ML20236A166
| ML20236A166 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Catawba, McGuire, 05000000 |
| Issue date: | 10/20/1987 |
| From: | Tucker H DUKE POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-59111, TAC-59112, NUDOCS 8710220099 | |
| Download: ML20236A166 (8) | |
Text
- _ _ _ _ _ _ - _ _.
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.,W 10'CFR:50'.62 j
-l DUKE POWER GOMPANY P.O. HOX 30180 CitARLorrrE. N.O. 28242 IIAL U TUCKER TutzettoNE -
veos rassionne (704) 073-4531 nuotara ynoneretton October 20, 1987
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j U. S. Nuclear Regulatory Commission j
Attention: Document Control Desk-
~
Washington, D. C. 20555 Subj ect: Catawba Nuclear Station 4o Docket Nos. 50-413 and 50-414 McGuire Nuclear Station Docket Nos. 50-369 and 50-370 ATWS/AMSAC Design Review
Dear Sir:
Attached is our response to the request for additional information transmitted by your letter of October 13, 1987 regarding the Duke. Power ATWS Design.
Very truly yours,
/- &
f l
Hal B. Tucker B
LTP/108/sbn g em$
Attachment w/ enclosures N-N O
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w/o enclosures M
Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II
-1 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station
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LTP/105/sbn
.I RESPONSE TO REQtJEST I
FOR ADDITENAL INFORMATION AT4S/AMSAC (1) Discuss the changes made in Rev'ision 1 to the WCAP-10858P-A with respect to their impact on the Duke Power AMSAC design.
Specifically, discuss a),the i
turbine trip variable ti:m delay af specified io'the revised'WCAP and O the C-20 permissive mechanisms.
- t;
RESPONSE
Specific items which affect the Duke Power Company AMSAC design and are contained in the WCAP revision are:
1 (a) The Turbine Trip variable time delay based upon unit load and, 1
I (b) The C-20 permissive arming adjustment with respect to the turbine trip variable time delay.
l Duke Power Company intends to delete the turbine trip variable time delay from its logic diagrams submitted to the NRC and to maintain the plant-i designs for Catawba and McGuire in their original design status. Section 10.2.2 of each plant's FSAR describes the Turbine Triy' hputs.
We feel that it is conservative 91y desirable to maintain the plant dssign as close to that l
which was originally l uonsed and analyzed. Tripptrg ?% turbine directly (without time delay) upon_luss of both Main Feedwater Pump Turbines (MFWPT)
J l
and pumps is anticipatory to a Low-Low Steam Generator Level initiated trip through the Reactor Protecticta System (RPS). The Catawba and McGuire plant I
designs included the loss of both MJWPT's as part of the tr.ain Turbine Trips j
in their originel~ designs.
A compiate loss of feedwater event which would develop from loss of both pumps is not an event which allows continued plant operation even at extremely low power levels. The most prudent and conservative approach is that upon loss of both feedwater pwys, the main turbine should trip to avoid unnecessary depletion of steum generator i
inventories and reduce the amount of relatively cold auxil143 feeduater required to stabilize steam generator levels.
For loss of load events, of which the most severe is a loss hf condensor vacuum event, the main turbine would trip and the main'fendvate~' pump turbines would also trip.
Loss of both main feedwater pumps m uld not be required to trip the main turbine because it would already be. tripped and a time-delay in the turbine trip circuit would not provide any input anyway.
y Loss of both. main feedwater pumps will initiate auxiliary feedwater as l
required. " Loss 9f load (i.e., turbine trips without loss'of vacuum) does not cause a loss of feedwater and therefore, operator action would be relied upon to trip the reactor, trip both main feedwater pumps and verify initiati:n of auxiliary feedwater.
i The Westinghouse prescribed turbine trip variabb time delay provides no beneficial actions because of the existing plant designs for Catawba and J.
McGuire based on the above explanations.
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The C-20 permissive as described in the revision to the WCAP adds a variable-I.
timer whose time delay is based upon the same turbine loads associated with-M the turbine trip time delay.
In fact, these two timers are varied according to turbine load jointly. The'same argument for the Duke AMSAC design-exclusion of these time delays as described above applies to the C-20 time
. j.
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delay. The' Duke AMSAC design for Catawba and McGuire will maintain the p,
original turbine trip upon loss of both main.feedwater pump turbines and F
therefore, uc turbine load input is planned for.the C-20 permissive
. circuitry to Automatically instated a bypass of the AMSAC below 40% load as-in the WCAP.'L The'Dske AMSAC design incorporates e administrative 1y.-
controlled C-20 bypass below 40% load. TheLDuke bypass only affects the valve position ~ portion of AMSAC. Feedwater pump's status.cannot be bypassed.
