IR 05000219/1988080

Augmented Insp Team Rept 50-219/88-80 on 881005-13.Major Areas Inspected:Circumstances Surrounding Steaming Phenomenon on Both Isolation Condensers in Late Aug & Sept 1988 & Electrical Fault on Diesel Generator 2 on 881002

ML20195D704
Person / Time
Site:	Oyster Creek
Issue date:	10/28/1988
From:	Cowgill C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20195D702	List: IR 05000219/1988080 ML20195D698
References
50-219-88-80, NUDOCS 8811070115
Download: ML20195D704 (68)

Text

, t* s U.S. NUCLEAR REGULATORY C0teilSS10N

REGION I

Report No. 50-219/88-80 Docket No. 50-219 License No. OPR-16 Priority -

Category C Licensee: GPU Nuclear Corporation 1 Upper Pond Road barsippany, New Jarsey 070T4 Facility Name: Oyster Creek Nuclear Generating Static..

Inspection At: Forked River, New Jersey Inspection Conducted: October 5-13, 1988 Insp?ctors: W. Baunack, Project Engineer, DRP R. Brady, Reactor Engineer, DRP E. Collins, Resident Inspector, Oyster Creek C. Cowgill, Chief, Reactor Projects Section 1A, DRP (Team Leader)

J. Golla, Reactor Engineer, DRS T. Koshy, Senior Reactor Engineer, DRS D. Lew, Resident Inspector, Oyster Creek L. Lois, Senior Nuclear Engineer, NRR J. Wechs Ib rger, Senior Resident Inspector, Oyster Creek Approved by: 8d 1,'ME /Obfb'f Curtis . Cow ('i Chief, Reactor projects Section 1A Date Inspaction Summary: An Augmented Inspection Team (AIT) was dispatched to review the circunstances surrounding a steaming pheromenon on both Isolation Condensers in late August and September 1988 and an electrical fault associated with the No.

2 Diesel Generator on October 2, 1988. The t eam's charter was to provW NP.C man-agement with a comprehensive review of these events to assess the safety signific-ance and licensee response to the events.

Areas Inspected: See areas listed in AIT Charter (Attachment A).

Results: Results of the inspection are su'emarized in paragraph 1. Vfth regard to Uie isolation condenser event, the team concluded that the licensee pursued a pru-dent action in shutting down the reactor in light of the conditions as they were known on September 29,19SS. Followup actions appear appropriate and comprehensive.

For the electrical event, licensee followup was considered appropriate. A number of actions remain to be completed prior to reactor startup following refueling.

These actions are summarized on pages 15 and 21 of the report.

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TABLE OF CONTENTS PAGE PREFACE................................................................... 1 1. Conclusion / Summary................................................... 1 2. Background........................................................... 2 3. Isolation Condenser System Configuration............ ................ 3 4. Review of Previous Isolation Condenser Performance................... 5 4.1 Review of the June 12, 1985 Reactor Isolation Scram............. 6 5. Steaming of "B" Isolation Condenser, August 28, 1988................. 6 6. Steaming of "A" Isolation Condenser, September 26, 1988.............. 9 7. Thermal-Hydraulics of the Steamin0 Isolation Condensers....... .... . 9 8. Inspection Findings Associated with Isolation Condenser Operation.... 11 9. Equipment Effects / Impact............................................. 13 10. Evaluation of Licensee's Review of Events............................ 13 11. E1cetrical Event..................................................... 15 11.1 Event Summary................................................... 15 11.2 Plant Status Analysis and Conclusions........................... 16 11.3 Previous Electrical Bus Faults /Lossts........................... 17 11.4 Assessment of Oyster Creek 4160V Emergency Bus.................. 19 11.5 '.icensee Corrective Actions..................................... 20 12. Exit Interview....................................................... 22

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i t' s ATTACHMENTS Attachment A - Augmented Inspection Team Charter Attachment B - GPUN Letter, Isolation Condensers and Emergency Diesel Generators Attachment C - Chronology of Events Associated with Isslation Condensers July 5 -

October 1, 1988 Attachment 0 - Review of the June 12, 1935 Reactor Isolation Scram Attachment E - The Thermal-Hydraulics of the Steaming Isolation Condenser Figure 1 - Isolation Condenser Figure 2 - Thermal Hydraulic Model Figure 2a - Steam Line Branch Connection Figure 23-1 - Isolttion Condenser System Figure 23-2 - Isolation Condenser Natural Circulation Flow Path Calculation 1 Attachment F - Electrical Event on October 2, 1988 Attachment G - Simplified Sketch of Electrica! Power System Attachment H - Documents Reviewed Attachment I - Persons Attending E..t Meeting, October 13, 1988

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i *- s PREFACE As an aid to the readers' understanding of the steaming phenumenon experienced by the isolation condensers wnich prompted this inspection, a portfolio of photographs '

depicting some of the components which were prominently involved in the event has been added at the end of this report. The report details provide overv 4ws of cer-tain areas inspected. Attachments have been added which provide greater detail in several of these areas. Also, the Conclusion / Summary has been placed at the beginning of the report to identify the more important aspects inspected.

DETh!_L_S 1.0 Conclusion / Summary Certain primary findings resulted from the review of t h steaming of the isolation condensers with the condensate return valves closed. In addition, some secondary conclusions were also made.

Primary findings indicate that the "B" Isolation Condenser started spon-taneously steaming several hours after being returned to service following being isolated for maintenance for approximately six days. The "A" Condenser started steaming after being out of service for only several hours to perform a surveillance test which had been performed many timesin the life of the plant. This indicates 'he "B" Condenser being in the steaming mode and in-terconnected through the common vent system was most probably involved in the

initiation of the "A" Condenser steaming.

The vent system includes a single 400 foot run of 3/4 inch carbon steel piping which includes a loop seal and a single manual isolation valve. Any plugging of this line or faulty operation of the manual isolation valve has the poten-tial to make both condensers inoperable.

The design of the isolation condensers coupled with operations or evolutions that were unique, led to conditions not previnusly experienced or identified.

Certain indicatiens involv'.ng condenser steam line temperatures had been noted, Region I Inspection Report 88-23 discusses inspector observations relative to unexplained isol. tion condenser steam line temperatures. The licensee, after the second condenser started steaming, initiated a technical evaluation team review of the occurrence and after determining water to ha present in the steam lines promptly isolated the condensers and initiated a plant shutdown.

A secondary finding was that the extended out of service period of the "B" Condenser which preceded its steaming was, in part, due to a maintenance technician using a wrong instrument in backseating a valve which caused a valve operator motor to fail.

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A review of so ip chart recorder records did not indicate that exactly the same phenomenon had occurred in the past. However, certain anomalous condi-tions relating to the behavior of the isolation condensers were noted. In the past, steaming of a condenser had always been attributed to condensate return valve leakage.

The investigation of previous operating pe"formance was hampered by chart traces which could not be identified with certainty and by the unavailability of other supporting information during the inspection period. Also, certain records were eliminated by the prolonged jumpering of alarms. The basis for the placement and the alarm setpoint for the isolation condenser steam line thermocouples remains to be determined.

Using the limited data available, a model was postulated which describes a possible mechanism by which abnormal flow in the isolation condenser could be initiated and maintained. The licensee is performing a more detailed thermal-hydraulic analysis of the phenomenon.

4 The licensee will evaluate and report certain physical effects which resulted J from the improper operation of the condensers.

A review of the emergency bus failure shows the plant has underground cables connected to electrical buses which become an extension of these buses. Eight failures of these cables have been experienced, five since 198v. The presence i

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of these underground cables requires an aggressive surveillance program in

. order to prevent additional failures. The licensee will provide a final re-port describing proposed corrective action.

l 2.0 Background l

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The isolation condenser system, designed to remove heat from the reactor ves-sel during transients when the normal heat sink is unavailable, may have been partially placed in service by a unique set of circumstances that resulted in a steaming phenomenon of the atmospheric side of the isolation condensers.

This phenomenon occurred with the condensate return valves shut. Normally,

, the condensate return valves are opened to initiate the natural circulation I flow path from the reactor to the isolation condensers. Attachment E (The Thermal-Hydraulics of the Steaming Isolation Condenser) details one postulated model for heat transfer to the isolation condenser from the reactor to take ,

place with the condensate return valves shut. This phenomenon was first noticed on August 28, 1983, (see Inspection Report 50-219/88-23) while warming up the "B" Isolation Condenser prior to returning it to service from a six-day maintenance period. During the warm-up sequence the shell temperature was

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observed to increase significantly and seemed to coincide with the optration of the steam inlet isolation valve (see paragraph 5.0, Steaming of "B" Isola-tion Condenser, August 28,1988). Following condenser warm up, an operability surveillance was performed to return the isolation condenser to service. Dur-

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ing this surveillance the condensate return valves were not properly sequenced in accordance with the procedure. This resulted in an inadvertent initiation of the isolation condenser for a few seconds, which resulted in a slight reactor power increase of about 1% and a reactor vessel level fluctuation of i

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approximately 1 inch. S'bsequently, the isolation condenser steam line tem-peratures were observed to stabilize at about 300 degree!, F and 200 degrees F for the south and north steam lines, respectively. Prior to the isolatior.

condenser maintenance outage during the period August 23-28, 1988, the steam line temperatures indicated approximately 540 degrees F, indicative of the thermocouples sensing a steam environment. During the maintenance outage, steam line temperatures read approximately 100 degrees F, the expected tem-perature with the isolation condenser valves c1csed.

On September 26, 1938, during a surveillance of the "A" Isolt'lon Condenser high flow instrumentation, the shell temperature was observed to increase.

This particular surveillance closes the three open kolation valves (two steam and one condensate valve) when a simulated high steam or condensate flow sig-nal is inserted. The increase in shell temperature occurred following the valve realignment upon completion of the surveillance without any movement i of the condensate return valvo (see paragraph 6.0, Steaming of "A" Isolation Condenser, September 26,1988).

Upon stabilization of conditions, the steam line temperatures for the north

and south steam lines indicated about 300 degrees F and 200 tiegrees F, re-spectively. This condition represented nearly the same phencmenon experienced with the "B" Iso'ation Condenser. As a result of a detailed eva hation by

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September 29, 1988, the licensee determined that, based on the information i available, a concern existed whether the isolation condenser system was cap-able of fulfilling its design function (see paragraph 10.0, Evaluation of d

Licensee's Review of Events). As a result, the licensee elected to make the

isolation condenser system inoperable to avoid any potential water hammer and 1 to proceed to cold shutdown conditions. Cold shutdown was achieved at 9

55

a.m., September 30, 1988.

l 3.0 Isolation Condenser System Configuration i

i The Isolation Condenser System is an Emergency Core Cooling (ECC) System which

! can be actuated automatically or manually. It is a standby, high pressure i system for the removal of fission product heat from the reactor vessel fol-

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lowing a reactor trip with main steam isolation valve closure. It depres-l surizes the reactor vessel in the event the main condenser is not available as a heat sink. Natural circulation provides the driving head through the

isolation condenser tubes. The condensers are burizontal, shell and U-tube

. heat exchangers with a total rated heat removal capacity of 4.10X10E8 BTV/hr, i cach rated at 50', of total system capacity. The two isolation condensers are located in the reactor building at elevation 95 ft. The shell side of the l isolation condensers contain a water volume which boils off to remove heat transferred from the reactor. The design basis of the Isolation Condenser System is such that its operation in conjunction with the Automatic Depres-i surization System and the Core Spray System, must be able to maintain peak

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cladding temperatures below 2200 degrees F for any size LOCA, assuming a single failure occurs in the ECC System.

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The Isolation Condenser System is depicted in Attachment E, Figures 23-1 and 23-2, by a simplified drawing of one of the isolation condensers. The system consists of two isolation condensers; each condenser has steam supply isola-tic.: valves, condensate return isolation valves, isolation vent valves, and isolation condenser makeup water valves. The steam lines of the isolation condensers have installed thermocouples which extend into wells in the pipes at the inlet to the tube nests. The "A" Isolation Condenser thermocouples on the steam lines have a two foot elevation difference while the steam line ,

thermocouples on the "B" Isolation Condenser are at the same elevation. Tne '

shell side of the isolation condensers also have instslied thermocouples which i sense bulk coolant temperature. l When the isolation condensers initiate, steam flows from the reactor vessel up to the isolation condensers through motor operated steam inlet valves which are normally open. At the % ft. elevation the single rteam line (one per '

isolation condenser) splits into a "wye", rises ;)proxts.ately 18 ft. and loops around to the ends of the condensers where tney enter the condenser "tube nests." Both condensers have a tube nest at each end. Each tube nest has an effective heat transfer area of approximately 850 sq. f t. The steam condenses and flows back to the reactor through motor operated condensate return valves (1 AC & 1 DC MOV's on each return line) to points on the Reactor Recirculation System pump suction. There is approximately 60 ft.

of condensate piping from the condensate return valves to the reactor recirculation loops. The Condensate Transfer System is the normal supply of makeup water to the isolation condenser shell volume. The Demineralized Water Transfer System can supply makeup water to the isolation condensees for day-to-day evaporation. The water can be supplied from the Demineralized Water Transfer $3: tem to the condensers through sample connections using a flexible hose; this was accomplished for the events. Fire water can 'e used as an alternate source of makeup in the event that the Condensate Transf a System is unavailable. The shell sides of the isolation condensers are continuously vented to atmosphere through large vent pipes.

