ML17328A584

LER 90-002-00:on 900108,two MSIVs Exhibited Closing Time in Excess of Tech Spec 3.7.1.5 Limit of 5 S.On 900109 & 10, Confirmed That Excessive Condensation Collected on Vent Side.Caused by Inadequate insulation.W/900209 Ltr

ML17328A584
Person / Time
Site:	Cook
Issue date:	02/09/1990
From:	Blind A, Droste J INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-002, LER-90-2, NUDOCS 9002280017
Download: ML17328A584 (12)

Text

AC CELE RATED D1 BUTl 0 N DE }d 04 SYSI'EM REGULATO STATION INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9002280017 'OC.DATE: 90/02/09 NOTARIZED: NO DOCKET I FACIL:50-316 Donald C. Cook Nuclear Power Plant, Unit 2, Indiana & 05000316 AUTH. NAME 'UTHOR AFFILiATION DROSTE,J.B. Indiana Michigan Power Co. (formerly Indiana & Michigan Ele BLIND,A.A. Indiana Michigan Power Co. (formerly Indiana & Michigan Ele RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 90-002-00:on 900110,MSIV inoperability due to condensate accumulation on vent side of operating piston.

DZSTRZBOTZON CODE: ZE22T COPZES RECEZVED:LTR j ENCL [

TITLE: 50.73/50.9 Licensee Event Report (LER), Incidenti Rpt, etc.

NOTES:

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RECIPIENT COPIES ~

RECIPIENT COPIES XD CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL h PD3-1 LA 1 1 PD3-1 PD 1 1 GIITTER,J. 1 1 INTERNAL: D ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 S

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Indiana Michigan Power Company Cook Nuclear Plant P.O. Box "58

.Bndgman. Ml '9106 616 465 5901 INDIANA NICHIGAN POWER February 9, 1990 United States Nuclear Regulatory Commission

.Document Control Desk Rockville, Maryland 20852 Operating License DPR-74 Docket No. 50-316 Document Control Manager:

In accordance, with the criteria established by 10 CFR 50.73 entitled Licensee Event, Re ortin System, the following report is being submitted:

90-002-00 Sincerely, A.A. Blind Plant Manager AAB:clw Attachment cc D. H. Williams, Jr.

A.B. Davis, Region III M.P. Alexich P.A. Barrett J.E. Borggren R.F. Kroeger NRC Resident Inspector J.G. Giitter, NRC R.C. Callen G. Charnoff, Esg.

Dottie Sherman, ANI Library D. Hahn INPO S.J. Brewer/B.P. Lauzau

@00224<00/7 +00209 PDR ADOCI 0<00031b PDr:

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (689) APPROVED OMB NO. 31504104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLFCTION REQUEST: 50.0 HRS, FORWARD LICENSEE EVENT REPORT ILER) COMMENTS AEGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P630), V.S. NUCLEAR REGULATOAY COMMISSION, WASHINGTON, DC 20555. AND TO THE PAPERWORK REDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, OC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) PA E D. C. Cook Plant - Unit 2 0 5 0 0 0 3 1 6 1 OF "P TITLE<<I Main Steam Isolation" Valve Inopera i ity - Due to Con ensate Accumulation on Vent 1

Side of Operating Piston EVENT DATK (5) LER NUMBER (41 REPORT DATE,(7) OTHER FACILI'TIES INVOLVED (4)

MONTH DAY SEQUENTIAL IIEVISION FACILITY NAMES YEAR YEAR NVMSEtl re NVMSEII MONTH OAY YEAR DOCKET NUMBER(SI Cook Plant - Unit 1 0 5 0 0 0 3 1 5 0 1 1 0 9 0 9 0 0 0 2 0 0 0 2 0 9 9 0 0 5 0 0 0 THIS REPORT IS SUBMITTED PURSUANT T 0 THE REQUIREMENTS OF 10 CFR ('): (Cntce ont or mort ot rnt lottowrnd) (11 OPE RATING MODE IS) 3 20.402(SI 20.405(c) 50.73(el(2)(lv) 73.7)(S)

POWER 20.405 1 ~ I(lI(ll 50.34(cl(l I 73.71(c)

LEVEL 50.73(el(2llv)'0.73(el(2)(vSI p p p 20 406( ~ )(1)(lll 50.34(cl (2) OTHKR (Sptcrry in Aprtrtct Strow tnd in Ter I, HRC Form 20.405 ( ~ I( I I(IIl) X 60.73(e l(2) (I) .

