ML20092A443
| ML20092A443 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 06/12/1984 |
| From: | Rybak B COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.16, TASK-TM 8755N, NUDOCS 8406190215 | |
| Download: ML20092A443 (3) | |
Text
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/'D Commonwealth Edison a
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,) one First Nttional Pirra. Chicigo. Illinois
( O 7 Address Reply to: Post Offica Box 767 (j Chicago Illinois 60690 June 12, 1984 Mr. Harold R..Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission
-Washington, DC 20555
Subject:
Quad Cities Station, Units 1 and 2 NUREG-0737, Item II.K.3.16 Reduction of Challenges and Failures of Relief Valves NRC Docket Nos. 50-254/265 References (a):
D.B. Vassallo letter to D.L. Farrar dated April 3, 1984 (b):
J.S. Abel letter to D.G. Eisenhut dated May 1, 1981.
Dear Mr. Denton:
Commonwealth Edison Company (CECO) has reviewed Reference (a) and the following is our response to the three questions presented, which were:
(1)
Which, if any, of the staff recommended modifications have been implemented, (2)- Which, if any, of the staff recommended modifications you proposed to implement,
-(3)
Whether you have implemented or propose to implement any of the other modifications or actions discussed in NUREG-0737, Item II.K.3.16 or in the BWR Owners Group report.
Question (1) Response:
The staff recommended modifications are:
(1)
Low-Low Set Relief Logic System or Equivalent Manual Actions; (2)
Lower the reactor pressure vessel water level isolation setpoint for main steam isolation valve closure from Level 2 to Level 1; (3)- Increase safety / relief valve simmer margin; and (4)
Preventative Maintenance Program.
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CommonwealthL Edison Company'has not implemented modification 1, clow-Low: Set, however, as part of NUREG-0737, Item I.C.1, CECO will-zimplement'the-Emergency Procedure Guidelines developed-by the BWR Owners.
Group. zThese procedures address the equivalent manual-action identified as an. option to' Low-Low Relief' set.
These procedures will be in place C
by October,n1985.
As identified in-the SER attached.to Reference 1, Modification
!2-is notLapplicable to Quad Cities'.
Simmer-margin, Modification 3 applies to the. Target Rock type safety / relief valve.
G.E.. Serv' ice Information Letter, 196, Rev. 3 recommends la 120 psi differential pressure between the valve setpoint end normal operating pressure.
Quad Cities normal operating pressure is
'1000 psigLand-the Target Rock setpoint is ll35 psig, therefore, meeting the G.E.. recommendation.
~Likewise, CECO has in place a preventative maintenance program forLthe relief. valves. :Per the plant' Technical Specifications, the relieff valve setting is checked every. refueling outage to assure the set pressure 11s as specified in the Technical' Specification.
In addition, thesTarget' Rock relief valve is overhauled or replaced witti an' 6
overhauled valve every other refueling outage.. The Electromatic. type-
' relief valves ats replaced every other refueling outage with rebuilt
[
valves (i.e.: - 50% of the valves are replaced every refueling outage).
- The "E"'Electromatic is replaced every outage.
The pilot solenoid is-replaced withia rebuilt unit every refueling outage.
E Question-(2) Response:-
-In reference 2 of this' letter CECO. stated that modificationsi mereinot-'necessaryJfor Quad Cities because design currently meets the Owners Group criteria of -90% below that of the referenced plants Jprobability for a stuck-open relief valve.
Therefore, CECO does not Lplan.to implement recommended modifications 1 and 2.
- Question (3)' Response
As part of CECO's modification program for 10CFR50, Appendix R and I.E.aBulletin 79-10B,-Environmental Qualifiction of Electrical equipment, a7 redundant RCIC system will be added and an analog transmitter / trip _
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1 system will replace the reactor vessel level scram monitoring system.
- The' redundant RCIC system will' reduce-the probability of a stuck open
'reliefcyalve by increasing the availability of the RCIC system, which "can-'be used to reduce reactor pressure and potentially eliminate SRV
,. opening.
The:BWR Owners Group position on NUREG-0737, Item II.K.3-16, identified numerous candidate-modifications which would reduce the-probability.of a stuck open relief valve.-
The new analog transmitter /
. trip system being installed addresses lie.7. 3.1.4.1 of the BWR Owners
-GroupEreport again decreasing the probability of a stuck open relief valve.
(
g H. R. Denton-June 12, 1984 In addition, NUREG-0737, item II.K.3.16, recommended modification number-7 states, " offset valve setpoints to open fewer valves per challenge."
Currently, Quad Cities has two relief valves set cpproximately 20 psig lower than the other three reliefs, therefore, meeting this recommendation.
In light of reference 2 and the above additional information, Quad Cities Station Units 1 and 2 meet the Owners Group criteria for reducing challenges to the relief valves.
Therefore, no further modifications are needed or planned at this time.
'If you have any questions concerning this matter please direct them to this office.
One-(l)-signed original and forty (40) copies of this transmittal are provided for your use.
Very truly yours, B. Ryba Nuclear Licensing Administrator 1m cc:
RIII Inspector - Quad Cities R. Bevan - NRR 8755N
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