ML20042E796
| ML20042E796 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/27/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20042E793 | List: |
| References | |
| NUDOCS 9005030142 | |
| Download: ML20042E796 (3) | |
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ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OPERABILITY OF INDICATION-ONLY CHANNELS IN EAGLE 21 SYSTEM IN MODE 5 j
TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-327 s
1.0 INTRODUCTION
In its letter dated Apr11 24, 1990, the Tennessee Valley Authority (TVA) rquested that the NRC approve-the use of certain channels in the Eagle-21 upgrade to the Unit 1 Reactor Protection System for Mode 5.
The Eagle-21 System has been installed during the current Cycle 4 refueling outage and is described in the TVA application dated January 24, 1990 for Technical Specifi-l cation Change Request (TSCR) 89-27.
The request is to use certain " indication only" channels in Eagle-21 in Mode 5.
" Indication only" means that there are no decisions being made within the Eagle-21 System in processing the signal through the Eagle-21 System rack.
The signal is converted from analog to digital and back to analog within the Eagle-21 System rack cnd then are sent to the existing racks outside Eagle-21 for these systems, 2.0 DISCUSSION s
TVA stated that this request for limited scope approval to declare certain channels in the Eagle-21 System operable in Mode 5 prior to'the NRC approval of TSCR 89-27 is necessary to support operability-of the low-temperature over-pressure protection (LTOP) system, the reactor vessel level indication system (RVLIS), and the refueling water storage tank _ (RWST)' level indication in the main control room. These channels are the reactor coolant system RCS) wide range hot leg and cold leg temperatures, RCS_ wide range pressure'an(d' reactor water storage' tank water level.
TVA explained that the LTOP system is described in Final Safety Analysis Report (FSAR) Section 5.2.2.4 and 7.6.7.
The design, installation, and operation of RVLIS is. in accordance with the-requirements of NUREG-0737. Item II.F.2.
The RWST level indication is a typical instrument loop utilized for technical specification surveillance.
These three systems are required to be operable in Mode 5.
These channels in the Eagle-21 System are part of the definition of operable for these systems.
Therefore, for tWe systems to be considered operable, the NRC must approve the use of these new channels in accordance with 10 CFR 50.59.
TVA stated that for each of the features described above, the portion of the system utilizing Eagle-21 is essentially " indication only." There are no trip functions or protection actuations performed in this portion of the Eagle-21 system.
TVA explained that the signal is processed by an analog input module in Eagle-21.
The analog input module provides the interface among process transmitters, resistance temperature detectors (Rids), and the Eagle-21 computer hardware.
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,o n 1 The signal is then passed to a digital filter processor (DFP).
The DFP pro-vides continuous control of online calibration to eliminate potential gain and offset drift in the analog hardware of the input module and the analog-to-digital converter located on the DFP.
The values that the DFP receives for calibration references are used by the loop calculation processor (LCP) to calculate a correction factor that is applied to the input signal.
The LCP performs the conversion from engineering units to process units and performs-a range check on the instrument channels discussed above.
From the LCP, the signals are passed to the digital-to-analog converter module and then to the analog output module.
From this point the analog channels leave the Eagle-21 system. The analog signals are then used by the LTOP system and RVLIS (exter-nal to the protection system) to provide cold overpressure protection and indication of reactor vessel water, respectively.
The RWST channel is only for indication of water level.
3.0 EVALUATION Although the Eagle-21 instrument channels required to support Unit 1 Mode 5 operation are " indication only," the Eagle-21 System provides signal condition-ing and range check for these channels and thus could affect the signals.
However, no trip functions or protection actuations are initiated by Eagle-21 for the LTOP system. RVLIS, or RWST level indication.
In telephone discussions with TVA on April 25, 1990, TVA stated that all of the post-modification testing and Technical Specification operability testing of these channels has been completed.
By letter dated April 26, 1990 TVA provided documentation that the small amount of verification and validation work remaining to be done on the Eagle-21 System does not affect the operation of these channels. L remaining verification and validation work is in the Test Sequence Processor (TSP)'
subsystem and the Man-Machine Interface (MMI), which does not include potential code changes to any of the channels in the Eagle-21 System.
The TSP subsystem and MMI are electrically independent and separate for the Eagle-21 channels and are only used to perform surveillance tests and provide diagnostic and monitoring capabilities for the Eagle-21 System. The electrical power may be removed from the TSP suosystem and MMI with no impact to operation of the LCP, which is required for continuous on-line processing of the Eagle-21 channels.
All problem reports for the verification and validation work were screened to assure that none could potentially cause an impact to the software in the Eagle-21 System currently installed at Sequoyah.
The only channels in the Eagle-21 System which will be used in Mode 5 are these channels for the three systems discussed above.
The staff visited Westinghouse which built the Eagle-21 System on March 13 and-14 and April 18 to 20,1990.
These visits were part of the review by,the staff of TVA's TSCR 89-27 for the installation of the Eagle-21 System.
The visits-were to evaluate the Westinghouse verification-and validation program for'the Eagle-21 System for Sequoyah.
This program is the means by which Westinghouse and TVA assures that the Eagle-21 System will perform as it was designed.
l Based on discussions with Westinghouse and on an evaluation of the results of this program during its latter trip to Westinghouse and the letter dated-April 26, 1990, the staff concludes that there is sufficient assurance that these channels should perform as they were designed.
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4.0 CONCLUSION
Based on its review of the results of the validation and verification program and that the Eagle-21 System configuration as discussed above will not perform any trip functions or protection actuations in Mode 5, the staff concludes that it is acceptable to use those channels in the Eagle-21 System in Mode 5 for the three systems listed above.
This acceptance applies only for Mode 5 and only for the three systems.
This is also based on the acceptance and successful.
i operability testing of the channels for the three systems having been completed satisfactorily and on the control room operators and instrumentation personnel being informed before the channels are declared operable in Mode 5 that these channels must be operable in accordance with the Sequoyah Technical Specifications.
Principal Contributor:
J. Donohew Dated: April 27, 1990 i
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