ML20086M514
| ML20086M514 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/13/1991 |
| From: | Joshua Wilson TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-004, NUDOCS 9112170499 | |
| Download: ML20086M514 (4) | |
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'Deenmber 13. 1991 U.S. Nuclear Regulatory Cournission j
ATTN Document Control Desk j
Washington. D.C.
20555 1
Gentlement In the >"atter af
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEARlLANT (SQN) - REVISED CCSN!TMENT _ IN RESPONSE TO NRC BULLETIN 88 POTEN1:AL S4fETY-RELATE *> P'JMP LO53 i
Reference:
TVA letter to NRC dated March 13,.1990. "Sequoyah Nuclear Plan; (SQN) - Revised Response to NRC tulletin 88 ;
Potential. Saf ety-Related Pump Loss" The above reference provided TVA's revised response to NRC
?
As discussed in ;he referenced 1+tter TVA confirmed
'that pump-to-pwr.p interaction could occur if both residual heat removal L
(RiiH) pumps were operaten in parallel while on miniflow.- 'As a result,-
SQN coumitted to install check valves on'each units' RHR pun.p discharge piping to preclude the possibility for_ pump-to-pump interaction.
Following installation on each unit, SQN further committed to revise Emer6ency Operating' Instruction (E01) E-0, "'teacter Trip or Safety j
-Injection," and System Onarating instruction (SCI) 74.1, "Ruidual Heat Removal System," to remou interim measures currently used to prevent g j, extended pump-operation in-tne deadheaded candition.
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The interim measure containea in E-0 involves stopping one RHR pump when
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.both_RHR pumps are operating on mlniflow-following a safety injection r
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signal. This action was an interim measure to preclude having two RHk i
g pumps operating-in parallel post-accident causing pump-to-pump a.o ;
interactions (1.e., deadheading the weaker pump).
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40-During'the Unit l' Cycle $~ refueling outage, TVA it. stalled check valves in I
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'the RER pump discharge piping.
As a result of the installation of the M
Unit 1 check valves, the action to stop one RHR pump is no longer N
required:a8 an interim neasure on - Unit 1.
The interim measure will, r
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_}.NU,* 7) however,' remain appilcable to Unit 2'until the ched valves are it.s ta ll ed
. I {I IM during Unit 2 Cycle 5-refueling outage (scheduled to begin in
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March 1992).-
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U.S. Nuclear Regulatory Cor;*niasion Page 2 December 13. 1991 SQN fsaued unit specific E01s at, a result of extensive modifications to Unit i during the Cycle 4 refueline outage.
This condition (unit specific EDIs) existed when the commitment to remove Lae interim measure from E-0 for each unit was made.
However, at the end of the Unit 2 Cycle 4 refueling outage, SQN recombined the E01s into one set of instructions applicable to both units.
Rather than develop separate E0!s for each unit. SQN wi'1 retain the current b,,
wasures ia place :.ar toth units antil tr e l nit. :ne c e; valves have been installed on Unit 2 during the Unit 2 Cycle 5 refueling outage. This 'etter serves to inform NEC of a revisien to TVA's original c o=ni tmen t for revising E-; for each unit.
Accordingly, E-0 wil; be revised te remove tne interim neasures, before start-up trem the Unit 2 Cycle 5 refueling outage.
A second item related to the a' cove discussion involve s *VA's c omi tment for r; vising 501-74.1 to remove interin treasures e; prevent the possible pump-to-pump interactions.
As part of WN's procedure ggrade program, S01-74.1 has been renamed 3-50-74-1.
The interim measures :ontained in 0 74-1 (i.e., precautions f or the op erator ref are establishing parallel pump operation) J re no longer applicable to Unit 1 and have tnereby been removed for Unit 1.
The removal of the 'init 1 precautions within the 0-S0-74-1 fulfills TVA's Unit I conoitment far revising S01-74.1.
TVA's revised commitment associated with E-0 is stated in the enclosure.
Please direct qucations concerning this iscue to D. V. Goodin at (615) 843-7734.
Sincerely, k
D 'N J. L. Wilson l
Enclosure cet See page 3 E-- _--_-----------
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u U.S. Nuclear Regulatory Comission
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Page 3 Decernbe r 13, 1991 f
1 Enclosure cc (Enclosure):
- Mr. 3. E.1aBarge Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville. Maryland 20B52 NRC Resident' Inspector Sequoyah Nuclear Plant i
2600 Igou Terry Road l-Soddy Daisy. Tennesace' 37379 t
Mr. B. A. Wilson, Project Chief i.
U.S. Nuclear Regulatory Commission Reglon-11 101 Marietta 3treet, NW, Suite 2900 Atlanta, Georgia 30323 1
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ENCL.0SURE TVA COM1TMENT Following the installation of check valves in SQN's Unit 2 residual heat removal system. SQN Emergency Operating Instruction E-0 will be revised to remove the interim mear.ure currently used to prevent pump-to-pump interactions.
This revision vill be coreplete before the start-up from the Unit 2 Cycle 5. refueling outage.
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