ML20138Q550
| ML20138Q550 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/17/1985 |
| From: | De Agazio A Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TAC-43253, NUDOCS 8512270290 | |
| Download: ML20138Q550 (17) | |
Text
b December 17, 1985 Docket No. 50-346 LICENSEE:
Toledo Edison Company FACILITY:
Davis-Besse Nuclear Power Station, Unit No.1
SUBJECT:
SUMMARY
OF MEETING - NOVEMBER 26, 1985 ON SFAS MODIFICATIONS On November 26, 1985, a meeting between Toledo Edison Company and the NPC was held to discuss proposed changes to the Safety Features Actuation System (SFAS) at Davis Besse. The modifications are to resolve an ongoing concern regarding certain shared power returns which bring into question the adequacy of redundant channel independence and compliance with IEEE 279. The issue arose as a result of an event at the station on December 5,1980. As a result of system reviews being conducted as follows-up to the June 9,1985 event, Toledo Edison Company determined that this issue should be resolved prior to the unit being returned to power. is the discussion material presented by Toledo Edison Company. is a list of attendees.
Toledo Edison plans to make a formal submittal of the proposed modification by the first week of December.
Information which must be submitted for review includes:
Marked up electrical schematic / elementary diagrams of the SFAS changes.
Description of the changes.
Testing procedures that will be used to demonstrate electrical independence between redundant SFAS instrument channels following the modifications.
Discuss the periodic surveillance (monitoring) to be performed on the floating returns following the modifications.
Ortr!ml emad by Albert De Agazio, Project Manager PWR Project Directorate #6 Division of PWR Licensing-B
Enclosures:
As stated cc w/ enclosures:
See next page PBD-6 8512270290 851217 DR ADOCK 05000346
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TOED 0 EDISW CGPMY DAVIS-BESSE NUCLEAR POER STATIM
> LNIT 1 SEETY EATUES ACTUATIm SYSTEM i
014NEL INDEPENDENE r
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MEETING AGENDA:
Safety Features Actuation System Channel Independence
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PLACE:
B&W offices, Suite 220 7910 Woodnont Avenue Bethesda, Maryland TIME:
November 26, 1985 9:00 am PURPOSE:
Proposed Upgrade to SFAS (SLIDE 1)
I.
Description of Davis-Besse SFAS la (See Attached)
(SLIDE 2)
II.
Description of December 5, 1980 Event (Narrative Attached)
III.
Options Available (SLIDE 3) 1.
Monitor for Ground Faults' (SLIDE 4) 2.
Tie Floating Common to Ground (SLIDE 5) 3.
Physically Separate Commons Between Sa,b Channels (SLIDE 6) b 4.
Separate Sensor Channel Commons 6a, IV.
Implementation Schedule A.
Package Preparstion By 11/30/85 B.
Installed Post-Modification Tests Complete By 12/15/85 C.
Following Implementation, SFAS Monthly and 18-Month Tests Will Be Run V.
Questions and Answers 71.
NRC Staff Feedback I
e 5
5
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+
3 4
i SFAS - AS CURRENTLY WlRED CHI CH2 X.
CHANNELi g
CHANNEL 2 e SENSOR e SENSOR W
LOGIC 3
LOGIC TO LOGC*
TO LOGIC -
~
AND SFAS DEVIT DEVICE CH3 CH4 XMTR XMTR SENSOR
- SENSOR TO LOGlC+
W mc E
myg TO LOGIC-+--CHANNEL CH l.2,3,4 CH l.2,3,4 CHANNEL 3 CHANNEL 4 5 SENSOR CHANNELOPTICALLY ISOLATED FROM LOGIC CHANNEL Slide 1
-+.:,- --
m y
W
SFAS AS CURRENTLY WWED l
i UI XMTR Is0 siSTA:x.s N
PS A
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_ SENSOR g
g 1
1 g___
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i CHANNELS g
OUTPUT LOGIC SUPPLIES I l l l COMMON CUTPUT 1
TO N TED RELAY T
DEVICE' g
SMS CHANNEL i(2)
LEBE!D C= COMMON A= Il8MAC FEID COMMON (C)
+5s + SVDC POWER 15VDC POWER 24=24VDC F0WER h
RIs LA I U1
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ISO XMTR BISTABLE
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t % _d _ _ m ACTUATION l
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ll8VAC i
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OUTPUT LDGIC h
POWER SuPPuES 4
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l iI l COMMON f
OUTPUT L
TO ACTUATED p
RELAY T DEVICE g
SFAS CHANNEL S(4)
Ly Slide la
NARRATIVE OF DECEMBER 5, 1980 EVENT 1.