The Westinghouse prescribed C-20 time delay variance upon unit load between 40% gnd 100% provides no beneficial actions because the Duke AMSAC design
. includes.a' manual bypass below 40% unit load.
~
(2) Discuss what administrative procedures will be used'to direct operators regarding the use of the C-20 permissive (reset) below the 40 % load value.
RESPONSE
l The administrative procedures used to direct the operators regarding use of the C-20 permissive below the 40%. load value are developed as part of the Duke Nuclear Station Modification process. The Administrative Policy Manual for the Nuclear-Production Department requires that as part of the Safety Evaluation process per 10 CFR 50.59, each modification is evaluated for any required changes or additions to the stetion procedures.
Information pertaining'to the precautions governing use of the C-20 l
permissive bypass below 40% unit load prior to the timing out of the 30 B
second time delay in the Feedwater Control Valve status-logic will be included in the Final Scope Document for the modification. The Final Scope Document is-used as the collection document for all significant design.
inputs into the modification. This document is transmitted to the station for revi u and used in developing the implementation package for the modification. The Final Scope Document is also used in the development of l
4 the 10 CFR 50.59 safety evaluation performed by the Design Engineering 3
Safety Evaluation group prior to development of the implementation package
['
lat the station.
(3) ! Discuss the turbing trip on a) loss'of both main Feedwater Pump Turbines and b) closure of the MFW control / isolation valves with respect to the ATWS scenarios contained in Section 2.0, Design Bases of the.WCAP (Loss of Main
.Feedwater and Loss.of Load).
RESPONSE
l>
a) 7.The Turbine Trip 6a loss of both main feedwater pump turbines is part-L
- of the originallyilicen: sed Catawba and McGuire plant designs. The p
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l response to Itmi. I discusses muchlof the relationship regarding-the.
L' above trip and thU two ATWS scenarios as described in the WCAP Section l'
2.0.
The only additional discussions to add to those previously given I
are that the original plant designs for Catawba and McGuire previously j
contained much of the ATWS rule required. The Duke design for ALSAC l
l adds the feedwater valve status inputs, yet'does not implement the i
various time delays also described in Item 1 because of the previously discussed reasona. There is no value g41ned in trying to continue main l
i f turbine operation when the' water source for the turbine steam requirement.sLdoes not function. Tripping the turbine during either of I
the two scenarios results in an anticipatory response to low-low steam l
l l
generator water level. Maintaining the, steam generator inventory and j
not continuing turbine operation to the low-low level set point during loss of feedwater events is conservat vely more desirable.
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j (b) The main turbine trip on closure of the MFW control or isolation valves I
is initiated by the AMSAC circuits directly as' contained in the Final
~
l Design Description.
i'
'I,, )2espect to the ATWS scenario's' contained in Section 2 0 j
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, Design l
I Bases of the WCAP the turbine trip occurs as a direct result of either t
sce'narios. Closure of the valves is a direct trip input.
It is backed i
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up by the loss of both feedwater punps trip input. Whenever three out l
/
of & nr feedwater control valves are cleaed for 30 seconds or three out
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of fouf f eedwater isolation valves at e. closed, the main turbine will j
tr.ip. This response is the loss of' feetkater scenario described in the
, i QCA P.
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' ' The Lois.of Load scenario results in no action by the feedwater valves.
The fdsdwafpr control valves may open.up morn in response to loss of
.l 1
l feedwater due to u main feedwater pudp trip on loss of vacuum assuming j
/
the Feedwater Control System is functional.
The turbine trip will 1
still occur due to loss of vacuum.
For loss of load events where the i
tur h)e trips but there was no loss of vacuum, there is no loss of l
)feb.;} water,thefeedwatercontrol/isolationvalvesdonotclose,and j
operator action is relied,upon to trip the reactor, trip both main r
feedwater pumps and gerify initiation of auxiliary feedwater.
o (4) Provi/le' updated Logic [liagrams show'ing:
(a) The time delay increases to 30 seconds in the Feedwater Control Valve i
signal circuit
]
I (b) The deletien of tlie time, delay in the Turbine Trip. circuit
RESPONSE
{
i The two updated logic diagrams are enclosed with this submittal.
