ML20093K222
| ML20093K222 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 09/26/1984 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Bishop T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| ANPP-30663-TDS, DER-84-51, NUDOCS 8410170228 | |
| Download: ML20093K222 (6) | |
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-Arizona Public Service Company E OCT -2,yj g gg September 26, 19849EGl03 ypp ANPP-30663-TDS/TRB
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U. S. Nuclear Regulatory Commission Region V Creekside Oaks Office Park 1450 Maria Lane - Suite 210
- Walnut Creek, Calif ornia 94596-5368 Attention: Mr; T. W. Bishop, Director Division of Resident Reactor Prejects and Engineering Programs
Subject:
Final Report - DER 84-51 A 50.55(e) Reportable Condition Relating To Failure Of The Turbine-Driven Auxiliary Feedwater Pump To Quick Start From Ambient Conditions.
File: 84-019-026; D.4.33.2 Ref erence : A) Telephone Conversation between D. Hollenbach and T. Bradish on July 24, 1984 B) ANPP-30309, dated August 23,1984 (Interim Report)
Dear Sir:
Attached is our final written report of the Reportable Deficiency under 10CFR50.55(e), ref erenced above.
Very truly yours, j
CAA)
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E. E. Van B runt, Jr.
APS Vice President Nuclear Production ANPP Project Director EEVB/TRB/nj Attachment cc: See Page Two 8410170228 840926 PDRADOCK05000g S
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(. e -V Mr. T. W. Bishop DER 84-51 Page Two ec:- Richard DeYoung, Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington; D. C. 20555 ' T. G. Woods; Jr. D. B. Karner W. E. Ide 'D. B. Fasnacht A. C. Rogers L. A. Souza D. E. Fowler T. D. Shriver C. N. Russo J. Vorees J. R. Bynum J. M. Allen D. Canady A. C. Gehr W. J. Stubblefield W. G. Bingham R. L. Patterson R. W. Welcher H. D. Foster D. R. Hawkinson R. P. Zimmerman L. Clyde M. Woods T. J. Bloom D. N. Stover J. D. Houchen J. E. Kirby Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, GA 30339
FINAL REPORT - DER 84-511 l ~ DEFICIENCY EVALUATION 50.55(e) _ ARIZONA PUBLIC SERVICE COMPANY (APS) ... : t 4 PVNGS UNITS 1, 2,.3- 'I._ ' Description of Deficiency-Thd Terry Turbine which drives the; Auxiliary Feedwater (AF)- - Pump ' AFA-P01' trips'on overspeed when starting from a cold, I - ambient condition. This deficiency'was identified during the performance of Unit 1 Startup ' testing and is documented :in (- . Nonconf ormance' Report (NCR) SJ-4551. ~ The turbine-driven pump is one of the two essential Q-Class pumps which are required to perf orm the following : { a) To maintain water -inventory in the steam generators during emergency operation when the main feedwater system is inoperable. r t l-b) To provide feedwater to the steam generators for the . removal of decay heat f rom the reactor coolant system under j accident conditions. 1 In addition, the turbine-driven AF pump has ' the unique -safety l design requirement that it shall be available in the event' of a loss of AC power.- l' The C-E interface requirements specify that auxiliary feedwater be delivered to the steam generators within.20 5 seconds of receiving an Auxiliary Feedwater Actuation Signal (AFAS). The Terry Turbine Instruction Manual, Bechtel Log No. M021-158 speciff es that care must be exercised on an emergency quick start so that the turbine is not " tripped out" on overspeed by too fast an acceleration rate (for governor control) f rom opening the turbine stop valve too quickly. -In ~ 4 l the Palo Verde design, the turbine stop valve (trip and - 1 throttle valve) is normally kept open. Steam is supplied by opening upstream steam supply and bypass ~ valves as shown on I the attached sketch. 8-Evaluation (refer to sketch, attached) ~ During an emergency shutdown condition, following the initiation of an AFAS, the steam supply valves receive a 4 signal to open in order to start the steam turbine. Upon receipt of an AFAS signal, _the solenoid-operated bypass valves: open to bring the turbine up to idle speed prior to full steam prior to opening the supply valves. In the original design. admission. An adjustable Agastat relay provides a time delay the idle speed was set at 1300 rpm and the steam supply valves 4: ~ opened five seconds af ter the solenoid bypass valves received a signal to open. .i g 9 w w( gpr,7-pr-fvr+'gyear y g t- .-mmmy--.-.q-9-w,- y.*' T---h-% 7T+-* 9~7"T' 9-7" T--
