05000315/LER-1999-011, :on 990407,air Sys for EDG Will Not Support Long Operability.Caused by Original Design Error.Temporary Mod to Supply Makeup Air Capability in Modes 5 & 6 Was Prepared

:on 990407,air Sys for EDG Will Not Support Long Operability.Caused by Original Design Error.Temporary Mod to Supply Makeup Air Capability in Modes 5 & 6 Was Prepared

ML17325B581
Person / Time
Site:	Cook
Issue date:	05/04/1999
From:	Depuydt M INDIANA MICHIGAN POWER CO.
To:
Shared Package
ML17325B580	List: 05000315/LER-1999-011, :on 990407,air Sys for EDG Will Not Support Long Operability.Caused by Original Design Error.Temporary Mod to Supply Makeup Air Capability in Modes 5 & 6 Was Prepared
References
LER-99-011, LER-99-11, NUDOCS 9905110294
Download: ML17325B581 (4)

LER-1999-011, on 990407,air Sys for EDG Will Not Support Long Operability.Caused by Original Design Error.Temporary Mod to Supply Makeup Air Capability in Modes 5 & 6 Was Prepared

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded
3151999011R00 - NRC Website

text

)IRC Form 366 U.S. NUCLEAR REGULATORY COMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

(See reverse for required number of digits/characters for each block)

APPROVED BYOMB NO. 31604104 EXPIRES 06r30/2001 ESTFIIATED BURDEN PER

RESPONSE

TO COMPLY WITH THIS MANDATORY INFORMATIONCOLLECTION REOVEST: 500 HRS. REPORTED LESSONS LEARNEDARE INCORPORATED INTO THE LICENQNG PROCESS AND FED BACK TO INDUSTRY.

FORWARD COATUENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH Irar Fss).

V.S.

NUCLEAR REGVIATORY CoseaISSION. WASHINGTON. DC 20555OXI. AND TO THE PAPERWORK REDVCTION PR<MECT ISI500101L OFFICE OF MANAGEMENT AND BUDGET. WASIeNGTON. OC 20505 FACILITYNAME(I)

II Cook Nuclear Plant Unit 1 DOCKET NUMBERI2) 05000-315 PAGE IS) 1 of3 TITLEI4)

AirSystem for Emergency Diesel Generators (EDG) May Not Support Long Term Operability Due to Original Design Error LER NUMBER (6)

SEQUENTIAL NUMBER EVENTDATE (6)

REPORT DATE (7)

REVISION NUMBER MONTH DAY YEAR 04 1999 YEAR YEAR MONTH DAY 04 07 05 1999 1999

011

00 FACILllYNAME Cook Unit 2 FACIUTYNAM DOCKEr NUMBER 05000-316 DOCKET NUMBER OTHER FACILITIESINVOLVED(8)

OPERATING MODE (9)

POWER LEVEL(10) 00 e) (11) 20.2201 (b) 20.2203(a)(1) 20.2203(a)(2)(i) 20.2203(a)(2)(v) 20.2203(a)(3)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(i) 50.73(a)(2)(ii) 50.73(a)(2)(iii) 50.73(a)(2)(viii) 50.73(a)(2)(x) 73.71 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR g: (Check one or mor 20.2203(a)(2)(ii) 20.2203(a)(2)(iii) 20.2203(a)(2)(iv) 20.2203(a)(4) 50.36(c)(1) 50.36(c)(2)

UCENSEE CONTACTFOR THIS LER (12) 50.73(a)(2)(iv) 50.73(a)(2)(v) 50.73(a)(2)(vii)

OTHER Specity in Abstract below or n NRC Form 366A NAME Ms. M. B. Depuydt, Compliance Engineer TELEPHONE NUMBER01Ktvde Area Code) 616/465-5901, x1 589 COMPLETE ONE LINEFOR EACH COMPONENT FAILUREDESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPONENT MANUFACTURER REPORTABLE TO EPIX E

coMpoNENT MANUFACTURER REPORTABLE TO EPIX SUPPLEMENTAL REPORT EXPECTED 14 X

YES IfYes, corn lete EXPECTED SUBMISSION DATE Abstract (Umitto 1400 spaces, I.e., approximately 15 single-spaced typewritten lines) (16)

EXPECTED SUBMISSION DATE 15 MONTH 07 01 YEAR 1999 In February 1999, during the Expanded System Readiness Review ofthe Emergency Diesel Generator (EDG) system, the ability ofthe starting air/control air system to support long term operability ofthe EDGs was questioned due to the non-safety related design ofthe compressors.

