05000387/LER-1985-032, :on 851011 & 13,RWCU Sys Spilled Process Water & Resin Resulting in Isolation.Caused by Erosion of Valve Seat FV-14566A & Inadequate Single Valve Isolation.Valve Seat Replaced.Valve Control Circuitry Modified

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:on 851011 & 13,RWCU Sys Spilled Process Water & Resin Resulting in Isolation.Caused by Erosion of Valve Seat FV-14566A & Inadequate Single Valve Isolation.Valve Seat Replaced.Valve Control Circuitry Modified
ML20137Z251
Person / Time
Site: Susquehanna Talen Energy icon.png
Issue date: 12/02/1985
From: Sadvary D
PENNSYLVANIA POWER & LIGHT CO.
To:
Shared Package
ML20137Z226 List:
References
LER-85-032, LER-85-32, NUDOCS 8512110259
Download: ML20137Z251 (5)
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LER-1985-032, on 851011 & 13,RWCU Sys Spilled Process Water & Resin Resulting in Isolation.Caused by Erosion of Valve Seat FV-14566A & Inadequate Single Valve Isolation.Valve Seat Replaced.Valve Control Circuitry Modified
Event date:
Report date:
3871985032R00 - NRC Website
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LICENSEE EVENT REPORT (LER) i FACILITV psaast (U DOCKET fouteGR (2)

PAGE (3 Susquehanna Steam Electric Station - Unit 1 o l5 l 0 l 0 I o 13 I 817 1 lOFl 0 l 4 TITLE del Reactor Water Clean-up System Spills and Isolations.

EVENT DATE 153 LER NURISER ($1 REPOft? DATE (7)

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ASSTR ACT lllawt to f 400 mascas. i.e., aperomerery rdines wande4pece typewreren maest 043 On October 11 and 13, 1985, the Unit 1 Reactor Water Clean Up (RWCU) System (CE)~ isolated when placing the 1A Filter Dmineralizer (F/D) in service. The RWCU isolation valves are Primary Containtmnt Isolation Valves (Engineered Safety Feature (ESF)) and these unplanned actuations are reportable in accordance with 10CFR72. Both events occurred due to abnormal leakage through the EV-14566A Flow Control Valve (EU/) which pressurized the system's low pressure piping and caused. pressure relief valve PSV-14561 to lift and discharge. The first event resulted in spillage of both process water and resin in areas inmediate and adjacent to the affected system. Autmatic system isolation on HI-FIOW occurred approximately one minute after event initiation and terminated the spillage. Spill counter measures included the activation of a support team. One instance of personnel contamination occurred in that an operator's shoe contacted spillage and was contaminated.

An estimated twenty gallons of resin spilled. Approximately five gallons of water spilled through the same relief valve on October 13, 1985 during systm restoration. The system isolated autmatically on "RWCU HI IFAKAGE".

Subsequent review and investigation determined that the EV-14566A valve seat was eroded and that the as-designed single-valve isolation between the high and low pressure systems was inadequate.

The FV-14566A valve seat was replaced and a modification to the valve control circuitry installed to provide double valve isolation between the high and low pressure systems.

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RC Form 3644 U S. NUCLEAR KEGULATOAY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPRovEo cua No. siso-clo4 EhPIRES S/3115 PAC 8LITY NAME tu DOCKET NUMBER (2)

LER NUMBER (6)

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This report describes two isolations of the Reactor Water Clean Up System (RWCU) (CE) which occurred on 10/11/85 and 10/13/85. The RWCU System isolation valves are containment isolation valves (Engineered Safety Feature (ESF)), and unplanned actuations are reportable per 10CFR72 (B) (2) (ii).

Refer to Attachment 1 for a simplified drawing of the system discussed in this License Event Report.

On 10/11/85, with the Unit 1 Reactor at 100% power and the RWCU 1B Filter Demineralizer (F/D) in service, the lA F/D was isolated for Maintenance to investigate / work on the Flow Control Valve, EV-14566A. Operations, including supervision, Maintenance, and Health Physics personnel were assembled to support the maintenance activity which was initiated by 3 report that the FV-14566A valve appeared to be bound in the open positica.

Operations personnel assumed manual control of the F/D Program Sequencer and manually stepped through the RWCU "A" F/D program to establish a system configuration within which the FV-14566A problem could be investigated.

Having successfully sequenced through the backwa.sh and precoat cycles, the operator positioned the " Vessel Isolation Control Switch" to the "Deisolate" position. Personnel in the area heard flow and observed the RWCU 1B F/D flow indication to go offscale high. Water and resin were observed emanating frm the floor drains. No water hanmer noises wete haux1.

The operator quickly returned the " Vessel Isolation Control Switch" to the

" Isolate" position, and placed the IB F/D in " Hold". While performing these operations, the operator's shoe became contaminated as the radioactive water spread across the floor. During th,is sequence the "RWCU Hi Flow" alarm in the Control Rom annunciated followed by the RWCU System isolating appronmately one minute after receipt of the alarm.

