ML17310A418
| ML17310A418 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/30/1993 |
| From: | Conway W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML17310A419 | List: |
| References | |
| 102-02556-WFC-T, 102-2556-WFC-T, NUDOCS 9307080220 | |
| Download: ML17310A418 (19) | |
Text
ACCELERAT DOCVIKENTMST VTION SYSTEM REGULATORY INFORMATION DISTRIBUTION STEM (RIDS)
DOCKET 05000528 05000529 05000530
SUBJECT:
Forwards application to amends for licenses NPF-41,NPF-51,
& NPF-74,proposing TS 3/4.3.2 requesting addi operating margin in time response of turbine driven AF pump to SG low level signal.
DISTRIBUTION CODE:
A001D COPIES RECEIVED:LTR ENCL SIZE:
TITLE: OR Submittal: General Distribution ACCESSION NBR:9307080220 DOC.DATE: 93/06/30 NOTARIZED: YES FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi STN-50-529 Palo Verde Nuclear Station, Unit 2, Arizona Publi STN-50-530 Palo Verde Nuclear Station, Unit 3, Arizona Publi AUTH.NAME AUTHOR AFFILIATION CONWAYiW.F.
Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
NOTES:STANDARDIZED PLANT Standardized plant.
Standardized plant.
05000528 05000529 05000530 RECIPIENT ID CODE/NAME PDV LA TRAMMELLgC INTERNAL: ACRS NRR/DRCH/HICB NRR/DSSA/SPLB NUDOCS-ABSTRACT OGC/HDS1 EXTERNAL: NRC PDR COPIES LTTR ENCL 1
1 2
2 6
6 1
1 1
1 1
1 1
0 1
1 RECIPIENT ID CODE/NAME PDV PD TRAN,L NRR/DE/EELB NRR/DRPW/OTSB NRR/DSSA/SRXB OC EDCB R
G FILE Ol NSIC COPIES LTTR ENCL 1
1 2
2 1
1 1
1 1
1 1
0 1
1
-1 1
NOTE TO ALL"RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTEI CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DONT NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 23 ENCL 21
WILLIAMF. CONWAY EXECUTIVEVICEPRESLDENT NUCLEAR Arizona Public Service Company P.O, BOX 53999
~
PHOENIX, ARIZONA85072<999 102-02556-WFC/TRB/JNI June 30, 1993 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Units 1, 2, and 3 Docket Nos. STN 50-528/529/530 Proposed Amendment to Technical Specification Section 3/4.3.2 File: 93-005-41 9.05 93-056-026 Pursuant to 10 CFR 50.90, Arizona Public Service Company (APS) submits herewith a proposed amendment to Technical Specification 3/4.3.2, Table 3.3-5.
The proposed amendments are requested to provide additional operating margin in the time response of the turbine driven auxiliary feedwater (AF) pump to a steam generator low level signal.
The additional margin allows for longer turbine warm-up prior to opening the main steam supply valves and does not reduce the margin of safety.
Provided in the enclosure to this letter are the following:
A.
B.
C.
D.
E.
F.
Description of the Proposed Amendment Request Purpose of the Technical Specification Need for the Technical Specification Amendment Safety Analysis of the Proposed Technical Specification Amendment No Significant Hazards Consideration Determination Environmental Impact Consideration Determination Marked-up Technical Specification Change Pages Pursuant to 10 CFR 50.91 (b) (1), a copy of this request has been forwarded to the Arizona Radiation Regulatory Agency.
AZOOS~
9307080220 930630 PDR ADQCK 05000528 PDR
f
~S
U. S. Nuclear Regulatory Commission ATIN: Document Control Desk Proposed Amendment to Technical Specification Page 2 If you have any questions, please contact Thomas R. Bradish at (602) 393-5421.
Sincerely, WFC/TRB/JNI/rv Enclosure cc:
B. H. Fauikenberry J. A. Sloan A. V. Godwin
l
'l
STATE OF ARIZONA
)
) ss.
COUNTY OF MARICOPA )
I, W. F. Conway, represent that I am Executive Vice President - Nuclear, that the foregoing document has been signed by me on behalf of Arizona Public Service Company with full authority to do so, that I have read such document and know its contents, and that to the best of my knowledge and belief, the statements made therein are true and correct.
W. F. Conway Sworn To Before Me This SD Day Of
, 1993.
Notary Public My Commission Expires
- gy 'Ill'I
/
Q ~
$ pggg t/g c
r
ENCLOSURE PROPOSED AMENDMENTTO TECHNICALSPECIFICATION SECTION 3/4.3.2
A. DESCRIPTION OF THE PROPOSED AMENDMENTREQUEST Technical Specification 3/4.3.2, Table 3.3-5 specifies the maximum response times of 46 seconds for the electric motor-driven Auxiliary Feedwater (AF) pump and 30 seconds for the turbine-driven AF pump. The proposed amendment would increase the response time for the turbine-driven AF pump from 30 seconds to 46 seconds.