An operability determination was performed which concluded that the EDGs could not maintain long term operability without reliance on the non-safety related, non-seismic starting air compressors, and were therefore inoperable.

On April7, 1999 an ENS notification was made in accordance with 10CFR50.72(b)(2)(I),

for an unanalyzed condition with potential safety significance.

The apparent cause ofthe inadequacy ofthe EDG starting/control air system is original design error. The designers apparently failed to consider that the starting air system provides the control air to the EDG, and loss of air could result in shutdown ofthe engine.

Atemporary modification to supply makeup air capability in Modes 5 and 6 is being prepared.

Options forthe permanent solutions are currently under review and the method selected willbe implemented via a design change prior to restart of each unit.

The control air leakage rate and expected EDG run time without makeup air capability has not yet been quantified for the current system configuration. Testing is being conducted as part ofthe proposed temporary modification to quantify the expected leakage rate. Once the leakage rate is known, the results willbe evaluated to determine the safety significance ofthe identified condition.

9'2)05ii0294

'2)'2)0504 PDR ADOCK 050003% 5 8

PDR

0U.S. NUCLEARREGULATORYCOMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITYNAME(1)

Cook Nuclear Plant Unit 1 DOCKET NUMBER(2) 05000-315 YEAR LER NUMBER (6)

SEQUENTIAL NUMBER REVISION NUMBER PAGE (3) 2of3 1999

011 00 TEXT (ifmore space is required, use additional copies ofNRC Form (366A) (11)

Conditions Prior to Event

Unit 1 was in Mode 5, Cold Shutdown Unit 2 was in Mode 5, Cold Shutdown Descri tion of Event On February 18, 1999, during the Expanded System Readiness Review ofthe Emergency Diesel Generator (EDG) system, the ability ofthe starting air/control air system to support long term operability ofthe EDGs was questioned due to the non-safety related design of the compressors.

I The compressois, compressor drive motors, the piping between each compressor and the respective discharge check valve are not safety related components.

Although the EDG starting air compressors are supplied from a Class 1E power source and are anchored per Seismic Class 1 criteria, they are neither safety related, or seismically qualified.

When this question arose, Operations requested additional information from Engineering, which led to an operability determination being performed. The determination considered the design function ofthe EDGs, the starting air compressors and the control air function ofthe starting air system. Central to the determination is the design function ofthe control air forthe EDG, which is discussed in detail in the Analysis section ofthe LER, and the "mission time" or how long the EDGs would need to run after an accident.

In the course of performing the operability determination, no finite statement could be found in the design or licensing basis documentation that defined the mission time ofthe EDGs. A decision was made to use a value of seven days, which is supported by the Technical Specification requirements forthe amount offuel oil that is required to be on hand to run the EDGs.

Using this information, the operability determination concluded that the EDGs could not maintain long term operability without reliance on the non-safety related, non-seismic starting air compressors and were therefore inoperable.

Cause of Event

The cause ofthis event was a design deficiency in the EDG and its supporting systems that occurred during original plant design. The designers apparently failed to consider that the starting air system provides the control air to the EDG, and loss of control air could result in shutdown ofthe engine. Although the EDG starting air compressors are supplied from a Class 1E power source and are anchored per Seismic Class I criteria, they might not function in a seismic event because of their lack of qualification. The EDG air system was modiTied in 1994 and replacement compressors were installed, however, the replacement compressors were also classified non-safety.

Anal sis of Event On April7, 1999, 'at 1501 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.711305e-4 months <br /> EDT, an ENS notification was made in accordance with 10 CFR 50.72(b)(2)(i), any event found while the reactor is shut down, that, had it been found while the reactor was in operation, would have resulted in the.

nuclear power plant being in an unanalyzed condition that significantly compromises plant safety. This LER is therefore submitted in accordance with 10 CFR 50.73(a)(2)(ii)(A), forthe same criteria.