Health physics, maintenance, and engineering support personnel, under the direction of plant managment, were assembled to both initiate the appropriate clean-uo activities and to determine the cause of the event. Post-event investigation / follow-up consisted of: operator and health physics personnel interviews, two Plant Operations Peview Ccnmittee (PORC) meetings to review the recovery / restoration; syst s inspection and corrective maintenance on identified deficiencies, and the generation of technical procedure TP-161-007, Reactor Water Clean-up System Restoration Following System Isolation and Blow-down. No personnel errors or procedure violations were identified, and the deficiencies identified during system inspection were determined to be non-contributory to the event. No problems with program sequence logic or valve operation were identified.

1B F/D was precoated and returned to service approximately 0630 on 10/13/85.

'Ihe progranmer utilized during this sequence of operating activities is ccumon to both the lA and 1B F/D's.

1B F/D activities, e.g., backwash, precoat, deisolate, etc., were ccmpleted without incident.

The cause of this spill was initially attributed to manual cycling of the program sequencer allowing the F/D inlet isolation valve to open while the gaw 3.

1.

NRCF.em354A U S NUCLEAR KEGULATOav COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Areaovso ove No. siso-oio4 EXPlRES S/3125 FACILITY NAME l1)

DOCKET NUM8ER Qi (ER NUMBER (6)

PAGE (3)

Susquehanna Steam Electric Station ngp gy,p vE..

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, we,.,,, mmm HV-14510A and llB valves (backwash and precoat cycle isolation valves) were open thus allowing high pressure water to enter the low pressure piping. 'Ihis caused the relief valves on the low pressure piping to lift and discharge into the liquid radwaste drains. The drains backed up and overflowed on the floor.

Based on the above findings and conclusion, the decision was made to put the lA F/D back in service. At approximately 1130, on October 13, 1985, with the Unit 1 Reactor at 100% power, and the IMCU IB F/D in service, lA F/D was being returned to service using operating procedure OP-161-001. After precoating this F/D, the operator proceeded per the procedure to place the " Vessel Isolation Control Switch" in the "Deisolate" position. The influent and effluent isolation valves (HV-14531A and 32A) opened and the flow control valves (HV-14506A and W-14566A) remained closed per indication at the local panel. The operator heard a loud " bang" and saw the Pressure Relief Valve PSV-14561 on the low pressure piping discharge into the floor drain.

In the Control Rom, the alarm for "RWCU System Hi Leakage" annunciated. The systs flow indicator pegged high and after the designed time delay, the system isolated.

No personnel contamination occurred during this incident and the spillage was estimated at approximately five gallons of water and no resin.

Additional atts pts to restore the system to service were terminated pending empletion of an expanded review / evaluation of the circumstances leading to both incidents. Personnel interviews were conducted including in situ reviews of operator actions and observations made during the event; plausible scenarios with and without operator error were developed; filter demineralizer logic sequences were reviewed; and leak tests were performed on various valves within the systs.

During the leak tests, flow control valve W-14566A failed to provide adequate tightness such that a test pressure could be established for leakage measurement. Engineering review of the 1A F/D logic sequence determined that the normal program sequence allows deisolation of the system with the precoat cycle still in operation. In this configuration, isolation between the high pressure and low pressure piping is dependent upon ' single valve isolation'.

The single valve for isolation was the leaky W-14566A valve. With the RWCU 1A F/D System filled with water (i.e., " solid") and the system "deisolated",

leakage through the FV-14566A valve allowed the entire system to becme pressurized frm the high pressure to the low pressure piping. This caused the PSV-14561 relief valve to lift.

The HV-14531A Effluent Isolation Valve was disasserrbled and inspected. No wear or damage was found. However, the ball and seats were replaced. The FV-14566A Flow Control Valve was disassetrbled and inspected. It was found that the soft seat had been empletely eroded. The seat was replaced.

Post-maintenance leak testing per test procedure TP-161-008 established that the repairs were satisfactory and leakage was reduced to acceptable levels.

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DOCKET NUM8ER (2)

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PAGE 131 Susquehanna Steam Electric Station 5'typ,

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The valve control sequence change was ccmpleted on 10/23/85. Test procedure TP-161-010 was ccmpleted to prove the operability of the emplete backwash and precoat cycles with the double valve isolation protection.

'Ihe system was subsequently filled, vented and restored per test procedure TP-161-009 to prepare to put one of the F/D's back in service. The IB F/D was precoated and successfully placed in service at approximately 1930 on October 23, 1985. The lA F/D was precoated and successfully placed in service at approximately 0030 on October 24, 1985. A similar modification for the Unit 2 RWCU F/D Valves' Control Sequence is being initiated.

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