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4804 > 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 800#
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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 Non-Safety Related 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 541°F. Which ONE of the following is the correct Steam Dump Pressure Controller setpoint required to maintain RCS temperature at approximately 541°F 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

4804 (2 decks)

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