The vut arrangement for the "A" Isolation Condenser is slightly different than the "B". The "A" condenser vents consist of two 20" lines which combine to . >rm a common 28" vent that exits the east reactor building wall north of the two vents for the "B" Isolation Condenser. The atmospheric vents of the

d" Isolation Condenser consist of two 20" pipes that vent directly outside the adjacent reactor building wall (east'.

Normally open, small air operated steam line vent valves vent noncondensable gases from the isolation condensers through a common header to the north (B)

main steam line. The vent header connects to the "B" main steam line down-stream of the outboard main steam isolation valve outside the trunion room at elevation 27 ft. This is 3/4 in, piping largely without insulation. Non-condensables, if allowed to build up in the isolation condenser tubes, would inhibit effective heat transfer from the reactor to the isolation condensers.

The cor. mon vent header places the "A" and "B" Isolation Condensers in hy-draulic communication with one another at their highest elevations. The steam line vent valves isolate during operation of the isolation condensers. The

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3/4in,ventpipingfollowsalengthypath(approximately420ft.ofpiping) i from e'.evation 115 6" at the isolation condenser to a low point at elevation  !

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6'6" before turning up and intersecting the B main steam line at elevation 27'. This section of the vent could possibly provide a loop seal if steam ,

) is condensed in the vent line and accumulttes at this point.

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The isolation condensers are placed la standby by placing the steam supply and condensate return valve control swit:hes in the AUTO position. This opens both series steam supply valves and the AC motor operated condensate return valve associated with each condenser. The DC motor operated condensate return  :

valves (in series with the AC MOV's) the only valves normally shut. Upon re-ceipt of an autoniatic or manual initiation signal, the normally shut DC oper- 1 ated condensate return valves open to initiate flow through the condensers, i l 4.0 Review of Previous Isolation Condenser Performance l As part of the inspection effort, previous operating performance for the isolation cor.Jenser was reviewed to determine if similar or other anomalous conditions have existed in the past and provide some insight into the present phenomenon. This review examined recordei strip charts for the isolation condenser steam line und shell temperatures (i.e., North and South Steam Line and Shell Temperatures). This recorder w u replaced in the 1983-1984 outage with an updated model. The review was hampered by unidentifiable traces on some strip charts and unavailability of certain other records which could have

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, supported the traces. In addition, the licensee had bypassed the steam line temperatures for the isolation condensers for certain periods of time to eliminate the annoyance of a constant alarm condition, thereby eliminati.1 l these parameters from the recorder strip charts. This was conducted with a i

safety evaluation (see pc agraph 8.0).

The insp:ctors reviewed selected strip chart traces for the years 1970, ;972,

) 1974, 1982, 1984, 1985, 1987 and 1988. From this review, it is not clear that this same phenomenon had occurred in the past, but :ome interesting anomalous

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conditions were found.

A number of examples existed that indicated that some leakage was occurring

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past V-14-34 and V-14-35, the normally closed condensate return valves. The charts reflected steam line temperature increases from approximately 120 de-grees F and in equilibrium with stabilized shell temperatures, to grea*er than

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500 degrees F, during valve operability surveillances. This could be due to leakage past the condensate return valve. A steam line temperature of ap-proximately 120 degrees F indicates that a significant amount of steam had condensed in the vertical leg of steam line piping where the thermocouple is

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located. For temperatures to increase from 120 degrees to over 500 degrees

, F provides an indication that condensate displacement by steam during the valve operability surveillance was larger than normal. Other valve operabil-ity surveillances have resulted in only 40-50 degree F increases, as presum-i ably, a small amount of c.ondensate is displaced. Inspection of the valves

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after an ar.omalous condition in 1985 revealed that the valve was leak tight i

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with no >bservable indications of leakage. Having experienced anomalous tem-perature conditions and during a subsequent valve inspection finding no cb-servable indication of leakage may lead to a conclusior, that some type of thermal mechanism associated with the valve cycling may have caused some momentary leakage to occur. The conditions described above were observed with  !

V-14-35, but V-14-34 has displayed some indications of leakage also, In early ,

and late 1987 the "A" Isolation Condenser experienced steam line temperature l

readings of approximately 548 degrees F with elevated shell temperature read- .

ings of between 130 and 160 degrees F while the "B" isolation condenser shell t

, temperatures indicated between 75-115 degrees F and steam line temperature of approximately 548 degrees F for the same time period. This would provide j some indication that V-14-34 may have betn leaking under certain conditions. *

V-14-34 internals have not been inspected since these conditions were coserved. '

4.1 Review of the June _12, 1985 Reactor Isolation Scram A review was conducted of a June 1?, 1985 event in which the isolation  !

condenser was initiated to gather information on the isolation condenser  !

operaging parameters. The details of this review are presented in At-tachment D.

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During the actual operation of the condenser the shell and steam inlet i temperatures responded as expected and did not correlate to the tempera-ture responses of the recent isolation condenser pnenomenon. However, !

following the initiation of the isolation condenser the steam inlet ters-perature deviated from the saturation temperature corresponding to reac-t n pressure. The steam inlet temperature dropped from 350 degrees F to 220 degrees F and then, fif teen minutes later, increased to 300 de-i grees F. This decrease in temperature and subsequent increase cannot be fully explained. Although there was a limited amount of raw data

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available, analysis showed that there was a potential to set up condi-tions in the isolation condenser similar to the August 28 and September t 26, 1988 phenomenon. The licensee has been asked to independently review '

and assess this possibility. [

Though postulating that the "A" Isolation Condenser expericnced this i l phenomenon is based on circumstantial evidence, the occurrence of this '

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phenomenon on June 12, 1985 was nevertheless possible. The licensee has r been asked to independently review and assess the possibility that the .

, August 28 and September 26, 1988 isolation condenser phenomenon occurred  ;

in the "A" Isolation Condenser on June 12, 1985.

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5.0 Steaming of "B" Isolation Condenser, August 28, 1988 ,

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On August 23, 1988, the "B" Isolation Condenser was removed frem service and f isolated. 'he isolation valves and vent salves were closed. This alignment  :

remained untti August 28, 198A, when it was returned to service. Jalve align- '

ment during this period eas:

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Steam inlet valve (V-14-33). . . . . . . . . . . . . . closed

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Steam inlet valve (V-14-32) . . . . . . . . . . . . . closed

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Condensate return valve (V-14-37). . . . . . . . . . closed

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Condensate return vrive (normally closed) (V-14-35). . closed

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Ve n t Va l ve s ( V- 14- 1, V- 14- 19 ) . . . . . . . . . . . . . c l o s ed

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Isolation condenser shell temperature. . . . . . . . 93 degrees

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Temperature between valves V-14-35 & V-14-37 . . . . 255 degrees Procedure 307, Isolation Condenser System, section 8, was being used to return the system to operation. During this procedure, the control logic for valve V-14-32 is modified to allcw throttling of the valve from the control room.

This modification was performed and the valve was opened and closed to verify the ability to throttle.

The process to align system valves and control the rate of isolation condenser heatup is to open the redundant condensate return valve (V-14-37) and a re-dundant steam supply valve (V-14-33). One steam supply valve is left closed (V-14-32) and the "normally closed" condensate return valve (V-14-35) is left closed. Now, the isol:' un condenser vent valves (V-14-1 and V-14-19) are opened. Since the two isolation enndenser subsystem vents are cross connected, opening the vent valves establishes a flow path from the "A" to the "B" Isolation Condenser, and this would act to pressurize the "B" Co. denser. The process also allows for "throttling open" steam inlet valve V-14-32, to admit steam in order to warm-up/ pressurize the isolation condenser. Once the isolation condenser is near normal operating temperature and pressure, the steam inlet valve V-14-32 is fully opened, and the control logic modification is removed. The isolation condenser will now initiate when the normally closed condensate return valve, V-14-35, is openeo.

At about 3:29 a.m., the power was restored to the outboard (normally closed)

condensate return valve, V-14-35. This would also supply power to the isola-tion condenser vent valves, V-14-1 and V-14-19, but they were not opened.

At about 3:46 a.m., the inboard condensate return valve, V-14-37, was opened.

With this valve open, the temperature between valves V-14-37 and V-14-35 started to increase from 255 degrees at about 22 degrees / hour. This tempera-ture increase is expected due to convection heating from reactor coolant from the recirculation pump suction.

With steam inlet valve V-14-32 indicating closed, the redundant steam inlet valve, V-14-33, was opened. A sharp increase in isolation condenser steam line temperature was observed (120 to 300 degrees in 2 minutes), and V-14-33 war immediately closed. It was suspected that valve V-14-32 had not been fully closed after the earlier valve operations, and the contrni room operator cycled the valve open/close to ensure that the valve was fully seated. Valve V-14-33 was then ooened with no further heatup of the isolation condenser.

Since Procedure 307 limits the heatup rate of the isolation condenser to 90 degrees / hour (average), subsequent heatup was limited to ensure that the average heatup rate was not exceeded.

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At 6:15 a.m., the "B" Isolation Condenser vent valves (V-14-1 and V-14-19)

were opened. As discussed above, this would allow the "B" Isolation Condenser to be pressurized from the "A" Isolation Condenser. However, unknown to the operators at this time, a manual vent valve on the "A" Isolation Condenser (V-14-6) was closed, isolating the vent path of the "A" Isolation Condenser ,

from the "B". Because of this valve alignment and because the "B" Isolation Condenser was not pressurized, a reverse differential pressure would be established across the isolation vent line, and reverse flow would result from r the steam lines back to the isolation condenser. With sna isolation condenser '

isolated and depressurized, it is likely that reverse flow would be estab-lished from the main steam line to the condenser via the vent line piping. *

The isolation condenser vent valves were closed at 6:16 a.m., and were peri-odically opened / closed from 6:50 a.m. until 9:49 a.m. while attempting to  :

pressurize the isolation condenser. '

At 6:50 a.m., valve V-14-32 was "cracked" oper to pressurize the isolation i condenser. Three minutes later, the control som operator reclosed V-14-32, i Temperature in tha isolation condenser peaked at 395 degrees F af ter this  :

valve operation, and began slowly drifting downward. i At 10:00 a.m., valve V-14-32 was again opened (10:00 a.m.)/ closed (10:06 a.m.) I to heat up the isolation condenser, and, at 10:03 a.m. the isolation conden-ser shell tempe. ture started to increase. By 10:15 a.m. the shell tempera- ,

ture had increased from 93 degrees to 105 degrees and was steady. It was also .

during this time frame (10:20 a.m.) that the temperature between V-14-37 and l V-14-35 stabilized at 400 degrees, (the normal steady state temperature be- t tween V-14-35 and 37 during power operation). l At 10:35 a.m., valve V-14-32 was again opened to heat up the isolation con-densor. V-14-32 was closed at 10:50 a.m., and then at 10:55 a.m., valve V- .

14-32 was fully opened and remained open. l At 11:02 a.m., the isolation condenser shell temoerature indicated 107 degrees and was increasing at a rate of 47 degrees / hour. The isolation condenser  ;

valve alignmint was now:

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both steam inlet valves open (V-14-32, V-14-33) l

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AC condensate return open (V-14-37)  !

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OC condensate return closed (V-14-35)

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vent valves open (V-14-), V-14-19)

Before returning to service, surveillance test 609.4.001, "Isolation Condenser  :

Valve Operability and IST " was to be performed. It was during this test that t the control room operator inadvertently moved valve V-14-37 in the open direc- [

tion while valve V-14-35 was cpen. Thi> effectively resulted in initiation I

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of the "B" Isolation Condenser for about 6-8 seconds. The control room opera-tor immediately closed V-14-37 ard closed V-14-35. A minor plant transient resulted. The surveillance was subsequently completed and the isolation con-denser returned to service.

Subsequent to the inadvertent initiation, the temperature between valves V-14-35 and V-14-37 fell from 400 degrees to about 275 degrees in a twenty minute period. It then started to rise and even'.aally returned to about 400 degrees. >

By 1:17 p.m., the "B" isolation shell temperature reached 212 degrees. It was suspected that valve V-14-35 was leaking across its seat, so it was cycled open/ closed in an effort to "reseat" the valve.

1 By 1:38 p.m.. the low level alarm on the "B" Isolation condenser was received and makeup water was added. Eventually, continuous makeup would be supplied .

to the "B" conder ser shell side, at a rate of 18 gpm. ,

6.0 Steaming of "A" Isolation Cendenser, September 26, 1988

During performance of 609.3.002, "Iselation Condenser Isolation Test and Calibration," on the "A" Isolation Condenser on September 26, 1988, the shell temperature of the "A" Isola' ion Condenser started to increase. This test a results in the closing of the two normally open steam supply valves (V-14-30,

-31), and the normally open condensate return valve (V-14-36). This was per-formed at 10:34 a.m., and the va'ves were reopened at 11:42 a.m. to break for lunch. At approximately 12:30 p.m. the shell temperature on the "A" Isolation ,

i Condenser was observed to be 153 degrees F and increasing. Initially shell i i temperature was approximately 125 degrees.

At 1:32 p.m., the valves were once again closed to complete the testing of I the "A" Isolation Condenser. During this period of time, the rise in shell temperature stopped at 179 degrees. When the isolation valves were reopened ,

at 2:30 p.m., the increase in temperature of the "A" condenser shell resumed.

