SDCS

Question 1

What groups of steam dumps are armed on a Rx Trip ?

Answer 1

Groups 1 & 2

Question 2

When performing a cool down from 547 deg Tave what happens at P-12?

Answer 2

All steam dumps go close (stm Press mode=>only group 1 & 2 armed)

Must take both train A & B to bypass

This enables group 1 to be used to cool down past P-12 (543 deg)

Question 3

What is C-7a?

What is C-7b?

Answer 3

A- 10% LR = arms groups 1 & 2

B- 50% LR= arms groups 3 & 4

Question 4

If a load rejection occurred, but UI-500 is not high enough to open group 4 (10%’s), how can you open it?

Answer 4

Take individual pressure controller to manual and increase demand

Question 5

What steam dump valves are armed when in “steam pressure” mode?

Answer 5

Groups 1 & 2

Question 6

During a Rx Trip, are any steam dumps blocked?

If so, what signal blocks what valves?

Answer 6

Groups 1 & 2 armed, groups 3 & 4 blocked

P-4 train A blocks group 3 & 4

P-4 train B blocks group 4

Question 7

What does P-4 train B do w/respect to SDCS?

Answer 7

It blocks group 4

It tells the control system to use Rx Trip controller instead of LR controller

Question 8

Can steam dumps Trip open in “steam pressure “ mode?

Answer 8

No, there is only Trip bistable in Tave mode (Rx Trip or LR)

Question 9

How many groups of steam dumps are there?

Answer 9

Group 1 (4 valves, 40% er-->cond)
Group 2 (8 valves, 40% er-->cond)
Group 3 (9 valves, 35% er-->atm)
Group 4 (4 valves, 10% er-->atm)

Question 10

What happens when you cut in backup air to group 4?

Answer 10

All logic and controls to valves cutout, only control is from VB-3, by manual switch

Open–>more air to valve
Close–>bleeds air from valve

Question 11

What are positions of mode select switch, what do they do?

Answer 11

Tave- places SDCS in Tave mode(Rx Trip/LR)

Steam Press- SDCS armed, open based on press

Reset- removes C-7a & b arming signal

Question 12

What are positions for Steam Dump Control Bypass Select Switches?

Answer 12

Off reset- defeats all arming signals & resets P-12 interlock

On- allows steam dumps to be armed

Bypass intlk- bypass P-12 for group 1 only

Question 13

What actuates the following lights?

Unblock Steam Dump Valves

Trip open Steam Dump valves

Modulate Atmos relief valves

Answer 13

Usdv- groups 1, 2 or 3 armed

Tosdv- Trip open bistables made up any group

Marv- groups 3 or 4 armed

Question 14

What are functions of SDCS?

Answer 14

• match Tref to Tave on LR
• match Tnl to Tave on Rx Trip
• assist plant S/u and S/d until plant sync or sep from grid
• c/d plant to RHR conditions (350 deg)
• heat sink, depress, c/d various accident conditions
• 85% capacity
• open 10% er’s before safeties
• achieve subcooling after SGTR w/o condenser

Question 15

40% Steam Dump (Groups 1&2) Arming Signals

Answer 15

1. Selected to ON and
2. No P-12 Low Low Tavg (Can Bypass Grp 1), and
3. C-9 Condenser Available and
4. C-7A Turbine Load Rejection or
5. P-4 Reactor Trip Train A, or
6. Selected to Steam Press