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On January 8, 1990 with Unit 2 in Mode 3- (Hot Standby) surveillance testing of the Main Steam Isolation Valves (MSIV's) was conducted. Two MSIV's exhibited a closing time in excess of the Technical Specification 3.7.1.5 limit of five seconds. This condit'ion is believed .to have, existed during power operation. Additional MSIV testing on January 9, and 10, 1990 confirmed that excessive condensation was collecting on the vent side of the MSIV operating piston. When the dump valves were opened to vent-off steam from the MSIV operating piston, the accumulated condensate would flash to steam and result in increased MSIV closure times. Following an effort to blow out the MSIV condensate drain tubes, a series of tests were performed at various time intervals. to determine if the condensate problem had been resolved and verify MSIV operability. With the failure of 2-MRV-220 on January 11, 1990, at 0916 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.48538e-4 months <br />, it was evident that the condensate p'roblem was still present. All MSIV's were declared inoperable.and an Unusual Event was declared. A cooldown to Mode 5 (Cold Shutdown) was started.

Repair activities included disassembly of the MSIV's to enlarge the condensate drain tube port and the equalizing steam nipple. Additional insulation was placed on the MSIV's, vent piping and valves.

NRC Form 366 (669)

NRC FORM 366A V.S. NUCLEAR REGULATORY COMMISSION (6J)9) APPROVED OMB NO. 31500)OS EXPIRES: S/30/92 LICENSEE EVENT REPORT (LER) ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION" AND REPORTS MANAGEMENT BRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555. AND TO THE PAPFRWORK REDUCTION PROJECT (3(500104). OFFICE OF MANAGEMENTAND BUDGET. WASHINGTON, OC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEQVENTIAL REVISION NVMEER NVMSER

-D. C. Cook Plant -

TEXT /// more spece ie reqvirN/. Irse ~ Unit 2 HRC %%drm 3(SEA's/ (12) o s o o o 3 1 6 9 0 0 0 2 0 0 0 0 CONDITIONS PRIOR TO OCCURRENCE Unit 2 in Mode 3 (Hot Standby).

DESCRIPTION OF EVENT On January 8, 1990, surveillance testing of the Main Steam Isolation Valves (MSIV'-s) (EIIS/SB-ISV) was conducted. Two of the MSIV's exhibited a closing time in excess of the Technical Specification 3.7.1.5 limit of five seconds.

Following each MSIV failure, the MSIV was declared inoperable and immediately retested. In both cases the retest demonstrated the valve closed within the Technical Specification time limit and the, MSIV was declared operable.

Additional tests were conducted on January 9, 1990. A substantial amount of water was observed to flash out of the dump valve (EIIS/SB-VTV) vent stacks during the first'est of each MSIV. Three MSIV's. exhibited a closing time in excess of the Technical Specification 3.7.1.5 limit of five seconds.

Following each MSIV failure, the MSIV was declared inoperable and retested.

In- each case the retest demonstrated the valve closed within the Technical Specification time limit and the MSIV's were declared operable. (See attached test table).

The January 9, 1990 testing verified that enough condensation could accumulate on the vent side of the piston within a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period to'ender the valve inoperable. Unit 2 was held in Mode 3 to further diagnose the root cause of this issue.

On January 10, '1990, a series of diagnostic tests were performed to determine the extent that condensate within the MSIV operating cylinder volume could affect MSIV stroke time. A strip chart was used to record pressure within the volume as a function of time. Closure time was measured in the control room, measuring the time from the dump valve switch actuation until the MSIV valve light indicated the valve was closed. MSIV stem travel time was measured locally. The following time. line is similar to each MSIV tested and represents typical circumstances experienced by all MSIV's.

0 1 Sec: 2 Sec. 3 Sec. 4 Sec. 5 Sec. 6 Sec.

TIME CONTROL ROOM SWITCH ACTUATION TO LIGHT MSIV STEM TRAVEL FLASHING r NRC Form 366A (669)

NRC FORM 355A U.S. NUCLKAR REGULATORY COIAMISSION APPROVED OMS NO. 31504104

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EXPIRES. 4/30/92 ESTIMATED bURDEN PER AESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REQUEST) 500 HRS. FORWARD COMMENTS REGARDING SURDEN ESTIMATE TO THE RECORDS TEXT. CONTINUATION AND REPORTS MANAGEMENT SRANCH IP430). U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. OC 20555, AND TO 1HE PAPERWORK REDUCTION PAO/ECT 13150410i)i OFFICE OF MANAGEMENTAND SUDQET, WASHINGTON. DC 20503.

