05000387/LER-1984-017, Updated LER 84-017-01:on 840310,during Performance of Weekly Preventive Maint Activity,Spray Pond Riser Networks A-1 & B-2 Found Frozen.W/Advent of Mild Weather,Networks Thawed & Pumped down.Long-term Fixes Investigated

Updated LER 84-017-01:on 840310,during Performance of Weekly Preventive Maint Activity,Spray Pond Riser Networks A-1 & B-2 Found Frozen.W/Advent of Mild Weather,Networks Thawed & Pumped down.Long-term Fixes Investigated

ML20091P633
Person / Time
Site:	Susquehanna
Issue date:	06/06/1984
From:	Keiser H, Kuczynski L PENNSYLVANIA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
LER-84-017, LER-84-17, PLA-2228, NUDOCS 8406130119
Download: ML20091P633 (4)

LER-2084-017, Updated LER 84-017-01:on 840310,during Performance of Weekly Preventive Maint Activity,Spray Pond Riser Networks A-1 & B-2 Found Frozen.W/Advent of Mild Weather,Networks Thawed & Pumped down.Long-term Fixes Investigated

Event date:
Report date:
3872084017R00 - NRC Website

text

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""""} No ol9 9 l3 gl4 AeST ACT (bmst M 7400 more, u, aseroseviemy hfmen sempeasce rueentma haeW 088 The A-1 (89 risers) and B-2 (43 risers) spray pond riser networks were found to be frozen during the performance of a weekly preventive maintenance activity to pump down the risers. Af ter four days of milder weather, all four networks were thawed out and successfully pumped down. Unit I was shut down throughout the event; Unit 2 was in a pre-fuel load status. All spray headers and risers were inspected and no damage was found. The networks were pumped down every two days and monitored for leakage every day until March 31, 1984, when it was considered that the probability of the risers freezing again would be very low. Long term fixes are being investigated that will ensure that freezing of the spray networks does not occur again.

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e NRC Feren 3e4A U S. NUCLE AR KEGULATO3Y COMMIS$lON LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AreRovEo oMe No siso-oio.

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0l 1 0l 2 OF 0l3 TEXT rs o m <wer.ni.asse,nm During the investigation performed in response to spray pond riser crm damage caused by ice formation on the spray nozzles (LERs84-002 and 84-002, Rev. 1), concerns were raised that leakag a past the seats of the spray pond riser network inlet valves (2-30 in butterfly) could lead to ice formation in the risers themselves. A preventive maintenance activity was instituted to pump down the riser networks on a weekly basis to min-imize the possibility of freezing in the risers. Routinc maintenance of the riser network inlet valves is impractical since complete isolation of ESW is required and results in a one hour L.C.O.

The A-1, A-2, B-1 and B-2 spray pond networks were pumped down for the first time under the new procedure in February 27, 1984 at 2240 hours0.0259 days <br />0.622 hours <br />0.0037 weeks <br />8.5232e-4 months <br />.

On March 7, 1984 at 1505 hours0.0174 days <br />0.418 hours <br />0.00249 weeks <br />5.726525e-4 months <br /> the B-1 and B-2 networks were successfully pumped down. The A-1 and A-2 network pumpdown was not attemped because of a prerequisite in the pumpdown procedure which required RHttSW and ESW systems to be shut down. When ESW and RHRSW are running, it is very diffi-cult to pump down the networks associated with this loop. The spray piping drain pump discharges into the RHRSW Bypass line upstream of a restricting orifice. When RHRSW and ESW pumps are running (discharging through the bypass line), sufficient back pressure is created by the restricting orifice to drive the capacity of the drain pump far back cn its pump curve (small flow). A combination of this small flow and the leakage past the isolation valves, makes the time to drain down a network excessively long. The A loop of RHRSW was required to be running to support other plant evolutions and was not able to be shut down. On March 10, 1984, the A-1 and A-2 spray networks were attemped to be pumped down. The A-2 network was successfully drained but the A-1 network had indications of being frozen (no flow ob-served thru the A-1 spray network). After determining the A-1 network was frozen, the B-1 and B-2 networks were examined for similar conditions.

The B-1 network was not frozen and the B-2 network was suspected to be frozen. Outside air temperature was approximately'6*F when the frozen networks were identified.