At 4:05 p.m., the shell temperature reached 212 degrees and the "A" Isolation :

Condenser was "steaming" in a manner similar to the "B" Isolation Condenser.

j It is significant to note that the normally closed condensate return valve

' l (V-14-34) had not been repositioned. In addition, when the condenser isola- !

tion valves were closed, the condenser vent valves (V-14-5 and 20) remained

, open.  ;

i 7.0 Thermal-Hydraulics of the Steaming Isolation Condensers i

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l This section describes a possible mechanism by which abnormal flow in the isolation condensers could be initiated and maintained, which produces shell [

side Steaming with a condensate return valve on each isolation condenser

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______ __ _ _ ___ -__ _ _ _ __________ _ _ ___. _ _ _ _ _ _ __ _ _ . _____ _ ___

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closed. This section will also pro /ide a basis for interpreting the licen-see's model when it becomes available and facilitate the evaluation of cor-rective and preventive measures required before returning the isolation con-densers to service.

When the isolation condenser steaming was first observed, the possibility of a tube leak was investigated and eliminated. Radiation measurements in the shell side fluid were below minimum detectable. Three hypotheses were then advanced for interpretation:

(a) condensate isolation valve leaking, (b) some kind of level oscillations in the tube side of the isolation con-denser which allowed for steam condensation in the coils, and (c) some unidentified circulation pattern.

The "B" Isolation Condenser was out of service for valve maintenance from August 23 to August 28, 1988, and when returned to standby status started i steaming for no apparent reason. Efforts were made to identify the reason for this steaming. (Refer to Attachment E, Figure 1 and FSAR Figures 23-1 and 23-2). The licensee drilled through the insulation and recorded the average temperatures shown on Figure 1 in the corresponding locations. These temperatures show that the "south" (left) coil is producing shell side steam-ing and the "north" (right) is not. This indicatr that possibly an internal circulation pattern which prcmotes steaming was established as indicated in Figure 2. In this postulated circulation pattern, condensate from the south coil goes up through the north coil, descends through the north steam pipe back into the steam supply pipe. Steam ascends through the south steam pipe to the south coil where it candenses. In this model there is practically no evidence that there exists any significant oscillatory pattern, at least not to the extent that the coils change roles in condensing steam. Therefore, attention was given to the identification and quantification of the driving heads (and losses) for this continuous model.

Known facts were used to construct the model where they were available. Where

! suf ficient factual information wasn't known, reasonable assu'nptions were made. '

i Refer to Attachment E for a discussion of driving heads, and initiation

mechanisms involved in the inspectors' model.

The inspectors have concluded, based on this engineering evaluation of the isolation condensers, that:

• the steaming in either isolation condenser takes place only on one tube bundle of each condenser,

• the postulated flow patterns required a very small head and are a com-biration of gravity, temperature differences, and small flow-induced pressure differences,

________ __________ ___ _.

,

. .. .

• the design of the isolation condensers is such that under certain condi-tions there is a built-in source of instability,

there is a possibility that water hammer might have occurred if the isolation condensers were required to operate while steaming.

there is no reason to believe that the steaming condition would be detri-mental to heat removal during system initiation, except for the possibil-ity of water hammer as mentioned above.

As part of the charter of the AIT 88-80, the inspectors collected and reviewed all of the available information regarding the conditions and the causes of steaming in both isolation condensers. The available information is not com-plete and we hypothesized the flow patterns and tempera +ure distributions in an attempt to find an explanation as to why steaming was initiated and how it attaiaed a steady state condition. The circulation model arrived at in-corporates all of the known relevant information, but it is not complete.

However, it provides a perspective of one possible circulation model, the magnitude of the required driving heads, and the condition of toe condenser steam vent pipe. Similarly, some hypothesis of initiating mechanisms is pre-sented. Besides raising questions, the above models form a framework for the review of the licensee's model when it becomes available.

8.0 Inspection Findings Associated with Isolation Condenser Operation During the course of the inspection, certain facts associated with the opera-tion of the isolation condensers were identified. These are presented as follows:

--

The safety signifiunce of operating with the isolation condensers in the steaming mode coild not be determined. Clearly the shell water volume was being mair.*.ained as was the condenser actuating logic.

The major concern invened in the actuation of the condensers would be the possibility of initis ting a water hammer se 'are enough to cause dam-age to the isolation conde'ser system piping or condenser tubes. The pressure differences associa ed with the operation of the condensers are relatively low generated primarily by the head of water. However, the amount of water in the steam lines and the behavior of this water fol-lowing condenser initiation could not be determined. Consequently, the generation of a water hammer condition could not be eliminated. Also, the additional water upstream of the tube bundles might briefly delay the condensers' effectiveness. For these reasons the isolation conden-sers were potentially in an unanalyzed condition and their operability was questionable.

--

The isolation condenser steam lines are provided with well-type thermo-couple temperature sensors before they connect to the tube bundles.

These temperatures read out and are recorded in the control room. A com-mon temperature alarm is also provided which alarms on high temperature

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in the steam lines or shell side of the isolation condenser. The alarm setpoint is 225 degrees F. The manual actions specified for the alarm are, "Check position of valves V-14-34 and V 14-35 for system initiation or leakage past valve. Check level at Pane: 2F for increasing level  :

indicating tube leaks, or decreasing level, indicating system in opera- l tion or isolation vsive leaking." '

The basis for the alarm setpoint of 225 degrees F could not be found, i Some evidence exists which suggests that at one time the alarm had been .

350 degrees F. Since the steam line temperature is frequently higher than 225 degrees F the alarm had been identified as a "nuisance alarm" and has been bypassed since May 15, 1937. Other evidence also shows the '

"A" condenser steam line alarms had been bypassed in 1982.

It is unlikely that a shell side alarm of 225 degrees F would ever be ,

relied upon to indicate isolation condenser initiation. Also, steam line temperature recorder traces show that for extended periods of time i (months) these temperatures are above the alarm setpoint. These recorder  !

traces and other tempe. 6un i mnis show that staam line temperatures j vary from in the le,, 100's to 540 degrees F. Consequently, it appears a temperature sensor has been installed with an associated alarm for which no basis exists and for which any temperature reading is acceptable.

The licensee has been requested to provide a basis for these alarm set-  ;

i pots.  !

l l The FSAR in describing the isolation condenser steam lines where they ,

enter the tube bundles states, "These lines are provided with a five-foot i vertical water trap section at the entrance of each tube bundle to pre-  ;

vent condensate drainage from the tubes (which are flooded) into the  ;

) steam lines, and thus preclude flux cteaming during standby." The steam line thermocouples are located in these vertical water trap sections.

Perhaps these thermocouples and their associated alarm were intended to i provide an indication of condensate level in the vertical section of the j steam line. At the time of the inspection the licensee could not provide  ;

-

a design basis for the thermocouple placement or the alarm setpoint. l

--

The maintenance histories for the isolation condenser steam and conden-sate valves were reviewed. These histories as well as discussions with [

personnel and other docut entation indicate that on many occasions the >

) normally closed condensate isolation valves leaked or were suspected of [

leaking. Outage reports which provided some detail of the maintenance  :

performed in each instances where the normally closed condensate return valves were disassembled and inspected; they showed evidence of leakage j and required some repair. These valves have nn been inspected since 1985; consequently, it is possible that some leakage past these valves i existed. However, any significant leakage would nave been identified through elevated shell temperatures. Leak rate determinations associated with these valves is discussed in Inspection Report 50-219/83-23.

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,

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The isolation condenser steam lines are provided with vents at the high points in the line. These vents are installed to vent noncondensables to the main steam line downstream of the main steam isolation valves.

These vent lines are provided with isolation valves and downstream of  :

the2e valves join together into a single line which extends approximately 400 feet to the main steam line. In traveling these 400 feet the eleva- t '

tions of the line are such that an approximate 18 foot loop seal is established. A single manual isolation valve is provided where the line entars the main steam line, j

The vent line is a 3/4 inch schedule 40 carbon steel pipe which has been in service for over 20 years. This line may have rusted and may contain some amounts of debris in thr; lower portions. This debris may prevent l the free flow of steam. In this way a single blockage 3r valve failure i has the capability to adversely affect the operation of both condensers, i Records show that in the past the manual valve at the main steam line has been "throttled closed" in an effort to reduce the shell temperature.

The licensee has been requested to address the potential of a single failure to adversely affect the operation of both condensers. '

9.0 Equipment Effects / Impact  ;

j The licensee has initiated steps to evaluate certain concerns which developed l as a result of the improper operation of the isolation condensers. The speci-fic concerns to be evaluated are:

,

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analyze dead weight stress due to hydraulic loading to ensure there was

,

no overstress on piping or equipment nozzles,

--

ensure no thermal fatigue concerns exist due to any transient conditions.

--

Inspect system hangers and supports, and

.

--

determine possible effects of water flow in the isolation condenser vent

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lines on msin turbine blades. .

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Final reports including results of these evaluations will be provided to the I

NRC.

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10.0 Evaluation of Licensee's Review of Events  :

i In response to the unusual occurrences which precipitated tre unscheduled 1 shutdown of the facility the licensee has taken actions to evaluate, correct and prevent this situation from recurring. This paragraph provides an inde- i pendent (NRC) evaluation of the ifcensee s efforts in this regard.

!

As indicated in paragraph 3, the "B" Isolation Condenser exhibited unexplained i sti.mir.g af ter a brief unintentional initiation of the "B" Isolation Condenser I

(see inspection Report 88-23) on August 28. The inspectors expressed concerns ,

i regarding the unexplained respense of the "B" Isolation Condelser steam line >

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thermocouples. The licensee indicated that their literature research and i preliminary analysis did not provide any answers. On September 26, a sur-

< veillance of the line break instrumentation on the "A" Isolation Condenser included shutting all four isolation valves. Upon returning the condenser to service, it exhibited the same phenomenon as the "B" Isolation Condenser.

t Upon observing steam through the "A" isolation condenser shel' side vent,  ;

which followed steamtrg from the "B" isolation condenser shell side, the '

licensee assembled a team of specialists from Technical Functions and Plant Engineering to investigate the phenomenon. The team evaluated the sequence  !

of events which took place August 23 to September 26, 1988. The beginning 1 of the sequence which set up the thermal-hydraulic conditions in the "B"

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, Isolation Cor. denser was on August 23, 1988. Events which initiated similar 4 conditions in the "A" Isolation Condenser took place on September 26, 1988

)

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as a result of a routine surveillance test. The licensee at this point was aware of possible safety implications due to inlet / outlet temperatures "

in the isolation condensers which suggested abnormal flow conditions.

The licensee's initial evaluation of the abnormal operating characteristics in the isolation condensers included the acquisition of temperature data which was in addition to data accumulated from installed thermocouples in the isolation condensers and steam lines. Surface temperature readings on the steam and condensate piping of the "B" Isolation Condenser were taken. As L previous noted, this was done by boring holes in the insulation around the piping through to the outside surface of the pipes at four azimuthal locations each on the outlet of the condenser tube bundles and at the "wye" at the bot- F tem of the steam risers (see Figure 1), and utilizing a contact pyrometer to t read the temperatures. While performing these temperature measurements at the "wye" section of the steam riser, licensee personnel noted (1) "... low  ;

amplitude vibration in the piping...on the order of 5 cycles per second...," >

(2) "...a rumbling noise...like flow going through a pipe...in sync with the rumbling. . . ," and that (3) ".. .the intensity (of vibration) felt erratic given...the impression that some turbulent event was occurring in the pipe..." l It is through the acquisition of this data that the licensee was able to draw l soma preliminary conclusions / explanation for the phenomenon in the isolation condensers. Upon concluding an abnormal flow path existed, the condensers ,

were made inoperable and the plant promptly shutdown. (

f A plant shutdown began on September 29, 1988 due to steaming at an unprece- i dented rate from the shell side of the condensers and an assumption that water '

had filled the steam lines. The licensee *s decision to shut down the plant was based on the possibility that, if during normal operation of the facility l the isolat. ion condensers were called upon to perform their design function, -

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severe water hammer might result upon initiation which could cause damage to the isolation condensers. Since a tube break would result in a direct pathway for primtry coolant release to the atmosphere, water hammer needed to be guarded against. The team felt the licensee's action to shutdown was prudent.

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Since the shutdown the licensee has reorganized and expanded its team of specialists investigating the problem. A task force assigned to evaluate eight areas has been organized and instituted. The task force is charged with

%vestigating the following areas: 1) Explanation of the thermal hydraulics 1 of the phenomenon and construction of a workable computer model; 2) Recon-struction of a detailed sequence of events leading up to the plant shutdown; e

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3) Stress analysis of related components; 4) Possirle operating methods and procedure changes to prevent the abnormal flow phenomenon from recurring; 5) Possible required modifications to the isolation condenser piping network to preclude recurrence; 6) Accumulation of information regarding similar occurrences or events in the industry; 7) Review of outage maintenance plans to assure as-found data important to the operation / evaluation of the isolation condensers is preserved, additionally, consider the effects of water in the

, steam vent line on the turbine blades; and 8) Preparation of an integrated report on the findings of the task force.

