IR 05000295/1990018

Insp Repts 50-295/90-18 & 50-304/90-20 on 900730-0803.No Violations Noted.Major Areas Inspected:Operability of Svc Water Sys

ML20059M692
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	09/24/1990
From:	Burgess S, Slover W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20059M684	List: IR 05000295/1990018 ML20059M682
References
50-295-90-18, 50-304-90-20, NUDOCS 9010050199
Download: ML20059M692 (9)

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U. S. NUCLEAR REGUIATORY COMMISSION

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REGION III

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Report Nos. 50-295/90018(DRS); 50-304/90020(DRS)

Docket Nos. 50-295; 50-304 Licenses No. DPR-39; DPR-48

Licensee:

Commonwealth Edison Company Opus West III 1400 Opus Place

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Downers Grove, IL 60515

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Facility Name Zion Nuclear Generating Station - Units 1 and 2

Inspection Att Zion Site, Zion, Illinois Inspection Conducted:

July 30 through August 3, 1990 t

Inspectors:

MD bus-

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9 2A 4c S '.' D. Butgess Date A

M f90 W. A.

Slover Date

.I contractor:

L. L. Larson Approved By: 9[28 N #

b'/dd F.IJ. Jablonski, Chief Date

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Maintenance & Outages Section Insoection Summarv

Inspection on July 30 throuch Auaust 3.

1990 (Recort Nos.

50-295/90018(DRSir 50-304/90020(DRS))

Areas Insoected:

Special inspection in response to significant Diagnostic Evaluation Team (DET) findings regarding the operability of the service water (SW) system, and to gain an insight into the pervasiveness of those findings by also assessing the operability of another similar system, component cooling water (CCW).

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i ResultLL Overall, we concluded that the SW and CCW systems were operable.

However, several weaknesses were noted with the design and operating configuration of both systems.

For ' example, we

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noted: Technical Specifications which permit operation with the SW l

crosstie valves in contradiction to the FSAR description of the

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system; SW flow instrumentation inaccuracies that could preclude proper water flow balancing of essential equipment; qualitative surveillance testing of the CCW system that could preclude early detection of component failures; lack of operator guidance in Abnormal Operating Procedures to align the CCW system in a split system if an active or passive failure occurred within the system;

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and a lack of documented maintenance on the CCW pump,

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9010050199 900924 PDR ADOCK 0500029371

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DETARS 1.0 PersonsContact1d Commonwealth Edison Comoany (Ceco)

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• T. Joyce, Station Manager i

• K. Henderson, Technical Staff System Engineer

• L. Laspisa, Technical Staff Supervisor

• F. Lentine, Engineering / Construction Engineering

• E. Martell, Technical Staff System Engineer

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• T. Rieck, Technical Staff Superintendent

• W. Stone, Regulatory Assurance Supervisor

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• Denotes those present at the exit meeting on August 3, 1990.

2.0 Bickaround

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A Diagnostic Evaluation Team (DET) inspection was conducted at the Zion Station June 4 through 15 and June 25 through 29, 1990.

The DET identified a number of concerns abou' the overall operability of the SW system. The two

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principal concerns were ump capacity verses system resistance in three pump i

mode with single failun, and adequate flow balance of the system to provide minimum design flow to all components.

In response to the DET concerns and to i

gain insight into the servasiveness of the findings, this inspection assessed the operability of bot 1 the SW and CCW systems.

To determine operability, various system attributes were evaluated:(1) were

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the systems capable of performing the safety functions required by their design basest (2) was testing adequate to demonstrate that the systems would i

perform all of the safety functions required by their design bases; (3) and

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were management controls, including procedures, adequate to ensure that the

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safety systems would fulfill the safety functions required by their bases?

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3.0 Service Water System 3.1 Desian of the SW System

The design basis of the SW system as described in the Final Safety Analysis Report (FSAR), was to supply all equipment cooling water for the plant, including emergency shutdown requirements.

Each unit of the f ant had a SW header sunplied by three SW pumps.

The headers were crosst -

. rough two crosstie alves so that any combination of pumps could sers n units under normal o$ tating conditions.

