Section 3.73 MFRV and FRV Bypass

Question 1

What is T.S. 3.7.3 Main Feedwater Regulating Valves (MFRVs) and MFRV Bypass Valves?

Answer 1

During MODES 1, 2,

AND

Mode 3 except when both MFRVs and both MFRV bypass valves are either closed and de-activated, or isolated by closed manually actuated valves.

One or more MFRVs or MFRV bypass valves inoperable. Close or isolate inoperable MFRV(s) or MFRV bypass valve(s). Verify once every 7 days.

Not met, be in Mode 3 in 6 hours AND Mode 4 in 30 hours.

Question 2

Why do we have T.S. 3.7.3 Main Feedwater Regulating Valves (MFRVs) and MFRV Bypass Valves?

Answer 2

Closure of the MFRV and MFRV bypass valve effectively terminates the addition of feedwater to an affected steam generator, limiting the mass and energy release for
Main Steam Line Breaks (MSLBs) inside containment, and reducing the cooldown effects.

Question 3

What is included in the mass release calculation for MSLB?

Answer 3

Volume of piping configuration downstream of MFRVs and MFRV Bypasses.

Question 4

Are the MFRVs and FR Bypass Valves safety related?

How do the valves fail on loss of air?

Answer 4

No

As is

MFRVs can be pinned and operated via handwheel to isolate.

Question 5

What isolates main feed regulating valves and the main feed regulating bypass valves?

Answer 5

Containment High Pressure

• HIC-0703/0701 signal is grounded, closing valves

Low Steam Generator Pressure

• Only affected steam generator is isolated
• HIC Signal is grounded

High Level Overide

• HIC Signal is grounded
• Only on high level 84.7% in affected Steam Generator
• Can be disabled/bypassed with keyswitch.

Handswitch to close

Question 6

Which accident is more severe per the analysis, MSLB in orginal analysis or MSLB in containment with continued feedwater used in PRA?

Answer 6

MSLB in containment with continued feedwater.

• Not expected to result in unacceptable consequences.

Question 7

What makes the MFRV and MFRV bypasses Operable?

Answer 7

Considered OPERABLE when the isolation times are within limits, and are closed on an isolation signal.

Closure time for each MFRV and MFRV bypass valve is ≤ 22.0 seconds on an actual or simulated actuation signal.

Question 8

What is the basis for applicability of this technical specification?

Answer 8

Whenever there is significant mass and energy in the Primary Coolant
System and steam generators.