ML20006E489
| ML20006E489 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 02/20/1990 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20006E485 | List: |
| References | |
| NUDOCS 9002230338 | |
| Download: ML20006E489 (4) | |
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ENCLOSURE SUPPLEMENTAL SAFETY EVAL.UATION REPORT ZION NUCLEAR POWER STATION, UNIT 5 1 & 2 CumrLIANCE WITH ATW5 RULE 10 CFR 50.62 DOCKET N05. 50-295-304
1.0 INTRODUCTION
By letter dated May 22,!1939(Ref.1),theNRCforwardedtoCommonwealthEdison Company (CE), the licensee for Zion Nuclear Power Station, Units 1 and 2, a Safety Evaluation Report (SER) stating that the ATWS/AMSAC design proposed by CE for the Zion Station, Units 1 and 2 is in compliance with the ATWS Rule, 10 CFR 50.62,' paragraph (c)(1) pending staft resolution of Technical Specifications (TS) for ATWS requirements.
Subsequent to the issuance of the SER, the licensee by letter dated November 3, 1989 (Ref. 2) notified the staff of changes that were being made to the previously approved AMSAC design.
2.0 DISCUS $10N AND EVALUATION Of the changes initiated by the licensee, the most important changes from the i
viewpoint of the Review Criteria are:
- 1) the licensee selected a different AMSAC system. vendor and supplier, 2) different isolation devices were selected, and 3) the AMSAC system power supplies changed.
The original submittals called for the licensee to design and configure the AMSAC system using existing 7300 Series equipment.
By selecting a different system vendor, the licensee introduced maximum diversity with respect to the AMSAC and the RPS. The system vendor used logic modules and isolators which were completely diverse from the existing 7300 and 7100 Series equipment (the 7100 Series equipment is becoming obsolete). The 7100 Series isolators scheduled for use by the licensee were replaced by the Technology for Energy l
Corporation (TEC)analogisolatorsandStruthersDunn(SD)Model219 relays.
i Both of the isolators are Class 1E electrical isolation devices and have been reviewed and approved by the staff. The system power supply was changed from an UPS with I hour of battery backup capability to one with 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of backup capab_ility.
Other changes made by the licensee dealt with the Control Room alarms, indicators, status lights, and computer input signals. These changes did not affect the original SER as issued.
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c The net result of these mtdifications to the formerly approved AMSAC design is that Sections 3.0-1 (Diversity). 3.0-2 (Logic Power Supplies), and Section 3.0-9 (Electrical Independence From Existing Reactor Protection System), of the previously issued SER required some changes in their wording. Corrected versions of the affected Sections follow:
3.0-1 DIVER $1TY 1
The plant design should include adequate diversity between the AMSAC equipment and the existing Reactor Protection System (RPS) equipment. Reasonable equipment diversity, to the extent practicable, is required to minimize the potential for connon-cause failures.
Thelicenseewillusetheexistingsteamgenerator(SG)waterlevelsensing instrumentation as input to AMSAC. The licensee has verified that the AMSAC logic circuitry will be of a different design and manufacturer and will be diverse from the RPS logic circuitry. The AMSAC output signals will interface with the existing circuitry of the feedwater pump and the turbine trip. This I
interf ace will utilize safety-related output relays that will be diverse from the relays used in the RPS.
3.0-2 LOGIC' POWER SUPPLIES Logic power supplies need not be Class 1E, but must be capable of performing the required design functions upon a loss of offsite power. The logic power must come from a power source that is independent from the RPS power supplies.
The licensee has provided information verifying that the logic power supplies selected for the Zion AMSAC logic circuit will be nonsafety-related and independent from the RPS power supplies. They will be able to perform their function following loss of offsite power for a period of at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The logic power supplies will be designed and procured to meet the quality assurance guidance of Generic Letter 85-06.
3.0-9 ELECTRICAL INDEPENDENCE FROM EXISTING REACTOR PROTECTION SYSTEM l
Independence is required from the sensor output to the final actuation device, at which point nonsafety-related circuits must be isolated from safety-related circuits by qualified Class IE isolators.
The licensee discussed how electrical independence is to be achieved.
The 1
proposed AMSAC design requires isolation between the AMSAC and the Class 1E circuits associated with the steam generator level transmitters, the j
Auctioneered Nuclear Power (ANP) signal, and the Class 1E AFW pumps.
The licensee has stated that the required input isolation will be achieved through the use of TEC-156 isolators, while the required output isolation
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will be achieved through the use of S-D 219 relays.
In both cases, the l
l isolation devices are safety related and have been tested to Class IE J
electrical equipment requirements.
In addition, the isolators have been i
' qualification tested as described in Appendix A to the safety evaluation (Ref. 1).
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3.0 CONCLUSION
.The staff concludes, based on the above discussion, that the changes and modifications proposed by Commonwealth Edison to the previously approved AMSAC system for the Zion Nuclear Power Station, Units 1 and 2, are acce are in compliance with the ATWS Rule, 10 CFR 50.62, paragraph (c)(ptable and 1). The staff's. statements contained in the conclusion of the original SER with respect i
to the Technical Specifications and the successful completion of certain noted human factors engineering reviews are still valid.
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4.0 REFERENCES
1.
Letter, C. Patel (NRC) to T. Kovach (CE), " Compliance With ATWS Rule (10CFR50.62) Zion Station, Units 1 and 2," May 22, 1989.
2.
Letter, G. F. Trzyna (CE) to USNRC, " Zion Nuclear Power Station, Units 1 and 2, License Nos. DPR-39 and DPR-48, NRC Docket 50-295 and 50-304, Installation:of ATWS Modification " November 3,1989.
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