B. PURPOSE OF THE TECHNICALSPECIFICATION The Steam Generator Level - Low trip provides protection against a loss of feedwater flowevent and assures that the design pressure ofthe Reactor Coolant System (RCS) will not be exceeded due to a decrease in heat removal by the secondary system.
This specified setpoint provides assurance that there willbe sufficient water inventory in the steam generator at the Low Level set-point to provide a margin of at least 10 minutes before AF is required to prevent degraded core cooling.
The OPERABILITYof the AF system (including water inventory requirements of the condensate storage'tank) ensures that the RCS can be cooled down to less than 350' from normal operating conditions in the event of a total loss-of-offsite power.
The electric motor-driven AF pump and the turbine-driven AF pump are each capable of delivering adequate feedwater flow to remove decay heat and reduce the RCS temperature to less than 350', at which time the shutdown cooling system can be placed into operation.
C. NEED FOR THE TECHNICALSPECIFICATION AMENDMENT The purpose of the proposed Technical Specification is to improve the cold start capability of the AF pump turbine by preventing inadvertent turbine trips due to cold piping downstream of the steam supply valves.
An Auxiliary Feedwater Actuation Signal (AFAS) causes the steam supply bypass valves to open.
The system logic provides a time delay between opening the bypass valves and the opening of their associated steam supply valves (approximately 10 seconds at the present time).
The need for increasing the time delay resulted from the investigation of an AF pump turbine trip during surveillance testing in July of 1990 in Unit 2.
The root cause of failure for the AF pump turbine trip was excessive condensate accumulation in cold piping downstream of the steam supply valves, which prevented the turbine governor from gaining speed control of the turbine during the time delay period (i.e., prior to opening the steam supply. valves and after the pre-warming bypass valves are opened on receipt of an AFAS). The condensate apparently resulted from refurbishment of the steam supply valves, which reduces the steam leakage across the supply valves.
1of5
I
Interim measures to monitor leak rate of steam across the valves which keeps the downstream piping warm (i.e., approximately 190-212') were implemented using Temporary Modifications. As a long term resolution, three options were considered:
- 1) add another small bypass around the steam supply valves to keep the line warm;
- 2) increase the steam bypass flow time delay to increase the time of the warming period forthe downstream piping and;
- 3) make the interim resolution permanent and soft seat the valves as necessary to control the leakage rate.
Option 2 was selected on the basis that it was the most cost'effective means of accomplishing the warming of the downstream piping'without challenging the High Energy Line Break (HELB) criteria exemption status of the downstream lines and meeting the existing safety analysis response time (i.e., 46 seconds) for AF delivery to the steam generator(s)
~
During the review of documentation for the proposed options, it was noted that the Technical Specification response times were different between the turbine-driven pump and the motor-driven pump (30 seconds vs. 46 seconds for a steam generator low level event concurrent with an LOP, respectively).
A review of in-house documentation revealed that during the initial testing program at PVNGS (1984-1 985 time frame), it was determined that in some cases, actual system performance did not meet the assumptions used in the safety analysis that existed at the time.
The turbine-driven pump response time was one of the identified items and the reported value was 29 seconds (note: Technical Specification response time of 30 seconds includes an additional delay of approximately 1 second to account for the time the process variable is sensed to the time the equipment receives a start signal which is included in the safety analysis).
In order to reconcile the safety analysis with the actual plant performance results, CE performed a reanalysis of the UFSAR Chapter 6 and 15 events.
This reanalysis was transmitted to the NRC under PVNGS letter ANPP-32401-EEVB/WFQ, dated April 15, 1985.
The CE interface requirements indicate that the emergency feedwater system shall be available to deliver flowto the steam generators automatically upon receipt of an emergency feedwater actuation signal within 45 seconds (note:
again Technical Specification response time of 46 seconds includes an additional delay of approximately 1 second to account for the time the process variable is sensed to the time the equipment receives a start signal which is included in the safety analysis).
The difference in times between the turbine-driven pump and the motor-driven pump is due to the fact that the motor-driven train must be sequenced onto the diesel generator bus, whereas the turbine-driven train is steam powered and its train electrical components are battery powered.
It was noted that the CE interface requirement does not make a distinction between trains since from a safety analysis standpoint, a single failure of either train is possible and that the failed train could be the turbine-driven train.
Hence, the safety analysis for UFSAR Chapter 6 and 15 scenarios use the 46-second response time even though the turbine-driven train currently has a required response time of 30 seconds.
To support the increase in the time delay for the pump turbine steam supply valves, APS has reviewed the safety analysis and verified that the 46-second response time was used.
2of 5
Based on the above, APS proposes to increase the required response time from 30 seconds to 46 seconds.
APS concludes that it is prudent to increase the time delay which will allow an increased pre-warming period for the steam supply line and increase the starting reliability of the turbine-driven pump. This can be accomplished without any reduction in the safety margins including the existing safety analysis since the safety analysis uses the 46-second response time.