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4-Mr. T. W. Bishop. DER 84. Page Two1 Evaluations have' indicated lthat the five-second delay'is not sufficient to. allow for. the warming.up of the lines and pump casing and attain the turbine idle speed. 'Since the turbine., l spee'd control system maintains the' governor valve.in a full open position'until the idle speed is reached, the start of main steam admission within five seconds af ter the initiation. of a turbine startup command results. in the entry of " ungoverned" steam flow to the turbine causing an cverspeed-condition and consequently the rapid closure of the trip and throttle valve. ~ The. solution to this problem is to make the necessary design = changes in order to establish the turbine idle speed.and place the turbine 'on governor control prior to the admission of fullE steam flow. This objective is being accomplished by the , 4: implementation of'the following modifications:
- 1. Th i.4 eond delay time has been changed to 10 seconds. -
- 2. The discharge ~ piping f rom the two solenoid bypass valves has been routed to a single orifice with an injection point closer to the turbine. This modification allows the sizing of a single orifice rather than two parallel forifices, as well as reducing the mass of pipe requiring heating before' the turbine reaches idle speed. One orifice assures the same bypass' steam flow to the turbine with one'AFAS signal-or two AFAS signals which corresponds to one steam admission valve or both steam admission valves opening.
- 3. The idle speed was reduced f rom 1300 rpm to 800 rpm.
- 4. The governor ramp start has been delayed' until the steam admission valves are full open. In the original design, the ramp began as soon as the admission valves came off '
their seat.
- 5. The condensate drains on both the turbine casing and the steam supply piping are being modified to increase the capacity of the low point drain system to eliminate the' condensate generated during the warar-up period prior to a cold start.
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2 ^ J i Mr[T. W.' Bishop i 4 - DER : 84, ' Page ;Three The changes described:in Items 1 through 4 above have been .g implemented and the turbine has undergone five successful cold .O, u tart s. The average time required for the turbine to start ~ f rom cold and reach rated ' speed has been 19 seconds. [- Combustion Engineering has performed an analysis and has accepted a 30-second ' interface requirement in lieu of the previously established 20 seconds for delivery' of the rated 'feedwater flow to the steam generators following the generation of an AFAS (Ref._ V-CE-30850, August 28, 1984). II. Analysis of Safety Implications-The turbine-driven auxiliary feedwater pump is essential for plant safety. It is one of the two redundant pumps that delivers emergency feedwater to the steam generators following a main steam line break or a main feedwater line break inside the containment, or steam generator tube rupture. Of the two redundant pumps, it is given operating priority. Based on the above, this condition is evaluated as reportable under the requirements of 10CFR50.55(e); since, if this condition were to remain uncorrected, it would represent a significant safety condition. The project has evaluated this condition as not reportable under 10CFR21, since the subject system had not been turned over for use by operations. 1 III. Corrective Action Design Change Package (DCP) No. ISM-AF-077 has been issued and implemented on Unit 1 to make the changes listed under Section II, Items 1 through 4 Units 2 and 3 will be modified per DCP Nos. 2SM-AF-077 and 3CM-AF-077 res pectively. - DCP No. ISM-AF-078 will be issued to implement the modifications listed under Section II, Item 5, on Unit 1. The'se modifications will be complete prior to fuel load. DCP Nos. 2SM-AF-078 and 3CM-AF-078 will be issued to modify Units-2 and 3 respectively. . Bechtel Revision 3 to the C-E interf ace requirement (Bechtel Log Number N001-22.01-9) and SAR Change Notice 1239 have been j initiated to reflect the feedwater delivery time change f rom 20 seconds to 30 seconds. j
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4 a Report'No. 84-51 AFAS STEAM SUPPLY VALVE M AIN STEAM v i j / r-SYPASS VALVE ~ z / / e $N$ W TRIP S THROTTLE VALVE "i: 'l UVl34A AFAS tat M AIN STEAM e Y~;>< N-y b.gs ->4h TO TURBINE GOVERNOR BEFORE MODIFICATION AFAS STEAM SUPPLY yg vg y , MAIN STEAM /. evPASS VALVE N !UV134 TRIP & THPOTTLE VALVE e,, ? MilM UV 134 A Y AFAS Tat , M AIN STE AM e s l ?-9< N l e. f { M TO TURBINE GOVERNCR i AFTER MODIFIC ATION SKETCH FOR DER 84-51 ..}}