ML20059M785
| ML20059M785 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 11/15/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20059M774 | List: |
| References | |
| NUDOCS 9311190320 | |
| Download: ML20059M785 (4) | |
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4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.150 TO FACILITY OPERATING LICENSE NO. DPR-39 AND AMENDMENT NO. 138 TO FACILITY OPERATING LICENSE NO. DPR-48 COMMONWEALTH EDIS0N COMPANY ZION NUCLEAR POWER STATION. UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304
1.0 INTRODUCTION
In a submittal dated April 27, 1993, Commonwealth Edison Company (Ceco, the licensee) proposed revisions to the reactor protection and engineered safeguards Technical Specifications (TS) and the limiting safety system settings to:
(1) add steam generator overfill protection requirements, and (2) modify the equations for the overpower AT (0PDT) and overtemperature AT (0 TDT) protective functions for Zion Nuclear Power Station, Units 1 and 2.
The addition of the steam generator overfill protection fulfills the licensee's commitments related to Generic Letter (GL) 89-19. The modification of the OPDT and 0 TDT equations will correct inconsistencies between the current TS cauations and the Eagle 21 Process Protection System and will relocate certain lag compensators from the TS to licensee controlled documents.
2.0 EVALUATION 2.1 Steam Generator Overfill Protection By GL 89-19, the staff recommended that all Westinghouse plant designs provide automatic steam generator overfill protection to mitigate main feedwater (MFW) overfeed events. The Zion Nuclear Power Station is a four loop Westinghouse designed pressurized water reactor (PWR) which provides automatic steam generator overfill protection. The overfill protection circuitry utilizes safety grade equipment employing two-out-of-three initiating logic to isolate MFW flow by closing the MFW isolation valves and tripping the feedwater pumps.
This logic is part of the Reactor Protection System. The overfill protection system is independei.. of the feedwater control system in terms of power supply
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and signal processing cabinet location.
In its submittal in response to GL 89-19 dated March 23, 1990, the licensee did not specifically identify the surveillance or operability requirements for the overfill protection system. The licensee committed to specifically l
address the overfill protection system in the TS as part of the Zion Station Technical Specification Upgrade Program.
It was expected that a TS amendment for the TS Upgrade Program would be submitted by the end of the first quarter of 1992. This submittal has been delayed and the licensee hence submitted the 9311190320 931115 PDR ADDCK 05000295 P
. steam generator overfill protection system surveillance and operability requirements in its April 27, 1993, submittal.
The proposed change includes the addition of Steam Generator Hi-Hi Level feedwater isolation signals to Tables 3.4-1 and 4.4-1 under the heading " Steam Generator Overfill Protection" along with corresponding additions to the Section 3.4 TS Bases.
The instrumentation required for the steam generator overfill protection function is currently in place and in use and is being tested regularly. This amendment adds the operability and surveillance testing requirements for the overfill protection system to the TS and prescribes the required action if the steam generator overfill protection function is inoperable.
2.2 Ecuations Describina the Overoower AT (0PDT) and Overtemperature AT (0 TDT) Functions An amendment to the TS for the Zion Nuclear Power Station, Units 1 and 2, is required to revise equations that describe the calculation of OTDT and OPDT functions for the recently installed Eagle 21 Process Protection System. These changes are needed for two reasons:
1.
Although the software installed in the Eagle 21 Process Protection System is correct and in accordance with the safety analysis, as a result of an administrative error, the TS equations that describe the Eagle 21 calculations for OTDT and OPDT identify the time constants using the nomenclature used for the replaced 7100 Protection System rather than the currently installed Eagle 21 System. These equations are not referred to in the day-to-day operation of the plant, but the equations should be corrected to preclude confusion during future work on parameters of the Eagle 21 System.
2.
The requirements for the lag compensators on measured AT and measured Tavg are being relocated to plant procedures. These lag compensators are currently used in the OTDT and OPDT calculations to compensate for the fast responding resistance temperature detectors (RTDs) used in the RTD bypass manifolds at Zion. The AT and Tavg response time safety analyses include assumptions regarding the response time of these functions.
Installatic a of fast responding Rosemount RTDs shortens the instrument response time and could result in spurious turbine runback signals at elevated reactor power. The lag compensation allows the response time to be adjusted to avoid spurious turbine runback signals.
Controlling the values assigned to the lag compensators by procedure will allow the licensee to change the values as necessary to support plant operations within the limits of the safety analyses using procedural controls in accordance with 10 CFR 50.59.
, The equations that require revision are:
Specification 2.1.1.B.4a Overtemperature AT Note 1 This equation describes the Eagle 21 (pages 10a and 10b) calculation of OTDT.
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I Specification 2.1.1.B.5a Overpower AT Note 2 This equation describes the Eagle 21 (pages 10c and 10d) calculation of OPDT.
Currently, OTDT and OPDT are continuously calculated by the Eagle 21 System as l
described in TS 2.1.1.B.4a, Note 1, and 2.1.1.B.Sa, Note 2.
An administrative error exists in Note 1 and Note 2 in that time constants are identified by the Greek letter Tau but with subscripts associated with the 7100 Protection System instead of the subscripts associated with the Eagle 21 System. The Eagle 21 System uses software that employs the correct equations for calculating OTDT and OPDT. Revising these equations to be consistent with the Eagle 21 software will prevent confusion but will not change the manner in which the plant is operated.
This change will correct nomenclature errors associated with subscripts to Tau that identify time constants used by the Eagle 21 System in the calculation of OPDT and OTDT. The values assigned to the lag compensators on measured AT and measured Tavg are being relocated from the TS to plant procedures. The 10 CFR j
50.59 process which governs changes to plant procedures will ensure that values used for lag compensators will maintain instrument response time within the assumptions used in the safety analyses of AT and Tavg functions.
TS Bases Section 2.1 has been updated to note that the OTDT and OPDT functions include lag compensation on measured AT and measured Tavg and that these lag l
constants have been accounted for in the safety analysis and provide allowance for RTD response characteristics. These statements have been added to ensure i
that, with the lag constants relocated from TS, configuration management is maintained.
This change deletes reference to the 1971 setpoint study which is no longer f
used on these channels since the completion of the Eagle 21 upgrade.
In addition, the Zion nuclear steam supply system (NSSS) Setpoint Evaluation has l
been revised to reflect the changes in the equations for the OPDT and 0 TDT reactor trip functions. Therefore, the reference to the setpoint document has been specified as the " Zion NSSS Setpoint Evaluation, Protection System Channels, Eagle 21 Version, Revision 2, March 1993."
The addition of the steam generator overfill protection requirements fulfills the licensee's commitments related to GL 89-19. The revisions to the TS are consistent with the intent of GL 89-19 to provide periodic verification and testing of the steam generator overfill protection system including appropriate limiting conditions of operation and surveillance requirements.
Therefore, the TS change related to the steam generator overfill protection j
systems is acceptable.
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The modification of the OPDT and OTDT equations corrects inconsistencies between the current TS equations and the Eagle 21 Process Protection System and relocates certain lag compensators from the TS. The Eagle 21 system uses software that employs the correct equations for calculating OTDT and OPDT.
Revising these equations to be consistent with the Eagle 21 software will prevent confusion, but will not change the manner in which the plant is operated. Therefore, this modification of the equations is acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 52981). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will. not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Comission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
Sang Chil Rhow Date:
November 15, 1993