Plant was in shutdown condition, following a December 3,1980 reactor trip due to DC ground fault (outside SFAS).
l 2.
Shortly.after December 3 trip, a ground fault was identified in SFAS.
This fault caused SFAS SAM, lights which are normally off to flicker on.
3.
In the course of troubleshooting, SFAS Channel 3 was de-energized.
This channel was chosen randomly, as fault was either in Channel 1 or Channel 3.
j 4.
' Channel 3 was re-energized Channel 3 bistables were still in a tripped state, which is normal following loss of power.
5.
One Channel 3 output module had a light out. When bulb was removed,
)
an inadvertent tie between cabinet (station ground) and power supply common occurred (this is functionally shown as 2).
6.
This inadvertent tie caused 3 amp AC supply fuse to power supply PS
'1 107 to blow. This was due to tha failure of PS 107 (functionally shown as 1) in which a fault in supply caused 118 VAC on power supply secondary (DC) side.
~
7.
Loss of PS 107 caused Channel I bistab'les to trip. Since Channel 3 bistables were already tripped, a 2-out-of-4 condition resulted, causing a full SFAS actuation.
l e
DECEMBER 5, 1980 EVENT Il8VAC (Yl) r--------------
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IlPSIO7 lPSIO9l l
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si L _ _ _ _$r^S = a" ' '
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T CAUSING ll8VAC ON T COMMON (Fl.OATING')
CASINET POWER WPPLY TlED TO STATION SECONOUlY GROUND ll8VAC (Y3) r-------------
7 ud %.@
and ud u@ u@
u 1
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PS 305 PS 306 PS 307 PS 32 l
1 1
m voc
+ voc
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I PS 310 PS 311 PS312 l
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2
[ _jhINADVERTENT t
_ _ _SLASEANNE 3_,
T TIE TO STATION CABINET GROUND TIED TO STATION GROUND Slide 2 i
L TTIW: MONITOR FOR GRCUND FALTCTS MANTAGES DOESNOTCOMPRQ4ISESYSTEMRELIABILITY.
o CURRENTLY BEING DONE ON A MONTHLY BASIS.
o DISADVANTAGES
'o RENFR SFAS TO A TWO CH#4NEL SYSTEM.
DiTECTION OF A. FAULT. AFFECTING TWO SENSOR CHANNELS MJST o
BE PHYSICALLY CLEARED..
Slide 3 l
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G7fl@: IIE Ctr+1oN TO GROLND AtNANTAGES ASSURES -THAT SFAS IS.ItttNE TO A SINGLE FAILLRE Mi!CH COULD o
AFFECT TWO SENSOR CHMNELS.
CHANGE REGUIRES NO NEW OR C m PLICATED HARDWARE.
o CHANGE IS SIMPLE TO ACCCWLISH.
o R
PROVIDESPOSITIVERESULTS. -lFAFAULTOCCURSITIS o
IffEDIATELY-CLEARED, NO WILL RESULT IN A TRIP OF CHNINEL CMTAINING FAULT.
DISADVANTAGES CHANGE t%KES SFAS MORE. SUSCEPTIBLE TO SPURIOUS TRIPS.
o c-POTENTIALPERSCNNELSAFETYFROBLEMS.
o r
M Slide 4 L tr.
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TTIm: PkYSICALLY SEPARATE C0ft10NS BETWEEN 0%NNELS
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MANTAGES ASSURES THAT SFAS -IS 4PtplE-TO A SINGLE FAILWE WICH o
00UQ AFFECT TWO SENSOR CHAPNELS.
DOES.NOT.MAKE SFAS.MORE SUSCEPTIBLE:TO SPURIOUS TRIPS o
OR EGLIIPtENT DHAGE.
DISADVANTAGES ExrENSIVEFIELDWIRINGANDHARDWAREREQUIRED.
=
QJRRENT SYSTEM SPACE LIMITATIONS WOULD NOT ALLOW COR '
o AIE!TIONAL TERMINATIONS REQUIRED.
SYSTEMRELIABILITYREDUCTION.
o Slida 5 i
4 i
Rf/SICALLY SEPARATED C01DE ETWEEN OWlES i
.=
5"AS SFA,5 CW l(Z) BUS CH 3(4) sus
+24 VDC
+ 24 VDC LA LB l
'LA IS ', 1 i
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Bus -
1 bus r
I ' WIRES To EE 1
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SAS(4)
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OVDC O VDC~
WIRES ( CONTACTS -
TO SE.ADDED
(, REFLECTS REVISION REQUIRED TO DWG.E-30B,SH.4)
?
l Slide Sa c.
PHYSI.CALLY SEPARATED C@lTNS BEBEEN OWiELS 5FA5 SFAS.
