ML17352B113
| ML17352B113 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 04/12/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17352B110 | List: |
| References | |
| NUDOCS 9504170141 | |
| Download: ML17352B113 (5) | |
Text
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SAF UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&0001 A U 0
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G L C NS O.
-3 AND NDHENT NO. 166TO AC LITY OP ING C
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DPR-1 F ORIDA POWER AND LIGHT CO PANY TURKEY POINT UN T NOS.
3 AND DOCKE NOS. 50-250 AND 50- 51 T.O
~IN NOONOTION By [[letter::L-94-128, Application for Amends to Licenses DPR-31 & DPR-41,modifying TS 3.1.3.6, Reactivity Control Sys CR Insertion Limits, 3/4.2.2, Heat Flux Hot Channel Factor - Fq(Z) & 6.9.1.7, COLR & Associated Bases,Per GL 88-16.COLRs Encl|letter dated July 19, 1994]], Florida Power and Light Company (FPL or the licensee) requested a revision to the Turkey Point Units 3 and 4 Technical Specifications (TS) to reduce the maximum power level allowed with decreased main steam safety valves (HSSV) relief capacity.
By letter dated January 20,
- 1994, Westinghouse issued Nuclear Safety Advisory Letter 94-001 (NSAL) which notified the licensee of a deficiency in the basis of the TS 3/4.7.1.1, which allows the plant to operate at reduced power levels with a specified number of HSSVs inoperable.
The licensee proposed to amend this section of TS as recommended by Westinghouse to specify the correct maximum allowable reactor thermal power operation with inoperable HSSVs.
The request was modified and resubmitted by letter dated October 20,
- 1994, primarily to specify the maximum allowable power level with HSSVs inoperable without requiring a reduction of the neutron flux high setpoint trip if the moderator temperature coefficient (HTC) is not positive.
This provided closer conformance with the standard TS.
Additional information in support of the request is provided by the licensee's letter of February 20,
- 1995, which did not change the staff's proposed no significant hazards determination.
2.0 DES AND V
0 There are four HSSVs located outside containment on each of the three steam generator main steam lines.
The HSSVs discharge to atmosphere and are designed to provide overpressure protection for the secondary system.
The HSSVs also provide protection against overp} essurizing the reactor coolant pressure boundary by providing a heat sink for the removal of energy from the reactor coolant system if the preferred heat sink, provided by the condenser, is not available.
The events that challenge the relieving capacity of the HSSVs are those characterized as decreased heat removal events, of which loss-of-load/turbine trip (LOL/TT) is the limiting anticipated operational occurrence.
This event is analyzed in Chapter
- 14. 1. 10 of the Updated Final Safety Analysis Report 9504170141 9S0412 PDR ADQCK 05000250
,P PDR
(UFSAR).
This analysis shows that core protection margins (Departure from Nucleate Boiling Ratio) are maintained, the reactor coolant system (RCS) will not overpressurize, and the main steam system will not overpressurize.
The analysis assumes an immediate loss of steam relieving capability through the turbine and coincident loss of all main feedwater.
The transient is terminated by a reactor trip on high pressurizer
- pressure, overtemper ature bT, or low-low steam generator water level.
The transient does not rely on the reduced neutron flux high setpoint currently specified by TS with HSSVs inoperable to terminate the event.
- However, secondary side overpressure protection is provided by actuation of the HSSVs.
The HSSV capacity must be sufficient to prevent secondary side pressure from exceeding 110 percent of the design pressure.
The core protection margins are not affected by the deficiency identified in the NSAL.
Therefore, only the ability of the HSSVs to prevent exceeding 110 percent of secondary design pressure is affected.
The UFSAR analyzes the LOL/TT transient from the full power initial condition, with cases examining the effects of assuming primary side pressure control and different reactivity feedback conditions.
With fully operational
- HSSVs, secondary system overpressure protection is provided for all initial power levels.
With a reduced number of operable
- HSSVs, secondary overpressure protection is provided by reducing the maximum allowable reactor power level and, therefore, the heat output of the primary 'system.
The power level limits were based on the assumption that the maximum allowable power level was a
.linear function of the available HSSV relief capacity rather than on a
detailed analysis.
After further review, Westinghouse determined that under certain conditions and with typical conservative safety analysis assumptions, a LOL/TT transient from reduced power conditions may result in overpressurization of the main steam system when operated in accordance with the current TS.
Consequently, the linear function assumption is not valid for all postulated cases.
If main feedwater is lost, a reactor trip is necessary to prevent secondary side overpressurization for all postulated core conditions.
At high initial power levels a reactor trip is actuated early in the transient as a result of either high pressurizer pressure or overtemperature hT.
For Turkey Point, the reactor trip occurs as a result of either the high pressurizer pressure setpoint or low-low steam generator water level setpoint being reached.
