Main Steam

Question 1

What does main steam provide steam to

Answer 1

• High Pressure turbine
• MSR’s
• Feedwater pump turbines
• Steam seal system
• AFA
• AS

Question 2

What do the ADV’s provide

Answer 2

• Allow cooldown/ heat rejection without the main
  condenser
• Allows Rapid C/D / depressurization during SG tube
  rupture

Question 3

What is installed at the outlet nozzles of the SG’s

Answer 3

Flow restrictors to limit flow of steam in case of line break (limit heat load in CNTMT)

Question 4

What are the 8 safety design basis of the MSSS

Answer 4

1. Dissipate heat even without condenser
2. Automatic Isolation vlvs
3. SG’s and piping up to MSIV’s designed for safe
   shutdown earthquake (SSE)
4. Accommodate and tolerate environmental condit.
5. Single failure will not contribute to
   -Initiation of LOCA
   -Integrity of other stm lines
   -safe Rx shutdown
   -transmit excess load to CNTMT
6. Class welds are accessible for inspection
7. Flow restrictors to limit flow in case of break
8. Provide stm to AFA

Question 5

What is the quantity and characteristics of Main Steam Safeties

Answer 5

• 5 per line
• relieving capacity divided equally
• Total capacity is > 100% steam flow
• Located UPSTREAM of MSIV’s (CANT be isolated)

Question 6

How does the MSIV actuate during an MSIS

Answer 6

• Accumulator will apply full pressure to operator

- Designed to close within 4.6 seconds

Question 7

How does the MSIV Bypass actuate during an MSIS

Answer 7

• Mod installed new acutator
• Designed to close within 4.6 seconds against
  1400psid

Question 8

How does SBCS support the RCS

Answer 8

• Automatically modulates to maintain steam header
  pressure and therefore RCS Temperature
• Used during Start up, Shutdown, post trip

Question 9

What are the characteristics and failure mechanisms of MSIV’s

Answer 9

• Hydraulically operated
• Control Power: directly from battery or PK bus
• Spring and Wedge gate vlv
• Fast Close in 4.6 seconds

Loss of Power - Fail Closed
Loss of IA - As Is, can still FAST CLOSE

Question 10

What are the characteristics and failure mechanisms of MSIV Bypass vlvs

Answer 10

• Air operated
• Control Power PK
• Balanced Globe vlv
• Close in 4.6 sec against 1400 psid
• Each vlv has a A&B powered solenoid, both needed
  to operate the vlv

Loss of Power - Fails Closed
Loss of IA - Fails Closed

Question 11

What are the setpoints of the Main Steam Safeties

Answer 11

1250 psig
1290 psig
1315 psig
1315 psig
1315 psig

Question 12

What is the design accumulation and blowdown of the Main Steam Safeties

Answer 12

Accumulation - 1%

Blowdown - 3%

Question 13

How long does it take for an ADV to stroke fully stroke

Answer 13

up to 3 minutes

Question 14

What are the normal and back up modes of force to operate ADV’s

Answer 14

Normal - IA
B/U - N2 auto if IA <100 psig
Emergency - Manual

Question 15

What is the sizing basis for ADV N2 accumulators

Answer 15

16 hours of Station Blackout Coping Strategy

Question 16

What is the failure mechanisms of the ADV’s

Answer 16

Loss of Power - Fail Closed

Loss of IA & N2 - Fail Closed

Question 17

How are the SG Downcomer Isolation vlvs normally operated

Answer 17

• IA moves shuttle vlv

- N2 aligns to operator to open or close vlv

Question 18

How long will the Downcomer N2 B/U last

Answer 18

8 hours

Question 19

What is the failure mechanism of SG Downcomer Isolation vlv

Answer 19

Loss of power - Fails OPEN

Loss of IA & N2 - Fails Closed

Question 20

What is the power supply for SG Downcomer Isolation vlvs control power

Answer 20

PK

Question 21

What is the failure mechanisms of FWIV’s

Answer 21

Loss of power - Fail Closed

Loss of IA - Fail As is can still FAST CLOSE

Question 22

What is the power supply for ADV Controller and permissives

Answer 22

Controllers - PNA/B
Permissives - PKA/B/C/D

A loss of any of the power supplies will inop 2 ADV’s

Question 23

What indication is there for a blown fuse in an ADV permissive

Answer 23

When the permissive switch is operated, it will indicate the Red light and BOTH green lights will be dimly lit

Question 24

Which SG vlvs will close upon a MSIS

Answer 24

• Downcomer Isolations
• Economizer Isolations
• MSIV’s
• MSIV Bypasses
• Upstream Trap Isolations

Question 25

What is the FWIV/MSIV Exer/Test Switch for

Answer 25

- EXER - slow close vlv to 90% and then reopen verifies vlv is operable - ACC CH TEST - Disch accumulator to reservoir, no longer used

Question 26

What is the pressure range of the MSIV/FWIV accumulators

Answer 26

5000-5400 psig

Question 27

What is required for MSSV's to be "Operable"

Answer 27

Mode 1-3 2-5 MSSV's operable in mode 3 >5 up to 10 MSSV's operable as power increases All 10 MSSV's required at 100%

Question 28

What is required for MSIV's to be "Operable"

Answer 28

Mode 1 Mode 2-4 except when all MSIV's closed and off 4 MSIV's and assoc. actuator trains shall be operable ≥2 MSIV's inop: 1 HOUR -Restore to 3 operable

Question 29

What is required for ADV's to be "Operable"

Answer 29

Mode 1-3 Mode 4 if relying on SG for heat removal 4 ADV's shall be operable