The inspectors reviewed the proposed organization of the task force plan and discussed its cbcrter with the licensee. The licensee has assigned an overall project manager from Technical Functions who is dedicated to the task force i

as well as a subtask manager for each of the eight tasks. Additionally, team

members have been selected for each task and the scop? and target completion date of each task has been defined. The licensee has committed to evaluate the event and provide corrective / preventive action before starting up from this out2:e (see Attachment B). The team concluded that proposed licensee actions a o appropriate and comprehensive.

11.0 Electrical Event

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! On October 2, 1988, Oyster Creek Nuclear Station lost power to one half of

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the safety related electrical system (B) train. This was later determined to be as a result of a cable insulation failure.

I 11.1 Event _ Summary I

The plant was in shutdown with the safety related electrical buses ener-

gized from offsite power sources. Reactor temperature was 145 degrees i F and the reactor level 162" above the top of active fuel with A and B l shutdown cooling pumps in service. On October 2, 1988, at 1

57 p.m.

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emergency diesel generator 2 locked out and the feeder breaker for 4160 V safety related Bus 10 tripped. The existing shutdown cooling was lost 1 as both runnir.g pumps were on the tripped bus. The ro: tor water ten-perature increased to 162 degrees F. The licensee promptly reestablished

shutdown cooling using the A train power supply and stabilized the tem-perature at 158 degrees F. The operations department tried to energize i

the tripped bus by reclosing the breaker but the breaker immediately I tripped open. The maintenance department located the fault 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> later j as being in the cable between diesel generator 2 and 4160 V emergency Bus 10. The faulted cables were disconnected and Bus 10 was energized

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)

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• a

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from the offsite power source within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of the event. The emergency diesel generator 2 remained unavailable due to the disconnected bus cable.

A detailed chronology of events is provided in Attachment F.

11.2 Plant Status Analysis and Conclusions An Augmented Inspection Tecm sent to the site by the NRC management was directed to inspect the following aspects of the electrical evert:

• Assess the plant condition with an unavailab'le emergency diesel generator.

• Develop a chronology of the events.

• Review and assess the logic of diesel generator lockout feature.

• Review the prior history of electrical bus faults.

• Evaluate the adequacy of the licensee's review and corrective actions.

The lockout of tne Emergency Diesel Generator (ED3) is a design feature to prevent the EDG from starting and loading on a faulted bus. This signal is generated when the starting and the loading of the EDG is not practical due to an electrical fault on the bus that cannot be isolated

.

or removed by virtue of the installed automatic features on protective relaying.

During the shutdown condition of the plant, emergency train B (Bus 10)

is energized from an off site source through breaker 10 and Bus 18. A around fault was sensed at a relay above breaker 10 (see attached Elec-trical Power System Sketch, Attachment G) which tripped breaker 10. This is due to a fault at the ID Bus or a significant fault at any location below the feeder breakers on Bus 10 which was not isolated by the imme-diate servicing breaker. Either of these canditions indicate a sustained fault on the bus making it unsafe for the emergency diesel generator to be connected. The setpoint of the grourd fault relay is at a reasonable setting to distinguish a ground fault without causing any permanent dam-age to plant equipment. This condition prompts an EDG lockout. Any other conditi ans, such as undervoltage, fault on Bus 18 or loss of power to Bus 0, would not have caused the diesel lockout. Therefore, this re-view indicates the diesel lockout was generated only when the fault was  ;

confirmed tn be on the bus and it functioned in accordance with the Oyster Creek design (see Astessment of Oyster Creek 4160 V Emergency Bus, Section 11.4).

Because of the above event, half of the safety related electrical system (one train) lost power. The licensee design has provisions for cross connecting the safety buses in case of emergency. The team reviewed th?

instructions documented in procedures 337 and 333. As the plant was in

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17 i

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shutdown condition during this event, shutdown cooling was established i with the available train "A". The licensee has Station Procedure 2000- '

OPS-3024.27, Rev. 3, "Shutdown Cooling System-Diagnostic and Restoration Actions " in place for establishing shutdown cooling. This procedure also addresses alternate decay heat removal using the core spray pump and torus water utilizing the relief valves. The team verified the sup-port systems, reactor buf ding closed cooling and service water system !

to be powered from safety buses. This arrangement permits the estab- ;

lishment of long-term shutdown cooling if any of the safety train is i energized with offsite power source or onsite emergency ciesel generators. (

11.3 Previous Electrical Bus Faults / Losses I Oyster Creek emergency diesel generators (EDG) are located 200 feet away from the turbine / reactor building. The diesel generator, control panel, auxiliary systems and the breaker that connects the generator to the emergency bus are located in the diesel building. This breaker is con-nected to six single conductor cables (2 per phase) that run underground for 200 feet and another 150 feet inside the building to reach the re-spective 4160 V emergency bus. The underground cables in this arrange-ment become an extension of the Class 1E Bus always energized as the part of the bus and there are no breakers in betwoen the safety bus inside the building and the diesel generator building. Any failures on these cables result in power loss to the respective Class IE train.

Each of the 4160 V buses also feeds the unit substations that service the intake structure through an outdoor underground cable fled of 150 feet. Another underground cable feed is to the dilution plant (water makeup to reduce change in water temperature due to plant use) and it originates from the A startup transformer. Even though the above two cases are not safety related applications, faults an these cables can influence the availability of the safety bus, so tne history on failures of these cables are also listed below:

1975 EDG-1, One Phase of the Spliced Cable Section Failed: The team reviewed the test report presented by the Electrical Testing Laboratories dated December 29, 1979. This report indicated the failure was due to a voltage surge. This is consistent with the licensee reported lightning event discussed in a 1973 reportable occurrence. The test laboratory's report recom-mended periodic high potential testing of power cables at 25KV DC volts, use of heavier wall insulation and an extruded outer semicon shielded cable.

1977 EDG-2, One phase of tne Spliced Cable 53ction Failed: Observed pinholes in the insulation which cow.o be from a lightning surge resulting from the lightning strike in 1973. All DG cables were replaced.

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1978 Ground Fault in Cable Connecting Offsite Power and Startup Transformers (Bank 5) Main Cable Bus: St$<equent review indi-cated that all outdoor SKV nonshielded ce. es have undergone accelerated corona degradation. All cables were replaced with ,

shielded copper cable according to the original Architect '

Engineer (AE) specification instead of unshielded aluminum.

l 1980 Dilution Pump Feeder Cable Failed: The licensee inspection found that water completely filled the cable vault. The con-

'

duit was reduced from 4" to 3.1/2" just inside the vault wall, i

, This conduit was submerged and filled with water. The cable  ;

Jacket was found severely cut and damaged (from original con- l struction) in the area of the conduit reducer. Water was found  !

inside the inner conductor and between the out jacket and in- -

sulation layer, i The licensee installed a 4" duct to replace the 3.1/2" and 3"  !

sections. Sump pumps were also installed in the cable vault. .

1983 Dilution Pump Feeder Cable Terminations we_re Tested as Water {

Seepage was Found in Turbine Building Mat: The leakage current

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was too high for several cables. Determination was made that i i the cause of the failures were due to a cut in the insulation as well as improper installation methods. Stress cones at

cable ends were replaced. Cable was verifled to be in good condition.

j 1983 EOG-1. One Cable of One Phase With a Splice Failed: The failed l cable was replaced in February, 1984. The cable inspection by Hanby Associates indicated that the cable with the faulted

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section (tested adjr. cent sections to the fault) showed no L leakage current at 20 or 30 Kilovolts. The licensee attiibutes  ;

the failure to a manufacturing defect.  ;

1986 Dilution Pump Feeder Cable Failed: Damage to cables indicated  !

that water incursion was the cause of failure. The licensee

! replaced stress cones and cable was found to be in good condi- ,

,

tion. Water entrance was due to wicking of moisture along the l

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shield drain wires and up into the stress cone. Drain wires I were vented below stress cones to prevent entrance of water r into the stress cone area.

1988 USS 1A3 Feeder Failed: Failure of cable did not pierce outer  !

Jacket. Failure was small and localized in nature. The copper  !

foil shield was discolored from heat and current within 6 .

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inches of each side of the fault suggesting that ground current i

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was being carried for a long period of time. Review of the l original plant high potential tests showed that one of the l

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three phases was high in 'eakage in 1968 during construction.

It was concluded that an original defect was the cause of failure. The corrective action was the replacement of all cables in the feeder.

The licensee's corrective actions in the above failures appear to be reasonable. The team reviewed the records on the testing done on cables after installation. However, in spite of the repeated failures and con-trary to the recommendation from the Electrical Testing Laboratories (addressed in 1975 event), the licensee did not institute a surveillance program to monitor the integrity of the safety related electrical cables.

The cable failure on October 2 1988 remains to be analyzed when the cable is pulled out of the duct.

11.4 Assessment of Oyster Creek 4160 V Emergency Bus The emergency diesel generators are located 200 feet away from the tur-bine building and a total of 350 feet away from the main switchgear in-side the building. Two hundred feet of cable ren is through outdoor underground ducts that are below the switchyard and a plant service road inside the protected area. The cable failures discussed in paragraph 9.3 indicate the susceptibility of outdoor cables for failure. The diesel generator cables are designed to be an extension of the 1E Bus, always energized, and there are no breakers in between the bus in the turbine building and the diesel generator building. This cable normally serves the diesel generator auxiliary systems and functions as the feeder when diesel generator is supplying the load.

Any potential fault on these cables makes the corresponding safety train immediately ur.available and locks out the diesel generator. The control circuit is de ,1 ned3 such that the lockout signal is generated only when a fault ie :enfirmeo to be on the safety bus and not isolated by the tripping o' the downstream safety grade breakers. Even though locking

out a diesel under such bus fault condition is unique to the Oyster Creek station, it appears prudent in this application as the most probable failure is on the cable which can be promptly isolated and the bus re-covered in minimum time. As the cables for one EDG are run in two inde-pendent raceways, the failure may be limited to one cable and therefore the unfailed cable can be connected back to feed almost 60% of the EDG capacity in case of emergency. The ampacity requirements and the in-stalled size of the conduit in the duct limits any substantial upgrade of the cable insulation (changing to 15KV insulation) while utilizing the existing raceway system.

Substantial improvement (use of 15KV insu'ation) in cable insulation thickness can be achieved through the use of 3 triplex cables using the existing underground raceway instead of 2 single conductor cables per

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phase. The licensee considers this option to be prohibitive due to the cost of installing 150 feet of cond 't inside the turbine building to each of the safety trair, switchgear.

Lightning surges and other switching suiges can cause gradual degradation of the insulation and can lead to potential common mode failures, es-pecially when cable insulation for the rated voltage currently installed has exhibited failures in the past. The probability of such cable fail-

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ures needs to be evaluated when the licensee corrective actions and sur-veillance program are finalized, 11.5 Licensee Corrective Actions  ;

l The opening of breaker 10 deenergized half of the safety related elec- '

trical system. The licensee started pronipt measures to restore this 4160 V bus. The first alarm that came on was "LK0UT RELAY TRIP". This indicates that EDG-2 has been locked out. The alarm response procedure 2000-RAP-3024.02, Revision 10 has the following confirmatory actions:

"Verify trip of diesel generator 2 breaker (and Bus 10 if affected).

Find any targets at diesel generator and at the Bis ID in 4160 V room".

Contrary to the above, the licensee personnel looked for targets only at the 4160 V room and elected to close the breaker within 11 minutes t from the first alarm. The breaker closed on to the fault and tripped [

instantaneously.

The electrical maintenance crew started troubleshooting. The maintenance i staff made the following observations:

(1) The ground fault relay on D Bus was tripped and the diesel generator was locked out.

! (2) The B phase differential relay on diesel generator 2 was tripped.  !

(3) Two phase shield ground leads on phases B & C in the EDG-2 breaker

, cabinet (located in the diesel generator building) were detached.

The licensee's investigation is in progress to determine how ground leads f became disconnected.

[

The above indications confirmed the fault to be on the EDG-2 cable and l

>

the cable was disconnected at both ends. The 4160 V Bus was subsequentiy i energized by aligning the breakers to the offsite power supply. This activity was complete in 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

!

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i r

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The root cause Dalysis for the current cable failure will start at soon as the failed cable is available for inspection. However, based on the history of failures the following commitments were made. The immediate

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corrective actions scheduled before restart are as follows:

(1) EDG-2 cable that failed will be replaced with a cabi. that has 33%

more insulation.

(2) EDG-2 cable that failed will be analyzed by an external specialist  :

and further action will be taken as appropriate. I (3) EDG-2 cable that did not fail will be D-C Hi-Pot tested at a minimum *

of 15 KV prior to plant restart.

(4) EDG-1 cable (s) will be D-C Hi-Pot tested at a minimum of 15 KV prior ;

j to plant restart.  ;

"

(5) 183 Fe er will be tested prior to restart due to the failure of the IA3 cable in July of 1938.

i  :

(6) The need for surge suppression on the offsite feeders to th? plant 4160 buses will be evaluated and scheduled if necessary.

(7) part of the ground system including the ground connection for the EDG switchgear will be tested during 12R.

The licensee's previous practice was to test the cables at 10 KV with the motor connected to it. The industry standards recommend DC high

, potential test at 25 KV for maintenance testing. The team expressed the need to substantiate the licensee's position for using 15 KV as test

,

voltage. The licensee letter, Attachment B, has conmitted to provide j a final report of the corrective actions for NRC review and resolution i of technical issues prior to restart. i Based on the concerns shared by the team, the licensee made the following

long-term commitments for the early detection of potential cable problems and to limit the degradation of insulation failure:

(1) Doble Testing and AC Hi-Pot testing will be evaluated as an alter-native to DC Hi-pot testing.

