IR 05000289/1993015

Insp Rept 50-289/93-15 on 930727-30.No Violations or Deviations Noted.Major Areas Inspected:Review of Licensees C/As of Three Previously Identified Edsfi & follow-up of Unresolved Item Which Resulted in non-cited Violation

ML20056H648
Person / Time
Site:	Three Mile Island
Issue date:	08/27/1993
From:	Kay L, Ruland W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20056H642	List: IR 05000289/1993015 ML20056H641
References
50-289-93-15, NUDOCS 9309100251
Download: ML20056H648 (8)

Text

. - . .. -

,

'

.

,

-

>

'

!;

.

>

U.S. NUCLEAR REGULATORY COMMISSION . l REGIONI t

!

REPORT N /93-15-l DOCKET N ,

!

l t I

'

LICENSE N DPR-50 t

.

LICENSEE: GPU Nuclear Corporation j

!

-

t l FACILITY NAME: Three Mile Island Nuclear Station, Unit 1  !

l  !

I INSPECTION DATES: July 27-30,1993 i

i

!

INSPECTOR:

~Y W l

,, b(Ind %

%ne M. Qy, Reactor Engineer Dste -

Electrical Section, EB, DRS -

l APPROVED BY: A Y 7['13 )

illiam H. Ruland, Ghief /Date i Electrical Section, EB, DRS - j I

-

l

,

l l-l

,

4 l

!

9309100251 930827 .> -

PDR G

ADOCK'05000289 3 q PDR i i

- , -- ~

, ,.. - , , , . .

.

!

!

.

2  ;

t l Area Insoected: This was an announced mspection to review the licensee's corrective actions of three previously identified electrical distribution safety functional inspection (EDSFI)

findings; the process for addressing Information Notices and Generic Letters related t<> i

electrical issues; and follow-up of unresolved item 89-24-03 which resulted in a non-cited '

violation related to the cleaning and inspection of emergency diesel generator fan drive gear box component Resuks: No violations or deviations were identified. Of the three open unresolved items reviewed in Unit 1, one unresolved item was closed. These items are discussed in Section ,

,

!  !

,

i 1 ,

.

~

l l

l

)

.

,

l

.

_ _ - _ _ _ _ _ _ _ __

-

I 3 l

!

DETAILS l l

l PURPOSE i

The purpose of this inspection was to review and verify the licensee's corrective actions for previously identified NRC findings including Electrical Distribution System Functional Inspection (EDSFI) open items and the licensee's process for addressing Generic letters and Information Notice .0 FOLLOWUP OF PREVIOUS IDENTIFIED FINDINGS (Open) Unresolved Item (50-289/90-81-02) for the 120 Vac voltage drop i calculation l i

i This item pertains to the verification and acceptability of voltage levels at end device l terminals supplied from 120 Vac vital distribution panels. The Electrical Distribution Safety l Functional Inspection (EDSFI) team requested documentation that described indisidual loads ,

I on vital bus circuits to determine inverter loading and actual voltage drops. With respect to the voltage drop, the licensee had performed calculations to confirm that the voltage at the end devices would not fall below the minimum required voltage. However, the criteria and assumptions used by the licensee for the verification were not clear. The licensee expressed  ;

confidence that the design limits were not exceeded based on past experience, but agreed to I address the team's concerns and perform the necessary analysi In response to the team's concerns, the licensee calculated the voltage drops for the incoming l and outgoing circuits for each of the four vital power ac distribution panels. Based on these '

i calculations, the voltage levels at the end devices including the inverters were evaluated to verify that the available voltage was greater than the minimum voltage needed for operatio i Calculations C1101-735-5350-005 and -006 contained the voltage drop calculations and l

'

evaluations for vital ac panels VBC and VBD. Calculations C1101-735-5350-003 and -004 contained the voltage drop calculations and evaluations for vital ac panels VBA and VB The inspector reviewed all four voltage drop studies. Calculations for ac panels VBC and l

i VBD were approved, however, the calculations for panels VBA and VBB had not been ,

'

approved based on recommendations presented within the calculations to improve voltages for certain components. Assumptions made within all four calculations were determined to be appropriate and conservative. A base voltage for inverter output of 115.64 V and voltage drop considerations for feeder and branch circuits were used to determine the voltage at the end device terminals. Based on this review, the calculations for vital ac panels VBC and VBD demonstrated that the available voltages at the end devices were greater than the l l minimum pick-up voltages needed for operation. These calculations verified that the end l

device voltages would not fall below the minimum required voltage of 102.00 :

l l

.