D. SAFETY ANALYSIS OF THE PROPOSED TECHNICAL SPECIFICATION AMENDMENT Table 3.3-5 ofthe Technical Specification lists maximum response times of 46 seconds forthe electric motor-driven AF pump and 30 seconds forthe turbine-driven AF pump.
The proposed amendment would increase the response time forthe turbine-driven AF pump from 30 seconds to 46 seconds.
The safety analysis uses the more conservative value of 46 seconds for the AF response time. The exception is the UFSAR analysis (Section 15.2.3) of the Loss of Condenser Vacuum (LOCV). This analysis assumed AF delivery 10 seconds after the actuation signal instead of proposed <46 seconds.
Since the RCS pressure (UFSAR figure 15.2.3-5) and secondary pressure (UFSAR figure 15.2.3-1 0) have peaked before the start of AF flow, this delay will not have any impact on the peak pressures.
The purpose of AF flow is to provide long term cooling. Thus, this 36-second delay in AF injection would mean a reduction of about 450 gallons of water (at the current minimum auxiliary feedwater flow) and the AFAS reset setpoint will be delayed by approximately 36 seconds.
This has negligible impact on long term cooling since the 450 gallons of water is a small fraction of the amount of condensate required for entry into shutdown cooling (300,000 gallons available per Technical Specification 3/47.1.3).
The proposed amendment would increase the allowable response time forthe turbine-driven pump start.
A review of the PVNGS Probabilistic Risk Assessment (PRA) indicated that, because the AF pump time-delay scheme is not specifically included in the PRA model, the proposed amendment would have no adverse effect on the PRA results.
The review of the plant-specific data incorporated in the PRA indicated a favorable effect of the proposed amendment.
The plant-specific data for turbine-driven AF pump starts included seven pump start failures.
For one of these pump starts, the turbine failed to come up to rated speed in the required time. Another of these pump starts resulted in a turbine over-speed trip due to excessive condensation buildup in the piping. Increasing the bypass valve time delay should increase the start reliability of the turbine AF pump.
In consideration of the above evaluations, it was concluded that, from a risk perspective, increasing the pump start time-delay will have no adverse effect on l
3of5
t I
j
In addition, the proposed amendment may serve to improve future turbine-driven AF pump start reliability.
Therefore, the time response entry in Table 3.3-5 of the Technical Specification for the turbine-driven AF pump may be increased to 46 seconds without an impact on plant safety.
E. NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION The Commission has provided standards for determining whether a significant hazards consideration exists as stated in 10 CFR 50.92.
A proposed amendment to an operating license for a facility involves a no significant hazards consideration if operation of the facility in accordance with a proposed amendment would not: (1)
Involve a significant increase in the probability or consequences of an accident previously evaluated or; (2) Create the possibility of a new or different kind of accident from any accident previously evaluated or; (3) Involve a significant reduction in a margin of safety.
A discussion of these standards as they relate to this amendment request follows:
Standard 1 Involve a significant increase in the probability or consequences of an accident previously evaluated.
This amendment request does not involve a significant increase in the probability or consequences of an accident previously evaluated based on the safety analysis for the electric motor-driven AF pump response time.
The proposed change would increase the response time of the turbine-driven AF pump from 30 seconds to 46 seconds (46 seconds is the required time response for the electric motor-driven AF pump).
Increasing the required response time of the turbine-driven AF pump is expected increase the reliabilityofthe turbine-driven AF pump reducing the probability of actuation failures. The consequences of an accident previously evaluated are not affected by the proposed change.
Standard 2 Create the possibility of a new or different kind of accident from any accident previously analyzed.
P, This amendment request does not create the possibility of a new or different kind of accident from any accident previously analyzed based on the existing analysis for the electric motor-driven AF pump.
In the case of steam generator low level, the response time for the turbine-driven AF pump would be the same as the response time for the electric motor-driven AF pump.
In the case of LOCV, the implementation of the proposed change modifies the time of AF delivery. The change in delivery time for the turbine-driven AF pump is after the limiting conditions (RCS and Secondary peak pressures) are reached and has no significant effect on long term cooling.
4of5
Standard 3 Involve a significant reduction in a margin of safety.
The margin of safety presently provided is not reduced by the proposed change in the turbine-driven AF pump response time, based on the margin of safety as established by the electric motor-driven AF pump response time. The reliabilityof the turbine-driven AF pump is expected to increase, increasing the reliability of the AF safety function.
F.
ENVIRONMENTALIMPACT CONSIDERATION DETERMINATION APS has determined that the proposed amendment involves no change in the amount or type of effluent that may be released offsite, and that there is no increase in individual or cumulative occupational radiation exposure.
As such, operation of PVNGS Units 1, 2, and 3, in accordance with the proposed amendments, does not
~involve an unreviewed environmental safety question.
G. MARKED-UP TECHNICAL'SPECIFICATION PAGES Units 1, 2, and 3 page 3/4 3-29 (Table 3.3-5) 5of5
t J