FACILITY NAME l1) DOCXET NUMSER (21 LER NUMSER IS) ~ AGE 13)

YEAR SEQUENTIAL REVISION NUM Kll @ NUM 9 II D, C. Cook Plant - Unit 2 2.' 000 OF o s o o o 3 1 6 9. 0 0 0 1 0 TEXT /// vere PPPCP )I /Pquia/, MPP //I/bbP//YRC %%dnt) 30SA'P/ )IT)

Local observation verified substantial quantities of water and steam being discharged from the vent stack from T 0 until MSIV stem travel began.

Two of the MSIV's exhibited a closing time in excess of the Technical Specification 3.7.1.5 limit of five seconds. 'Following each MSIV failure, the MSIV was declared inoperable and retested. In each case the retest was an acceptable value and the MSIV was declared operable (see attached test table).

The Action Requirements of Technical Specification 3.7.1.5 were fulfilled at all times for Modes 2 and 3. When an MSIV fai'lure occurred, an immediate retest demonstrated that the valve was operable. On January 10, 1990, it was realized that the failures which occurred on January 8, 1990, were believed to have existed during power operation. Notification to the NRC was made on January 10, 1990, reporting that we were outside the plants'esign bases on January- 8, 1990. At the time this notification was made, the MISV's were operable per Technical Specification Action Requirements for Modes 2 and 3 operation. The MSIV's were operable since the testing resulted in expelling the condensate, from the vent side of the valve's operating piston. The MSIV's would remain operable as long as the valves were cycled frequently enough td prevent excessive amounts of condensate from collecting on top of the operating piston. ~

The MSIV testing confirmed that the slower, main steam stop valve stroke times were symptoms of an unacceptab1e quantity of condensate accumulating in the upper valve volume; When a dump valve is opened the condensate flashes to steam 'this causes increased venting time due to delaying the development of sufficient Delta-P across the MSIV piston, to close the MSIV's. A"logical hypothesis was formulated that condensate was'not draining down into the lower volume through the drain tube (see attached drawings) fast enough to prevent accumulation in the upper volume. Acting under the premise that this flow path was in some way restricted, possibly due to mineral deposits plating out on the inside diameter of the drain tube, it was decided to attempt to blow-out this drain tube.

A process was devised to remove (blow-out) any possible restrictions located within each MSIV drain tubes. This was accomplished by maintaining the MSIV in its closed position and for approximately one hour with the dump valves open. In'doing so, main steam was capable of forcing its way past the parallel closure disc, through the drain tube into the upper volume, and exhausted out the vent stack., It was hoped that this exhausted steam would be of sufficient velocity to carry away any restrictive material.

NAC Form 395A 1509)

NRC FORM SSSA ISeS) t LICENSEE EVENT REPORT ILER)

TEXT CONTINUATION P

U.S. NUCLEAA REGULATORY COMMISSION APPAOVED OMS NO. S)504104 E)IPIR ES: S/20/02 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REOUESTI 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPOATS MANAGEMENT BRANCH IPe30). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PRO/ECT 121504)OS). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, OC 2050K IrACILITYNAME )1) DOCKET NUMBER )2) LER NUMBER IS) PAGE IS)

YEAR 4g sEovsNTIAL oE IISVISION NVMSSR NVM SN D. C. Cook Plant - Unit 2 o s o o o '3 1 6 9 0 0 0 2 0 0 0 4. OF 1 0 TEXT lllmore <<eoe /e reevrw/, ow //r/orO/ //RC %%dnII SSSAB/ ) 12)

Additional testing was performed to determine if the maintenance action was successful and ensure .MSIV operability. This series of tests had staggered intervals to ensure MSIV operability w'as maintained. On January 11, 'est 1990, at 0916 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.48538e-4 months <br />, 2-MRV-220 exceeded the allowed closing time. An Unusual Event was declared as all four (4) MSIV's were declared inoperable causing a Technical Specification 3.0.3 shutdown. This was classified as a 'One-Hour

,Reportable Event and NRC notification was made at 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />. A cooldown to Mode 5 (Cold Shutdown) was commenced.

CAUSE OF EVENT Investigation revealed that the failure of'he MSIV's was caused by excessive condensate accumulation on the vent side of the MSIV 'operating piston. The excessive condensate accumulation was a result of the following contributing factors:

Insulation Less than Current Desi n-Insulation on MSIV, the vent piping and associated valves was less than current design specifications. The insufficient insulation resulted in increased condensation rates in the MSIV.

