WEEK 4 > Steam Dumps > Flashcards

Steam Dumps Flashcards

(50 cards)

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1
Q

What are the steam dump controls based on?

A
  • Auctioneered High Tavg
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2
Q

Which group(s) stagger open instead of opening all together?

A
  • Group 1 only
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3
Q

Where are the arm/block solenoids powered from?

A
  • VDCD (Train “A”)

- VDAB (Train “B”)

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4
Q

How do the arm/block solenoids fail?

A
  • Fail to Vent (Blocks Steam Dumps)
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5
Q

What are CRID 1 loads?

A
  • Turbine Trip Controller
  • Load Rejection Controller
  • MPC-253 (T-Ref)
  • UPC-101 (bypass steam header)
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6
Q

What are CRID 2 loads?

A
  • Steam Pressure Controller
  • MPC-254
  • Tref Computer
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7
Q

What are CRID 3 loads?

A
  • No CRID 3 loads are associated with steam dumps
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8
Q

What are CRID 4 loads?

A
  • Arm/Block Solenoid Relays

- Auctioneered High Tavg computer

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9
Q

What is Conditional C7A and is it an arming or blocking signal?

A
  • Arming signal (Load Rej)

- 10% Step Load Change or 5% / min on MPC-254.
Allows operation of Group 1 and 2 Valves

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10
Q

What is Conditional C7B and is it an arming or blocking signal?

A
  • Arming Signal (Load Rej)

- 30% Step Load Change on MPC-254.
Allows operation of Group 3 Valves

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11
Q

What is Conditional C8 and is it an arming or blocking signal?

A
  • Arming Signal (Turb Trip)
  • 4/4 Main Turbine Stop Valves Closed
    OR
  • 2/3 Oil Pressure switches below 800psig
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12
Q

What is Conditional C9 and is it an arming or blocking signal?

A
  • Blocking Signal
  • 1 Circulating Water pp breaker closed.
  • CRID 2 energized.
  • Pressure switches on 3/3 Condensers ≥ 20.6 inHg
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13
Q

What is Conditional P12 and is it an arming or blocking signal?

A
  • Blocking Signal
  • 2/4 Tave < 541°F - Status Light ON
    (P-12 Active (Status Light ON) Steam Dumps are Blocked in All Modes until placed in “Bypass Interlock“)

(3/4 Tave > 541°F - Status Light OFF)

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14
Q

What does the bypass interlock for P12 allow?

A
  • allows group I steam dumps to operate when P12 met

Bypass seals in until reset or P-12 block clears

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15
Q

Which ctrl switch will reset C7A and C7B conditionals and how are they reset?

A
  • Mode Ctrl Switch and must be taken to off/reset
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16
Q

Which steam dump groups are allowed to operate when the turbine trip controller is activated?

A
  • Groups I and II
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17
Q

Which steam dump groups are allowed to operate when the load rejection controller is activated?

A
  • Groups I, II, and III
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18
Q

What is the design of the steam dumps?

A
  • Plant design accepts a step load reduction of 50% from full power by using the 40% from Steam Dump system and 10% from Rods
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19
Q

What is the purpose of the steam dumps?

A
  • Reduce RCS transients following substantial turbine load reductions by dumping steam to the condensers.
  • Remove decay and sensible heat stored in the RCS following a reactor & turbine trip without actuating SG safety valves.
  • Control RCS temperature when the turbine is at low load, or during startup, cooldown, and when maintaining mode 3.
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20
Q

What is Tavg?

A

Thot + Tcold (rcs legs) divided by 2

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21
Q

What is high Auctioneered Tavg?

Study These Flashcards
A
  • The highest Tavg of all 4 rcs loops
22
Q

What signals does the turbine trip ctrlr use to open steam dumps?

Study These Flashcards
A
  • Auctioneered High Tavg - Tno-load
23
Q

What signals does the load rejection ctrlr use to open steam dumps?

Study These Flashcards
A
  • Auctioneered High Tavg - Tref
24
Q

What signal gives you Tref?

