ML18153C340

LER 90-008-00:on 900727,determined That RCS Leakage Greater than 10 Gpm as Indicated by Level Drop on Vol Control Tank Level Recorder.Caused by Broken Gage Sensing Line in Letdown Sys.Sensing Line repaired.W/900824 Ltr

ML18153C340
Person / Time
Site:	Surry
Issue date:	08/24/1990
From:	Kansler M VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
90-526, LER-90-008-01, LER-90-8-1, NUDOCS 9008310122
Download: ML18153C340 (7)

Text

August 24, .1990 Virginia Electric and Power Company Surry Power Station P. 0. Box 315 Surry, Virginia 23883 U. S. Nuclear Regulatory Commission Document Control Desk Serial No.: 90-526 Docket No.: 50-280 Washington, D. C. 20555 License No.:

• DPR-32 Gentlemen:

Pursuant to Surry Power Station Technical Specifications, Virginia Electric and* Power Company hereby submits the following Licensee . Event Report for Unit 1. REPORT NUNIBER 90-008-00 This report has been reviewed by the Station Nuclear Safety and Operating Committee and will be reviewed by Corporate Nuclear Safety. Very* truly yours, Enclosure cc: Regional Administrator Suite 2900 101 Marietta Street, NW Atlanta, Georgia 30323 f8~83 b8lf~ iggg~J8o :::; 9oot9 31012 F:*r:,:::

NRC fo,m :tM 19-SJI LICENSEE EVENT REPORT (LERI U.S. NUCLEAR REGULATORY COMMISSION APPROVED DMB NO. :t1li0-0104 EXPIRES: l/:t1/* FACILITY NAME 11) I DOCKET NUMBER 121 I PAGE 131 Surry Power Station, Unit 1 01s101010121s1n 1!0F1n*1i:, TITLE ,, RCS Leakage Exceeds 10 gpm Due to Gage Sensing Line Break El/ENT DATE 151 LER NUMBER 16i REPORT DATE 171 OTHER FACILITIES INVOLVED 181 MONTH DAY DPERATI ... G MOOE 18i YEAR YEAR ?::;::: SEQUENTIAL F'::': REIIISION

NUMBEl'I (:;:;::::

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.. 1 73.711bl --1--20.olO!il1111llil I0.3111cll1 I II0.7:tlall2llwl 73.711*1 .__ -20.olO!il111111Wl II0.311cll21 II0.73.1111211**1 0TH E 11 (St>>eil't in Ab1rrKt 1--1--1>>101111 ind in T1*r. NRC Form POWER I LEVEL Q 19 I 9 1--1101 -20.olO!il111111illl Jl II0.73111121111 II0.7311112lMIIIIAl 366AJ -20 . .o&lallt lltwl II0.731all2lllll 110.n1a11211,m1111

--20.'°511111 llwl I0.7311112111111 II0.731111211*1 iillli~ LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER AREA CODE M. R. Kansler, Station Manager COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIDED IN THIS REPORT 1131 CAUSE SYSTEM COMPONENT TURER COMPONENT TURER X IT I B I G X 1 x I XIX I I I I I I I I I I I I I I I I I I I IUPf'LEMENT AL IIEPOIIT EXPECTED l'ICl MONTH DAY -YEAR n.-YES (If....,, comol*rw EXPECTED SUBMISSION DATE/ Ei NO EXPECTED SUBMISSION DATE (151 I I I NIIC Form JN 19-SJI On July 27, 1990, at 0530 hours0.00613 days <br />0.147 hours <br />8.763227e-4 weeks <br />2.01665e-4 months <br />, with Unit 1 at 99% reactor power, the Unit 1 Reactor Operator (RO) determined that Reactor Coolant System (RCS) leakage was greater than 10 gpm as indicated by the level drop indicated on the Volume Control Tank (VCT) level recorder.

This was contrary to Technical Specification 3.1.C.5 which limits the amount of total RCS leakage. The source of the leak was a broken gage sensing line in the letdown system. The system was isolated in accordance with procedures, and no radiation

-monitor alarms were received.

The sensing line has been repaired.

Appropriate follow-up actions will be initiated pending determination of the failure mechanism of the tubing. The failure of the sensing line occurred after flow was diverted to. a previously isolated portion of the system. The previous shift had closed manual isolation v_alves for the unit's deborating demineralizers (deborator) in accordance with an optional section of an approved procedure.

The relief RO, during. the event, attempted to place the deborator in service using the divert valve only. Operating procedures will be clarified.

to eliminate confusion on operating practices.

---

---NRC FORW. 366A 16-891 FACILITY~AME

11) U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER 121 APPROVED 0MB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP-5301. U.S. NUCLEAR REGULATORY COMMISSION.

