ML20045A448
| ML20045A448 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 06/03/1993 |
| From: | Samworth R Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9306100279 | |
| Download: ML20045A448 (38) | |
Text
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- t UNITED STATES
}j ,j NUCLEAR REGULATORY. COMMISSION WASHINGTON, D.C. 20555-0001 5 '~ i p June 3,' 1993 n Docket No. 50-263 LICENSEE: Northern States Power Company FACILITY: Monticello Nuclear Generating Plant
SUBJECT:
MEETING
SUMMARY
OF APRIL 21, 1993 On April 21, 1993, representatives of the Northern States Power Company'(NSP) met with members of the NRC staff at the Monticello Nuclear Plant site to provide the staff information regarding fire protection issues. Specifically, the meeting focused on the NSP analysis of associated circuits and the potential for hot shorts to impair safe shutdown of the plant in the event of a fire in the cable spreading or control room. Northern States Power Company presented an overview of alternate shutdown 1 methodology to be employed in the event of a fire in the cable spreading room. Northern States Power Company had just completed a revision of the procedure for transferring control to the alternate shutdown panel. The new procedure includes specific guidance to the control room staff.for determining when control should be transferred. Northern States Power Company explained the-independent routing of the Division' 2 cables 'in a hardened duct around the - cable spreading room. The routing is actually in a tunnel around the outside of the buf1 dings. Northern States Power Company presented a cable spreading room analysis which they used to identify shorts which would have the potential for equipment damage. Their procedure identified three such shorts: diesel fuel ' oil i transfer pump, emergency service water pump for cooling diesel, and RHR discharge valve. Northern States Power Company provided risk arguments which they believe eliminate concern over these three items. The NRC staff indicated that there may still be concern over the' service water pump. Although NRC conclusions will await completion of the trip report by Plant i Systems Branch (SPLB) and their consultant from Brookhaven. National Laboratories, we conveyed to the licensee that the information which they presented alleviated much of the staff concern. 0900G i ,,--'4 1 9306100279 930603 PDR ADOCK 05000263 l F PDR i
- ' At the simulator.in the training center,.NSP walked through the procedure for transferring control to the alternate shutdown panel and for bringing the plant to safe shutdown. Documents presented by NSP at the meeting are attached to these minutes. Original Signed By: Robert B. Samworth, Sr. Project Manager Project Directorate III-1 Division of Reactor Projects.- III/IV/V Office of Nuclear Reactor Regulation
Enclosures:
As stated cc w/ enclosures: See next page FILE: G:\\WPDOCS\\MONTICEL\\ MON 0421.MTS d Office . LA:PDIII-I PM:PDIII-l CAPD:PDIII-I f MMRushbrook MIRSamworth/sw Ib WDean Name i Date S( 75 /Qh/93 5/tf/93 b/3 /93 Copy YES/N0 YES/N0 YES/N0 i s 1 e-- t"
