ML20235Y727

Insp Rept 50-289/89-09 on 890213-16.Potential Violation Noted.Major Areas Inspected:Diesel Generator Air Sys Failures

ML20235Y727
Person / Time
Site:	Cooper
Issue date:	02/28/1989
From:	Bennett W, Constable G, Greg Pick NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
Shared Package
ML20235Y718	List: ML20235Y715 ML20235Y727
References
50-298-89-09, 50-298-89-9, NUDOCS 8903140529
Download: ML20235Y727 (5)

See also: IR 05000289/1989009

Text

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

. - - . - - _ - _ _

• '

,

,' .,r .

. .

ge -

,

p

e

.-

'

' APPENDIX'

U.S.' NUCLEAR REGULATORY COMMISSION

REGION IV

.,

NRC Inspection Report: 50-298/89-09 Operating' License: DPR-46

Docket: 50-298

Licensee: Nebraska Public Power District (NPPD) .:

'P.O. Box 499  ;

Columbus, Nebraska 68602-0499 i

' Facility Name: Cooper Nuclear Station (CNS)

Inspection At: CNS, Nemaha County, Nebraska l

Inspection-Conducted: February 13-16, 1989 j

Inspectors: M A JM9

G. A. Pick, Resident Inspector, Project Section C, Date

Division of Reactor Projects  !

[ l

!

WAlbf  ;

W. R. Bennett, Senior Resident Inspector, Project Date  !

Section C, Division of Reactor Projects .j

.

~}i ') I

',/j,j;

- W. /M / -M', ,

-

Approved: ,

GrL? Constable, Chief, Project Section C, Division

2Mffy

Date

of Reactor Projects

C

Off} ~

- - - - - _

..

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

. ..

, ,

.. .

,

'

-2-

1

1 -Inspection Summary

Inspection Conducted February 13-16, 1989 (Report 50-298/89-09)

Areas Inspected: Special, unannounced inspection of diesel generator (DG) air.

~ system failures.

Results: On February 13, 1989, a fitting on the control air system to

DG No. I failed'during the monthly DG operability surveillance. The failure

. was due to personnel error and inadequate corrective actions following previous

similar failures, which allowed installation of an incorrect fitting.

One potential violation (failure to maintain diesel generator operable) was

identified. An enforcement conference to discuss this potential violation will

be held in the Region IV office.

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

._ __

' *

, ,

b

-3-

DETAILS

'

1. Persons Contacted

Principal Licensee Employees

• G. R. Horn, Division Manager of Nuclear Operations

• V. L. Wolstenholm, Division Manager of Quality Assurance

• J. M. Meacham, Senior Manager, Technical Support

• E. M. Mace, Engineering Manager

• R. Brungardt, Operations Manager

• D. M. Norvell, Maintenance Manager

• K. C. Walden, Licensing Manager

• L. E. Bray, Regulatory Compliance Specialist

J. R. Flaherty, Engineering Supervisor

• G. A. Schmielau, Instrument and Control Foreman

• G. E. Smith, Quality Assurance Manager

D. Dageforde, Systems Engineer

• Denotes those present during the exit interview conducted on

February 16, 1989.

The NRC inspectors also interviewed other licensee employees during the

inspection period.

2. Followup of Plant Events (93702)

13, 1989, the monthly operability test of Diesel

On February (DG) No. I was being performed. Approximately 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> into the

Generator

surveillance, licensee personnel manually shut down DG No. I after

observing control air system pressure decreasing, as indicated on a local

pressure gauge. After shutdown, the DG was declared inoperable.

The licensee determined that air pressure was decreasing due to a cracked

fitting connecting a control air pressure gauge to the overspeed trip

mechanism. This fitting had previously failed on January 17, 1989. If

,

1

the DG had not been manually shut down, the cracked fitting would have

eventually allowed 30 psi control air to bleed off from the overspeed trip

valve. The loss of control air to the overspeeo trip mechanism would then

secure 80 psi air to the fuel racks. The fuel racks would have closed,

shutting off fuel flow to the cylinders, thereby stopping the engine.

