ML19206B203
| ML19206B203 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/11/1978 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7905080052 | |
| Download: ML19206B203 (3) | |
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.a DIS,TRIBUTION:
g MCKET FILE NRR READING Apg i 1978 PS READIliG FASHE READING PSB READING MEMORAHOUM FOR:
D. Vassallo, Assistant Director for Light Water Reactors, DPM FROM:
R. Tedesco, Assistant Director for Plant Systems, DSS
SUBJECT:
OPTIMIZATION AND VERIFICATI0!! 0F THE VOLTAGE LEVELS AT THE SAFETY-RELATED BliSES Plant Name: Three Mile Island Unit Number 2 Docket No: 50-320 Licensing Stage: Post-Operating License Milestone No: N/A Responsible Branch: LWR-4 and Project Manager: Harley Silver Requested Coc:pletion Date: N/A Review Status: Complete The Power Systems Branch, DSS. has reviewed and evaluated the infomation sutmitted by the licensee on the optimization and verification of voltage levels at the safety-related buses for Three Mile Island Unit 2 (THI 2).
This ottimization and verification was a licensing condition (Ite=s1 of, DDR-73, February 8,1978) for TMI 2.
On the basis of our evaluation we conclude that the required optimization has been perfor=ed in an acceptable manner, and we consider that the above cited licensing condition has been met.
Our detailed evaluation is provided in the enclosure.
R. E. Tedesco, Assistant Director for Plant Systen:s Division of Systems Safety
Enclosure:
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ENCLOSURE THREE MILE ISLAND 2 CPTIMIZATION AND VERIFICATION OF THE VOLTAGE AT THE SAFETY-RELATED BUSES As stated, in item D1 of Attachment 2 to operating license DPR-73 dated February 8, 1978, the licensee is required to optimize the voltage levels at tne safety-related buses for the full and minimum load con-ditions expected throughout the anticipated range of voltage variations of the offsite power source.
This is done by adjustment of the voltage tap settings of the intervening transformers.
Further, this. ;em requires that prior to initial entry into Mode 1 (power operation),
this optimization snall be verified by actual measurement and by corre-lation of measured values with analytical results.
In addition, a des-cription of the method for performing the verification and the documen-tation establishing that verification has been accomplished shall also be provided to the staff.
In response to the above the licensee occumented that adequacy of the elec-trical design in regard to optimization of voltage levels at safety related buses would be proved by the implementation of a program of electrical measurements on the various buses throughout the plant.
In accordance with this documentation, measurement readings were taken on the 6900, 4160 and 280 volt buses.
For the 6900 and al60 volt buses these readings consisted of voltage, amperes and watts; for the 280 volt buses they consisted of voltage and arperes.
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', measured values were then converted to equivalent loads on the various buses and these loads were in turn fed to a voltage drop calculation computer program.
Comparison of the actual measured values of voltage and the values of voltage obtained from the computer analysis shows that the analytical results are within two percent of the measured values in most cases.
By obtaining these field measurements and comparing the analytical results for similar plant conditions, a level of confidence on the ability of the analytical program to predict bus voltage behavior during limiting plant load conditions was estab-lished.
By using the same analytical program, it has been determined that in order to optimize the voltages at the various buses, the transformer taps at ell unit substation buses must be set at minus two point five percent with the tap at the auxiliary transformers set at nominal.
(These settings have been subsequently verified).
We have reviewed all of the information provided by the licensee on the methodology and results of his program for optimization of the above cited bus voltage levels.
On the basis of this review we con-clude that the required optimization and verification of voltage levels has been perfomed and is acceptable.
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