2. Dum Valve Seat Leaka e The quantity of condensate that can collect is related to the mass of saturated steam permitted to enter the upper equalizing steam volume.

When steam is allowed to escape this volume, it will be replaced by additional saturated steam which increases the Delta-P and prevents drainage.

3. MSIV Actuator Desi n The combined effects of one and two above resulted in increased condensation rates, developing greater Delta-P across the operating piston than assumed by design during normal operation (MSIV's in steady-state open position). The rate at which condensate can flow down from the upper volume through the drain tube is limited by the diameter of the drain tube port holes. Condensate will accumulate within the upper equalizing volume if it cannot be drained faster than it forms.

If the steam nipple is insufficiently sized, a Delta-P will exist across the piston restricting condensate drainage.

NRC Fomr SSSA ISeS)

NRC FORM 355A US. NUCLEAR REGULATORY COMMISSION APPROVEO OM8 NO, 3150010>>

ISJ)91 EXP IR ES: >>/30/92 ESTIMATED 8UROEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUESTI 50.0 HRS. FORWARD COMMENTS REGARDING 8URDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT SRANCH IP430). U.S. NUCLEAR s REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT 13150010l). OFFICE OF MANAGEMENTAND 8UDGET, WASHINGTON, DC 20503.

FACILITY NAME 111 DOCKET NUMSER 12) LER NUMSER 15) ~ AGE 13)

YEAR ,>>jj SEOVENTIAL HVM 5<<

yg: AEVOON

<~+ HVM D. C. Cook Plant - Unit 2 o s 0 o o 3 1 6 9 0 0 0 2 0 0 0 50F 1 0 TEXT ////>>P/>> <<eC>> /1 I>>qvnd, u Je PI/P5/>>/ HJIC fcnn 38559/ )12)

ANALYSES,OF EVENT In addition to Technical Specification 3.7.1.5, slow MSIV closure times affect Technical Specification items 3.3.2.1, Table 3.3-5, 5.h (High Steam Line Flow - Low Low Tavg), 6.h (Steam Line Pressure Low), and 7.c (Containment Pressure-High High). These items use the valve closure time as part of their overall time response requirement. Examination of surveillance data for these items show that item 7.c, steam line isolation on high-high containment pressure in seven seconds, would not be met. This was reported to the NRC on January 10, 1990, under the provisions of 10 CFR 50.72.b.l.ii.B as a condition that was outside of the plant's design basis.

The investigation of this problem has identified that the slower closure times were caused by water accumulation on the top of the steam piston. With water present, the piston movement is slowed as the water flashes to steam during the venting process. The water. accumulation occurs over time and is also affected by the leakage past the MSIV dump valves. Once the water is removed from the top of the piston, as would occur during a valve test,. a retest conducted immediately thereafter would indicate normal va3ve actuation times.

As water would accumulate during operation, there is evidence that the condition may have existed prior to the surveillance. Thus, it is probabl'e that Technical Specification 4.7.1.5.1 was not met.

Westinghouse has evaluated the consequences of increasing all applicable Technical Specification response times by three seconds, and they have concluded that the FSAR acceptance criteria are met using the longer response times. The mass and energy releases for an outside of containment steam line break were compared with the current FSAR values, and the'nvironmental qualification of the equipment in the affected locations has not been compromised. Thus, there has been no significant degradation of plant safety as a result of the increased MSIV closure times.

Since Unit 1 has the same type of valve, an evaluation was also performed concerning the 'impact on .Unit 1. The evaluation concluded that the MSIV's on, Unit 1 are considered to be operable and fully supportive of the Chapter 14 accident analyses. At the last surveillances, all Technical Specifications applicable to steam line isolation were met, and the historical data indicate no pattern of closure time deterioration. Further, the recent Westinghouse analysis shows that sufficient margin exists with MSIV closure time such that plant safety is not compromised if the'system response time is increased by three seconds. Thus, the recent events associated with the Unit 2 MSIV's do not cause undue concern with respect to the continued safe operation of NRC Fons 355A (5891

NRC FORM 344A U.S. NUCLEAR REGULATORY COMMISSION APPROVEO OMS NOl31500)0O

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ExpIREs: el30)92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REOUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT. CONTINUATION AND REPORTS MANAGEMENT SRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT 131504)104), OFFICE OF MANAGEMENTAND SUOGET.WASHINGTON. DC 20503.

