWCI.

37
Q

How do Scram valves scram their associated rod?

A
  1. De-energize to open.
  2. Scram outlets open first.
  3. Rod will insert (slower than expected) as long as scram outlet opens. Inlet not needed for rod insertion.
38
Q

During operations of an HCU what valve should be operated first and last and why?

A

101 insert riser must be closed first when isolating a HCU (also must be last to open) or else a scram will cause damage if valve lineup is done incorrectly.

39
Q

What are the causes of excess rod speed during a scram and what does it damage?

A
  • Caused by excessive accumulator pressure or worn stop seals. This can damage the Bellville washers and graphite seals.
  • Excessive accumulator pressure can also damage index tube.
40
Q

Describe operation of the Full Core Display scram lights.

A

One blue scram light indication for each rod. Both scram valves for an HCU must be open for light to go ON.

41
Q

Purpose of scram pilot valves positive vent valves.

A

Minimize time required to exhaust scram valve header (each HCU) to shorten scram time.

42
Q

Describe operation of scram accumulators.

A

It stores enough energy to fully insert rod at lower RPV pressures (~600#). Supplemented by Rx pressure when operating at higher pressures.

43
Q

What happens when both Rx and accumulator pressure are low?

A

Scramming ability of rod may be degraded, thus the IOA in AB.IC-0001.

44
Q

Function of PCVs.

A

Controls pressure to the drive header.

45
Q

Function of FCVs.

A

Maintains flow to the cooling header constant.

46
Q

CRD Housing

A

Prevents ejection of a control rod.

47
Q

Velocity Limiter

A

Limits freefall of CRDA to <5ft/sec.

48
Q

Causes of Rod Drift IN

A
  • Scram inlet leak by.
  • 123 valve leak by.
49
Q

Causes of Rod Drift OUT

A
  • Collet finger break.
  • Excessive cooling water D/P.
  • 122 valve leak by.
50
Q

How do the scram valves work during a scram?

A
  • Scram outlet opens faster than inlet.
  • Blue scram light energizes when both are open.
51
Q

What can cause excessive scram speed and what can it cause?

A
  • Excessive accumulator pressure. This can damage the index tube.
  • Worn stop seals.

Both can damage the Bellville washers and graphitar seals.

52
Q

In what order should HCU valves be operated in order to prevent a scram from causing damage?

A

A scram can cause damage if the valve lineup is performed in the wrong order.
- BF-V101 must be shut prior to closing either BF-V102/V112.

53
Q

At what pressure can the reactor scram the rods.

A

RPV >600# should scram valve HCU.

(Lesson Plan) Scram Accumulator - stores sufficient energy to fully insert a control rod at lower reactor vessel pressures (less than 600 psig). At higher reactor vessel pressure, scram accumulator pressure is supplemented by reactor pressure.

54
Q

Loss of Instrument Air.

A
  • Scram flowpath opens charging/cooling water pressure drives rod.
  • SDV vents and drains go closed.
  • Scram inlets and outlets open.
55
Q

Retainment Override
What conditions will require the operator to LOCK Mode switch in SHUTDOWN?

A

Reactor Pressure < 900 psig
AND
Charging Water Header Pressure < 940 psig
AND
ANY WITHDRAWN Control Rod Scram Accumulator INOPERABLE.

56
Q

How does the idle CRD pump maintain its seals at pressure and ready for operation?

A

The operating pump provides the driving water and pressure via a pump cross connect

ILOT (93 decks)

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