Double isolation valves were i

. red in each main heaC ' to isolate supplies to non essential equipment under accident

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condition.

Since certain auxiliary and support system equipment was shared

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by both units 1 and 2, the criteria followed in the design was that each unit i

was required to operate independently of the other.

An equipment malfunction

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or operator error in one unit was not permitted to initiate a malfunction or error in the other unit nor affect the continued operation of the other unit.

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3.1.1 Double Valve Isolation of Screen Wash Syfltm The DET was concerned that significant emounts of cooling water losses were possible (50,000 GPM) due to a design basis earthquake (DBE) which could induce passive failure of the non essential screen wash system piping, which was not isolated by double valves as required.

During this inspection it was noted that in the event of a loss of coolant accident (LOCA) with a loss of offsite power (LOOP) and no DBE, a six inch non-safety related air operated flow control valve in the screen wash system piping would fail open and provide a path for the diversion of water (approximately 6000 gpm) from essential loads. The inspectors observed that the valvo was gagged closed, but the structural stability under DBE was suspect. The licensee made further structural enhancements that eliminated the immediate concern.

With regard to the original DET concern, the licensee had committed to take timely action to correct the double isolation valve deficiency.

Since the probability of the DBE was low, the inspector concluded the licensee's action was reasonable.

3.1.2 Reouirement for Open Crosstie Valves One concern that prompted this inspection was the capability of the SW pumps to provide adequate flow with the 48 inch crosstie valves open as described in the FSAR and as shown on FSAR figure 9.6.1-(l).

The inspectors determined that this concern did not constitute an operability problem based on the licensee's issuance of a standing order to operate with a minimum of four SW pumps (as described in Paragraph 3.2.1 of this report) which provides additional flow.

However, as a result of examining this issue, the inspectors noted an additional concern regarding SW operation with the crosstie valve closed.

The licensee indicated that earlier practice, particularly 1973 through 1981, was te operate with the crosstie closed.

The Techniul SpecificationITS)

rmitted operation with the crosstie valves open or closed. With :Se... stie valves closed, an accident scenario was identified that could lead to station blackout if the normal lineup of SW cooling water supply was not also changed to the diesel generators coolers.

The licensee was aware of this situation.

Since it was possible for other accident l

l scenarios due to other inter unit SW crossties, the inspectors concluded that operatinn with the 48 inch crosstie closed was not described in the FSAR and would require a safety evaluation in accordance with 10 CFR 50.59; therefore, this matter is unruolved (295/90018-01; 304/90020 01).

3.2 Testina of the SW System The inspectors reviewed the SW mechanical test program to determine if the test results demonstrated that the system would perform all of the safety functions required by the design basis.

3.2.1 Test of SW in Crosstied Confiauration The DET was concerned that in the crosstied configuration the TS would permit the plant to be in an accident condition with insufficient SW to essential loads because the crosstied configurat% had not been tested.

With one unit operating and the other shuiduwn, tne TS allowed the plant to be configured with only three operable SW pumps and the SW supply piping crosstied.

If a

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LOCA occurred with this configuration on the operating unit, and one of the SW operable pumps or its power supply failed, only two SW pumps would be available to supply both units. The SW system was never tested in this

configuration nor were system head curves created that showed the adequacy of

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two pumps. Standing Order 90-24 was issued on August 1, 1990, that required a minimum of four operable SW pumps.

The licensee also stated that calculations

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would be performed and confirmed by tests to justify returning to operation

with three operable SW pumps, i f the calculations and testing are not conclusive, the FSAR and TS will be revised to reflect the standing order for

four operable SW pumps.

The licensee confirmed a target completion date of February 1991.

This matter is unresolved (295/90018 02; 304/90020 02) pending final resolution of SW pump combinations and capability.

3.2.2

_ Reactor Containment Fan Coolina Throttle Valve Ad.iustment f

The DET was concern'ed ' hat the reactor containment fan cooling (RCFC) outlet valves were not adjusted at 20'/, as determined by pre-operational (pre op) test results and that gross flow imbalances could occur during an accident.

Procedure 501 61, " Service Water Line Up," Appendix A-1, Revision 1, required the RCFC outlet valves to be fully open; however, the inspectors noted that

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the are op test had been changed.