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R
t%IN FEEDWATER FLOW CONTROL VALVES ( FCV)
Ms MAIN FEE 0 WATER MAIN FEEDWATER 2 W OPEN LIMIT SWITCHES FOR F:
Pthe TUR81NE A PltP TUR8INE e EACH STEAM GENERATOR FLOW PATH El TRIP PRESSURE SWITCHES TRIP PRESSURE SWITCHES FCV FIV FCV FIV FC)
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DELAY DELAY
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VALVE STATUS Ir4TERLOCK WITH BYPASS SWITCH ANO TURBINE IW ULSE PRESS i
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.0ESCRIPTION fMI PS = PRESSURE SWITCH
&20VoC NorH E PWR AND LOGIC, ALL INPUTS REQUIRED FOR OUTPUT
[h OR LOGIC, ONE INPUT REQUIRED FOR OUTPlTT
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COINCENDENT LOGIC FOR EXAti'LE. TWO 007 0F THREE INPUTS REQUIRED FOR CUTPN ADJUSTABLE TIME DELAY. DELAYS OUTPUT CONTROL ROOM ANNUNCIATOR ALAPM
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PERTURE
,h CONTR0t ROOS TuRsINe TRIe FIRST OuT ANNUNCIATOR bi h PLANT STATUS LIGHT Also Available On (ISOLATI0d1 EXISTING AND ACCEPTED ISCLATION DEVICE EVICE / BETWEEN CLASS 1E AND NON 1E CIRCUITS
Aperture Card t2svoc CLASS iE CONTR0t e0wER tasvoc FON IE CONTROL POWER f
e DUKE POWER COP 4'ANY 8
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ATWS/AMSAC
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MAIN FEEDWATER FLOV CON' MAIN FEE 0 WATER MAIN FEEDWATER 25% OPEN LIMIT SWITCHES-PUtf TURBINE A Putf TUR81NE 8 EACH STEAM GENERATOR FL TRIP PRESSURE SWITCHES TRIP PRESSURE GWITCHES
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VALVE STATUS INTERLOCK i
WITH BYPASS SWITCH AND
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i u o EXISTING CONTROL SYSTEMS
- - 125VOC LOCATED IN THE PLANT Norb1E PWR AUXILIARY BUILDING 1
125VOC
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[ISOLAT10 ( NOTE 7%9) d A
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125VDC I
CLASS 1E POWER 1,
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TRIP MAIN i
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( NOTE 6)
I START 80 MOTOR CLOSE ST GEN.
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CLOSE STM. GEN.
ORIVEN AUXILIARY l
SAtfLE ISCLATION OLOWOOWN FEEDWATER PUtfS VALVES i
ISOLATION VALVES (NOTE 5)l (NOTES SLB){
(NOTES 5LB)l l
l tCLASS IE CONTROL AND MOTIVE POWER)
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NOTLSs 1.
PRESSURE SWITCHES LOCATED AT MFWPT IN THE TURBINE BUILDING.
- 2. LIMIT SVITCHES LOCATED ON VALVES IN THE TURBINE BUILDING.
- 3. BYPASS SWITCH LOCATED ON MAIN CONTROL BOARD WITH INTEGRAL RESET INDICATING LIGHT.
4.
PRESSURE SWITCHES LOCATED ON TURBINE !>f'ULSE CHAT 43ER.
5.
START OF M.D.
AUXILIARY FWP.S, CLOSURE OF St+f' LING VALVES AND RLOWDOWN VALVES ACCCtPLISHED AS PART OF NORMAL SYSTEM CONTROLS.
- 6. TUR81NE TRIP ACCCtfLISHED THROUGH TFEE TURBINE CONTROL AND INSTRtkENTATION SYSTEM ( TSI).
7.
ISOLATION DEVICE LOCATED IN ESSENTIAL AREA TERMINATION CA81 NET IN AUXILIARY BUILDING.
8.
ISOLATION VALVES LOCATED IN AUXILIARY BUILDING, 00GHOUSES AND INSIDE CONTAltfENT.
9.
ISOLATION DEVICE IS AN EX13Ut[Q DEVICE PRESENTLY INSTALLED.
OR 10.
RELEASEC NO.
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% UALVES-YQTH Q
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CONTROL ROOM STARTUP
. MAIN TUR8INE BYPASS SWITCH C
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(NOTE 3)l BYPASS RESET (
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125VOC NON-1E PWR SYSTEM BYPASS RESET 4
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eROCESS iHSTRt eNTS R5VDC l
LS = LIMIT SVITCH, PS = PSE9SUAE Sw!TcH.
h lE PWR H AND LOGIC, ALL INPUTS REQUIRED FOR OUTPUT
[h OR LOGIC, ONE INPUT REQUIRED FOR OUTPUT
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i COINCENDENT LOO!C, FOR EX.W LEs TWO OUT OF THREE INPUTS l
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REQUIRED FOR CUTPUT ADJUSTABLE TIFE DELAY, DELAYS OUTPUT
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CONTROL ROOM ANNUNCIATOR ALARM N
PLANT CO>PUTER INPUT h
APERTURE q cas,,cc,cc,,u,,,,,,,1,.,,,,,ou,.
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' Aperture Card
- - - - - 125VOC CLASS 1E CONTROL power hh f
't25VDC NON 1E CONTROL POWER a
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