ML20029C184
| ML20029C184 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 03/20/1991 |
| From: | Stols R COMMONWEALTH EDISON CO. |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9103260394 | |
| Download: ML20029C184 (8) | |
Text
{{#Wiki_filter:- - - _ _ _ - - - _ - _ _ - - _ - ^ .C:mmonw:alth Edis:n - '[ 1400 Opus Place ..J' 1 .., ( Downsrs Grove, Imnois 60515 March 20, 1991 Dr. Thomas E. Hurley, Director Office of Nuclear. Reactor _ Regulation
- U.S. Nuclear Regulatory -Cond ssion' H
=Hashington, D.C. 20555 Attn: Document Control _ Desk
Subject:
Quad Cities Nuclear Power Station Units 1 and 2 Proposed Modification to High Pressure Coolant Injection (HPCI) Steam Exhaust Line Vacuum Breaker Configuration NRC Docket No. 50-254/265-
References:
(a) H.J. Miller to Cordell Reed letter dated' October 26 -1990. (b) 04G. Eisenhut to D.M. Muslof letter dated June 3, 1984, q Dr. Hurley: l On September.25, 1996 members of the NRC's (including-representatives from Region III-and NRR) and Commonwealth Edison's staffs conducted a meeting to discuss Quad Cities Station's actions to improve the performance of: containment isolation valves.during-10_CFR 50_ Appendix J testing (Reference -(a)). -During that-meeting -Commonwealth-Edison presented a proposed . modification-to eliminate the need to perform Type C: testing of the High Pressure Coolant: Injection (HPCI) steam exhaust line check valve-(2301-45). -Commonwealth Edison indicated that:we'would seek NRC concurrence on the 10 CFR 50 Appendix J testing requirements following the completion of the conceptual ?. design. 3 l Attachment A provides a description of the existing configuration and the-proposed modification. Commonwealth Edison requests the NRC's review and concurrence on our assessment of testing requirements for the proposed: modification. g\\ o h f.HLD908 /1 9103260394 910320 PDR-ADOCK 05000254 P pop
I Or. T. E. Hurley March 20, 1991 Currently, this modification is scheduled for installation during the upcoming Unit 2 Refueling Outage which is scheduled to begir in Sentember, 1991. (The installation schedule is subject to change based on (.,rts availability.) Commonwealth Edison respectfully requf s that NRC concurrence be received no later than May 1, 1991 to accommodate tnial design of the nodification. 4 Please direct any questions or comments to me at (708) $15-7763. Very truly yours, R. Stols Nuclear Licensing Administrator cc: A.B. Davis, Region III Administrator H.P. Phillips, Section Chief F.A. Maura, Inspector, Region III L.N. 01shan, Project Manager, HRR J.A. Kudrick, Technical Staff, HRR B.L. Durgess, Section Chief T.E. Taylor Senior Resident Inspector i Attachments: A: High Pressure Coolant Injection (HPCI) Steam Exhaust Line 1: HPCI Turbine Exhaust Line 2: ' Isolation Logic 3: HPCI Sparger Conceptual Design f.HLD A 08 /7 l ____m--
ATTACHMENT'A t HIGH PRESSURE COOLANT INJECTION (HPCI) .4 STEAM.EXHAUS1 LINE c MCEGROUliD On June 15, 1990 Region III issued Inspection Report 50-254/89024 and 50-265/89024 which sammarized the results of their inspection on the Quad-Cities 10 CFR-50 Appendix J Test Program. A Notice of Violation dich cited ineffective corrective actions to repetitive valve Tallures was,ssued. -One of the valves which was cited as a concern was the High Pressure Coolant Injection (HPCI) steam exhaust check valve (2301-45). In response to the Notice of Violation, Commonwealth Edison committed to accelerate the test interval for the 2301-45 valve to ensure that its containment function remains effective. On September 25, 1990 members of the NRC's (including both Region !!! and NRR representatives) and Commonwealth Edison's staffs conducted a meeting to further discuss the prcposed corrective actions. During that meeting, Commonwealth Edison proposed a modification to the HPCI steam exhaust configuration to eliminate the need for Type C testing of the 2301-45 valve. Commonwealth Edison' indicated that we would seek NRC approval on future Appendix J_ testing requirements for the modified system. IMSIIRG_C0HILGUEal10fi The existing configuration of the HPCI steam exhaust line is provided in Attachment =1. The E*'CI turbine exhaust line runs from the exhaust of the HPCI -turbine through the RhR corner room, penetrates the torus and discharges below-the torus water level. The line contains two large check valves (2301-45 and
- 74) which are designed to prevent water from backing up into the turbine.