y 9 Mr. R. O. Anderson Monticello Nuclear Generating Plant Northern States Power Company cc: J..E. Silberg, Esquire Lisa R. Tiegel .Shaw, Pittman, Potts and Trowbridge Assistant Attorney General. 2300 N Street, N. W. Environmental Protection Division Washington DC 20037 Suite 200 520 Lafayette Road U.S. Nuclear Regulatory Comission St. Paul, Minnesota 55155 Resident Inspector Office 2807 W. County Road 75 Monticello, Minnesota 55362 Mr. Roger O. Anderson, Director Licensing and Management Issues Site General Manager Northern States Power Co. Monticello Nuclear Generating Plant 414 Nicollet Mall Northern States Power Company Minneapolis, MN 55401 Monticello, Minnesota 55362 ' Robert Nelson, President Minnesota Environmental Control Citizens Association (MECCA) 1051 South McKnight Road St. Paul, Minnesota 55119 Comissioner Minnesota Pollution Control Agency 520 Lafayette Road St. Paul, Minnesota 55119 Regional Administrator, Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Commissioner of Health ~ ~ Minnesota Department of Health 717 Delaware Street, S. E. Minneapolis, Minnesota 55440 Darla Groshens, Auditor / Treasurer Wright County Government Center 10 NW Second Street Buffalo, Minnesota 55313 Kris Sanda, Comissioner Department of Public Service 121 Seventh Place East Suite 200 1 St. Paul, Minnesota 55101-2145 i
r DISTRIBUTION LIST-FOR MEETING
SUMMARY
4/21/93: Docket File NRC & Local PDRs PDIII-I RDG File T. Murley/FMiraglia (12-G-18) J. Partlow (12-G-18) J. Roe-J. Zwolinski L. Marsh R. Samworth W. Dean P. Madden (8-D-1) D. Schrum, RIII S. Ray, SRI, RIII OGC E. Jordan, (MNBB 3701) ACRS (10) G. Grant, ED0 W. Shafer, RIII M. Phillips, RIII i -l
i ENCLOSURE April 21. 1993 - Monticello Nuclear Generatina Plant Meetina List of Attendees Name Oraanization Bob Samworth USNRC/NRR/PDIII-1 Bill Dean USNRC/NRR/PDIII-I Patrick Madden USNRC/NRR/SPLB Wayne Shafer USNRC/RIII/DRP Monte Phillips .USNRC/RIII/DRP Darrell Schrum USNRC/RIII/DRS Steve Ray USNRC/RIII/MONTICELLO Bill Stearns USNRC/RIII/MONTICELLO Ken Sullivan BROOKHAVEN NATIONAL LAB-Nick Fioravante TENERA David Sexton TENERA Gerald Goldsmith BECHTEL j Steve Engelke NSP 1 Marv Engen NSP Dave Olson NSP Karen LeGoullon-List NSP Ward Andersen NSP Rick Rohrer NSP Matt Blaskowski NSP Bill Hill' NSP Roger Anderson NSP Paul Albares NSP
h# Q-NRC MEETING APRIL.21,1993 APP. R FIRE PROTECTION ASSOCIATED CIRCUITS ANALYSIS O ALTERNATE SHUTDOWN METHODOLOGY O ALTERNATE SHUTDOWN SYSTEMS O RESOLUTION OF l.N. 92-18 O ASSOCIATED CIRCUIT ANALYSIS OVERVIEW 9 Common Enclosure O Common Bus 9 Spurious Signal O EVALUATION OF G.L. 86-10 O ASDS ASSOCIATED CIRCUITS O HOT SHORTS O PRA EVALUATION O
SUMMARY
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ALTERNATE SHUTDOWN METHODOLOGY DESIGN FEATURES j O CONTROL OF DIVISION 11 SAFETY SYSTEMS O CAPABLE OF SHUTDOWN WITH OR WITHOUT j OFF-SITE POWER {cnou Aa a 0-XF4p(M/L W 0 O ALL CONTROLS AT CENTRAL LOCATION O NO REMOTE PLANT OPERATOR ACTION REQUIRED O NO EQUIPMENT REPAIR REQUIRED O INDEPENDENT FUSES AFTER TRANSFER -'$fp'pga O INDEPENDENT FROM CONTROL ROOM / CABLE 1 SPREADING AFTER TRANSFER i O TESTABLE DURING REACTOR SHUTDOWN _a r% v G $* 0>h4 wt*'""%$p%+ 0 TEN MINUTES FOR TRANSFER ASSUMED FOR THERMAL HYDRAULIC ANALYSIS (PCT 936 F) que tw % hxxlw K$ nyw4 b l/oh151 suav. a+"il