After the DG failure on January 17, part of the licensee's corrective

u

action was to replace the cracked fitting. During the repair activity,

I

the licensee determined that no exact replacement nipple for the fitting

was available on site. The cognizant engineer determined that a

thin-walled nipple was satisfactory as a replacement for the failed

nipple. This determination was made without performing the required

Equipment Specification Change for form, fit, and function. The thin-walled

nipple did not meet vibration resistance requirements and subsequently

l

1

b___ _ _ . - - i

- ___ __

-

, . .

,

'

.

4

I

failed after the diesel had been operated for less than 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. The

replacement part did not allow DG No. I to perform its intended function,

therefore, DG No. I was inoperable from the time of its initial failure

(January 17,1989). Technical Specification (TS) 3.5.F.1 allows reactor

operation for only seven days with one DG inoperable. Operating from

January 17 to February 13, 1989, with one DG inoperable was identified by

the NRC inspectors as a potential violation.

In response to the February 13, 1989, failure, the licensee reduced reactor

power and replaced the failed fitting with a required thick-walled

fitting. In addition, Maintenance Work Requests (MWR) 89-0853 and 89-0868

were approved which replaced a large portion of control air, fuel oil, and

lube oil tubing. The MWRs also installed stainless steel flexible tubing

on the overspeed safety shutdown valve to reduce vibration between the

j

diesel engine and off-engine components. The NRC inspectors observed that

the modifications were properly reviewed and approved by the Station

Operations Review Committee on February 13 and February 15, 1989. The

modifications were performed in accordance with the MWRs and approved

maintenance procedures. Postmaintenance testing was specified in the MWR

and properly performed and documented.

During the maintenance activities on the DGs, TS required surveillance

were properly performed and Limiting Conditions for Operations were

correctly followed. Maintenance was completed on DG No. I and it was

declared operable on February 16, 1989. Maintenance was then performed on

DG No. 2, and it was declared operable on February 18.

Additionally, an NPPD investigation team consisting of the QA Division

Manager, the CNS QA Manager, the Nuclear Overview Manager, and the Nuclear

Licensing and Safety Manager assembled to evaluate the history and root

cause of the DG No.1 failure. The team discovered that a thin-walled

Nonconformance

fitting

Report (failure

NCR) No.had occurred

16 was issued previously.

on November 27, 1973, documenting a failed

nipple in the control air system of DG No. 2. Corrective action for the

NCR was to replace all fittings with thick-walled nipples in both DGs.

This NCR was not discovered during root cause analysis for the January 17,

1989, fitting failure or for a previous air system failure which occurred

on DG No. 2 on October 21, 1988. The licensee's program requires that

NCRs be reviewed for only the last 5 years during root cause determination.

In addition, no changes had been made to the applicable drawings or

specifications to require that thick-walled fittings be installed. The

team also identified several other instances of vibration induced failures

on both DGs. The team noted several other documents which indicated a

continuing problem with vibration associated failures on diesel generators

which, if they had been properly evaluated, could have prevented the

failure in January 1989 or ensured that the subsequent repair would have

been identical to the previous installation. The licensee has committed

to implementing design modifications to move vibration sensitive

instruments from the DG to instrument racks, and to upgrade tubing during

the 1989 refueling outage.

. . -

_ __ - _ _ ___ _ _ _ _ - - - - _ _ _ _ _ _ _ _ _ _

,

2 i

,

.'s O . .

,

- '

-5-

An inoperable DG,in excess of 7 days was identified as a potential'

violation. The cause for the inoperability was~an inadequate replacement

part installed after a previous DG failure. The root cause was determined

to be personnel error and inadequate corrective actions in response to

previous failures.

3. Exit Interview (30703)'

An exit interview was conducted February 16, 1989, with licensee I

representatives (identified in paragraph 1). During this interview, the

NRC inspectors reviewed the scope and findings of the inspection. The

licensee did not identify as proprietary any information provided to, or

reviewed by, the inspectors.

<

)

I

i

t

!

l

i

1

i

1

,

!

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