Inside the forus, a vacuum breaker line which is equipped with two small_ check valves ties into the HPCI turbine exhaust line downstream of the two large check valves. During normal HPCI operation, this vacuum breaker line relieves the vacuum which is created by steam condensing in the exhaust line downstream of the large check valves. The vacuum breaker line inside the torus provider a path for-communication between the-inside'and outside containment atmospheres. The large check valves-are,-therefore, required to prevent post-accident containment-atmosphere from escaping. Appendix J Section II.H requires local leak. rate (Type C) _ testing of-these containment isolation valves; The 2301-45 has experienced repeated Local Leak Rate Test (LLRT) failures. It is believed that the 2301-45 valve condition deterioratas dua to unstable steam condensation during HPCI turbine low steam flow cond tions. -Previous-attempts to improve valve performance consisted of rede=1gning the 2301-45~ valve and/or changing the seating materials. These upgrades have not comoletely eliminated the leakage problems. 1HLO906 s --,.y
y ..g, ER0E01EDJ1001LLCM10N ' The propossd modification (Attachment'I) eliminates the air path between inside and outside containment atmospheres and the HPCI exhaust-line and . addresses the'cause ofithe' 2301-45 valve deterioration. First,Tthe existing vacuum breaker line inside the torus will be removed and capped. LThe HPCI exhaust line terminates below the minimum water level of-
- the suppression pool and, therefore, will not communicate directly with the containment atmosphere. The 11guld inventory of the suppression pool provides an effective water-seal for the exhaust line during the post-accident period.
Following the removal of the existing air pathway between the containment atmosphere and the HPCI exhaust line, the HPCI exhaust check valves will not require Type C testing. This determination is consistent-with the NRC position contained in_ reference (b). Eliminating the existing air leakage pathway between the torus and HFCI exhaust line also eitminates the vacuum breaker protection. In--order to -protect the HPCI turbine exhaust line from unstable steam condensation (chugging) and water hammer damage as well as to provide a vacuum relief function,Ean. exhaust line:sparger and a new vacuum breaker configuration is proposed. The sparger would-be installed on the end of the HPCI turbine exhaust line inside'the' torus, and is designed to promote more stable steam scondensation. The first_ row of holes on the'sparger will be located.at or. below the-current HPCI' exhaust line submergence -(See Attachment 3)..The new vacuum breaker line-would be external-to the torus and would be-equipped with .containmentlisolation valves (See Attachment 1).. Table-3.7-1.(Primary Containment Isolation) of the Quad Cities Technical Specifications would be: revised to include the two new isolation valves. This -.new vacuum line would be an isolatable air leakage pathway between the containnent and the HPCI exhaust Ilne. The outboard valve will be powered- -from~250.VDC Division 11 power source..The inboard-valve will be fed ' rom 480 VAC Division II power source. The new valves will have a control switch on Main Control Panel 90X-3. Valve position indicating lights will be located J adjacent to the control switches and within the Graphic Display Panel en Panel '90X-3. 4 i q l WLD606/4