(2) A formalized preventive maintenance program for cables that are

! important to safety will be developed prior to the 13R refueling outage.

l i (3) An electrical ground test program will be evaluated to determine ,

i its need and scope.

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The presence of class 1E 4160 V cable constantly energized in outdoor underground duct warrants an aggressive surveillance program for pre-I serving the availability of the safety bus. The licensee recognizes the  ;

safety significance of this program and agreed to provide the details of this program to the NRC for review.

12. Exit Interview ,

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Periodically during the inspection, the team briefed the licensee representa- I tives on the progress of the inspection.

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An exit interview was conducted at the conclusion of the inspection to sum- f marize the results of the inspection to Senior Licensee Management, Persons '

attending the exit meeting are identified in Attachment F of this report.

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ATTACHMENT A '

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OCT e 4 IIIB

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MEMORANDUM FOR: William K. Kane, Director, Division of Reactor Projects ;

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FROM: William T, Russell, Regional Administrator SUMECT:

AUGMENTED ins'ECTION TEAM - INOPERABLE ISOLATION CONDENSER $ ,

AT OYSTER CREEK  !

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You are directed to perform a prompt inspection of the causes, safety implications, ,,

and associated licensee actions which led to the inoperability of both trains of ;

the isolation condensers on September 29, 1988, and the later loss of a vital electrical bus on October 2, 1988. The inspection sell be in accordance with NRC Manual Chapter 0513, Part III, and additional instructions in this memorand a.

ORP is assigned to conduct this inspection and Curtis J. Cowgill is designated as !

the Team t.eader. The team will also include the provision for participation by the Divtsien of Reactor Safety and NRR. t j

00ECTIVE I

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l The general objectives of the AIT are to:

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a. Conduct a timely, thorough, and systematic inspection related to the circum-stances surrounding the troperab'lity of the isolation concensers and later l

loss of a vital electrical bus. i b. Assess the safety significance of tre events and cowwnicate to Regional and !

Headquarters management the f acts ard saf ety concerns related to tne problems l identified. '

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c. Collect, analyze, anc cocument all relevant cata and factual information to determine the causes, corcitions, anc circumstan:es pertaining to the events. l

d. Evaluate the adequacy of the Itcensee's internal review of the events. !

SCOPE OF THE INSPECTION i

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The AIT respense snovic identify and docu eat tre relevert f acts arc dete mire tre i I

prcbable causes and shculc be limited to tre issues directly related to the events l the licensee response.

I Specif^cally, the A]T should: i

, s. Develop a chrono 1cgy of the events,  ;

b. Determine the scope and quality of Itcensee's internal revie. of the events. {

c. Develop a nistory of operability preblems with tre isolation condensers for the past 3 months.

' i d. Review prior history of electrical bus favits/ losses and logic of diesel

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generator start. l r

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Wi111 0 F. Kane 2 OCTto M e. Review the s sintenance operations activities leading to the events.

SCHEDULE The AIT shall Se dispatched to the Oyster Creek Nuclear Generatir.g Station no later than October 5, 1988, and shall remain there as long as necessary to accomplish the objectives of this inspection. It is expected that this will take no longer than five working days.

A written report on this inspect. ion will be provided to re by October 30, 1988.

TEAM COMPOSITION The assigned team rembers are as follows:

C. Cowgill, ORP, R!

J. Wechselberger, SRI - Oyster Creek D. Lew, RI - Oyster Creek W. Baunact. ORP, RI J. Golla, DRS, RI L. Lois, NRR R. Brady, CRP, RI T. Koshy, OR$, RI hhilliam f =eAS T. Russell Regional Acministrator cc:

C. Cowgill Team Members

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ATTACHMENT B OPU Nusdoer CorporsWon

. Nuclear t'::;;;=

Forhed Let.New Jetsey 087314366 609 971 4000 WrWs Direct Dial Number:

October 10, 1988

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Of rector of Nuclear Reactor Regulation U.S. Nuclear Regulatory Comission Mail Station Pl.137 Washington, DC 20555

Dear Sir:

Subject: Oyster Creek Nuclear Generating Station Docket No. 50-219

! solation Condensers and foergency Diesel Generators On September 26, 1988, following 4 surveillance test of the ' A' ! solation Condenser, it was observed that its shell temperature was increasing which ultimately resulted in steaming of the Isolation Condenser to the atmosphere. Follorirg this event, GeMral Public Utilities Nuclear Corporation (GPUN) initiated an investigation in order to determine the cause of this steaming and also to review the evaluation of the 'B' Isolation Condenser which had been steaming previously. When the '8' ! solation Condenser had begun steaming, the cause was ai'ributed to leakage through the condensate return valve. After 'A' ! solation Londenser began steaming following the surveillance test, GPUN became concerned that the cause of both occurrences say not h1ve been fully understood.

GPUN establisheo a dedicated evaluation team of Plant Engineering and Technical Functions personnel to perforra a detailed review of the Isolation Condenser system and the circumstances leading to steaming. Af ter a few days, the team detersined there was a high probability that the steam lines to the Isolation Condensers contained a significant volume of water. Station management, in response to a recomendation from the evalustf or team, directed that the isolattos condensers be isolated and a plant shutdown be initiated in accordance with the Oyster Creet Technical Specifications. This action was taken due to the industry experience with water harsner events in Isolation Condenser stea'n lines. Water hassner in these lines has the potential to cauw sigreificant damage to the system.

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GPil Nur!P at r.mr)nr.tl.W is e tuus4Ji, ci tre Gereisi Pwbt.c UtM es Ceipeistion

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Following reactor shutdown, GPUN cucpenced ths cycle 12 refueling outage and developed a formal plan unoer the direction of a project manager to address the issues related to the events which have occurred on 'A' and 'O' Isolation

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Condensers since restart from the last outage. The plan includes:

(1) Development of a thermohydraulic model to assist in the analysis.

(2) Reconstruction of a detailed sequence of events.

(3) A stress analysis of system piping and equipment nozzles.

(4) An evaluation and modification, if necessary, of procedures in order to prevent recurrence, identify the onset of abnormal flow conditions, and to recover should abnormal flow conditions occur.

(5) A determinatten of those modifications, if warranted, that prevent or minimize at< .* mal flow conditions and/or that monitor the onset of such conditions.

(6) A review of industry experience as well as maintenance and test activities.

Also following reactor shutdown, an event occurred on October 2,1988 in which power to the 'O' 41b0 voit emergency bus was lost while being powered from the startup transformer. An investigation revealed that the cables from

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the emergency diesel generator nad degraded placing a fault condition on the bus, GDUN is reviewing this occurrence and the circumstances surrounding tnis event to determine the root cause and any necessary lung term currective actions in conjunction with replacing the faulted cables.

The NRC nas established an Augmented Inspection Team ( A!T) to review the events associated with the Isolation Condensers and the loss of the 'O'

, emergency bus. GPUN and the NRC AIT have exchanged informattun regarding

these events and the above GPUN actions which are being taken to address tae identified issues. This has proven beneficial in asswring an in-depth review of the events and proper identification of the issues.

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, GPUN will complete any necessary actions required prior to restart from the 12R refueling outage to assure the Isolation Condenser > and Diesel Generatoe s

, are fully capable of performing their design function. GPUN will continue to

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advise the NRC inspection personnel of tnose actions in progress and the I

results acnteved following ccmpletion of the identified reviews. Final reports providing the results of the GPUN evaluation and the conclusions reached will be developed. These reports will be provided to the NRC and

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outstanding issues resolved prior to restart from the 12R refueling outage.

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Should you have any questions or comments, please contact Mr. George W. Busch at (609) 971-4909.

Very truly yours, ,

E. E. Fitzp Wick Vice President and Of rector Oyster Creek EEF/GB/sez (0144A:20)

, cc: Mr. William T. Russell, Administratse Region !

U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. Alexander W. Dromerick, Project Manager U.S. Nuclear Regulatory Consission i Division of Reactor Projects I/!! *

Washington, DC 20555 NRC Resident inspector .

Dyster Creek Nuclear Generating Station Forked River, kJ 08731 t

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ATTACHMENT C OYSTER CREEK CHRONOLOGY OF EVENTS ASSOCIATED WITH ISOLAf!ON CONDENSERS JULY 5 - OCTOBER 1, 1988 f i

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DATE/ TIME SOURCE DESCRIPTION July 5 v 1:07 p.m. Control Room Operator Filled the "B" isolation condenser shell  :

Log (CRO) to 7'6". Shell level had drifted down over  !

a period of time, and this event was per- i formed to return level to the upper end .

of the control band. [

8:44 p.m. CR0 log and completed Performed routine surveillance testing on test "A" Isolation Condenser per procedure 609.3.002 "Isolation Condenser Isolation l Test and Calibration", This test verifies  !

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the ability of the isolation valves to close upon the appropriate isolation signal.  ;

During this test, the two steam supply  !

valves close a.id the redundant condensate [

return valve closes. This isolates the +

condenser with the vent valves open. This alignment may exist for an hour or more. l i

July 6 i 10:30 a.m. CR0 log and completed Performed routine surveillance testing on i test "B" Isolation Condenser per Station Pro- t cedure 609.3.002.

Performance of this test isolated the con- -

i denser, and returned it to service and did  ;

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not result in increases in isolation con- I denser shell temperatures. '

July 8 e i 12:30 p.m. CR0 log Performed surveillance testing per Station l Procedure 609.4.001, "Isolation Condenser Valve Operability and In-Service Test". l This test verifies the operability of the j i

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isolation condenser valves. The valves -

are sequenced so each can be opened and/or {

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closed without initiating the isolation condenser, j i

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Attachment C C-2 DATE/ TIME SOURCE DESCRIPTION July 8 12:30 p.m. (Centinued) Also completed MOVAT's on valves V-14-32 V-14-33, V-14-35 as part of the procedure.

(Figure 1 identifies the valves in this discussion.

July 9 7:37 p.m. CR0 log Main turbine tripped during plant shutdown.

10:15 p.m. CR0 log Opened and closed valve V-14-35 at reactor a coolant temperature of 445 degrees during plant cooldown.

NOTE: V-14-35 has a history of becoming thermally bound in the closed position. l In order to minimize these thermal effects ,

during plant cooldown, the valve is cycled every 100 degrees.

July 10 i 12:25 a.m. CR0 log Opened and closed valve V-14-35 at a reac- '

tor temperature of 352 degrees.  ;

3:40 a.m. CR0 log Opened and closed valve V-14-35 at a reac-tor temperature of 280 degrees.

4: 13 a.m. CR0 log Broke vacuum on the main conderser.

6:00 a.m. CR0 log Reactor coolant temperature less than 212 l degrees,

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July 13 l 10:35 a.m. CR0 log and switching "A" and "B" isolation condensers tagged l and tagging log sheet for maintenance primarily to repack the t l 88-591 steam line vent valves. l July 22 l 12:45 p.m. Switching and tagging Tags cleared on the "A" and "B" isolation i l

log sheet 88-591 condensers. Manual vent valves V-14-2 and V-14-6 were returned to the open position. .

V-1-71, the common vent isolation, was left  !

i closed. '

July 31 1 12:00 p.m. Test documentation Performed local leak rate test (tLRT) per  ;

Station Procedure 665.5.003, "Main Steam Isolation Valve Leak Rate", section 10.

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Attachment C C-3 DATE/ TIME SOURCE DESCRIPTION August 2 -

5:00 a.m. Test documentation Performed LLRT per Procedure 665.5.003, section 10.

August 3  !

9:40 a.m. Test documentation Performed LLRT per Procedure 665.5.003, section 7. V-14-19 failed.  ;

I August 4 l 1:20 p.m. Switching and tagging Tagout issued to support repairs to vent i to log sheet 88-707 valve V-14-19. Valves V-14-2 and V-1-71 l

'agged closed.

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j 9:55 p.m. Switching and tagging Tags cleared on "B" isolation condenser. l log sheet 88-707 V-14-2 and V-1-71 returned to open position.

l l 10:45 p.m. Test documentation Performed LLRT per 665.5.003, section 10 f to test valve V-14-19 (this left valve V- l 14-6 closed).

August 5 t 1:05 p.m. CR0 log and test Performed isolation condenser valve oper- i i documentation ability surveillance per Station Procedure 609.4.001, to return condenser to service. >

i August 10  !

1:40 a.m. CR0 log Closed reactor head vents. .

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5:02 p.m. CR0 log Reactor is critical, temperature 217 de-grees.

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7:00 p.m. CR0 log Established condenser vacuum. l August 19 9:10-12:52 a.m.  !

CR0 log Performed routine surveillance testing per Station Procedure 609.3.003, "Isolation Condenser Automatic Actuation Sensor Cali-bration and Test". This test results in the isolation condenser vent valves being f closed for short periods of time. L August 23 1:43 p.m. Licensee Critique Performed valve operability test for the [

"A" Isolation Condenser to support work j en stem repacki;:g of valve V-14-33 ("B" j Isolation Condenser),

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t Attachment C C-4  ;

DATE/ TIME SOURCE DESCR!pTION l

f August 23 (Continaed)  ;

6:07 p.m. CR0 log and test Performed valve operability on V-14-32 '

docunntation using 609.4.001 in preparation to elec- '

trically backseat V-14-33. This was being performed in order to repair a parking leak l on V-14-33. l 6:30 p.m. CR0 leq Three attempts to lectrically backseat V-14-33 were unsu essful. '

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NOTE: The ele:trician then realized the wrong amprobe was being used. The correct :

probe was obtained and the valve correctly  !

backseated.  !