WASHINGTON, DC 20555, AND TO 1'HE PAPERWORK REDUCTION PROJECT 13150-01041, OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. LER NUMBER 161 PAGE 131 Surry Power Station, Unit 1 _ VEA~ :::::,:::

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_ I o Is I o I o I o I 2 18 I o 9 I o _ o I o 18 _ o I o o 1 2 joF o 16 TEXT (If more -co ii requitWI, usa *ddftlofltll NRC Form 366A'1J 1171 1. 0 DESCRIPTION OF THE EVENT On July 27, 1990 at 0530 hours0.00613 days <br />0.147 hours <br />8.763227e-4 weeks <br />2.01665e-4 months <br />, with Unit 1 at 99% reactor power, the Unit 1 Reactor Operator (RO) determined Reactor Coolant System (RCS) leakage to be approximately 15 gpm calculated from a level drop noted on the control room recorder for Volume Control Tank (VCT) level. The abnormal procedure (AP-16) for excessive RCS leakage was entered, and operators were dispatched to the Auxiliary Building to determine the source of the leak. A

• Senior Reactor Operator (SRO) noticed ' water flowing on the floor outside the area which encloses RCS letdown filter l-CH-FL-5, and notified Operations*

personnel m the mam control room. Normal letdown was promptly secured, and the Unit was* placed on excess letdown m accordance with AP-16. These actions resulted in isolating the leak and the RCS leak rate was then verified to be significantly less thari 10 gpm at 06.09 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> using the pressurizer and VCT recorder trends. A Notification of* Unusual Event, as defined by

• the Surry Emergency Plan, was not declared, since no power reduction was required.

The SRO determined the source of the leakage to be a sensmg line for the letdown filter pressure indicator which had failed at a 1/2 inch diameter "Swagelok!I fitting. The SRO isolated the sensmg line at 0629 hours0.00728 days <br />0.175 hours <br />0.00104 weeks <br />2.393345e-4 months <br /> by closing sensmg line isolation valve 1-CH-119 (EIIS-V).

At 0923 hours0.0107 days <br />0.256 hours <br />0.00153 weeks <br />3.512015e-4 months <br />, RCS total leakage was calculated to be .2.07 gpm with an unidentified leakage of 0.24 gpm. The above event is contrary to Technical Specification

{T.S.) 3.1.C.5, which allows a maximum leakage of 10 gpm from the RCS. This event also required a T. S. Limiting Condition for Operation be entered to identify the source of leakage within four hours.

NRC.FORP,I 366A (6.S9) FACILITY-t,jAME (11 U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LERI TEXT CONTINUATION DOCKET NUMBER (21 APPROVED 0MB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION

• COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-5301. U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1*He PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. LER NUMBER (61 PAGE 13) *vEAR :;:;>::::

SEQUENTIAL

REVISION ::::?;:; NUMBER :::::::-::

NUMBER Surry Pow~r Station, Unit 1 o 1s101010121s1091 o-0101s -010 013 oF 016 TEXT Ill mo,w -09 is r,quir.d.

uu *ddnional NRC Form 366A'&/ 1171 2. 0 SAFETY CONSEQUENCES AND IMPLICATIONS A limited amount of leakage from the RCS is expected, -but the maximum allowable values are 1 gpm from unidentified sources and 10 gpm from identified sources. These values are sufficiently low to ensure corrective actions are taken prior to the leakage becoming excessive.

Leak rate calculations are performed once per day, or more often if required.

During this event, the normal charging system was in service and was able to compensate for all RCS leakage and the leak was promptly isolated rn accordance with the AP. In addition, no radiation monitor alarms were received which indicates minimal amounts of -entrained gases from the leakage were released into the Auxiliary Building.

Gaseous release monitor recorders were checked, and it was verified that no releases above the alarm set point had occurred.

As a precaution, the Auxiliary Building was placed on filtered exhaust.

• Therefore, the health and safety of the public were not affected.

3.0 CAUSE The cause of the excessive RCS leakage was .the failure of the sensmg line (for pressure indicator PI-1166 for RCS letdown filter l-CH"'"F~-5) which occurred approximately 20 minutes after letdown flow was diverted to a previously isolated flow path. The operating crew pnor to this event had locally isolated the "A" deborating demineralizer 1-CH-I-3A FDM) by closing the manual inlet and outlet isolation valves for the deborator.

This was done rn accordance with an optional portion of the operating procedure for removmg the deborator from service. Log entries and communications made at the time did not explicitly indicate the deborator had been manually isolated.

The RO at the time of the event attempted to place the deborator m service by solely operating the divert NRC FOR~! 366A 16-89) FACILITY'tiAME 111 U.S. NUCLEAR.REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (21 APPROVED 0MB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS ANO REPORTS MANAGEMENT BRANCH IP-5301. U.S. NUCLEAR REGULATORY COMMISSION.

WASHINGTON.