Currently, the HPCI 230 -4 and 2301-5 valves (HPCI steam supply) isolate on a Group IV isolation signal. These signals are: High HPCI steam flow; High HPCI room temperature; or low reactor pressure. The new "tives will also be featured with an automatic isolation. The new containment isolation valves will start to close after the first closure of the two HPCI steam supply isolation valves (Reference Attachment 2). The new motor-operated valves will have a 30 second closure time which will allow sufficient time for the line to perform its vacuum relief. The new containment isolation valves will remain open during periods when the HPCI system is required to be in operational readiness (reactor pressure > 90 psig). In the event of a HPCI line break (which would result in HPCI high steam flow or high room tempera 6ures), the vacuum breaker line containment isolation valves will close. Duritg a large line break loss-of-coolant accident, the reactor woulo rapidly depressurize to less than 80 psig and the vacuum line containment isolation valves would clo:e. These isolations would eliminate the air leakage pathway from the torus thi 1gh the HPCI exhaust line. 10 CFR 50 Appendix J, Type C testing will be perfoi tad on the new containment isolation valves to demonstrate the leak-tight integrity. BEEUIS._0LldE_P.ROPQS E QjiQD lHCM IQN The proposed modification provides the following benefits: 1. Adds the ability to isolate the vacuum breaker line, to avoid the potential for a containment atmosphere leakage path through the HPCI turbine exhaust. 2. Improved reliability of the vacuum breakers with the "one-out-of-two twice" check valve configuration. 3. Ease of maintenance for vacuum breaker valves, since they will be external to the torus and, therefore, more accessible. 4. Improved steam condensation stability, since the new sparger is designed to provide stable condensation over a wide range of steam flows. This, in turn, should reduce the cyclic " slamming" or " chugging" loaj on the 2301-45 valve, and thus improving its reliability and performance. ZHLD800/5
i ATTACl! MENT 1 l HPCI TURBINE EXHAUST LINE MODIFICATION To CONTROL RaoM <- i i2 5 3 Il 30 N N [B0 6 4 Nd N N-- 4, f 7 ( 2306-24'-LX >' BLOCK VALVE (MANUAL GATE) / ~~TO iE' N '~ CUT LINE / REMOVED N STOP
- 8. CAPPED s%
/ '\\ ~*- C,V, t 2301-74 2399-5 's %,,j - f j' - - - -N- ,,q 2399-6 7 l [-cx; ~ TEST TAPI i ( / WATER o' LINE -- ? s ~ ~ \\ '[8,! 2301-45 [<' ~ 8 CHECK 'N j SPARGER VALVE (C V.) ~ N. / TURBINE SUPPRESSIbN 'l ~~ ~~ ~~ CHAMBER [-'.- , A _':y[] NOTES:
- 1. PHANTOM LINES DEPICT EXISTING PIPING.
- 2. NEV VACUUM BREAKER LINE VALVE NUMBERS ARE FOR REFERENCE ONLY.
- 3. TEST TAPS VILL BE ADDED TO PERFORM MDV LLRT AND CHECK VALVE FUNCTIONAL TESTS.
ATTACHMENT 2 !i lll!. ~ ell,!!!lli gli i a li1 E lll i l Elf i!g 8 v i e ill ill $g 8 a il lil ll! 4
e a 1 o l I I 1 l e i 1 I 24* DA I 4 1 g g g sg. s- ~~~ CONCENTRIC f' REDUCER e i / '- 3 ^ _. My y t _ /_,c ~_ --] Z ~ ^ _ _ ct EL.57r-s~ - -- n r e .It I I h I h Ilf 1 4 f 7 ? ils i M:N. y-2%* I h iii e 'l' mx. y-s%- EtEvanan or 1. L l ili .._e_ _ Ensypo PirE orece sli 85 i sii 8* MDL AREA 8I8 StPPORT PAO Ie I -{ BLOCKED OUT FOR l als il ~ 45* l 1G* DR 1 M EL D 4 4' ' I d h \\ O a s a tv I Ze NOTES: SUGGEST SCR129 DR SCH.160 PIPING l UNIT 2 HPCI SPARGER CONCEPTUAL DESIGN m - -}}