Study These Flashcards
A
  • MPC-253 (First Stage Impulse #)
25
When will group I open with the Turbine Trip Ctrlr?
- 0°F to 10°F ΔT - Modulates open - 0%-33% Demand - If > 10°F ΔT -Trips Open
26
When will group II open with the Turbine Trip Ctrlr?
- 10°F to 20°F ΔT - Modulates Open - 33%-67% Demand - If > 20°F ΔT - Trips Open
27
When will group I open with the Load Reject Ctrlr?
- 5°F to 9°F ΔT - Modulates open - 0%-33% Demand - If > 9°F ΔT - Trips Open
28
When will group II open with the Load Reject Ctrlr?
- 9°F to 13°F ΔT - Modulates open - 33%-67% Demand - If > 13°F ΔT - Trips Open
29
When will group III open with the Load Reject Ctrlr?
- 13°F to 17°F ΔT - Modulates open - 67%-100% Demand - If > 17°F ΔT - Trips Open
30
Why do none of the steams dumps open in the first 5°F ΔT on a load rejection?
- Rods are good for a 10% load rejection
31
What are the two modes of the steam pressure controller?
- Auto (setpoint is 1005#) | - Manual
32
Which mode only allows modulating of steam dumps?
- Steam Pressure Mode | No trip functions
33
How much turbine load are the steam dumps designed to handle on a load rejection?
- 40% Load
34
How do the Trip Open Solenoids fail?
- Fail to Modulate
35
What is the Power Supply for the trip open solenoids?
- VDAB
36
A Unit 2 reactor trip occurred from 90% power. The following plant conditions exist: * Reactor trip breakers: OPEN * Main turbine stop valve (C): OPEN * Condenser vacuum: 21.4 in. Hg. * RCS Tavg: 561°F * Auto Stop Oil Pressure: 400 psig Assuming all other equipment operated as designed and no operator actions are taken, the Steam Dump system is: A. armed and dumping steam to the condenser with group 1 trip open solenoid bistables energized. B. armed and dumping steam to the condenser with groups 1 and 2 trip open solenoid bistables energized. C. armed but not dumping steam to the condenser because of a blocking signal. D. not armed and not dumping steam to the condenser.
A. armed and dumping steam to the condenser with group 1 trip open solenoid bistables energized.
37
If MPC-253 or MPC-254 Fail High in Tavg mode, what affect will it have on steam dumps?
- Will have no affect
38
If MPC-253 Fails low in Tavg mode, what affect will it have on steam dumps?
- Will have no affect because it has no arming signal
39
If MPC-254 Fails low in Tavg mode, what affect will it have on steam dumps?
- Will have no affect because it has no demand signal
40
If you take the ctrl selector switch to off/reset, what will it do?
- If you previously bypassed your P12 signal, it will re-enable P12
41
What are the trip open signals for Turbine Trip bistables for steam dumps?
- 10°F Group I - 20°F Group II (Direct 20# air to the trip/open valves)
42
What are the trip open signals for Load Rejection bistables for steam dumps?
- 9°F Group I - 13°F Group II - 17°F Group III (Direct 20# air to the trip/open valves)
43
If CRID 1, 2 and 4 are lost, can steam dumps still operate?
No, steam dumps remain closed
44
Whats the fastest cooldown rate allowed with steam dumps?
- 100°F per hour
45
If UPC-101 fails high while in steam pressure mode, what will happen to steam dumps?
- Groups I and II will go full open until P12 is met
46
If UPC-101 fails low while in steam pressure mode, what will happen to steam dumps?
- Any open steam dump valves will close
47
If Tavg fails high > 20°F ΔT with no turbine trip, what will happen to steam dumps?
- Nothing will happen, because the C7A and C7B arming signals are not in
48
If Tavg fails high > 20°F ΔT with a turbine trip, what will happen to steam dumps?
- Groups I and II will go full open and stay full open until P12 is met and then it will cycle at 541°F
49
During the final stages of an RCS heatup, the Steam Dump System is set to automatically control RCS temperature at 541oF. Which ONE of the following is the correct Steam Dump Pressure Controller setpoint required to maintain RCS temperature at approximately 541oF Tavg? A. 940 psig B. 955 psig C. 970 psig D. 985 psig
B. 955#
50
Load Rejection control will maintain temperature within ___ between Auctioneered High Tavg and Tref with no rod motion.
- 5°F
WEEK 4
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