CH.I(2) SUS Ch.3 (4) SUS 12 4VOC 424VDC T_
T LA 16 L A B U'S ;
d LE BU5 ;
w 13 WlRES TOBE DELETED AM
_ _ _ _ _ _ _ _ _ _;_ _E h
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SAi(2)
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WIRES ( CCNTACTS C l.C_
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To SE Acomo I
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C21 dg d R,,G, T
f* DELETEDWIRES TO BE (
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FA RC C
5 A3(4)
.ffB)- C4-C4C o='C 4Cp.C,0 f9 I
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[ REFLECTS REvtsloN REQUIRED To DWG.E-G08,5H.14D (ELEM.oNLY)]
i Slida 5b l
4 L
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l G7[l@: DARATIONf0F SENSOR OMNNEL [kPf10NS (IED PREFERRED OFTION) b/ANTAGES ASSURES THAT SFAS IS.I>ttNE TO A. SINGLE FAILURE Wi!CH o
COULD AFFECT TWO SENSOR CHANNELS.
DOES NOT PMKE SFAS MORE SUSCEPTIBLE TO SPLRIOUS TRIPS o
OR ECUIPPENT IW%GE.
REQUIRES'NC FIELD WIRING O WiGES.
o DisAwANrAses -
REGUIRES VERY.#BITIQUS SCHEDULE TO ALLOW INSTALLATION o
PRIOR TO PUWT RESTART.
Slide 6 e
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SFAS-AS PROPOSED CH:
CH2 XMTR CHANNELI XMTR CH NNEL 2
~
SENSOR SENSOR O'
1.O GIC TO LOGIC +- CHAN E TO LOGIC
- Sm S NSOR
-X LOGIC R
LOGC TO LOGIC-TO LOGIC +-
4
- SENSOR POWER SUPPLY ISOLATED FROM LOGIC POWER SUPPLY
' SENSOR CHANNEL OPTICALLY ISOLATED
~
FROM LOGIC CHANNEL Slide 6a 8
.-?
-... ~. -.. - - -. - - - - - -. -, - ~, - -
SFAS MOOlFICATION-SEPERATION OF SENSOR COMMON 1
SENSCR
- gjg, XWR l
PCMR ggg suPPUEs
-t5 BISTABLE PS i
_SE_N g
7 7 Q[Q.
R 0
0 ACTUATION i.,
m ll8 M C
$l $$$
Yl(Y2)
Sanom oneen
,.$EEs o,
u o l
24 OUTPUT LOGIC POWER SUPPLIES
([
1 l l l l COMMON OUTPUT 1-TO A N TED
_ RELAY T
' OEVICE f;
a
.i SFAS CHANfEL i(2)
LEGD O j
I 5FROM SENSOR CS= SENSOR COMMON POWER SUPPLY (CHISCH3 ISOLATEDFROM COMMON (CL)
CH l CL AND FROM EACH OTMF CL = LOGIC COMMON OI
- OPTICAL ISOLATION a
RI= RELAY ISOLATION SENSOR I/I Mr XMTR POMR iso suPPUEa 81 STABLE ps
.7 0 0 0 0 A
SENSOR I
I I
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~~~
ACTUATION
[
F LPe="?4.
7 8"*" a s il8 H C i
~
L7,pg"g Y3 (Y4) y o y 9 OUTPUT LOGIC SNikS 4
i i
l l COMMON CUTPUT
.L.
TO ACTUATED RELAY T.
DEVICE 1l i
SFAS CHANNEL 3(4) t FROM SENSOR POWER f
SUPPLY CH 3 i
Slida 6b
[
~
November 26,1985 TOLEDO EDISON /NRC MEETING SFAS 6
ATTENDEES NAME ORGANIZATION ALBERT W. DEAGAZIO NRC SUSHIL C. JAIN TED
~
CONRAD MCCRACKEN NRC/PDB 6 JACK R. GRIGG BETA DALE R. WUOKKO TED/NLD GEORGE GARRITY CONSOLIDATED CONTROLS CORP.
CHRIS K HN TED/I&C ENGR.
GEORGE DICK NRR/PD 6 4
RICK KENDALL NRR/PEICSB OLAN PARR NRR/PEICSB LARRY STALTER TED BOB PETERS
. TED/NLD l
l l
e
. ~
0 MEETING
SUMMARY
DISTRIBUTION Licensee: Toledo Edison Company
- Copies also sent to those people on service (cc) list for subject plant (s).
Docket File NRC PDR L PDR PBD-6 Rdg JPartlow (Emergency Preparedness only)
JStolz ADe Agazio OELD EJordan BGrimes ACRS-1.0 NRC Participants I
CMcCracken GDick j
RKendall,
)
OParr' l
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