Calculations C1101-735-5350-003 and -004 were reviewed and determined to have used the same assumptions as calculations C1104-735-5350-005 and -006. However, these two calculations for distribution panels VBA and VBB presented recommendations for replacing certain cables. The recommendations were to replace some of the existing cables with larger cables to reduce the voltage drop across them and improve end device terminal voltage. The licensee stated that they are considering these recommendations but intend an performing current / voltage measurements to verify the necessity of the recommendation The inspector concluded that the voltage drop calculations were adequate and assumptions used were clearly presented. This item remains open pending NRC review of the licensee's actions to improve the available voltage for the circuits identified in calculations C1101-735-5350-003 and -004 and verification that minimum voltage available at the devices is greater than the minimum voltage required. (Unresolved Item 50-289/90-81-02) (Open) Unresolved Item 50-289/90-81-03 regarding the ac system fault analysis The EDSFI team's review of the adequacy of the interrupting capability of the Class IE distribution system equipment identified discrepancies between the short circuit study and actual plant equipment settings. Calculation G/C2734, Revision 0, " Electrical System Studies, Short Circuit and Coordination Review, Technical Report" assumed the auxiliary transformers' tap position to be the central one (0%) instead of the actual setting of -2.5%

and assumed a lower maximum grid voltage than the voltage actually observed. The team noted that only a narrow margin existed between available short circuit current and the interrupting capability of the 4.16 kV breakers. Based on these differences involving the tap settings and grid voltage, the team stated that this margin would be further reduced. The !

team further explained that, in consideration of the fact that only minimum margin had been calculated to exist, the impact of this difference could not be ignored without adequate justification. The licensee concurred that the study needed to be upgraded to take into

!

account the different tap settings and agreed that the revised calculation would also address maximum grid voltag In response to this item, the licensee initiated Licensing Action Item (LAI) 91-9060 to perform a short circuit study with proper considerations for auxiliary transformer impedances based on actual tap settings of-2.5% and a maximum grid voltage of 242 kV. During this l inspection, the licensee provided a Memorandum, dated July 20,1993, stipulating the i planned scope and basis assumptions to be used in the revised calculation. The scope of the l study included several DAPPER program models previously described in calculation G/C 2734 and verification of valid loads used in the DAPPER models using licensee technical data report no. 836, revision 5, for determining fault contributions and multiplier The licensee committed to completing this study by October 31,1993, in Letter no. C31I-91-2003 dated January 15, 1991. This item remains open pending completion of the study and review by the NRC. (Unresolved Item 50-289/90-81-03)

,

l  !

'

i l

,

.

I

,

l

'

(Closed) Unresolved Item No. 50-289/90-81-06 for the makeup pump motor l i performance verification i j

The EDSFI team's comparison of makeup pump motor nameplate information with data used to perform load calculations revealed that the maximum horsepower (Hp) required for the pumps during LOCA conditions exceeded the nameplate rating of the motors. In response to the team's question regarding the capability of the motors to provide the required Hp, the l licensee presented a letter from the manufacturer, Westinghouse, dated February 27,198 '

This letter stated that based on calculations performed, the motors were capable of providing the required 837 Hp for 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> with a temperature rise ofless than 80 degrees However, the licensee could not provide any analysis from the manufacturer to support the letter's statement that the motor's design temperature limits would not be exceeded under accident condition ;

l During a follow-up inspection as documented in inspection report 93-07, the licensee

!

presented an analysis performed by Westinghouse in support of the motor's capability. The l

inspectors found that the motor temperature did not agree with the actual nameplate data drawing. In addition, motor frame type, reavited motor operation duration, and shop order numbers did not agree between the makeup pump motor nameplate information and analysis presented. At the conclusion of this inspection, the licensee had no additional clarification ,

On May 24,1993, in letter C311-93-2083, the licensee provided clarifying inn.rmation to support the acceptability of the Westinghouse analysis discussed above. The inspector reviewed each variation between the nameplate data and input data used as the basis for the

analysis. Based on review of these clarifications, the inspector concluded that the Westinghouse calculation was adequate to support the analysis for operation of the makeup i pump motors at 837 Hp. The inspector noted that this analysis had recently been updated to ,

reflect an updated required Hp of 750, thereby providing additional margin for motor !