The EDG system is a safety related system that provides reliable and readily available onsite AC power in the event ofthe loss of offsite power supply to the essential loads necessary to safely shutdown the reactor under any normal operating or accident conditions.

The EDGs are designed to start automatically upon receipt of a safety injection signal and/or a loss of offsite power signal and be ready to accept loads within 10 seconds of receiving a start signal.

The starting air system supplies compressed air for starting the EDG. Each EDG has its own starting air system consisting oftwo redundant starting air compressors.

Each compressor has one receiver of sufficient volume, 285 cubic feet, for atU.S. NUCLEARREGULATORYCOMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITYNAME (1)

Cook Nuclear Plant Unit 1 DOCKET NUMBER(2) 05000-315 YEAR 1999 LER NUMBER (6)

SEQUENTIAL NUMBER 011 REVISION NUMBER 00 PAGE (3) 3 of 3 TEXT (Ifmore space Is required, use additional copies ofNRC Form (366A) (17) least two EDG start attempts when pressurized to 220 psig. Each ofthe two starting air trains supplies starting air within the pressure range of220 to 247.5 psig. Both starting air trains are independently actuated by the diesel engine control system upon receipt of an EDG start signal. Ifeither compressor/receiver should fail the other is capable ofstarting the EDG. The system is designed to have the EDG at speed and ready to accept load within.10 seconds of start initiation.

The starting air system also provides compressed air forthe starting air supply valve actuators, the diesel engine control system and the turbocharger aftercooler cooling water regulating valves.

The starting air system consists oftwo independent trains of one air compressor and one air receiver each. Each starting air receiver is replenished by its associated starting air compressor that cycles as necessary to maintain the receiver air pressure between 220 and 247.5 psig. The air receivers also supply the diesel engine pneumatic controlsystem with 100 psig air via pressure reducing valves. The 100 psig engine control air is required to maintain the throttle control cylinder's actuating rod retracted and thus maintain fuel flow to the engine. The minimum control air pressure required to maintain the throttle control cylinder's actuating rod fully retracted is 60 psig.

Ifthe starting air compressors are unavailable to replenish the air receivers following an EDG start, the volume of air remaining to supply the control air requirements is limited. Based on pre-operational test data, starting air receiver pressure could range from 188 to 132 psig following an emergency start.

It was postulated that the leakage from the system would result in a loss of air receiver pressure of approximately 25 psi in a twelve hour period. At this postulated leakage rate, the control air pressure could drop below the critical value of 60 psig in a period less than 7 days.

However, since the evaluation was based on engineering judgement, the actual leakage rate and expected EDG run time without air makeup after start ofthe engine has not been quantified for the current system configuration. Testing is being conducted as part of a temporary modification to quantify the leakage rate. When this testing is completed, the safety significance ofthe identified condition willbe evaluated and provided as a supplement to this LER.

Corrective Actions

This condition was discovered with both units in cold shutdown.

Allfour EDGs had previously been declared inoperable on January 11, 1999 due to HFA relay problems (see LER 315/99-001-00).

No immediate corrective actions were necessary to maintain compliance with the Technical Specifications since the EDGs were already inoperable.

In order to support EDG operability in Modes 5 and 6, a method ofsupplying control air makeup for extended EDG operation, without reliance on the starting air compressors, will be established.

This willbe done via the temporary modification process, and any required operator actions willbe controlled by an approved procedure.

Prior to declaring any EDG operable, a test ofthe makeup air method willbe performed to demonstrate the acceptability of operator actions and to verify performance ofthe makeup air source.

A permanent solution fprthe control air problem willbe developed to restore conformance with the plant design basis and to support EDG operability in all Modes. Options forthe permanent solution are currently under review and the method selected willbe implemented via the design change process prior to restart of each unit.

Actions to prevent recurrence have been previously provided in AEP:NRC:1260GH, "Enforcement Actions98-150, 98-151, 98-1 52 and 98-186, Reply to Notice ofViolation Dated October 13, 1998", dated March 19, 1999.

Previous Similar Events

315/98-019-02 315/98-031-01 315/98-029-00 315/98-046-00 315/88-014-00 315/87-024-00 315/87-020-00 315/98-049-00