ALTERNATE SHUTDOWN METHODOLOGY DESIGN FEATURES (CONTINUED) O FULLY SIMULATED AT TRAINING CENTER SIMULATOR O INDEPENDENT DIVISION 11 CABLE ROUTE (DUCT BANK)- e O NO CABLE RACEWAY WRAPS i i ~ 1/oh151 j
4 4 ASDS - DIV 11 CABLE ROUTE i I . INTAKE h N RATOR ROOMS -.07, g4 M ' bl ~ ~ g / 0" ss4&>+ SWITCH GEAR ROOM i + TUR B ANE BUILDING BOILE R ROOM ) MCC EFT )\\ AREA BUILDfNG h V})# b CONTROL REACTOR ROOM / CABLE SP RE ADING j HPCI gyllotNG ROOM ROOM l l Div : Div i ADMINISTRATION SUILDING I I I \\ RADWASTE BUILDING .j h.. TUNNEL ROUTE '
l ~ ALTERNATE SHUTDOWN SYSTEM (ASDS) TRANSFER SWITCHES-l O ASDS MASTER TRANSFER SWITCH (KEY LOCKED) 9 SCRAM AIR HEADER DUMP VALVE SWITCH 9 MSIV CLOSURE SWITCH O SRVTRANSFER SWITCH 9 FOUR SRVs O RHR B TRANSFER SWITCH l 9 SUPPRESSION POOL COOLING MODE O CORE SPRAY B TRANSFER SWITCH 9 CORE SPRAY SYSTEM O
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- 12 EDG CONTROLS BUS #16 BREAKER CONTROLS (65SMA' 9
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ASSOCIATED CIRCUIT ANALYSIS COMMON BUS FIRE AREA \\ \\ k \\ 5 .e I \\ s \\ 5I \\ N
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.i ASSOCIATED CIRCUIT ANALYSIS . COMMON ENCLOSURE FIRE AREA \\ 5 1 \\ $l \\ \\ \\ I ?! \\ E sL~ N \\ '~~s'l y N e \\ l y \\NNNNNN ~ Common Enclosure O RESOLUTION PER G.L. 81-12 GUIDELINES 9 R ATED FIRE BARRIERS TO PREVENT PROPAGATION OF FIRE O CABLING ELECTRICALLY PROTECTED BY FUSES / BREAKERS 1 I r l/oh151
ASSOCIATED CIRCUIT ANALYSIS SPURIOUS SIGNAL. FIRE AREA N I N N $j x .e 1 N m y ?! N 5 x N i $l \\ s gl-N N e! N \\NNNNkN i l Valve ' Pump O RESOLUTION PER G.L. 81-12 GUIDELINES 9 MANUAL CONTROL TO ASDS PANEL CAN CORRECT ANY SPURIOUS OPERATION. 9 FOR HIGH-LOW PRESSURE INTERFACES, THREE MOVs DE-ENERGlZED o MO2029 RHR SHUTDOWN COOLING SUCTION ~p>, MO2032 RHR TO RADWASTE f# /( MO2401 REACTOR WATER CLEANUP TO RADWASTE OR HOTWELL e N 1/oh151
ASSOCIATED CIRCUITS ANALYSIS O NRC APPROVAL FOR ALTERNATE SHUTDOWN SYSTEM, SAFETY EVALUATION BY NRR DATED: SEPTEMBER 11,1985 "The proposed methods for protection the safe shutdown are consistent with the guidelines in Generic Letter 81-12, as discussed below." (p. 6) s O NRC APPENDIX R INSPECTION REPORT DATED DECEMBER 3,1986 i "The licensee's analysis of the Common Bus Concern and corrective action taken to resolve deficiencies identified by the analysis were.found l to be satisfactory." (p.16) "The licensee's analysis for f. ire instigated spurious signals and methods of isolation were found to be satisfactory." (p.18) " Cabling was randomly. selected to determine if. common enclosures existed and to verify the-licensee's cable routing records and analysis for Section Ill.G.2 separation requirements. Results of the random cable checks are satisfactory." (p.19) t 3 3 i v~ w-w-- s, m r- ~
9 GENERIC LETTER 86-10
SUBJECT:
IMPLEMENTATION OF FIRE PROTECTION REQUIREMENTS
- 5. ALTERNATE AND DEDICATED SHUTDOWN CAPABILITY 5.3 Safe Shutdown and Fire Damage hd 5.3.1 Circuit Failure Modes
[ au ed g ggv QUESTION What circuit failure modes must be considered in identifying circuits #d associated by spurious actuation? M*' pMy yanur.
