ML17352A503
| ML17352A503 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 04/04/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17352A501 | List: |
| References | |
| NUDOCS 9404060214 | |
| Download: ML17352A503 (5) | |
Text
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+y*~0 SA RE UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 A UA BY THE OFFICE OF NUCL AR R
CTOR REGU ATIO A
M N
NO.
T FAC TY OP R TING IC NS NO DPR-31 A
AM NOME T N.155 TO FAC LITY OP RATING C
SE NO, PR-4 FLORIDA POWER AND LIGHT COMPANY TURKEY POINT UNIT NOS.
3 AND 4 DOCKET NOS. 50-250 AN 50-251 1.2 ~IO ON By letter dated April 20, 1993, Florida Power 8 Light Company (FPL or the licensee) proposed license amendments to change the Technical Specifications (TS) for the Turkey Point Nuclear Generating Units 3 and 4 (Turkey Point or the facility).
The proposed changes would revise TS Table 2.2-1, Reactor Trip System Instrumentation Trip Setpoints, to remove the lead/lag compensator term from the overtemperature (OT)hT and overpower (OP)ET reactor trip functions.
This would be accomplished by revising the time constants, v', and T'z in Note 1 Table 2.2-1, from 8 and 3 seconds, respectively, to zero seconds.
2.
~NNKNNN The OTBT and OPBT are protective reactor trip functions and are defined, respectively, in TS Table 2.2. 1, Notes 1 and 3.
bT is the difference between the hot and cold legs reactor coolant temperatures.
The OTBT provides core protection to prevent Departure from Nucleate Boiling (DNB) for all combinations of pressure, power, coolant temperature, and axial power distribution, provided that the transient is slow with respect to piping transit delays from the core to the temperature detectors, and pressure is within the range between the pressurizer high and low trip setpoints.
The OPGT trip protects fuel integrity (e.g.,
prevents fuel pellet melting and limits cladding strain to less than 1X) under all possible overpower conditions, limits the required range,"for the OTBT reactor trip, and backs up the high neutron flux reactor trip. ~.In addition to their reactor trip functions, the OTBT and OPGT provide a signal to generate a turbine runback before the reactor protection system reaches a reactor-trip setpoint.
The turbine runback reduces turbine power and reactor power to alleviate the OTBT and OPBT conditions and precludes the need for a reactor trip.
The protective functions are accomplished by comparing the hT values (hot and cold leg reactor coolant temperature difference) measured by the resistance temperature devices (RTD), to the continuously calculated OTBT and OPGT setpoints.
When the measured values exceed the calculated setpoints, a reactor trip signal would be generated.
To better anticipate the reactor trip signal, the measured OPbT and OTGT values are multiplied by a lead/lag compensator term 94040602i4 940404 P
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(which includes time constants, t, and v'z) before comparing them to the calculated values.
The licensee is experiencing spurious OTGT turbine runbacks caused by reactor coolant system (RCS) hot leg temperature oscillations which the licensee attributes to its removal of RTD bypass manifolds and implementation of direct mounted RTDs.
Based upon industry information provided by Westinghouse, and a
review of Turkey Point's plant-specific data, the licensee has determined that elimination of the lead/lag compensator term (by setting the time constants, r,
and r to 0 seconds in the OTBT and OPGT reactor trip functions) would reduce the potential for a spurious turbine runback or reactor trip signal.
3.0 EVALUATIO The staff has reviewed the impact of the changes to the OTBT and OPBT reactor trip functions to assess their effects on the events in the Turkey Point Final Safety Analysis Report (FSAR) that rely upon these trips for protection.
By TS amendments 140 and 135, the licensee eliminated RTD bypass manifolds and ".
implemented direct mounted RTDs with the Eagle-21 digital protection system.
The Eagle-21 digital protection system provided the capability to have a lead/lag compensator term on the measured hT signal for use in the OTZiT and OPBT reactor trip functions to anticipate a reactor trip signal.
By TS amendments 140 and 135, the licensee added the lead/lag compensator term.
Based on Westinghouse experience and recommendation, the licensee used the typical values of 8 and 3
seconds for time constants, v, and vz.
Prior to the implementation of the Eagle-21, Turkey Point TS did not include a lead/lag compensator term, i.e., time constants r, and v
set to 0 seconds.
Currently, other plants of Turkey Point's vintage also do noR include this lead/lag compensator term.
The function of the lead/lag compensator term is to amplify changes in measured hT for comparison to the OPBT and OTBT trip functions.
In general, the lead/lag compensator term is used in instances where a faster response to a change in the measured hT is required to satisfy the plant's safety analyses.
The licensee has verified that this compensator term is not required or assumed for accident mitigation in any of the safety analyses that comprise the Turkey Point licensing basis.
The licensee performed a review of its licensing basis accident analyses to determine those: analyses where either OTBT and OPBT reactor trips were used as the primary method for system protection.
The licensee's review indicated that three Updated FSAR accident scenarios:
Rod Withdrawal at Power, Dropped Rod at
- Power, and Boron Dilution Node 1, include the OTBT trip as the primary protection.
Within these accident
- analyses, the licensee has verified that the lead/lag compensator term is neither required nor assumed for accident mitigation and without this term the reactor would be tripped prior to reaching the DNB ratio and fuel centerline temperature limits.
Based on its review, the licensee has determined that changing the time constants v, and rz to 0 seconds from the typical values of 8 and 3 seconds, provides a signal gain of unity and the reactor would trip on a valid input signal.
As a result, the licensee concluded that elimination of the compensator term would not affect the FSAR accident analyses.
The OPET reactor trip is not used as the primary protection for any FSAR accident scenario; however, it is assumed in the overpower kw/ft analysis performed by Westinghouse for each fuel cycle.
Based on the discussion
- above, the staff concluded that the proposed amendment does not either create the possibility of a new or different kind of accident from any accident previously evaluated, or impact the margin of safety as calculated in the licensing basis analyses.
As a result, the licensee's proposal to remove the lead/lag compensator term on measured bT from the OPBT and OTbT reactor trip functions by setting the time constants v', and vz to zero seconds
- each, from 8 and 3 seconds, respectively, is acceptable.
- 3. 0 S ATE CONSU TION Based upon the written notice of the proposed amendments, the Florida State official had no comments.
4.0 E
RONME TAL CONSIOERATION These amendments involve a change in 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 32383).
Accordingly, these amendments meet the eligibilitycriteria 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 Based on the staff evaluation in Section 2.0 above, the staff concludes that the proposed Technical Specifications changes are acceptable.
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 Commission'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:
L. Raghavan, PDII-2 Date:
April 4, 1994
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