OC 20555. ANO TO 1'HE PAPERWORK REDUCTION PROJECT (3150-01041.

OFFICE OF MANAGEMENT ANO BUDGET. WASHINGTON.

OC 20503. LER NUMBER (61 PAGE (31 YEAR *:-:-:-:-:

SEQUENTIAL

REVISION Surry Power Station, Unit 1 *:::*::::

NUMBER :*:::::.:

NUMBER 0 1 5 I O I O I O I 21 8 I O 9 I O -0 I . 01 8 -0 IO O I 4 OF O I 6 TEXT (If rr1019 -,,.r:e is f9'1Uif9d.

u .. additional NRC Farm 3156A 'sl 1171 valve switch from the control room. This is common practice after the deborator is initially manually aligned to the system (normally at the end of core life) and is verified as functioning correctly.

When the operator attempted to place the deborator m service using only the control *room switch,* the system pressurized up to the letdown pressure relief valve (l-CH-RV-1289) set point (200 psi) which lifted and diverted flow directly to the VCT. Approximately 20 minutes later, the tubing failed, and the RO noticed the VCT level decrease.

He calculated the RCS leakage as approximately

15. gpm. The exact cause of the sensmg line failure has not been determined.

The pressurization of the piping due to aligning the letdown flow to the isolated deborator is not considered to be sufficient, by itself, to have caused the 1/2 inch diameter stainless steel sensing line (rated m excess of 2000 psig) to break unless tubing was already m a degraded condition.

A preliminary analysis was performed on the failed end of the

• tubing and determined that* the initial fracture was brittle m nature. A detailed.

analysis will be performed to determine the exact failure mechanism.

The event was initiated due to failure of the operating shifts to communicate the positions of the manual isolation valves for the deborating demineralizers.

The deborator 1s only used at* core end-of-life (EOL) to remove the last amount of boron from the RCS pnor to refueling.

It is placed in service by openmg manual valves and sampling pnor to use. Thereafter, common practice is to operate the divert valve switch, only, from the control room to put the deborator m the flow path . when required to control boron concentration.

The manual isolation valves are not normally closed unless a problem occurs. The

• N.'IC FORM 366A (6-89) FACILITY NAME (11 U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT-*CONTINUATION DOCKET NUMBER (21 APPROVED 0MB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-5301. U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104).

OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. LER NUMBER (6) PAGE (31 Surry Power Station, Unit 1 o Is Io I O Io I 21 8 I o 9 Io -o 1

• ol 8 -o Io o Is oF ol 6 TEXT (If moro space is n,quirod, uu addi&onal NRC Form 366A's/ (171 operating procedure for removing the deborator from service includes optional steps for closing the manual isolation valves. The RO prior to the event performed all steps of the operating procedure, including the closing of manual isolation valves, but did not make explicit communications because he was not aware of the common operating practice and the potential for confusion.

4. 0 IMMEDIATE CORRECTIVE ACTION{S)

The operations shift performed the

• required procedures and isolated the leakage path well within allowable Technical Specification time limits. 5. 0 ADDITIONAL CORRECTIVE ACTION{S)

The failed end of the tubing was cut off and retained for. analysis.

The existing sensing line has been repaired.

Visual inspections showed no obvious conditions which *could have caused the failure. 6. 0 ACTIONS TO PREVENT RECURRENCE Operating procedures which contributed to the event will be clarified to indicate that closing the manual isolation valves is not commonly done during normal operation of the deborator.

In addition, to eliminate confusion on' operating practices, an administrative procedure is .currently being written to clarify which operating evolutions are considered "skill of the craft". Also, this event has been discussed with the. operating shifts. Following completion of analysis of the failed end of tubing, appropriate additional inspections and repairs will be initiated.

• I L_ ~lC FORM 366A (6-89) FACILITY NAME.(1) U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2) APPROVED 0MB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS

• INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS.MANAGEMENT BRANCH (P-530). U.S. NUCLEAR REGULATORY COMMISSION.

WASHINGTON.

DC 20555. AND TO 1HE PAPERWORK REDUCTION PROJECT (3150-0104).

OFFICE OF MANAGEMENT AND BUDGET. WASHINGTON.

DC 20503. LER NUMBER (6) PAGE (3) Surry Power Station, Unit 1 0 I 5 I O I O I O I 21 8 IO 91 0 -0 IO I 8 -0 I O 01 6 OF O J 6 TEXT (If more -co is ,..quit9d, use oddmonol NRC Form 366A's/ (17) 7. 0 SIMILAR EVENTS LER 87-13: RCS Leakage Greater Than T.S. Limits Due to Failed. Packing on a Loop Stop Valve. LER 87-25: RCS Leakage Greater Than T.S. Limits Due to Valve Seat* Leakage. 8. 0 MANUFACTURER/MODEL NUMBER Not known.