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10:00 p.m. CR0 log Mechanical maintenance on V-14-33 completed. l l

10:43 p.m. CR0 log V-14-33 fails its post maintenance test  !

and is declared inoperable due to motor failing. "6" isolation condenser removed ,

from service and is isolated (i.e., valves i

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V-14-37, V-14-32, V-14-33 were closed).  !

t NOTE: Valve V-14-35 was not cycled during this condenser cooldown.

August 24

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1:55 a.m. Switching and tagging Tagout to replace motor on V-14-33 imple-  !

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log sheet 88-772 rented. The "B" isolation condenser vent valves were closed (V-14-1 and V-14-19).

t 4: 11 a.m. CR Chart Recorder The temperature between valves V-14-35 and

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V-14-37 started to fall from 400 degrees after V-14-37 was closed. The temperature i eventually reaches 256 degrees.

11:30 a.m. CR0 log Performed surveillance 609.4.001 on "A" i Isolation Condenser while the "B" Isolation ,

Condenser is out of service. (Required  ;

to be performed daily.)  ;

August 25 .

11:16 a.m. CR0 log Performed surveillance 609.4.001 on "A" l j isolatics condenser while the "B" Isolation f Condenser is out of service, j l  !

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Attachment C C-5 t

DATE/ TIME SOURCE DESCRIPTION August 26 .

11:02 a.m. CR0 log Performed surveillance 609.4.001 on "A" >

isolation condenser while the "B" Isolation  ;

Condenser is out of service.

August 27  !

9:30 a.m. CR0 log Performed surveillance 609.4.001 on "A" isolation condenser while the "B" Isolation '

Condenser is out of service, j

6:30 p.m. Licensee Critique DC motor for V-14-33 replaced and partial MOVATS corrpleted. Packing leak observed to be increased. Decision made to recheck packing adjustments. Repacking on backseat  ;

not acceptable. Decided to assess accept- l ability of operation with packing leak.  !

When V-14-33 was finally opened, the pack- '

ing leak significantly decreased.

August 28 l

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Switching and tagging Cleared tags on "B" isolation condenser. [

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log sheet 88-772  !

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CR0 log Shell side temperature of "B" Isolation  !

Condenser = 94 degrees  ;

l 3:45 a.m. CR0 los Commenced warming "B" Isolation Condenser '

l per Station procedure 307, "Operation of i l the Isolation Condensers." i l l

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l 3:58 a.m. CR Chart Recorder Temperature between V-14-35 and V-14-37 l starts to incraase when valve V-14-37 is  ;

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opened.

4:50 a.m. CR0 log Opened valve V-14-33. Temperatures and pressures irtreased in "B" Isolation Con-l denser Steam Line, and valve V-14-33 was closed, t

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Operations Engineer "B" Isolation Condenser Steam Line terpera- f Notes tures went from 120 to 300 degrees in 2 i

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minutes. This temperature is obtained from isolation condenser steam line pressure.

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Attachment C C-6 DATE/ TIME SOURCE DESCRIPTION August 28 4:55 a.m. CR0 log Cycled V-14-32 open/ closed in an attempt to seat valve. Reopened valve V-14-33; i this time no temperature or pressure in-  !

creases were observed.  !

6:50 a.m. CR0 log Opened V-14-32 to heat up "B" Condenser.

f 6:53 a.m. CR0 log Closed valve V-14-32 to slow the heatup rate. *

6:53 a.m. NOTE: Valve position information from the ft

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plant computer does not indicate any move-ment of valve V-14-32 during this time  !

l frame (6:50-6:53 a.m.). Discussions with l

the reactor operator indicate that the l valve was "bumped" in +.he open direction such a small amount, that the "red" open  !

indicating Itght did not illuminate. If !

the open light did not illuminate, then ,

I the plant computer would not detect valve  !

r.o t i o n . Plots of isol.. tion condenser I heatup snow that valve V-14-32 was at least I partially open during this time interval. f Also, the isolation condenser vent valves I were cycled open/ closed periodically from l

< 6:15 a.m. until 9:49 a.m. [

j 6:58 a.m. CR0 log "B" Isolation Condenser steam Line tempera-tures peaked at 395 degrees F and began '

drifting down sicwly. l

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10:00 a.m. CR0 log Equalized across "B" Isolation Condenser r and opened valve V-14-32.

10:03 a.m. CR Chart Recorder "B" Shell Temperature begins to increase.

i 10:07 a.m. CR0 log Closed valve V-14-32.

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10:15 a.m. CR Chart Recorder "B" Shell Temperature steady at 105 degrees.

) 10:20 a.m. CR Chart Recorder Temperatures between valves V-14-35 and  !

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V-14-37 steady at 400 degrees.

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Attachment C C-7 DATE/ TIME SOURCE DESCRIPTION i

August 28 (Continued) i 10:55 a.m. Licensee Critique Opened valve V-14-32.

11:02 a.m. CR Chart Recorder "B" shell temperature begins to increase again.

12:30 p.m. CR0 log Shell side temperature of "B" Isolation Condenser = 184 degrees.

During this period of time shell tempera-ture was increasing at the rate of 47 degrees / hour.

12:43 p.m. Plant computer, Ouring performance of surveillance licensee critique 609.4.001, CR0 inadvertently moves V-14-37 in the open direction while V-14-35 is open.

This effectively results in "B" isolation condenser initiation for about 6-8 seconds. l A minor plant transient is experienced (IR 50-219/83-23 discusses). V-14-37 i s im- l mediately closed. [

l During this event, the temperature between !

valves V-14-35 and V-14-37 decreased from !

400 to 270 degrecs in about 20 minutes, I then slowly started increasing again, eventually to 400 degrees. [

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1:01 p.m. CR0 log and test Surveillance 609.4.001 is satisfactorily I documentation completed. [

1:10 p.m. CR Chart Recorder "B" Isolation Condenser shell temperature j reaches 212 degrees F. i 1:38 p.m. CR0 log "B" isolation condenser shell side low f level alarm received. Shell side tempera-

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ture is 213 degrees. Initially, the tem- L perature was 94 degrees. At 12:30 p.m. [

the temperature was 184 degrees. [

i 1:39 p.m. CR0 log Closed V-14-37.

1:44-3:50 p.m.

CR0 log Added water to "B" isolation condenser 3 times.

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F Attachment C C-8

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OATE/ TIME SOURCE DESCRIPTION i

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August 28 (Continued)

2:05'p.m. CR0 log Opened / closed V-14-35. Reopened V-14-37. .

This was an attempt to seat the suspected ,

leaking valve V-14-35. '

3:52 p.m. CR0 log Making up to "B" isolation condenser using demineralizer water, t

5:32 p.m. CR0 log Closed V-14-37, cycled V-14-35 opened /

closed again in an attempt to reseat valve.

Reopened V-14-37, l 7:32 p.m. CR0 log "B" holation cordenser shell side activity t below MDA.  !

4 8:00 p.m. Licensee Critique Reactor power reduced by 10 L't to at count l for beat removed by the "B" Isolation Con- j denser. t

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t j August 29 +

2:42 p.m. CR0 log and test Performed "A" Isolation Condenser valve t

documentation operability per 609.4.001 in preparation j to remove "B" from service in order to troubleshoot the suspected leaking conden-

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sate return valve, V-14-30,

l 2:45 p.m. CR0 log Closed V-14-37, "B" isolation condenser

removed from service to troubleshoot V- l 14-35, t

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8:30-9:45 p.m. j CR0 log Cycled V-14-35 three times during isolation l condenser cooldown.

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, August 30

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2:50 p.m. CR0 log and test performed surveillance 609.4.001 on "A" r documentation isolation condenser while the "B" Isolation !

Condenser is out of service. l 4:21 p.m. CR0 log Closed V-14-32 to attenpt to reseat valve f V-14-37, i l

Comment: The redundant condensate return {

valve, V-14-37, had been closed the pre- !

vious day, yet "B" condenser shell side }

temperatures remained at 212 degrees, thus :

leading to the conclusion that both V-14-35 and V-14-37 were leaking at this time, i (

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Attachment C C-9 DATE/ TIME SOURCE DESCRIPTION August 30 (Continutd)

4:23 p.m. CR0 log Cycled V-14-37 opened / closed.

4:25 p.m. CR0 log Reopened V-14-32.

August 31 L

2:15 p.m. CR0 log and test Performed surveillance 609.4.001 on "A" l documentation isolation condenser while the "B" Isolation Condenser is out of service.

l 8:07 p.m. CR0 log Manually closed V-14-35 to measure "leak rate". The valve handwheel moved 9-1/2 turns and the stem coved about an aighth of an inch.

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Comment: During MOVATS testing of V-14-35, the "B" isolation condenser vent valves

, were closed, yet nu observable decrease in the steaming rate was evidcat.

September 1 2:15 a.m. CR0 log Cycled V-14-35 open/ closed manually.

4:50 a.m. CR0 log Action plan for "B" isolation condenser completed.

2:15 p.m. CR0 log and test Perform 3d surveillance 609.4.001 on "A" documentation Isolation Condenser while the "B" Isolation Condenser was out of service.

6:51 p.m. CR0 log Opened V-14-35 electrically.

September 2 11:30 a.m. CR0 log Manual vent valve on "A" Isolation Conden-ser found closed (V-14-6). The valve was then opened.

1:10 p.m. Licensee critique Plant shutdown starts at a rate of 25 Mde/

hour as both isolation condensers were out of service.

6:50 p.m. Licensee critique and Valve lineups complete on both isolation Valve Lineup Sheet condensers.

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Interview Equipment operator verifies V-1-71 open.

Steam observed coming from valve packing.

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Attachment C C-10 DATE/ TIME SOURCE DESCRIPTION September 2 (Continued)

7:48 p.m. CR0 log Surveillance test 609.4.001 completed on both isolation condenser systems.

7:52 p.m. Licensee Critique Plant management declared "A" Isolation Condenser operable. Plant shutdown is secured.

8:17 p.m. Licensee Critique Plant management declared "B" Isolation Condenser operable, ,

8:21 p.m. Licensee Critique Plant increasing power.

September 3 l 00:00 a.m. Licensee Critique Plant reaches full load.

September 15

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STA data Steam line temveratures for "A" Isolation Condenser begin to fall from 540 degrees.

September 26 10:20 a.m. CR0 log Performing surveillance 609.3.002 on the i "A" Isolation Condenser.

10:34 a.m. Licensee Critique Both "A" Cer. dense steam supply valves and the redundant condensate return valve (V-14-30, 31, and 36) are closed. This isolates the condenser while the vent valves remain open.

NOTE: The normally closed condensate return valve V-14-34 is not repositioned during performance of thit surveillance.

11: 42 a.m. Licensee Critique Valves V-14-30, V-14-31 and V-14-36 are reopened.

Performance of the surveillance is sus-pended for lunch.

12:30 p.m. CR0 log "A" Isolation Condenser shell temperature obscrved to "ncrease.

12:45 p.m Licensee Critique "A" Isolation Condenser shell temperature indicated 153 degrees.

_ - _ _

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o .

Attachment C C-11 DATE/ TIME $00RCE DESCR!pTION September 26(Continued)

1:32 p.m. Licensee Critique Valves V-14-30 V-14-31, and V-14-36 are once again closed to complete surveillance.

Shell temperature stabilized at 179 degrees.

2:30 p.m. Licensee Critique Terminated performance of 609.3.002 and opened V-14-36, V-14-31, V-14-30. ,

2:45 p.m. CR0 log Pertormed surveillance 609.4.001 to attempt to reseat valve V-14-34, 2.55 p.m. Licensee Critique Shell temperature observed at 185 degrees.

3:30 p.m. Licensee Critique Shell temperature observed at 199 degrees.

'

3:34 p.m. CR0 Log Secured the performance of the surveillance test after the "A" isolation condenser valve alignment was returned to normal in order to investigate the rising shell tem-peratures.

4:05 p.r,. Licensee Critique Shell temperature reached 212 cegrees.

---

STA data "A" isolation condenser steam line tempera-tures: North-increase from 230 to 290 de-grees; South-falls from 400 to 220 degrees.

I 5:30 p.m. Interview Plant engineer verifies V-1-71 open, water i is observed at the valve packing.

l l At the same time the technician who sup-plied makeup water to the isolation con-densers noticed water "raining" on the floor from the isolation condenser vent valve area.

7:05 p.m. CR0 log Performed surveillsnce 609.4.001 on "B" Isolation Condenser before removing "A" isolation condenser from service.

9:40 p.m. CR0 log "A" Isolation Condenser removed from ser-vice.

l

I

_ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ - _ _ _

. .. .

,

Attachment C C-12

OATE/ TIME SOURCE DESCRIpTIE  ;

September 27 I 1:50 a.m. Licensee Critique Closed valve V-14-36. l 3:15 a.m. CR0 log Cycled valve V-14-34 open/ closed for MOVATS.  !

!

NOTE: Ouring MOVATS on V-14-34, the "A" '

isolation condenser vent valves c1csed,  !

