ML042960366

Discussion and Proposed Resolution of NRC AIT URI (Unresolved Issue) Relating to MSIS Impact on AF-A Operability (6/14/04 Three Unit LOOP Trip).

ML042960366
Person / Time
Site:	Palo Verde
Issue date:	07/02/2004
From:	Oakes D, Vogt D Arizona Public Service Co
To:	Office of Nuclear Reactor Regulation
References
FOIA/PA-2004-0307
Download: ML042960366 (2)

Text

Discussion and Proposed Resolution of NRC AIT URI (unresolved issue) Relating to MSIS Impact on AF-A Operability (6/14/04 Three Unit LOOP trip)

During the three Unit LOOP (6/14/04) a question was raised concerning MSIS impact on AFA-P01 OPERABILITY. The MSIS actuation closes solenoid isolation valves SGA-UVI 133 (steam trap SGN-M23 isolation valve) and SGA-UV1 134 (steam trap SGN-M24 isolation valve). These traps are upstream of the MSIV's and remove condensate from the steam supplied to the Terry Turbine (AF-A) pump. Procedure 400P-9SG01 "Main Steam" Section 4.9 "Critical Steam Trap Blowdown Operation" identifies these traps as affecting the operability of AFA-PO1. The basis is stated in the procedure hidden text as follows: Thtese steam trapsare requiredto be "blown-down" on a periodicbasis whlen the trap is removedfroin service and the unit is in Modes I through 4 with the steam generatorsrequiredforheat removal because condensation buildup can occur. EER-90-AF-Oil, overspeed trip IMAFA-KOl on 4-24-90, identified the Root Cause of Failureas excessive amounts of condensation in the steam lines due to out-of-service steam traps. The EER recommends that i'ith a trap identifled as being out-of-service alternateactions to remove the moisture are required. These alternateactions 'ill prevent the buildup of condensation in the main steam lines to the point that the steam driven Aux FeedwaterPump might trip on overspeed wihen trying to start.

Proposed Correction Actions This EER should be revisited. We have installed numerous plant Mods since 1990 to enhance AFA-PO1 availability. If the steam traps are no longer required for AFA-POI OPERABILITY, this issue is resolved and we can remove the steam trap requirement from 400P-9SGOI. If the EER 90-AF-01 1 conclusion remains valid, we should provide AOP/EOP guidance for maintaining AFA OPERABILITY following an MSIS. CRDR 2719463 was written to address this issue.

Discussion with the EOP Procedure Owner confirmed that our EOPs do not consider the impact of AFA-POI OPERABILITY following an MSIS. Our review confirmed that this impact is not addressed in 40AO-9ZZ17 "Inadvertent PPS-ESFAS Actuations" (Section 6.0, MSIS) either. I also discussed this condition with Carl Landstrom - SG system engineer, and Jim Moreland, STA. There appears to be three basic mitigating strategies -

these are listed in what we believe to be the order of preference. Obviously, ifAFA-POI is already INOPERABLE, the strategies are no longer applicable.

1) Override and open SGA-UVI 133 & SGA-UVl 134 following an MSIS. This is not an immediate concern since moisture buildup occurs over several hours. This could be included in EOPs/AOPs such that this step is not necessary if AFA-POI is already running. If AFA-P0I is started later, that step should consider instructions to close/ensure closed SGA-UV1 133 & SGA-UV1 134. Engineering should take a look at this recommendation to ensure that we're not excessively loading the condenser during LOCV or LOOP conditions. This approach would H:\OPS\STA\U2_STA\WORD\Trip reports\061404 Rx Trip LOOP\MSIS impact on AFA.doc z99350 Page I 7/2/2004

Discussion and Proposed Resolution of NRC AIT URI (unresolved issue) Relating to MSIS Impact on AF-A Operability (6/14/04 Three Unit LOOP trip) seem to be the simplest for the secondary board operator and should not have a significant impact on plant cool-down, condenser internals or induce any water-hammer.

2) Start AFA-PO 1 shortly after MSIS. When AF is required, the informal consensus is that most operators will first start AFB-PO1 due to ease of operation. If this is the case, AFA-P0 I could be started shortly afterward (after AF flow has already been established) to share some of the AF flow needs. The step should include a caution to align steam supply from the non-faulted/ruptured SG. AF-B could be left running to share AF flow or secured at the secondary operator/CRS' discretion. AF-A should probably be left running until SG pressure has dropped to the point where it no longer has enough enthalpy to adequately drive AFA-KO1.

3) Stage HP hoses and vent rigs in an E-Plan locker in or near the MSSS building.

Develop a Standard Appendix for steam trap blow-down. I believe this is an acceptable, (especially as an interim measure) but the least desirable, approach due to the potential industrial and radiological safety concerns, particularly while battling an event such as ESD or SGTR. It would also be an impact on AO and RP resources. These hoses/ vent rigs are still necessary to support steam trap isolation valve maintenance in modes 1-4.

4)

The last aspect is more philosophical. Addressing AFA-P01 OPERABILITY while still in an EOP is consistent with our current approach of only addressing those Tech Spec requirements that are necessary to mitigate the event. Addressing AFA-PO 1 early in an event reflects PVNGS' desire to maximize availability of our most important safety-related pump.

David A. Oakes 6/30/04 Don Vogt 7/2/04 Digitally signed Oy:-Vogt, Donald W(Z96416)

Date: 07/02/20d17§i A0 Reason: I am apprfig this document Location: PVNGS-H:\OPS\STA\U2_STA\WORD\Trip reports\061404 Rx Trip LOOP\MSIS impact on AFA.doc z99350 Page 2 7/2/2004