ML20101G883
| ML20101G883 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/18/1984 |
| From: | Fiedler P GENERAL PUBLIC UTILITIES CORP. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| GL-84-23, NUDOCS 8412280056 | |
| Download: ML20101G883 (2) | |
Text
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o GPU Nuclear Corporation NggIgf Post Office Box 388 Route 9 South Forked River.New Jersey 08731-0388 609 971-4000 Writer's D?ect Dial Number:
December 18, 1984 Darrell G. Eisenhut, Director Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Eisenhut:
Subject:
Oyster Creek Nuclear Generating Station Docket No. 50-219 Response to Generic Letter 84-23
" Reactor Vessel Water Level Instrumentation in BWRs" Our responses regarding the two water level indication system improvements are as follows:
IMPROVEMENT 1 At the Oyster Creek plant, Yarway (heated reference leg type) and Barton (cold reference leg type) reactor vessel water level instrumentation are employed within the reactor protection system. These instruments will function, for example, upon a low reactor vessel water level to trip the reactor and to actuate various plant safety systems. Fecdwater control is performed by means of a cold reference leg type (GEMAC) reactor water level instrument which is compensated for variation in the thermodynamic operating point of the plant.
Both types of level instrumentation are calibrated for a specific containment temperature.
In addition, Yarway instrumentation is calibrated for specific operating conditions.
Consequently, the instrumentation is susceptible to errors in indicated level as the result of variation in containment temperature and/or operating conditions.
Regarding the vertical drops of the reference legs, Yarway instrumentation utilitizes a heated reference leg whereby both the variable and reference legs are enclosed within an insulating structure.
Consequently, only 17 inches of the 123 inch instrument span are not enclosed within that structure.
(The performance of Yarway instrumentation is addressed below.) For GEMAC instrumentation, the overall error in indicated level attributable to variation in drywell temperature alone (1350F to 2810F) is on the order of 6.8 inches.
The approximate reference leg length for GEMAC instrumentation is 119 inches. The elevation differences between the variable and reference legs (for these instruments) at the drywell penetrations are perceived not to be a major contributor to error in indicated level. For drywell temperatures of 2810F or above, the operator will employ the Emergency Operating Procedures to reduce containment temperature.
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I GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation
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Mr.. Darrell G. Eistnhut Page 2 Divisien of Licensing Thermocouples have been installed in close proximity to the condensing chambers on Yarway (2 instruments) and GEMAC (2 narrow range and 1 wide range) feedwater control instrumentation at the Oyster Creek plant.
Indications from these instruments are currently used in the emergency operating procedures to allow the operator to predict the onset of reference leg flashing.
An analysis perfomed at GPUN on the dynamic response of Yarway instrumentation (for high energy line breaks and loss of coolant accidents) has shown proper safety systems actuation at elevated containment temperatures. The overall error in indicated level for those transients studied was on the order of 0 to 17 inches.
Current administrative procedures at Oyster Creek require continuous monitoring of the bulk containment temperature provided that the fan coolers are in operation.
Considering the addition of themocouples to reactor water level instrumentation and the analytical studies, the errors in indicated level are predictable at different drywell conditions. Moreover, the monitoring of those conditions includes appropriate actions in the Emergency Operating Procedures. Consequently, additional upgrades to the level ins,trumentation are not necessary.
IMPROVEMENT 2 GPUN plans to replace existing mechanical level indication equipment (Yarway indicators and Barton Switches) during the next refueling outage at Oyster Creek. Preliminary engineering for this replacement specifies either local level transmitters with a remote analog trip system or new switches with improved performance characteristics such as Static-0-Ring or other comparable model.
In the event that any comments or questions arise, please contact Mr. Drew Holland of my staff at (609) 971-4643.
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- yours, V ~ }-J J fin.
eter B. Fiedig/
g)/ ice President and Director
- J0yster Creek PBF/GJS/ dam cc
- Dr. Thomas E. Murley, Region I Administrator U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406 NRC Resident Inspector Oyster Creek Nuclear Generating Station Forked River, NJ 08731
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