,

.

'

1:05 p.m. CR0 log Received double indications on vent valve V-14-20.

I 1:24 p.m. CR0 log V-14-20 open w/o assistance.  !

1:50 p.m. CR0 log Performed 609.4.001 on "A" Isolation Con- l denser.

5:45 p.m. CR0 log Cycled valves V-14-34 arj V-14-36 cpen and closed. ,

11:07 p.m. CR0 log "A" Isolation Condenser declared operable.

i l September 29 1 1:15 p.m. The isolation condensers are isolated.

l All steam supply and condensate return valves are closed, but the vent valves i remain open. Plant shutdown commenced due i to concerns regarding water in the isola- i-tion condenser steam lines.  !

l l 2:30 p.m. CR0 log declared unusual event.  !

!

Septe.tber 30  !

2:27 a n. CR0 log Tripped turbine. l

!

3:00 a.m. CR0 log Manually scram.med reactor.

4:40 a.m. CR0 log Stroked isolation condenser valves open/ l closed during cooldown. l 5:05 a.m. CR0 log Stroked isolation condenser valves open/ I closed during cooldewn. i 6:20 a.m. CR0 log Stroked isolation condenser valves open/  ;

closed during cooldown,  :

9:25 a.m. C.20 log Completed cycling isolation condenser i valves at 230 degrees reactor temperature, i

!

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. _ _ _ _ _ _ _ _ _ _ . _ _ _ ____ __

o .

Attachment C C-13

.

!

OATE/ TIME SOURCE DESCRIPTION September 30 (Continued)

9:35 a.m. CR0 log Broke main condenser vacuum, i

9:55 a.m. CR0 log Reactor in cold shutdown. Reactor vessel l vented. l 10:00 a.m. CR0 log Terminated Unusual Event.  !

5:25 p.m. CR0 log Commenced action plan to quantify water in the isolation condenser steam and con-densate return lines. Licensee conducted ISO concenser drain down to reactor vessel.  !

!

With the reactor vessel vented and reactor .

water level steady, the licensee opened '

the isolation condenser isolation valves i to etasure the reactor water level increase. [

This measured volume would be the amount l of liquid in the isolation condenser piping.  ;

5 0; p.m. Steam val"es opened: i

"B": measured volume =715 gallons calcu-  ;

lated volume =744 gallons  !

"A": measured volume =550 gallons calcu-  ;

lated volume =665 gallons [

!

Condensate valves opened: t

"B": measured voluee=676 gtons calcu- o lated volume =584 gallons i

"A": measured volume =1053 gallons calcu- l lated volume =662 gallons }'

'

These volume measv'ements indi- ed that l the isolation condenser piping, ,ncluding I l steam piping, was effectively full of water, j l i l Night shift interview The steam vent line was blown with instru- i ment air into the steam line. To do this '

l valves V-14-98, -99 were used.  !

!

Because on the type of test used to verify ,

flow, it could not be ascertained whether i or not there was water in the line. l l

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!

l l

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._ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _

,

, . . . j i

'

Attachment C C-14 i

!

OATE/ TIME SOURCE DESCRIPTION '-

i

'

October 1  ;

2:15 a.m. CR0 log Closed all MSIV's, j 3:35 a.m. CR0 log Closed reactor head sents V-25-21 and . I 25-22. I i

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ATTACHMENT D  :

!

_REVIEV 0F THE JUNE 12, 1985 REACTOR ISOLATION SCRAM -

l A review of a June 12, 1985 event in which a reactor isolation scram occurred was conducted to gather information o.s the isolation condenser operating parameters following actuation. The event was ir.itiated at 9:35 n.m. by a malfunction in the ;

electrical pressure regulatcr which caused a turbine bypass valvt to open. AP a result, reactor pressure dropped rapidly and the main steam isolation valves closed on low reactor pressure. A reactor scram from 101*; power c,: curred, ,

The "A" Isalation Condenser was rnanually initiate! To control reactor pressure at 10:15 a.m. The two temperature strip charts whici. ere availabl0 for the isolation condensers were the "A" Isolation Condenser shell temperature and the "A" Isolation Condenser steam inlet temperature (north steam line). The initial "A" Isolation Condtnser shell temperature and steam inlet temperature were 102 degrees F and 117

,- degrees F, respectively. The 117 degrees F steam inlet temperature was inoicative

'

that tha thermocouple was submerged in condensate. After the initiation of the I isolation condenser, the shell temperature increased to 212 degeses F in approri-I mately 11 minutes. The steam inlet temperature was observed to increase to 540 >

degrees in approximately 40 seconds, ahich was indicative tf the condensate level '

on the tube-side falling below the level of the thermocup',e. During the operation I

of the "A" Isolation Condenser to control reactor pressure, the steam inlet tem- l l perature followed changes in reactor pressure, -

l i

During the operating period in which the "A" Isolation Condenser was utilized to ll l control reactor pressure, the shell and $1 m inlet

. temperatures responded as ex-pected and do not correlate to the temperature resunses of the recent isolation ;

l condenser phenomenon, j 1 h later in the event, at approximately 2:00 p.m., tne "A" Isolation Condenser steam I inlet temperature deviated frc.n the saturation temperature corresponding to reactor {

pressure. The steam inlet temperature dropped from 350 degrees F to 220 degrees i F. Fifteen minutes later, steam inlet temperature increased to approximatei/ 300 ;

degrees F and remained at this temperature until approximately 6:00 p.m. when the i reactor was vented through the isolation condensers. This decrease in tes trature [

and subsequent increase cannot fully be explained from the an11able plant operat- [

ing data and information during this period. [

l Although there was a limited amount of raw data available on this event, analysis {

'

showed that there was a potential to set up conditions in the isolation condensers '

similar to the August 28 and September 26, 1988 isolation condenser phenomenon.

The following are facts gathered in the assessment of this event which may be i pertinent to the evA Wation of the isolation condenser performance. [

t

-- Shutdown Cooling System was placed in servi'.e a*, approximately 12:17 p.m. (

When no recirculation pumps operating, reactor level was raised above 185" [

above top of active fuel (TAF) t3 facilitate natural circulation through the l reactor. Raising the level to 285" provides for spillover from the core j

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Attachment 0 0-2 1 i

region to the annulus area and thus prevent thermal stratification when the Shutdown Cooling System is placed in service without recirculation pump operation.

--

Plant System Procedure 307, "Isolation Condenser System," and Abnormal Proce-

, dure 2000-ABN+3200.01, "Reactor Scram," require that the DC condensate return l valve V-14-34 and V-14-35, are placed in the closed position when reactor I level is above 180" above TAF, but does no address the closing of the DC steam

! inlet valve, V-14-31 and V-14-33. The Energency Operating Procedures in 1985 l similarly addressed closing only the DC condensate return valves and not the l DC steam inlet valves. A change to tM Erargency Operating Procedures to in-l clude closing the DC steam inlet valves did not occur until 1987. To resolve the inconsistency with Emergency Operating Procedures, the licensee is cur-l rently making changes the Plant System Procedure 307 and Abnormal Procedure l 2000-ABN-3200.01. These changes will require the closure of valves V-14-31

and V-14+33 when reactor level reaches 100" above TAF.

--

The "A" Isolation Condenser was initiated at 10:15 a.m. When the isolation condenser is initiated by npening the DC condensate return valve, an automatic interlock shuts the isolation condenser vent valves. The vent valves, however, i do not automatically reopen when the DC condensate return valve is shut. The I

operator is required to reset the isolation condenser vent valves to reopen them.

--

The reactor pressure at aporoximately 2:30 p.m. was 150 psig.

--

The isolation condenser steam in!et temperature dropped to 220 degrees F at 2:00 p.m. which may be indicative that the water in the tube side of the isolation condenser had risen above the thermocouple level. This temperature drop occurred while the DC condensate return valve was shut. As indicated above, the DC isolation condenser return valves would have been shut prior i to raising reactor level above 180" above TAF for placing the Shutdown Cooling l System in servi.;4.

--

The steam inlet temperature increased from 220 degrees F to 300 degrees F with no operation or initiation of the isolation condensers. This was the approxi-mate tempsrature noted on one of the steam inlet temperatures for the isola-tion condensors during the August 28 and September 26, 1988 phenomenon.

Based on the above information and discussions with operators, the following could be postulated.

--

The isolation condenser DC cor.jensate .eturn valves were Wut before 12:17 p.m. when the Shutdown Cooling System was placed in n ov i t. This assumption ja based on the above procedural information and dis m ions with operational personnel who stated that they would expect these valves to he shut when reactor level is above 180" above TAF.

_ _ _ _ . _ _ _ _ - _ - -

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Attachment D D-3

<

--

The isolatica condenser vent valves were shut at 10.15 a.m. and emained shut l i

until approximately 6:00 p.m. when the reactor was vented through the isola-tion condenser. This assumption is based upon the above interlock description between the DC condensate return valve and the vent valves, and interviews with operations personnel who stated that normally there would be no require-ment to reopen the vent valves once the isolation condenser was initiated.

With the given information and assumptions, a possible mechanism to fill the "A" Isolation Condenser existed. As reactor level is raised to 185" above TAF, the isolation condenser steam line penetrations which are located in 183" above TAF may have been covered with water. Since the vent valves and the DC condensate return valves were probably shut and the steam inlet valves probably opened, the isolation condensers communicated with reactor vessel hydraulically. As the steam in the isolation condensers condenses thus reducing pressure, water will be drawn up into the isolation condenser (reactor prassure was at approximately 150 psig)

and thus fill :t. This is one possible interpretation for the steam inlet tempera-tura drop which occurred at 2:00 p.m.

Assuming that the isolation cu. tnsers were filled as described above and the vents valves were shut, the "A" Isolation Condenser experienced circumstances similar to those in which the August 28 and September 26, 1988 phenomenon occurred. Al-though the reactor was shutdown, decay heat was adequate to provide the energy to sustain the recently observed phenomenon. Postulating that the "A" Isolation Con-dense experb,ced this pheno:,,enon af ter being filled with condensate would account for toe steam inlet temperature rise from 220 degrees F to 300 degrees F which occurred fifteen minutes after the steam inlet temperature drop.

The postulate that the "A" Isolation Condenser experienced this phenomenon is based on circumstantial evidence. The licensee has been asked to independently review l and assess the possibility that the August 28 and September 26, 1988 isolation condenser phenomenon occurred in the "A" Isolation Condenser on June 12, 1985.

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ATTACHMENT E THE THERMAL-HYDRAULICS OF THE STEAMING ISOLATION CONDENSER The "B" Isolation Condenser was out of service for valve maintenance from August 23 to Augnt 28, 1988, and when returned to standby status started steaming for no apparert reason. Efforts were made to identify the reason for this steaming.

(Refer to Attachment C, Figure 1 and FSAR Figures 23-1 and 23-2). The licensee drilled through the insulation and recorded the average temperatures shown on Figure 1 in the corresponding locations. These temperatures show that the "south" (lef t) coil is producing shell side steaming and the "north" (right) is not. This indicates that possibly an internal circulation pattern which promotes steaming was established as indicated in Fiaure 2. In this postulated circulation pattern, condensate from the south coil goes up through the north coil, descends through the north steam pipe back into the steam supply pipe. Steam ascends through the south steam pipe to the south coil where is condenses. In this model tFere is practically no evidence that there exists any significant oscillatory pattern, at least not to the extent that the coils change roles in ccndensing steam. Therefore, attention was given to the identification and quantification of the driving heads (and losses) for this continuous model.

Thermal Head on the North Side Bundle The condenser is supplied with makeup water through a 4 inch diameter opening at the bottom of the shell. Two approximately 22 foot tube bundic.s enter the shell from both ends and extend for almost all of the 12 ft, diameter of the lower por-tion of the shell. From the temperatures shown in Figure 1 it is concluded that only the south side is steaming. Therefore, it is reasonable to conclude that the shell side circulation is as shown in Figure 2. This means that the north bundle is exposed to a driving thermal head from the shell which delivers a temperature dif ference as high as 160 degrees F. This model also sugges*.s that the north side tube is receiving heat from the shell. A quantification of this effect (see Cal-culation 1) shovs that for DT=80 degrees F. the north side will develop about 2 f t. of water driving head. For 100 or 120 degrees F it may be as high as 3 ft.

This conclusion is inconsistent with the measured temperatures at locations 0 and E of Figure 2, i.e., the north side tube bundle outlet temperature (Point E, which u;, der normal flow patterns is the tube inlet) should be higher than its inlet (Point 0). However, there are a number of possible explanations:

(a) the measured temperatures may be inaccurate. For both locations a hole was drilled through the insulation ana outside pipe temperatures measured. Any film on the pipe skin would yield a lower temperature measurement. Also, instrument accuracy is + 3 degrees F.

(b) there may be internal (tubeside) circulations which could explain the incon-sistent pipe skin temperatures. It is evident from the measured temperatures that the north side does not steam. However, they do not support the suppo-sition of the model that heat is being transferred from the shell side to the north bundle tube side.

s

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Attachment E 0 ..

