HL-5212, Special Rept:On 960721,flood-up Range Reactor Vessel Water Level Instrument 1B21-R605 Out of Svc for Greater than 30 Days.Caused by Packing Leak on Equalizing Valve.Packing Leak on Equalizing Valve Repaired

Special Rept:On 960721,flood-up Range Reactor Vessel Water Level Instrument 1B21-R605 Out of Svc for Greater than 30 Days.Caused by Packing Leak on Equalizing Valve.Packing Leak on Equalizing Valve Repaired

ML20116F348
Person / Time
Site:	Hatch
Issue date:	07/30/1996
From:	Beckham J GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
HL-5212, NUDOCS 9608060320
Download: ML20116F348 (4)

Text

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Georgia Power Cornpany 40 inverness Center Parkway Post Of@ce Box 1295

. Birmingham. Alabama 35201 -

- Telephone 205 877-7279 pj8*cihagrg,,

,, ,n GeorgiaPower Hatch Project Fe souttwiekernc sptorn July 30, 1996 Docket No. 50-321 HL-5212 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 Edwin I. Hatch Nuclear Plant - Unit 1 Post Accident Monitoring Instrumentation Report Flood-Up Range Reactor Vessel Water Level Instrument Inoperable for Greater Than 30 Days Gentlemen:

In'accordance with the requirements of Unit 1 Technical Specification 5.6.6, Georgia Power Company is submitting the enclosed report describing a flood-up range reactor vessel water level instrument which has been out of service for greater than 30 days.

Should you have any questions in this regard, please contact this office.

l Sincerely, Nb f J. T. Beckham, Jr.

JKB/eb Enclosure Post Accident Monitoring Instrumentation Report, Flood-Up Range Reactor Vessel Water Level Instrument Inoperable for Greater Than 30 days.

cc: (See next page.)

I 9600060320 960730

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GeorgiaPower b

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! U, S. Nuclear Regulatory Commission Page 2 l l July 30, 1996 1 i

i cc: Georeia Power Company l

6 Mr. H. L. Sumner, Jr., Nuclear Plant General Manager i NORMS i 1

l l U. S. Nuclear Rezrdatorv Commission. Washington. D. C.

j Mr. K. Jabbour, Licensing Project Manager - Hatch i U. S. Nuclear Regidatorv' Commission. Region if i Mr. S. D. Ebneter, Regional Administrator i

Mr. B. L. Holbrook, Senior Resident Inspector - Hatch i i

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Enclosure Edwin I. Hatch Nuclear Plant - Unit 1 Post Accident Monitoring Instrumentation Report Flood-Up Range Reactor Vessel Water Level Instrument Inoperable for Greater Than 30 Days A. REQUIREMENT FOR REPORT This report is required by Unit 1 Technical Specifications Limiting Condition for Operation 3.3.3.1, Required Action B.I. This action must be entered if the plant has less than the required number ofoperable post accident instrumentation channels for a period greater than 30 days. When 30 days have elapsed, the action requires that a report be submitted to the Nuclear R.egulatory Commission within the following 14 days per Unit 1 Technical Specification 5.6.6 and 10 CFR 50.4. In this event, flood-up range reactor vessel water level instrument IB21-R605, required by Unit 1 Technical Specifications Table 3.3.3.1-1, item 2.d, was inoperable for a period greater than 30 days. Therefore, this report is required.

l B. DESCRIPTION OF EVENT '

On 7/21/96 at 0738 EDT, Unit I was in the Run Mode at a power level of 2558 CMWT (100 percent rated thermal power). At that time,30 days had elapsed since flood-up range reactor vessel water level instrument IB21-R605 was declared inoperable. The instrument was declared inoperable because it was indicating a

, reactor water level approximately 29 to 30 inches higher than actual reactor water level as measured by other instmments.

C. CAUSE OF EVENT This higher than actualindication appeared to be the result of a reduction in the _

instrument rcference leg water level which was caused by a packing leak on the equalizing valve for the transmitter associated with IB21-R605. This reduction of water level in the reference leg would cause a false high reactor water level indication.

The packing leak on the equalizing valve has been repaired. Condensation in the reference leg condensing pot was expected to refill the reference leg; however, proper instrument performance has not been re-established. Another potential action to restore accurate level indication to the instruments on the reference leg is to backfill the reference leg by injecting demineralized water. However, the instrument was not backfilled and returned to service within 30 days, as this activity poses a possibility for creating a plant transient since the IB21-R605 instrument shares a i

variable leg with other instruments which input into the Reactor Protection System logic. During backfilling, pressure perturbations can occur, which would cause instruments to trip, resulting in an automatic reactor shutdown.

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j', . Enclosure

. Post " Accident Monitoring Instrumentation Report Flood-Up Range Reactor Vessel Water Level Instrument i Inoperable for Greater Than Thirty Days t.

j The subject instrument provides no active safety function. All automatic and manual  ;

j safety functions related to reactor pressure vessel water level are provided by other  ;

redundant instruments. Also, turbine protection is provided by other redundant l instrumentation. To preclude a possible transient, backfill of the reference leg will  ;

i not be performed at this time, and instrument IB21-R605 will be returned to service during the next outage of sufficient duration.

D. PLANT RESPONSE TO THIS EVENT ,

i f 1. Preolanned Alternate Method: Reactor vesselwaterlevelinstrument I

IB21-R605 does not provide any automatic actuations of safety-related l functions. This instrument is normally used to monitor reactor water level when j level exceeds 60 inches above instrument zero (approximately 218 inches above

! the top of the active fuel). All automatic and manual safety functions are ,

! initiated by other redundant instrumentation used to monitor water level belcw I the + 60-inch range. A water level above + 60 inches occurs only when the l vessel is flooded, typically during refueling operations. A main turbine trip i i' occurs automatically on signals generated by other redundant reactor water level instruments which are completely independent ofIB21-R605. Additionally,

! turbine trips on high vessel level are generated by these independent instruments j for the High Pressure Coolant Injection System and the Reactor Core Isolation l Cooling System turbines. Therefore, the preplanned alternate method of g fidfilling the fbnction oflevel instrument IB21-R605 is to rely on the automatic

j. trips generated by independent instrumentation.

) 2. Schedule for Restorina Instrumentation to Ooerate Status: This instrument wili

! be backfilled and restored to operable status during the next outage of sufficier.1 i duration. The packing leak, which is believed to have contributed to this event, i has been corrected by tightening the valve packing nut. Other actions needed to j help assure the future availability of this instrument, such as ensuring proper j operation of the condensing pot, will be determined during the next refueling

outage when access to primary containment is possible.

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