FACILITY NAME 11) DOCKET NUMSER 12) LER NUMSER (4) I'AGE 13)

YEAR rX<O SEQUENTIAL ?P~W IIEYISION NVMFEA i.rX NVM D. C. Cook Plant - Unit 2 0 0 o s o o o 3 1 6 9 0 0 2 0 06 oF1 0 TEXT N more a>>oo Jr reqond, Irre orroeo'oner HRC form SOD'e) ) 12)

Unit 1. This conclusion is als'o based on the belief that the present performance of the Unit 1 MSIV's do not result in the probability or consequences of an accident being increased, any new type of accident being created, and any Technical Specification margin of safety being reduced.

CORRECTIVE ACTIONS Upon reaching Mode 5, all four MSIV's were disassembled and a visual examination performed. These examinations revealed that the drain tubes had not experienced any physical degradation that could have restricted the condensate flow path. All dimensions were verified. Electric ITE de France (FDF) was contacted concerning their approach at resolving similar circumstances. EDF provided their investigation findings and valve design modifications. We implemented the EDF recommendations.

After all available sources of information were technically evaluated, it was determined that all Unit 2 MSIV's would be modified via Minor Modification 2-Mf-079. Under this modification the diameter of drain tube port holes would be increased from 1'/8" (0.125") to 5mm (0.197") and the diameter of the equalizing steam nipple would be increased from 1/8" (0.125")'o 10mm (0.394"). Two performance related functions would be improved in this manner.

l. Increasing the size of the drain tube port holes provid'es a larger area to improve condensate flow through the actuator piston.

2. Increasing the size of the equalizing steam nipple will provide a less restrictive path for steam to pass up through the piston to maintain equilibrium and prevent steam from passing through the drain tube and inhibit drainage.

It was also discovered at this time that the insulation on the MSIV, vent piping and associated valves was less than the current design specification requirements.. This contributed to a larger variance in temperature (Delta-T) resulting in more heat transfer and increasing the condensation rate.

After completing all modifications and reassembling the,MSIV's, Special Procedure 2-THP.SP.MM-079 was used to verify operability. This procedure included a series of test cycles for all MSIV's at different intervals with the appropriate instrumentation required to measure and record all applicable performance variables, specifically the rate of pressure drop in the vent line.

NRC Form 344A I5$ 9)

P

NRC FORM SSSA U.S. NUCLEAR REGULATORY COMMISSION (5JISI APPROVED OMS NO. S1500104 EXPIRES: A/SO/52 ESTIMATED SUROEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 500 HRS. FORWARD COMMENTS REGARDING SURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT SRANCH IP 5201. U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 20555. AND TO THE PAPERWORK REDUCTION PROJECT (S(5041(M). OFFICE OF MANAGEMENTAND SUDGET, WASHINGTON, OC 20502, FACILITY NAME (1) DOCKET NUMSER (21 LER NUMSER (5) ~ AGE LSI YEAR YP>', SSQVSNTIA'L II5 Y IS IO N NVM Sll NVM SA D. C. Cook Plant - Unit 2 0 0 0 I 0 70F1 0 o s o 0 0 3 1 6 9 0 2 0 TEXT IIImcm apece JI IPSw'wI, PPP aAWonV HRC RPmI ~SI (12(

The acceptance criteria used within '2-THP.SP.MM-079 was twofold. First, each full closure stroke time must be within 5 seconds in accordance with Technical Specification 3.7.1.5. Second, the rate of pressure, drop in the vent line must not change as the test interval is extended to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. This second criteria was used to verify no additional condensate had accumulated within the upper steam volume that could lengthen stroke time and delay stem travel upon flashing to steam during the venting process.

All stroke tests performed in accordance with 2-THP.SP.MM-079, except the first test on MRV-210, provided .acceptable results and verified the generic condensate issue. had been resolved; The initi'al test performed on MRV-210 failed. The corresponding rate of pressure drop in the vent line signature verified significant quantities of condensate still present. Investigation .

revealed that Train B Dump Valve MRV-212 was not se'sting properly permitting a significant amount of- steam to be exhausted out the vent stack. Under these circumstances, additional steam was brought into the upper volume with condensate collecting at a rate faster than could be drained. MRV-212 was repaired and subsequent closure tests completed on MRV-210 verified that this

.isolated incident had been resolved. All MSIV's were returned to an operable status and Unit 2 returned to power operation.

As stated in the analysis, we do not expect to encounter similar difficulties with the Unit 1 MSIV's. However, we are currently adding insulation to the Unit 1 MSIV's, vent lines and valves to enhance the MSIV operating conditions.