RESPONSE
Sections Ill.G.2 and Ill.L.7 of Appendix R define the circuit failure modes as hot shorts, open circuits, and shorts to ground. For consideration of spurious actuations, all possible functional failure states must be evaluated, that is, the component coula De energized or de-energized oy one or more of the above failure modes. Therefore,[ valves could fail open or clo l JMil open or closed. For three-phase AC circuits, the probability of getting a hYstiB~rt on all three phases in the proper sequence to cause spurious operation of a motor is considered sufficiently low as to not require evaluation except for any cases involving Hi/Lo pressure interfaces. For ungrounded DC circuits,if it can be shown that only two hot shorts of the proper polarity without grounding could cause spunous operation, no further evaluation is necessary except for any cases involving Hi/Lo prc ssure interfaces. pssa @9@ id;e s W W -hp gw. 1/oh151
GENERIC LETTER 86-10 (cont'd) 5.3.2 " Hot Short" Duration QUESTION If one mode of fire damage involves a " hot short" how long does that condition exist as a result of fire damage prior to terminating in a ground or open circuit and stopping the spurious actuation?
RESPONSE
We would postulate that a " hot short" cond_ition exists until action has been~ taken to isolate the given circuit from the fire area, or other actions as appropnate nave been taken to negate the effects of the spurious actuation. We do not postulate that the fire would eventually clear the " hot short." 5.3.10 Design Basis Plant Transients OUESTION What plant transients should be considered in the design of the alternative or dedicated shutdown systems?
RESPONSE
Per the criteria of Section Ill.L of Appendix R a loss of offsite power shall be assumed for a fire in any fire area concurrent with the following assumptions: a) The safe shutdown capability should not be adversely affected by any one spurious actuation or signal resulting from a fire in any plant area. b) The safe shutdown capability should not be adversely affected by a fire in any plant area which results in the loss of all automatic function (signals, logic) from the circuits located in the area in conjunction with one worst case spurious actuation or signal resulting from the fire. c) The sate shutdown capability should not be adversely affected by a fire in any plant area which results in spurious actuation of the redundant valves in any one high-low pressure interface line. l l/oh151
~ ASDS ASSOCIATED CIRCUITS DESIGN REQUIREMENTS t AFTER TRANSFER: Capable of Shutdown with Fire induced: 1. Open Circuits 2. Shorts to Ground 3. Hot Shorts BEFORE TRANSFER: Capable of Shutdown with Fire Induced: 1. Open Circuits 2. Shorts to Ground 3. Single Hot Short Causing All Possible Functional Failure States (e.g.; Valves could fail open or closed; pumps could fail running or not running; breakers could fail open or closed. G.L. 86-10) l I/oh151 e y