The reactor trip terminates the transient and the HSSVs maintain steam pressure below 110X of the design value.
Therefore, no change is necessary under these conditions.
Westinghouse states in NSAL 94-001, that at lower initial power levels a
reactor trip may not be actuated early enough in the transient.
An overtemperature hT trip is not generated since the core thermal margins are increased at lower power levels.
A high pressurizer pressure trip is not generated if the primary pressure control system functions normally.
The reactor eventually trips on low steam generator water level, but this may not occur before steam pressure exceeds llOX of the design value if one or more HSSVs are inoperable in accordance with the current TS.
This may occur due to the longer time in which primary heat is transferred to the secondary side before the trip.
Westinghouse recommended reducing the maximum power level (heat input from the primary system) allowed for operation with inoperable HSSVs below the heat removing capability of the operable HSSVs.
This will prevent exceeding llOX of the design pressure of the secondary system.
2.
C es to Ss The existing TS 3.7. 1.1, applicable in modes 1, 2, and 3, required reducing the power range neutron flux high trip setpoint (trip setpoint) to 82X, 54X or 27X for one, two, or three inoperable safety valves, respectively.
The proposed changes to TS primarily involve reducing the allowable power levels with inoperable HSSVs, deleting the requirement to reduce the trip setpoint with a negative or zero HTC, and allowing entry into Mode 3 with inoperable MSSVs by stating that the provisions of TS 4.0.4 are not applicable for entry into Mode 3.
The proposed changes to TSs include reducing the allowable power levels with
- one, two, or three inoperable safety valves to 56X, 35X, or 14X, respectively.
These values are significantly more restrictive than previously required and are based on the Westinghouse algorithm matching the relief capacity with the heat output of the primary system at these power levels.
These power levels also reflect a reduction of 5.2X to account for instrument and calibration uncertainties.
Additional conservatism exists in these limits since the TS limits power on a per loop (or SG) basis.
For example, power would be limited to 56X if there was one of the twelve safety valves inoperable when 56X would prevent exceeding llOX of design pressure if three of the safety valves were inoperable, provided there was no more than one inoperable per loop.
The Westinghouse methodology presented in the NSAL was reviewed by the staff and found to be conservative in preventing exceeding llOX of design pressure.
The licensee's calculations and utilization of the NSAL method was reviewed and found to be adequate.
The power level limits proposed are acceptable to the staff since they will prevent exceeding llOX of design pressure.
The second major change to TS proposed by the licensee involves deleting the requirement to reduce the trip setpoint to the power level limits in most situations.
The trip setpoint's will only be required to be reduced by the proposed change if a positive HTC exists and the unit is in Hodes 1 or 2.
A positive HTC may exist for a few days following some refueling outages.
Reducing the trip setpoint with a positive HCT is desirable since a LOL/TT would cause a primary temperature increase and, therefore, reactivity addition with a positive MTC.
This reactivity addition would increase the power level above the relief capacity of the HSSVs.
By reducing the trip setpoint in this
- case, the heat input is limited to the relief capacity of the available HSSVs.
When HTC is zero or negative, the incr ease in primary temperature from the LOL/TT does not add positive reactivity to the core.
Core protection margins are maintained and the LOL/TT transient is terminated by a reactor trip on high pressurizer
- pressure, overtemperature hT, or low-low steam generator water level.
The transient does not rely on the reduced trip setpoint currently specified by TS with HSSVs inoperable for core protection.
Reducing
the power level to the values specified in the proposed TS, in itself, ensures that the available,HSSVs will prevent exceeding llOX of the design pressure.
Since the HCT is not positive in this case, power level will not increase above that existing at the initiation of the LOL/TT.
Since the relief capacity of the remaining HSSVs will be adequate to prevent exceeding llOX of the design pressure in this situation, the staff finds in acceptable.
In Mode 3 the turbine is not parallel to the grid so a LOL/TT event is not credible (turbine, is not loaded).
Therefore it not necessary to r educe the reactor trip setpoint with HSSVs inoperable in Mode 3.
The proposed action statement 3.7.1. l.b is adequate to protect the secondary side from overpressure.
3.0 S
C SULTAT 0 Based upon the written notice of the proposed amendments, the Florida State official had no comments.
4.0 These amendments relate to changes with respect to 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 amendment involves 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 amendment involves no significant hazards consideration, and there has been no public comment on such finding (59 FR 60380).
Accordingly, the amendment meets 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 amendment.
N.N
~CONC UN N
We find the requested changes acceptable since the relief capacity of the remaining HSSVs will be adequate to prevent exceeding llOX of the design pressure.
The proposed TS are more conservative than the existing TS.
The Commission has concluded, based on the considerations discussed above, that:
(I) 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 these amendments will not be inimical to the common defense and security or the health and safety of the public.
Principal Contributors:
R. Croteau Date:
Aoril ll, 1995
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