I FAILED COMPONENT IDENTIFICATION Component ID: Main Steam Isolation Valves 2-MRV-210, 2-MRV-220, 2-MRV-240 Manufacturer: Hopkinsons - Ferranti Model: 2379 W PREVIOUS SIMILAR EVENTS 050-316/83-57 NRC Form SSSA (SSSI

APPROVEO NRC FORM 344A

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fACILITYNAME Il) DOCKET NUMSER )3) LER NUMSER )4) ~ AGE 13)

YEAR SCOVCNTIAL IICVISION NVM CR NVM CA D. C.

TEXT Cook Plant - Unit lllmorp gfdcg lg nqvssd, we ~ 2 HRC Jtgwii SRSC'4) (17) o e o 0 o 31690 0 0 2 0008 oF 1 0 MAIN STEAM ISOLATION VALVE TEST TABLE Januar 8, 1990 Testin VALVE INITIAL CLOSING TIME (SEC) RETEST (SEC) 2-MRV-210 =

5.94 3.01 2-IIRV-240 5.18 1.95

'Januar ~

9, 1990 Testin 2-MRV-210 5.07 "2. 83 2-MRV-220 5.60 2.28 2-MRV-240 5.05 2.21 Januar 10, 1990 Testin 2-MRV-210 5. 78 3.08 2-MRV-220 5. 73 2.55

'anuar 11, 1990 Testing 2-MJRV-220 5.26 No Retest Performed NOTE: During the test program 2-HRV-230 closing times were high, hut 'did not exceed the Technical Specification Limit of five Seconds.

NR C F oIIm 344A 144)9)

NRC FORM 364A US. NUCLEAR AEGULATOAYCOMMISSION APPAOVED OMS NO, 31500)04 1640)

E XP I R E 5: 4/30/02 ESTIMATED SUADEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REQUEST: 500 HRS. FORWARD COMMENTS REGAROINO SUADEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT SRANCH IP430). U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON. OC 20655, AND TO 1HE PAPERWORK REDUCTION PRO/ECT 13)50410E).'OFFICE

~ OF MANAGEMENTAND SU OG ET, WASHINGTON, DC 10503.

FACILITY NAME 111 Doer ET NUMSER (2) LEA NUMSER (4) PAGE IS)

YEAR SEQUENTIAL HEY>>ION NVM 4 II )rvM ER D..C. Cook Plant - Unit 2, o s o o o 3 1 6 9 0 0 0 2 0 0'0 9 QF 1 0 TEXT ///nxro s/>>ce /s r)V/rer/ 1>>e ~ PT/Or>>/ HIIC Ferrrr AXLES/ (17) t MAIN STEAM ISOLATION VALVE NOTE: VALVE SHOWN IN CLOSED POSITION OPERATING PISTON

~VENT LINE TO STEAN DUMP VALVES STEAM NIPPLE CONDENSATE DRAIN LINE CONDENSATE DRAIN PORT VALVE MODIFICATIONS CONDENSATE DRAIN PORT INITIALLY- 0 125" MODIFIED TO -.0..'197" (5MM)

STEAM NIPPLE INITIALLY" 0'125" MODIFI'ED TO 0.394" (10MM)

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NRC Form 346A (680)

NRC FORM 385A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMS NO. 315040104 (54ISI EXPIRES; 4I30JS3 ESTIMATED SURQEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLL'ECTION REQUEST: 50.0 MRS. FQRWARQ COMMENTS REOAROINO bUROEH ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAOEMEHT SRANCH If@30). U.S. NUCLEAR REOULATORY COMMISSION. WASHINOTOH, DC 30555, AHQ TQ f

1HE APFRWORK REDUCTION PROJECT 131504)104), Qf ICE f OF MANAGEMENTAHD SUDOET,WASHINGTON, DC 30503, fACILITYNAME Il) DOCKET NUMSER 13) LER NUMSER Ibl PACE ISI YEAR SEOVENTIAL II5 V IS IO N NVMSEII NVM ~ II D. C. Cook Plant - Unit 2 o s o o o 3 l 6 9 0 0 0 2 0 0 1 0 OF ] 0 TEXT IllII>>IF Z>>ce JF IP0vbe4 uw FIRRSN>>F JYRC %%dYm ~3 I l)T)

HAIN STEAM ISOLATION VALVE VENT PIPING VENTS TO ATMOSPHERE DUMP VALVES 3-WAY MOTOR OPERATED VALVE MSIV HRC F~ SeSA ISJISI