ML20084T962
| ML20084T962 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/20/1991 |
| From: | Broughton T GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| C311-91-2015, IEB-88-011, IEB-88-11, NUDOCS 9103260187 | |
| Download: ML20084T962 (3) | |
Text
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o GPU Nuclear Corporation NggIgf Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057 0191 717 944 7ti21 TELEX 84 2386 Writer's Direct Dial Number:
(717) 948-8005 March 20, 1991 C312-91-2015 US Nuclear Regulatory Commission Attna Document Control Desk Washington, DC 20555 Gentlement
SUBJECT:
Three Mile Island Nuclear Station Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 GPU Nuclear Final Response t.o NRC Bulletin 88-11,
" Pressurizer. Surge Line Thermal Stratification and Striping" GPU Nuclear' Corporation (GPUN) submitted a Justification for Continued Operation, as required Dy Item 1.b of NRC Bulletin No. 88-11 in a letter dated January _1, 1990.
By letter dated Hay 16, 1990 the NRC stated that there was sufficient information to justify interim operat8.on of the individual plants until the final report was cubmitted.
The letter also identified those issues which the NRC stated would need to be resolved in the final report in order to support the conclusion that the pressuriza. surge line meets all appropriate Code limits for the 40 year plant life. The Babcock & Wilcox owners Group (B&WOG) submitted the final topical report, BAW-2127, to the NRC on December 31, 1990.
Errata pages were subsequently submitted on January 4, 1991. The purpose of this letter is to docket the topical report as being applicable to THI-1 and to advise you of the licensee specific actions taken with respect to the bulletin.
BAW-2127, in
- combination with this letter, addresses the is'aues raised by the NRC and completes the action per Item 1.d of the bulletin for THI-1.
The pressurizer surge line configuration for THI-1 differs from that described in BAW-2127.
The THI-1 drain piping connected to the one inch drain nozzle is two inches in diameter rather than one inch.
A second difference is that the THI-1 surge line does not utilize any seismic I p anubbers. These differences have been evaluated and do not affect the basis for the acceptaoility of the line as analyzed in BAW-2127.
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GPU Nuclear Corporation is a subsidiary of General Pubhc Utthtres Corporation
Document Control DOOk C311-91-2015 Page 2 As required by Dulletin Item 1.a, inspections of the pressurizer surge line were performed on November 30, 1989 at hot shutdown conditions and during the cycle 8 Refueling outage (BR) in January, 1990. The first inspection verified that movement of the THI-1 surgo line was unrestricted as there was no evidence of damaged insulation.
The second inspection included the removal of piping insulation, visual inspection of the piping, a survey of the horizontal piping sections, and ultrasonic examination of a section of horizontal piping adjacent to the elbow below the pressurizer. There was no noticeable piping distress and there were no reportable indications from the ultrasonic examination.
Item 1.c of the NRC bulletin requests acquisition of plant data on thermal stratification, thermal striping, and surge line deflection.
Such data were acquired as part of a B&WOG task, when Oconee Unit No. I was instrumented. A correlation between pressurizer level changes and end point (pressurizer and hot leg) temperatures was developed from this data to predict the magnitude and temperature profile of stratification cycles.
Figure Nos. 4-3 and 4-4 in BAW-2127 compare the predicted thermal stratification cycles to those measured at oconee. These figures show that the prediction corrolation bounds thn magnitude of the measured thermal cycles.
Pressurizer level changes due to operational occurrences were defined and predictions of resulting thermal stratification cycles (BAW-2127, Fig. No. 4-12) were used as the revised functional specification in the fatigue evaluation.
THI-1 plant specific data and plant operating procedures have been reviewed as requested in Item 1.c.
The results of that review confirm that the revised functional specification yields an acceptable, yet conservative, basis for defining the fatigue usage of the surge line and roepective nozzles. The review determined that:
1) the analysis conservatively estimated both the number of thermal stratification cycita experienced by the plant to date, and the number of heatup and cooldown cycles for the remaining plant life; and, 2) the revised functional specification bounds both the magnitude and number of thermal stratification cycles that are incurred with each heatup and cooldown.
THI-1 has taken steps to reduce future surge line thermal cycles by:
1) modifying the inservice test (IST) surveillance procedure (SP) 1303-11.54, " Low pressure Injection Test" to perform the test with the Reactor Coolant System (RCS) vented; and, 2) adopting the preferred lower RCS oubcooling margine for inclusion in plant operating procedures, as recommended in BAW-2127 (Fig. No. 8).
In addition, when the preferred lower RCS subcooling margin is not maintained, an evaluation of actual plant performance will be conducted in a programmatic manner to determine its impact on fatigue life.
1
Document control Desk C311-91-2015 Page 3 Item 1.d of the bulletin requested that the licensee update stress and fatigue analyses to ensure compliance with applicable code requirements.
The necessary code analysis which defines the surge line fatigue usage for tht:
40-year design life has been completed.
This completes our response to NRC Bulletin No. 80-11.
Sincerely, th (M
i T. G. L hton Vice President and Director, THI-1 OMG/ pip ces Region 1 Administrator, NRC THI-1 Senior Project Manager, NRC THI-1 Senior Rceident Inspector, NRC
_ _ _ _ _ _ _ _ ____________________-____ - ______ - - _