Apparently, the throttle globe valves, whic1 were intended for flow control, were not ready to be set when the pre op test was conducted. Instead, the RCFC outlet isolation gate valves had been used to adjust the flow.

The inspectors determined that subsequent to pre-op testing, the globe valves were throttled and the isolation valves were fully opened. The inspectors validated the Unit I settings by observing the RCFC SW flow indicators. All indications were within 50 gpm of the required 1950 gpm.

Based on these findings, the DET concern was resolved.

3.2.4 Inaccurate SW Flow Instrumentation The inspectors were concerned with the long term testing consequences of inaccurate flow instrumentation.

Flow imbalances and high flow readings on essential equipment were noted during the system walkdown.

The licensee indicated that much of the SW flow instrumentation was considered inaccurate because of silt in the SW water.

(This weakness did not apply to the RCFC flow instrumentation used to validate RCFC throttle valve adjustments.)

The accuracy of these measurements would become important if the licensee returned to a minimum of three operable pumps because of the reduced flow margin over minimum. A review of installed instrumentation was being made by the system l

engineer. Modification requests were to be submitted to the corporate

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i engineering department by November 1990.

This schedule was not consistent l

with the February 1,1991, torget date to resolve the pump configuration mentioned above.

The inspector did not ' consider these uncertain flow balances an immediate concern because the standing order that required four operable l

pumps would assure sufficient flow margins to bound these uncertainties.

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Adequacy and accuracy of the SW system flow instrumentation is considered an unresolved item (295/90018 05; 304/90020 05).

3.2.5 Inservice Testina of the SW Pumos The inspectors evaluated the DET finding about ASME Section XI tests being

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done on three of the six SW pumps only once, and twice on the three other pumps.

The inspectors determined the DET finding to be correct; however, based on what testing was available, the inspectors concluded the SW pumps were operable, one difficulty with SW pump testing (which was a discouragement to frequent testing) was that individual SW pump flow indications was not available.

The pipe between the discharge of the SW pumps and the SW header was too short to allow uniform flow to be established; therefore, accurate individual pump flow measurement was not i

feasible.

During the pre-op tests of the SW system the CCW heat i

exchanger flow instrumentation had been used, which was not now an option due to operational requirements (i.e.,

use of CCW heat i

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exchanger flow instrumentation would require splitting the CCW system and removing redundancy from the nontest unit).

In response to NRC questions concerning the adequacy of inservice pump testing, pitot type flowmeters were installed in 1988 in each of the unit headers under plant modification M22-1(2)-87-ll.

Use of these flowmaters provides adequace pump flow measurement;

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however, the licensee's IST relief request provided for only doing this testing during an outage and therefore, it has not been performed frequently.

The NRC is currently evaluating the relief

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request from the licensee.

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a 3.3 SW System Operability The inspectors concluded that while there were weaknesses with the design and testing of the system, the licensee had taken compensatory action which eliminated immediate concern.

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inspectors concluded that the SW system was operable.

I 4.0 Comoonent Coolina Water System 4.1 Desian of the CCW System i

The inspectors reviewed the design basis of the CCW system as described in the FSAR.

The CCW system was to supply cooling water to variou:s plant components during normal operations, remove residual heat from the reactor coolant system during the second phase of plant cooldown, and supply cooling to safeguard equipment loads during and after a postulated accident.

Component cooling

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water was provided by five CCW pumps arranged in parallel and operated as needed to supply cooling water for the combined heat load of both units through a common header which could be split

with installed valves.

According to FSAR CCW system diagrams, the design intent was to operate in a split header configuration.

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Based on information provided by the licensee, the CCW system was not being operated in its original design bases configuration; that is, it was typically being operated in a crosstied configuration, which was permitted by the TS for most plant operating modes.

Westinghouse recently (1990) submitted a CCW system design bases document for Zion.

The document was in draft form and, at the time of the inspection, had not been approved by the licensee.

Westinghouse analyzed LOCA scenarios for different operating conditions and also recognized that during nonal operation, Unit 1 and Unit 2 woro crosstied in a camon header configuration.