~ HOT SHORTS BEFORE TRANSFER THAT CAUSE EQUIPMENT DAMAGE (BEYOND APP. R IMPLEMENTATION) SINGLE HOT SHORT BETWEEN TWO CONDUCTORS OF SAME CABLE O MOV issue (IN 92-18) 1 ,e e RHR-SW PUMP SINGLE HOT SHORT BETWEEN TWO CONDUCTORS SEPARATE CABLES i e Mixing Voltages oo Oo l ! O O O sg, $$$i ve o 1/oh151
HOT SHORTS MIXING VOLTAGES T' 24 VDC e With 65 Combinations of Hot-Shorts,3 Shorts have 125 VDC Potential for Equipment Damager (120 to 277 VAC). 1 a 250 VDC e D.C. Circuits Not of Concern Due to Ungrounded Sys-120 VAC + tems and Low Energy. Neutral 277 VAC A Phase *- . Common Voltage Not of B Phase *- Concern Due to Same as C Phase < Shorts within Cable. i l I/oh151 lj
[# HOT SHORTS / s 4 og ' l 120 VAC TO 277 Vgs nG gw NW gt)tM- / g g w-LOW PROBABILITY DUE TO: / g j 1. 3 of 65 Hot Short Combinations tM24 j 2. If 480 VAC (3 phase) cable damage ] occurring, most probable fault would be phase to phase (480 VAC) because of large i voltage potential and less barriers. 3. Most 480 VAC cables are normally 1 de-energized thru cable spreading room 1 (e.g.; MOVs, sump pumps, SBLC, SBGT). c4m W Wu% y: b 4. Few ASDS associated cables in Cable Spreading Room and[cmTerailp not in raceways with 480 VAC energized cables.' ya i$u wts wita aCsWA Co h. n y k n M Q uA W s ASDS DESIGN FEATURES TO PROTECT AGAINST' "% HOT SHORTS: 1. Interface Relays (MOVs) 3 g T[frM 2. Component Fusing o) EWPf[ yqcupp Sw I/oh151
l 1 Use fault-tree approach based on NUREG/CR-0654 Use ignition frequency and u automatic suppression 1 probabilities from EPRI FIVE Methodology. tj l l
- }
XUREG/CR-0654: " Meaningful" fire is one which is "well established in a fuel supply" and should be detected by automatic equipment
- MEANINGFUL' FIRE
/ DEVELOPS IN CABLE SPREAD 4NG ROOM / l uEANINGFUt. l f,j$ [ I i CABLE SPREADING IGNITION SOURCE ROOM IGNITION PROPOGATES INTO FREQUENCY PER YEAR MEAN!NGFUL FIRE I IGNITION l l PAOPOG ATE S l 2.h 67 $.] I3 O 3 20E-03 /y r FIVE METHOD I I FAILURE OF ADEOUATE FUEL DETECTION AND SUPPLY TO SPREAD - SUPPRESSION OF FIRE FIRE DOES NOT BURN ITSELF OUT l SUPPAESS l 4 So25E-3 FUR f3 8 00E-01 NUREG/CR 0654 l 1 i FAILURE OF FNLURE OF MANUAL AUTOMATIC DETECTION DETECTION AND AND SUPPRESSION SUPPRESSION SYSTEM l AUTOV ATIC l l M ANU AL l Q[ 5 00E-03 FIVE METHOD I I FAILURE OF FAILURE TO PERbNNEL TO DETECT EXTINGUISH FIRE FIRE I DETECTION l l EYTINGUISH l I3 9.00E41 NUREG/CR-0654 I I FAILURE OF MANUAL FMLURE OF EXTINGUISHER TO PUT PERSONNEL TO START OUT FIRE HALON SYSTEM l MANDFWG A l [ ST AATH ALON l 5.00E-02 1.00E-02 NUREGCR4654 ESTIMATE
Assume " Meaningful" fire will-involve cable trays carrying 480 VAC and 120 VAC cables and smaller fires won't Must short 480 VAC phase to 120 VAC hot side before 480 VAC shorts to ground or phase to phase..:see drawing) 1 Estimated probability is 0.01 l actual is probably lower) ,3ge peg ')% Therefore frequency of 480 t 120 hot short is estimated as 4 about yr u
Possible Shorts in a 480VAC and 120 VAC system 480 VAC - 3 Phase 120 VAC - 1 phase 4$jk ff k th,,,,ff{gh,,ftf:hfj 8* ( l,4 1 l ~ l
