05000219/LER-1981-004-01, /01T-0:on 810116,studies Indicated That Emergency Diesel Generators May Exceed Load Rating During Accident Conditions.Caused by Using Different & More Conservative Methods to Calculate Load.Actions to Reduce Load Underway

/01T-0:on 810116,studies Indicated That Emergency Diesel Generators May Exceed Load Rating During Accident Conditions.Caused by Using Different & More Conservative Methods to Calculate Load.Actions to Reduce Load Underway

ML19345E946
Person / Time
Site:	Oyster Creek
Issue date:	01/30/1981
From:	Crosby P JERSEY CENTRAL POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19345E944	List: 05000219/LER-1981-004, Forwards LER 81-004/01T-0 05000219/LER-1981-004-01, /01T-0:on 810116,studies Indicated That Emergency Diesel Generators May Exceed Load Rating During Accident Conditions.Caused by Using Different & More Conservative Methods to Calculate Load.Actions to Reduce Load Underway
References
LER-81-004-01T, LER-81-4-1T, NUDOCS 8102060462
Download: ML19345E946 (3)

LER-1981-004, /01T-0:on 810116,studies Indicated That Emergency Diesel Generators May Exceed Load Rating During Accident Conditions.Caused by Using Different & More Conservative Methods to Calculate Load.Actions to Reduce Load Underway

Event date:
Report date:
2191981004R01 - NRC Website

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. OYSTER CREEK NUCIEAR GENERATING STATION Ebrked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/81-04/0lT Peport Date i

January 30, 1981 Occu m. Date i

i January 16, 1981 1

Identification of Occurrence 2

i Becent studies have indicated that the load on the Butu.yacy Diesel Generators,-

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l during an actual Ioss of Coolant Accident (IDCA) with a loss of off-site power plus a single bus failure, oculd exceed the full load rating of 2500 KW.

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'Ihis event is considered a reportable occurrence as defined in the Technical

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Specifications, paragraph 6.9.2.a(9).

Conditions Prior to Occurrence

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Not applicable.

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Description of Occurrence Due to future anticipated load expansion at the Oyster Creek Station a study was 3

l undertaken to document the present load profiles on all power buses throughout-1 the plant under several operating configurations. One aspect of this ' study performed for Jersey Central Power and Light included Maxinun Denand Safety Bus i

loading during the IOCA and Ioss of Offsite pcwer scenario. Preliminary data pre-sented to JCP&L indicated that a potE.ntial' exists for substantially overloading the diesel generator above its emergency rating of 2750 KW.

'Ihis result disagrees with measured inMing during annual testing and previously subnitted analysis to the NBC.

The primary differences are attributed to the use of nameplate data in addition to the inclusion of all non-safety connected load in the maximtrn demand study, therefore, resulting in highly ccnservative projections. Since the new calculational method introduces recognized conservatisms due to estimated or j

nameplate load vs actual load conditions it was determined necessary to use demonstrated loss of power test results with aMM factors accounting for single i

failures and possible runout values. - The maxinun load experienced during any loss of power test at Oyster Creek was 2460 KW under postulated IOCA conditions, with loss of offsite power,. and one assuned diesel generator failure. To this L

load an additional 219.4 KW was aMM to account for the aMM ' load resulting l-fran runout flows expected on Core Spray and Con + aim =nt Spray Systems for a t total of 2679.4 KW on Diesel Generator #2 (which is the most limiting case).

This calculated total exceeds the continuous full load rating of 2500 KW for the a

diesel generators.

Apparent Cause of Occurrence 1

'Ihe cause of.this occurrence was attributed to differences in-the methods used 3'

to calculate the diesel generator loads,'during a IDCA with a loss of offsite power and 'a single bus failure, during a recent study as ccupared to _an analysis perfhmM during the Oyster Creek ECCS modification in 1975.

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Reportable Occurrence Page 2 Report No. 50-219/81-04/0lT Analysis of Occurrence The nest limiting diesel generator load was found to be 2460 W on DG 2 which was detemined during loss of power testing. The procedure used to perform the loss of somr test is set up such that it reflects expected load conditions seen during a IDCA with a single failure. This single failure is a simulation of one faulted bus or diesel generator. However, certain pumps in the safety related systems muld be operating at " runout" ficw under accident conditions (approximated by using nameplate ratings) instead of rated systs flows which are those measured during the test. Assuming this occurs the difference between design pump load and nameplate load must be added to the actaal load of 2460 KW.

Another factor that must be included in the analysis is the load addal by smaller power panels in the distribution systs. Since these power panels will nomally transfer to other buses during the loss of pomr tests, these loads are not included in the expected value of 2460 KW.

The total of these power panel loads was determined to be 80 KW.

The suntrary of these calculations is as follows:

Actual Largest Diesel Ioad (with single failure) 2460 KW Transferable Power Panels 80 KW Two (2) Core Spray Booster Pumps (runout differential) 62.4 KW Two (2) Core Spray Main Pump (runout differential) 24.6 KW one (1) Containment Spray Pump (runout differential) 52.4 KW Total I. cad 2679.4 KW

'Ihis value compares satisfactorily with an allowable peak load rating of 2750 KW.

Although the manufacturer will allow operation at 2750 KW for 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> per year (a virtual " continuous" rating as applied at Oyster Creek), aaaitional margin was provided by issuing a Standing Order requiring the cperators to trip the Peactor Building Closed Cooling Water Pumps and Service Water Pumps, follow-ing diesel generator. load sequencing, in the event of a IDCA with a loss of off-site power, since these loads are unnecessary in that scenario. The net effect of these actions would be to reduce the load on the diesel generator by 336 KW to a total of 2343.4 KW which is less than the continuous load rating of 2500 KW for the diesel generators.

Corrective Action

i A Standing Order has been issued which reqaires the operators to trip the Reactor Building Closed Cooling Water (RBOCW) and Service Water (SW) pumps after load sequencing following a TACA with a loss of offsite power. This action reduces the load on the most limiting Diesel Generator to less than the full load rating of 2500 KW (assuming one diesel generator fails).

- her anticipated corrective actions include performing a study to install under voltage devices on non-essential loads and to install a modification which will prevent the RBCrW and SW pumps from starting during load sequencing under IDCA conditions.