Even though;a Limiting Condition for Operation was not incurred because of the risers being frozen, Unit I was in cold shutdown and Unit 2 was pre-fuel load, all risers were to be returned to service prior to re-start of Unit 1. Ambient temperatures moderated over the next few days and all riser networks were able to be pumped down when the procedure was run on March 14, 1984.- All spray headers and risers were inspected and no damage was found. '

From March 14, 1984 through March-31, 1984, the riser networks were pumped .

down every two days and monitored for leakage every day. Present directions regarding riser network pumpdown specify that, between September 1 and March.

31, the pumpdown will be done once per week, except when either of the following occur:

- when the outside air temperature drops 'to 35*F, riser' pumpdown will commence within 12 hrs., and will occur once every two days while temperature-is-below 35'F, or E ,"." N "" ""

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NRC Feem 3e6A u 5 huCLEAM P!MLATORY COMD SUON LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AreaovEo own No mo-oi a ExPtRES 8/31 M FACILITY NAME 11) , DOCKET NUMSER (21 LER NUMSEP (El PAGE (3)

Susquehanna Steam Electric Station . . . sagn 7v;5,y; Unit 1 1 0F 0151010101318 l 7 8 14 0 l1 l 7 l-- 0 10 0I3 0 l3 TEXT t# more apoco e regu.e4 see seutonalNAC form JK4'sJ 817)

-when the outside air temperature drops to 33*F, riser pumpdown will commence within one naur and will occur once every two days while temperature is below 33*F.

Guidelines have also been developed for spray pond operation to avoid freezing fo the risers and spray nozzles at low ambient temperature (32*F or below) when Residual Heat Removal Service Water (RHRSW) and Emergency Service Water (ESW) system heat loads make it desirable to direct flow through the spray networks. If pond temperature is above 75*F, the sprays may be run with the riser network bypass valves closed. This configuration insures that the pond can provide adequate cooling under even the worst case heat loads under the most severe hot weather meteorological condition anticipated. If pond temperature is between 60*F and 70*F, the sprays should be run with the riser netwcrk bypasu valves open. This configu-ration provides moderate cooling and regulation of the rate of change of pond temperature. If the pond temperature is A0*F or less, the cr7;/s should remain isolated with the riser ne.twork bypass valves open. If tne pond temperature is less than 60*F and the use of sprays is unavoidable, flow through the sprays should be maintained so that the height of the sprays is 4-12 inches above the nozzles (accomplished by opening the by-pass valve). If the sprays are ooerated in this range, a stagnant con-dition is avoided and the potential for free n ing is reduced because droplet sizes are maximized and the amount of time t he droplets are exposed to the air is minimized.

This occurrencs is reported under 10CFR50.73(a)(2)(v), because one large and one small spray network would have been unable to perform their safety function of heat removal from cooling water used in the Emergency Service Water system and the Residual Heat Removal Service Water system. Since positive assurance could not be provided that the frozen risers would be thawed prior to the need to utilize the spray network, it must be assumed that the single failure criteria for the spray network could no longer be met. The Station's FSAR (Section 9.2.7.3.1) contains analysis of spray pond capabilities under a LOCA/ Forced Shutdown scenario with only one spray network available, and concludes that the spray pond would still meet the performance requirements of an ultimate heat. sink. Thus, while the single failure criteria could not be met, the units could have been safely maintained under a LOCA/ Forced Shutdown situation (A-2 and B-1 spray arrays were available throughout this event). Also, engineering

. evaluation has shown that for single unit - operation, a LOCA can be safely dissapated by only one large array. (At the date of occurrence, only

. one unit was licensed for operation and one large and one small array were -

available for operation.) The bypass lines which allow returning water to be injected directly to the spray pond without passing through a spray network were available for operation throughout the. event.

Long term fixes'will be developed and submitted.to NRC Region.I by September 1

1, 1984, to ensure the freezing of the' spray header does.not. reoccur.

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June 6, 1984 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 84-017-01 ER 100450 FILE 841-23 Docket No. 50-387 PLA-2228 License No. NPF-14 Attached is Licensee Event Report 84-017-01. This event was determined to be reportable per 10CFR50.73(a)(2)(v) in that, during a preventive maintenance activity to pump down the spray pond network risers, portions 1 f the spray pond network risers were discovered to be frozen. A long-term fix will be developed and submitted to NRC Region I by September 1,1984.

H.W. Keiser Superintendent of Plant-Susquehanna LAK/pjg cc: Dr. Thomas E. Murley Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 Mr. R.H. Jacobs Senior Resident Inspector U.S. Nuclear Regulatory Commission P.O. Box 52 Shickshinny, PA 18655 ff*S$

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