~ Hot short by itself does not lead to core damage. Other failures must occur also. EXAMPLES: If a hot short disables a diesel, then offsite power must also be lost before core damage would result. 1 If a hot short disables a valve, then manual operation would usually be possible, or redundant systems could be used. Thus CDF << 1E$/yr - = l
4 CONCLUSION: 480 VAC phase to 120 VAC hot shorts do not contribute significantly to CDF at Monticello. n ,,-,,--..,-..n
t ASDS ASSOCIATED CIRCUITS
SUMMARY
-h O ORIGINAL ASDS DESIGN SATISFIED THE REQUIREMENTS OF APP. R. O MODIFICATIONS INSTALLED TO ADDRESS A HOT SHORT WITHIN A CABLE TO STRENGTHEN ASDS TOLERANCE TO HOT SHORTS. 9 kD&did!2@ kk % JWu% & P bueAW &(-o -Sk %, phM4vt T a h7 @ d O LOW PROBABILITY OF HOT SHORTS BETWEEN ADJACENT CABLES THAT COULD DEGRADE SAFE SHUTDOWN. NO ACTION PLANNED. S ttGES b Y - (o NMvh y fmA cn & & - e cdAc % e M /f<rihortat eubO -9nr h A pg,ssx e 960. 7 Owg "~L r t - vuptE O d
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4 M M SYR N O O DA O O O SI N EA IT R R ARP AR G G I mi U N I D A G FN E N O R WE C P 'C C S f3 o I + RE V N 4 ~ 0 E D e 1 L A B E O I C A P T n C S S8b D I 4 i l M O R M E P E t + R t P TRS A P Tn M S U P RE TAW EC IVRES N M M SYR A O O O DLN O O SEA ITA R R A RP R U G L N O G I R IF D T G N A N W IE N O ER O E S 6 C, N S C C P OI N 4 p'h LV CE O E D IT L A B E 4 O C A P T I C S F S1b I _ rA o D I 4 l M O R M EP T O , L-o + S P ( TRS ATn S ) t
~ " MEN 41NGFUL* FIRE DEVELOPS IN CABLE SPREADLNG ROOM l MEANINGFUL l / l$ [ = r3 I I CABLE SPREADING IGNITION SOURCE ROOM lGNITION PROPOGATES INTO FREQUENCY PER YEAR MEANINGFUL FIRE I IGNITION l l PROPOG ATES l 3 6 07 g ] IT A 3 20E43 /ye-FIVE METHOD I I FNLURE OF ADEOUATE FUEL DETECTION AND SUPPLY TO SPREAD - SUPPRESSION OF FIRE FIRE DOES NOT BURN ITSELF OUT FUEL I SUPPRESS l ff.Sb2SE-3 I3 600E41 NUREGCR4654 I I FAILURE OF FMLURE OF MANUAL AUTOMATIO DETECTION DETECTION AND AND SUPPRESSION SUPPRESSION SYSTEM I AUTOM ATIC l l M ANUAL I 00f e 5 00E-03 FivE METHOD I I FAILURE OF FAILURE TO PERd3NN.1 TO DETECT EXTINGUISH FIRE FIRE I DETECT 60N l l EYTINGUISH l I3 9.00E-01 NUREG/CR4654 I I FNLURE OF MANUAL FAILURE OF EXTINGUISHER TO PUT PERSONNEL TO START OUT FIRE HALON SYSTEM l HANDEXT GR l l ST ARN AtON l 5 00E42 1.COE-02 NUREGCR4654 ESTIMATE J
Assume " Meaningful" fire will involve cable trays carrying 480 VAC and 120 VAC cables ~ and smaller fires won't Must short 480 VAC phase to 120 VAC hot side before 480 VAC shorts to ground or phase to phase. :see drawing) i Estimated probability is 0.01
- actual is probably lower)
Therefore frequency of 480 - 1 120 hot short is estimated as l about 1E-7/yr
Hot short by itself does not lead to core damage. Other failures must occur also. EXAMPLES: If a hot short disables a diesel, then offsite power must also be lost before core damage would result. If a hot short disables a valve, then manual operation would usually be possible, or-redundant systems could be used. I Thus CDF << 1E-7/yr - - - -, +
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