Main Steam

Question 1

How many S/G safety valves are there?

What are the set points ?

Answer 1

5 per lead

1065 psig
1078 psig 
1090 psig
1103 psig
1115 psig

(1065+13+12+13+12)

Question 2

Purpose of in-line flow restrictor?

Where is it?

Answer 2

Develop small d/p for flow indication

Short distance from S/g in vertical section of main steam line

Question 3

What is purpose of steam traps?

What is a hazard?

Answer 3

Remove moisture from steam lines (reduce impingement and water hammer)

The are a burn hazard, to work properly they cannot be insulated

Question 4

Describe a MSIV

Answer 4

Two check valves back to back

• first is air opened, backwards, when air is reduced the valve falls into flowstream and steam closes valve
• to protect actuator, a rupture disc will blow out if valve is forced close too fast
• second check valve is normal check valve to prevent backflow

Question 5

MSIV numbers (FCV-41,42,43,44)

What is different about 42 and 41?

Why?

Answer 5

They have a thermal fuse

Possible, nearby xfmr fire could burn circuitry=> fuse, releases air keeping valve open, ensuring valve will close

Question 6

What will give a SLI signal?

Answer 6

Hi-hi Pcnmt (2/4 >22 psig)

Low steam line pressure (2/3 > 600 psig, 1/4 S/g, rate sensitive)(>P-11)

Hi Pstm rate (-2#/sec for 50 sec, rate sensitive)(<P-11)

Question 7

Why do steam line leads 2 & 3 MSIV bypass valves have a back up manual bypass?

Answer 7

If auto bypass valves cannot be opened, the steam traps down stream of bypass valves can be placed in service, making terry turbine operable

Question 8

Capacity of S/g safeties

Answer 8

110% flow @ 110% overpressure

Question 9

How are MSIV maintained open on degraded Instrument Air System?

Answer 9

Two backup air tanks down stream of check valves maintain air on MSIVs

Question 10

Main Steam Isolation/Bypass valve design features

Answer 10

-stop steam flow from 3/4 SGs on a steam line break downstream of MSIV(only one SG will blow down)
-stop steam flow from 3/4 SGs on a steam break upstream of an MSIV (only the faulted SG will blow down)

Question 11

Reasons for MSIV design features

Answer 11

-Limits rate of RCS temp drop(concern for return to criticality )

Question 12

AFW Steam Supply Design Features

Answer 12

-Redundant steam supplies
-Critical to maintain SG heat sink on loss of all AC power

Question 13

MSIV solenoid valves name, train, controlled from and how they work

Answer 13

SV-292 Train A (SSPS)
SV-298 Train B (SSPS and controlled by the CR)

Solenoid valves are energized to vent air, which closes the MSIV

Question 14

If steam flow increases what will happen to Tavg, Rods,Feed Flow, SG level

Answer 14

Tavg: decrease
Rod: out
Feed Flow: rise
SG level: rise

Question 15

If steam flow decreases what will happen to Tavg, Rods,Feed Flow, SG level

Answer 15

Tavg: rise
Rod: in
Feed Flow: lowers
SG level: lowers