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i Westinghouse determined that the CCW system's heat transfer capability was I

adequate with the minimum of three pumps and two heat exchangers with a full

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spent fuel pit heat load. Additionally, Westinghouse calculated that failure

of any one of the minimum complement of components in use would increase the time required for plant shutdown, but would not affect safe operation of the

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pl ant.

In the event of a single active or passive failure, Westinghouse provided that either unit might be aligned with two completely independent, parallel CCW

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paths each consisting of one pump and one heater exchanger.

In other words, a split header configuration. However, changing the system configuration to i

split header, or isolating a pipe break or a failed component was not a

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considered option in Abnormal Operating Procedure (A0P) 4.1, " Loss of

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Component Cooling Water."

If the operators followed A0P 4.1 and did not

isolate the point of component cooling water loss, it would eventually result

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in cavitation of the CCW pumps.

If cavitation became evident, AOP 4.1 would

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direct operators to " trip f!QIll reactors".

Reactor operation would then be governed by the Emergency Operating Procedures.

For the reasons described

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above A0P 4.1 was considered weak and is an unresolved item (295/90018 03; 304/90020 03).

b 4.2 CCW Surveillance Testina The inspectors reviewed the CCW test program to determine if the testing adequately demonstrated that the system would perform all safety functions required by the design bases.

Surveillance testing of CCW system components was done to meet TS requirements which were established for specific plant operating conditions.

The purpose of the surveillances was to demonstrate CCW system component operability, for all CCW Limiting Conditions for Operation (LCO), three types of surveillance tests were required: associated standby ac

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and de power supplies, CCW heat exchangers, and CCW pumps.

The inspectors

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concentrated on testing performed on the CCW heat exchangers and pumps.

4.2.1 CCW Pumn Tests

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Operability of the CCW pumps was demonstrated monthly by use of surveillance procedure PT-8A, " Component Cooling Pumps 0)erability Test." CCW pump performance acceptance criteria were that tie pump started upon actuation, operated for at least four hours, and satisfied the cooling requirements necessary for the routine operation of the component cooling system.

The acceptance criteria were easily met for pump starting and operating for four hours. However, satisfying the cooling requirements necessary for the routine operation of the CCW system could not be determined by performing PT-8A.

PT-BA tested individual pump operability with the CCW system in the crosstied configuration and the TS required a minimum of three pumps running at all times. A defective pump would pass the PT 8A performance test since the pump would start, operate for four hours and "ap> ear" to satisfy the cooling requirements of the CCW system loads, but tie other pumps would actually carry the cooling load for the defective pump; that is, operating in the crosstied configuration would result in header pressure developed by operating pumps which may mask low pressure caused by a defective pump.

For the reasons

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stated above PT-8A was considered weak and is an unresolved item (295/90018-

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04;304/90020-04).

4.2.2 CCW Heat Exchanaer Tests

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There was no specific surveillance test that demonstrated the operability of CCW heat exchangers; therefore, operability was demonstrated with generic procedure PT-14. " Inoperable Equipment Surveillance Tests." The inspectors concluded that PT-14 tests did not determine performance degradation of the heat exchangers because neither flows, inlet and outlet pressures, nor thermal capacity data were obtained due to the lack of instrumentation.

Operability

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of heat exchangers is a generic concern within the industry.

The inspectors noted that the CCW/SW heat exchangers would be expected to be evaluated by the licensee in response to Generic Letter 89 13.

However, the weaknesses noted above in testing of the CCW heat exchangers are considered aart of an

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unresolveditem(295/90018-04;304/90020-04) discussed in tie previous paragraph regarding weak surveillance testing of CCW.

i 4.3 CCW Maintenance i

Maintenance records were reviewed for major components of the CCW system and for minor components whose function is critical to the system's safety function.

4.3.1 CCW Pumo Maintenance Within the past two years, two of the five CCW pumps were dismantled and repaired due to mechanical failure.

Both pumps had a leaking outboard mechanical seal. The first pump required new bearings, a mechanical seal, and miscellaneous small parts to correct the problem, but the pump impeller was

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also replaced.