'

operation. This loading of the makeup pump and other ECCS pumps was presented in calculation C1101-212-5300-043, Revision 0. Based on this review of adequate supporting ,

documentation, this item is closed. (50-289/90-81-06)

,

t Implementation of Information Notices and Generic Letters i

The inspector performed a review of the licensee's process for addressing Information Notices and Generic Letters related to electrical issues. The review was made to assess licensee review of information for applicability to Three Mile Island and consideration of actions, as appropriate, to avoid similar problems presented in NRC generic communication i Licensee procedure 1000-ADM-1216.03, Revision 3, " Regulatory Correspondence Control" r was reviewed. This procedure sets forth requirements for the management of regulatory i

correspondence and the assignment of tasks associated with that correspondence. Based on the review of this procedure, the inspector determined that good controls had been .

'

established for the tracking ofitems/ issues and individual responsibilities related to the

r i

t

_. __ _ __ _

,

-

i l

6 .

l process were clearly defined. The dispositioning of a selected sample of Information Notices issued within the last 30 months, as listed below, were reviewed for licensee applicability i and consideration of necessary action IN 93-26: Molded Case Circuit Breaker Failures To Close  ;

IN 92-77: Applications of Electropneumatic Relays l IN 92-01: Cable Damage Caused by Inadequate Controls IN 90-18 Crosby Safety Relief Valves on EDG Air Tanks IN 91-62 Hydraulic Lockup Causing EDG Damage IN 91-34 EDG Potential Problems IN 91-29: Deficiencies Identified During EDSFIs (also Supplement 1)

!

The inspector concluded the licensee adequately addressed the regulatory informatioa for the sample reviewed and had established good controls for managing the information provide .5 Follow-up of Unresolved Item 89-24-03 regarding EDG Cooling Fan Failure On November 14,1989, as documented in inspection report 89-24, the licensee declared the

"A" emergency diesel generator (EDG) inoperable due to sludge build-up in the right angle j

-

gear drive oil sump. This sludge clogged the oil pump suction piping, strainer, and check valve resulting in loss of pump prime and a right angle gear drive upper bearing failur Following identification of the sludge build-up, the licensee observed this condition existed on the "B" EDG also which could have rendered both diesels inoperable. The root cause of l this sludge build-up was a combination of overheating of the lubricating oil and inadequate procedures for the inspection and maintenance of the EDG lubrication syste i Inspection report 91-05 presented the licensee's corrective actions including several maintenance procedure enhancements and a modification to decrease the thermostat setting and immersion heater size to reduce the likelihood of overheating the gear drive oil in the future. That follow-up inspection of the EDG failure classified this issue as a non-cited violation as reviewed against enforcement criteria presented in Part 2, Appendix C of 10 ,

CF l This inspection verified the procedure improvements to prevent the sludge problem from ;

reoccurring. Surveillance procedure 1301-8.2, Revision 56, " Diesel Generator Annual l Inspection" was reviewed to verify: oil sump immersion heater de-energization prior to draining oil; flushing of the fan drive gear box; cleaning and inspection of the lubricating oil j pump suction strainer; inspection of the oil pump suction valve; and disassembly of the fan drive gear box to inspect all component i Based on review of the change modification request to change to immersion heaters, reduce the thermostat settings, and verification of the maintenance procedure enhancements, the inspector concluded the licensee's corrective actions were adequately implemente l

!

i

.

,

.

.

UNRESOLVED ITEMS

!

Unresolved items are matters about which additional information is necessary to determine whether they are acceptable, a deviation, or a violation. Several unresolved items are discussed in detail under Section , EXIT MEETING The inspector met with the licensee's personnel denoted in Attachment 1 of this report at the conclusion of the inspection period on July 30,1993. At that time, the scope of the inspection and inspection results were summarized. The licensee acknowledged the inspection findings as detailed in this report and had no additional comments regarding the inspection result i

!

.

!

l l

s

!

_-__ -__ -

.

.

~

ATTACHMENT 1 PERSONS CONTACTED GPU Nuclear Corporation

• W. Heysek, Licensing Engineer V. Orlandi, Lead I&C Engineer

"H. Robinson, Manger, Electric Power

• E. Showalter, Lead Electrical Engineer 1 J. Valent, Plant Engineer  :

U.S. Nuclear Regulatory Commission

• D. Beaulieu, Resident Inspector, TMI

• E. Brown, Engineer's Aide, Region I

I l

* denotes attendance at exit meetmg l

l

{

l

-

,

I