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2. RO32 Systems > Steam Dumps > Flashcards

Steam Dumps Flashcards

1
Q

On a turbine trip/load rejection 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 steam dump 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 steam dump loads?

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

What are CRID 3 steam dump loads?

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

What are CRID 4 steam dump 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 capacity 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 high Auctioneered Tavg?

A
  • The highest Tavg of all 4 rcs loops
21
Q

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

A
  • Auctioneered High Tavg - Tno-load
22
Q

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

A
  • Auctioneered High Tavg - Tref
23
Q

What signal gives you Tref?

A
  • MPC-253 (First Stage Impulse #)
24
Q

When will group I open with the Turbine Trip Ctrlr?

A
  • 0°F to 10°F ΔT - Modulates open
  • 0%-33% Demand
  • If > 10°F ΔT -Trips Open
25
Q

When will group II open with the Turbine Trip Ctrlr?

A
  • 10°F to 20°F ΔT - Modulates Open
  • 33%-67% Demand
  • If > 20°F ΔT - Trips Open
26
Q

When will group I open with the Load Reject Ctrlr?

A
  • 5°F to 9°F ΔT - Modulates open
  • 0%-33% Demand
  • If > 9°F ΔT - Trips Open
27
Q

When will group II open with the Load Reject Ctrlr?

A
  • 9°F to 13°F ΔT - Modulates open
  • 33%-67% Demand
  • If > 13°F ΔT - Trips Open
28
Q

When will group III open with the Load Reject Ctrlr?

A
  • 13°F to 17°F ΔT - Modulates open
  • 67%-100% Demand
  • If > 17°F ΔT - Trips Open
29
Q

Why do none of the steams dumps open in the first 5°F ΔT on a load rejection?

A
  • Rods are good for a 10% load rejection
30
Q

What are the two modes of the steam pressure controller?

A
  • Auto (setpoint is 1005#)

- Manual

31
Q

Which mode only allows modulating of steam dumps?

A
  • Steam Pressure Mode

No trip functions

32
Q

How much turbine load are the steam dumps designed to handle on a load rejection?

A
  • 40% Load
33
Q

How do the Trip Open Solenoids fail?

A
  • Fail to Modulate
34
Q

What is the Power Supply for the trip open solenoids?

A
  • VDAB
35
Q

*** 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 and group 2 modulating.

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

A. armed and dumping steam to the condenser with group 1 trip open solenoid bistables energized and group 2 modulating.

36
Q

If MPC-253 or MPC-254 Fail High in Tavg mode, what affect will it have on steam dumps?

A
  • Will have no affect
37
Q

If MPC-253 Fails low in Tavg mode, what affect will it have on steam dumps?

A
  • Will have no affect because it has no arming signal
38
Q

If MPC-254 Fails low in Tavg mode, what affect will it have on steam dumps?

A
  • Will have no affect because it has no demand signal
39
Q

If you take the ctrl selector switch to off/reset, what will it do?

A
  • If you previously bypassed your P12 signal, it will re-enable P12
  • De-energizes arm/block solenoids
40
Q

What are the trip open signals for Turbine Trip bistables for steam dumps? ***

A
  • 10°F Group I
  • 20°F Group II
    (Direct 20# air to the trip/open valves)
41
Q

What are the trip open signals for Load Rejection bistables for steam dumps?

A
  • 9°F Group I
  • 13°F Group II
  • 17°F Group III
    (Direct 20# air to the trip/open valves)
42
Q

If CRID 1, 2 and 4 are lost, can steam dumps still operate?

A

No, steam dumps remain closed

43
Q

Whats the fastest cooldown rate allowed with steam dumps?

A
  • 100°F per hour
44
Q

If UPC-101 fails high while in steam pressure mode, what will happen to steam dumps?

A
  • Groups I and II will go full open until P12 is met
45
Q

If UPC-101 fails low while in steam pressure mode, what will happen to steam dumps?

A
  • Any open steam dump valves will close
46
Q

If Tavg fails high > 20°F ΔT with no turbine trip, what will happen to steam dumps?

A
  • Nothing will happen, because the C7A and C7B arming signals are not in
47
Q

If Tavg fails high > 20°F ΔT with a turbine trip, what will happen to steam dumps?

A
  • Groups I and II will go full open and stay full open until P12 is met and then it will cycle at 541°F
48
Q

Load Rejection control will maintain temperature within ___ between Auctioneered High Tavg and Tref with no rod motion. ***

A
  • 5°F
49
Q

While in Tavg mode if MPC-254 fails low, what will the happen to the steam dumps

A
  • Since no actual temperature deviation is present, no air signal will be developed to open the steam dumps even though C7A and C7B are present

2. RO32 Systems (54 decks)

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