Static Head in the South and North Le s This examines trie segments AB and DC in F ,

T u rR .tive b 90 leva-tions are the same (Reference 2) and so are -+ m .e s . m, iead in these two segments should be approximately Flow Losses in Segment BC and Bundle Exit and E g To obtain an estimate of the magnitude of flow relatet + estimate the velocity of the condensate :n ABCDEF Figure 2. The 1 te for the "B" condenser is that it required 18 gpm nakeup. Thi: out 9,000 lbm/hr. Using a single bundle as a heat exchanger, the h, (bundle to shell) required to boil off this amount would be about 10.c,. /hr. The re-quired amount of primary steam (heat input to the tube side to bail the shell side)

is 1,900 gal /hr.

Estimated velocities in the BC segment are so low that it is reasonable to ignore head losses due to skin friction, pipe diameter changes, and bundle entrance-exit losses.

Comments on the Validity of the Steady State Model There are several uncertainties in the model described. We shall attempt to list some of them and take the opportunity to comment on alternate models.

One of the difficulties is that we cannot account explicitly for the required driving head. For example, under the steady state conditions assumed by this model, steam at the "wye" formation between the north and south vertical steam pipes (Figure 2a) may create a lower pressure at BB relative to AA. This is possible due to the venturi effect produced from steam going up the south steam leg and tending to pull the head of the north leg. However, the amount of driving head produced by this effect is unquantifiable. Another is the inconsistency of the temperatures at D and E of the north leg, i.e., measured Td>Te, The model requires that Te>Td. There may be an explanation in terms of the uncertaint: of the contact skin temperature readings or another model. Due to possible errors in temperature measurement it could be that the real temperatures are such that Te>Td.

However, if it is accepted that Tc>Td, the model should include some form of level i oscillation. Any such oscillation to be sustainable would require another motive l

force like condensation in the south bundle. No such phenomenon is identifiable from the known facts.

Another model could be constructed by assuming leakage in the conden> ate isolation valves. Large leakage cannot be justified from observed parameters. However, small amounts of leakage could be present and the model could be appropriately modified. No information exists to indicate the condensate valves were leaking slightly.

We conclude that based on the known facts the proposed model is the most plausible among the alternatives.

_ _ _ _ _ - _ _ _ _ _ _ _ _ _ _

,

]

, .. , , u-Attachment E E-3 Initiation Mechanisms As pointed out earlier the steady state phenomenon was separated from the initi-ation mechanism. The following discusses some mechanisms which are suggested by the observed facts, conditions and plant parameters but does.not arrive at a con-clusive model because (a) the steady state model is not conclusive and (b) para- <

meters required for model validation are not known. '

The vent line which vents noncondensables from the high point of the condensate -

steam line to the main steam line extends approximately 400 ft and includes an approximate 20 foot loop seal. The DP across this line under full power is about 40 psi. It was assumed the loop seal or other possible restriction to free flow existed, consequently the pressure difference from this line was not accounted for in the model.

In addition there is experimental evidence to support this assumption:

(a) water has been observed to leak from the stem and the packing of the condenser steam isolation valve V-1-71, (b) shell side steaming continued with the vent valves closed, (c) in the model the required DP to overcome the 20 ft. of water head in the loop seal does not exist, and (d) even if there is some flow it is so small that it does not affect the steaming conditions.

The normal operating flow pattern in the isolation condensers is depicted in Figures 23-1 and 23-2 of the FSAR (attached). If, for any reason the flow through the vent line is seriously impeded and there exists some imbalance in the system then the steam will preferentially condense on one side of the vertical steam lines (in this case on the south side) and the steaming flow pattern will initiate.

Another initiation mechanism (which has been propossd by the licensee) supposes that af ter the isolation of the "B" condenser for maintenance a relative under-pressure was created resulting in suction of water from the reactor recirculation loop (Figure 23-2) through a possibly leaking condensate return valve such that it filled the entire system including the vertical portions of the condenser steam t supply pipes. The presence of the water in these pipes created the asymmetry when j the steam valves were reopened. Likewise the "A" Condenser was assumed to have !

filled, while it was isolated for a surveillance test, by flow from the "B" Con- l denser through the vent lines. '

t

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.- - - - - - -.

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FIG. 1 - ISOLATION CONDENSER ,-

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FIG. 2 - THERMAL HYDRAULIC MODEL -

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_ _ _ _ _ _ _ _ _

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CALCULATION 1 <

Approximate quantification of the thermal head in the north bundle.

At P=1000 psig from the steam tables:

Temperature Degrees F ft/lbm lbm/ft**

210 .01665 60.060 220 .01672 59.801 230 .01679 59.559 240 .01687 59.277 250 .01694 59.032 260 .01703 58.720 270 .01711 58.445 280 .01720 58.140 Sum =.006944X(60.060+59.801+ ... +58.140)=4.095 lbm/sq. inch.

For 210 degree F water under the same conditions:

Sum =.0069444X60.060X8=3.337 lbm/sq. inch.

Dm=4.095-3.337=1.368 lbm/sq. inch > .837 psi > 2 ft of water Thus 80 degrees F > 2 ft, water.

120 degrees F > 3 ft. water.

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ATTACHMENT F ELECTRICAL EVENT ON OCTOBER 2, 1988 SOURCE OF I TIME INFORMATION DESCRIPTION 1:57 p.m. Sequence of Ofesel generator 2 locked out.

Alarm Recorder (SAR)

1:57 p.m. SAR Main breaker ID tripped. Last half of Safety Related Electrical System RPS Motor generator tripped. This resulted in full reactor scram due to RPS Bus #2 trip.

1:57 p.m. Control Room All power lost to unit substations 181, Operator Log (COL) IB2 and 183 Sich were fed from Bus 10.

1:57 p.m. COL Instrument air was lost due to loss of the

"B" train 480 V Bus and vital AC panel (VACP-1) power supply transfer.

1:57 p.m. COL /SAR Containment high range radiation monitoring system was lost and caused the drywell and torus isolation.

1:57 p.m. COL The main steam isolation valves received an isolation signal.

1:57 p m. COL Reactor water cleanup system tripped due to loss of M^Cle21.

1:57 p.m. COL #2 Reactor build'ng closed cooling water pump was lost (lost MCC182).

COL #2 service water pump was lost (lost MCC183).

COL Shutdown cooling pumps B & C tripped (lost MCCB2)

COL Fuel pool cooling system tripped (lost MCC1821).

COL Control rod drive system tripped (lost MCC182)

COL Condensate transfer system tripped (lost MCC1832).

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Attachment F F-2 SOURCE OF TIME INFORMATION DESCRIPTION

.1:57 p.m. COL 1AB2, VACP-1'and IP4 transferred to their (Continued) alternate power supplies as designed.

COL- Core spray main pumps B & C were unavail-able due to loss of 4160 V Bus 10. Core spray booster pumps B & C were unavaili.ble due to loss of 4160 V Bus 10.

2:08:30.576 SAR 10 Breaker Closed.

2:09:22.528 SAR 10 Breaker Tripped.

2:15 p.m. COL Manually started standby gas treatment system.

2:58 p.m. Interview and Reestablished shutdown cooling with A. train (approx.) Computer Data and adjusted service water flow. Stabil-ized the reactor temperature at 162 degrees F.

3:05 p.m. COL Power was restored to Reactor Protection System #2 by transferring the power feed to the transformer powered from VMCC 1A2.

The drywell and torus ventilation isolation was reset. The MSIV isolation signal was cleared.

6:30 p.m. Diesel Surv. Test Commenced EDG-1 load test.

7:43 p.m. COL Opened EDG-1 breaker. Completed load test.

9:30 p.m. COL Source of fault located at EDG-2 cable to Bus 10. Disconnected cable at both ends.

10:15 p.m. SAR 10 Bus energized. Diesel remained un-available.

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ATTACHMENT H 00CUMENTS REVIEWE0 A. Drawings EM8397907 Revision 1 Electro Motive Decision schematic Drawing E1164 Revision 6 Elementary Diagram Diesel Generator 2 223R0173 Sh. 22, Rev 12 Elementary Diagram Tie Breaker to Switchgear

223R173 Sheet 14 Elementary Diagram Alternate Source Startup Transformer S1B Breaker Power and control circuit BR3002 Revision 22 Auxiliary One Line Diagram GE148F711 Revision 20 Piping and Instrumentation Diagram Reactor Shu'down Cooling System JCP-19433 Sheets 1-6 Piping Isometric Orawings Rev. 2 & 3 DWC No. 21413 Emergency Condenser Piping Plans, Section and Details in Reactor Building - As Built DWG No. H0101 Rev. 2 Existing 3/4" Emergency Condenser V<.n' to Main Steam - Reactor Building Pipe Support location.

B. Procedures 635.2.001, Revision 4, "Switchgear Buses (A, B, C, 0) and Circulating Water Pump Protective Relay Surveillance" 2000-0PS-3024.27, Revision 3, "Shutdown Cooling System Diagnostic and Restora-tion Actions" 2000-0PS-3024.10b, Revision 1, "Electrical Distribution 460 VAC Otagnostic and Restoration Actions" Station Procedure 337, Revision 21, "4160 Volt Electrical System" Station Procedure 338, Revision 15, "460 Volt Electrical System" Surveillance Test 609.3002, "Isolation Condenser Isolation Test and Calibra-tion"

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Attachment H H-2 Surveillance Test 609.4.001, "Isolation Condenser Valve Operability and In-Service Test" Surveillance Test 609.3.003, "Isolation Condenser Automatic Actuation Sensor Calibration and Test" Surveillance Test 605.5.002, "Main Steam Isolation Valve Leak Rate Test" System Operating Procedure 307, "Isolation Condenser System" C. Other Documents 0CMGS, FSAR, Chapter 8 OCMGS, FSAR, Chapter 6 Cable Test Data, ANACONDA, dated April 13, 1977 Cable Corporation specification for Unshielded EP Cable IEEE Guide for Mailing High Direct Voltage Tests on Power Cable Systems in the Field. ANSI /IEEE 400-1980 OCMGS, Operations Plant Manual Safety Evaluation for installation of jumpers on "A" isolation steam inlet temperature points 2 and 5 on recorder IF/2F, Dated June 25, 1982.

Records Associated with the failure of V-14-35 to open on February 7,1985.

Safety Evaluation for temporary variation EJ-87-66 which by passed isolation condenser inlet pipe high temperature alarms, dated May 15, 1987.

Memorandum A020-88-040, Is. Condensers Unusual Event, Dated October 3, 1988.

Preliminary results of isolation condenser steam valve leak rate tests.

Outage reports for 1974, 1977, 1978, 1980 1981, 1982, 10 M outage, 10 R outage, and 11 R outage.

Records of isolation condenser piping temperatures obtained on September 29, 1988.

Maintaining Histories of isolation condenser steam and condensate return valves.

Isolation condenser temperature recorder charts.

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Attachment H H-3 Operations Critique 88-07, Inadvertent Isolation of the "A" Isolation Conden-ser" Switching and Tagging Addendum Sheet, Form 108-2A dated September 2, 1988.

Isolation Condenser Sys'.em Valve Check-Off Sheet dated September 2, 1988.

Control Room Operator log books.

Switching and Tagging Log Sheets numbers88-591, 88-707,88-585, 88-588,88-590. 88-613,88-714, and 88-772.

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ATTACHMENT I l PERSONS ATTENDING EXIT MEETING OCTOBER 13, 1988 Oyster Creek Nuclear Generating Station (OCNGS)  !

General Public Utilities - Nuclear (GPUN) Corp.

R. Barrett, Plant Operations Director J. Barton, Deputy Director R. Blouch, Manager, Technical Support R. Brown, Manager, Plant Operations G. Busch, Licensing J. Camire, Manager, Plant Analysis P. Cervenka, Plant Engineering T. Dempsey, Reactor Plant Manager-Engir.eering & Design E. Fitzpatrick, Vice President / Director Oyster Creek V. Foglia, Technical Functions Site Manager T. Gaffney, Supervisor I & C Material Assessment M. Godknecht, Plant Engineering R. Hewarf, Vice Prer.ident/ Director, Maintenance, Construction & Utilities J. Kowalski, Licensing Manager D. MacFarlane, Site Audit Manager T. Quintenz, Manager, Material Assessment D. Ranft, Manger, Plant Engineering J. Rogers, Licensing A. Rone, Plant Engineering D ector P. Smith, Engineer, Systems Engineerirg E. Scheyder, Maintenance, Construction and Facilities Director N. Trikouros, Manager, Safety Analysis / Plant CL State of New Jersey M. Jacobs, Bureau of Nuclear Engineering (NJ OEP/BNE)

United States Nuclear Regu'atory Comission (USNRC)

W. Baunack, Project Engineer L. Bettenhausen, Chief, Projects Branch No. 1 E. Collins, Resident Inspector, Oyster Creek l C. Cowgill, Chief, Reactor Projects, Section 1A l J. Golla, Reactor Engineer [

T. Koshy Senior Reactor Engineer i L. Marsh, Chief, Mechanical Engineering Branch, Region I ,

J. Wechselberger, Senior Resident Inspector, Oyster Creek r

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LIST OF PHOTOGRAPHS 1. "B" Isolation Condenser North End 2. "A" Isolation Condenser North End 3. "B" Isolation Condenser South End 4 "A" Isolation Condenser South End 5. "A" Condenser Steam Wye 6. "B" and "A" Condenser Steam Wyes 7. "B" Isolation Condenser Condensate Returns 8. "A" Isolation Condenser Condensate Returns 9. Typical Steam Vent Connection 10. Steam Line and Vent

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