The reason for the impeller replacement was not documented.

The second pump required repairs similar to the first except the impeller was not replaced.

Results of the maintenance inspection were not documented for either pump.

With the exception of vibration testing, the remaining three pumps had not received any form of maintenance inspection or preventive maintenance (PM)

since originally put into service in 1973.

Without any historical maintenance information, neither the licensee nor the inspectors could determine the condition of these pumps.

This was considered a programmatic weakness.

4.3.2 CCW Heat Exchanaer Maintenance On June 2, 1990, the Unit-1 CCW heat exchanger was opened on the tube (SW)

side to inspect and repair suspected tube leakage, which was identified by decreasing level in the surge tank. A summary report was written about the heat exchanger ins)ection and the impact on heat exchanger operability. The findings are parapirased below, o the heat exchanger had an as-found estimated performance factor of approximately 60% - 70% of design

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o tube cleaning reduced the fouling of the heat exchanger to a minimum o pressure testing identified 15 leaking tubes o eddy current testing identified an additional 48 tubes with indications of reduced wall thickness greater than 40%

o all leaking tubes (63) and those with excessive thinning were plugged o borescope examination of the tubes' interior showed concentrated cell corrosion pittiag of an undetermined chemistry o based on cleaning, examination, inspection, and testing, the station technical staff concluded that the heat exchanger was capable of acceptably performing both normal operation and accident loads.

Silt from the SW system was identified by the station technical statf as the main cause of the reduced performance factor.

Photographs taken of the Unit-1 CCW heat exchanger clearly showed a significant accumulation of silt or sediment at the bottom of the inlet water box.

Based on viewing photographs of the heat exchangers the inspectors were not convinced that only silt was present. Silt build up is generally. regarded as a self-limiting phenomenon and as such, accumulation is small and has a minor impact on heat exchanger performance.

Besides silt, it appeared to the inspector that organic and inorganic compounds had accumulated in the heat exchanger inlet water box in the form of sediment.

The sediment was cumulative rather than self-limiting; therefore, could lead to significant flow obstruction through the heat exchanger.

Another contributor to reduced heat exchanger performance was tube fouling due to corrosion. According to a Zion Station System Materials Analysis Department (SMAD) report, corrosion was evident in the Unit-1 heat exchanger

tubes in the form of wall thinning, pits, and nodule formation.

The SMAD did not determine the exact corrosion mechanism but. acknowledged that future corrosion was likely to occur.

In 1979 tube leaks were repaired on the Unit 0 heat exchanger; however, the work request did not indicate the extent that the heat exchanger was inspected.

Based on the inspection results of the Unit 1 CCW heat exchanger, the inspectors concluded that similar sediment accumulation, tube wall thinning, and corrosion existed for the Unit 0 and Unit 2 heat exchangers, which could reduce the performance capability of these heat exchangers. A recommendation was made to inspect the Unit 0 and Unit 2 CCW heat exchangers.

However this inspection would not be done until the planned heat exchanger PM program scheduled in response to Generic Letter 89-

13. All of the above findings referred to the tube side (SW) side of the Unit

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1 CCW heat exchanger.

No inspection was performed by the licensee on the r

shell (CCW) side of the heat exchanger.

4.4 CCW Operability The inspectors concluded that even with the lack of complete knowledge of CCW pump performance discussed in paragraph 4.2.1, and performance reduction in heat transfer capability of the CCW heat exchangers noted in paragraph 4.3.2.,

adequate flow and he:,t transfer capability existed in the CCW system.

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conclusion was based on the inspectors' and the licensee's calculations of

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heat transfer capability using empirical data obtained from actual component

.i cooling pump data sheets, and the overdesign of the CCW heat exchangers that compensated for the reduction in heat transfer caused by fouling.

5.0 Exit Meetina The inspectors met with licensee representatives (denoted in Paragraph 1) on

August 3, 1990, at Zion Nuclear Generating Station and summarized the purpose, scope, and findings of the inspection.

The inspectors discussed the likely informational content of the inspection report with regard to documents or processes reviewed by the inspectors during the inspection.

The licensee did not identify any such documents or processes as proprietary.

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