ML20056G204
| ML20056G204 | |
| Person / Time | |
|---|---|
| Site: | 05200002 |
| Issue date: | 08/19/1993 |
| From: | Stewart Magruder Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9309020241 | |
| Download: ML20056G204 (34) | |
Text
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f \ UNITED STATES .ud__.__
- [';]jQ'[i gj j NUCLEAR REGULATORY COMMISSION WASWNGTON. D C. 20555 m
% .* . . + ,.e August 19, 1993 Docket No.52-002 APPLICANT: ABB-Combustion Engineering, Inc. (ABB-CE)
PROJECT: CE System 80+
SUBJECT:
PUBLIC MEETING OF AUGUST 5, 1993, REGARDING CONTAINMENT BYPASS DURING STEAM GENERATOR 10BE RUPTURES (SGTRs) FOR ABB-CE SYSTEM 80+
On August 5,1993, a public meeting was held at the headquarters of the U.S.
Nuclear Regulatory Commission (NRC) in Rockville, Maryland, between representatives of ABB-CE and the NRC. The purpose of the meeting was to discuss the staff's concerns regarding containment bypass during SGTRs and to attempt to arriv'e at a consensus for closure of the issue. Enclosure 1 provides a list of attendees. Enclosure 2 contains the material presented by ABB-CE.
ABB-CE began the meeting with a summary of their evaluation of the SGTR issue to date. Their hnalysis showed that: (1) with reactor power cutback and steam bypass systems operating, the main steam safety valves (MSSVs) are not challenged except for turbiu control valve and main steam isolation valve closure, (2) for severe accident scenarios with SGTR occurring along with severe core damage; the probability of containment bypass is quite low (<104) and almost independent of secondary side fixes, (3) for primary side fixes (automatic depressurization by N-16 signal), operator action is always necessary to prevent containment bypass; automatic actuation may not provide any benefit but does introduce some concerns, and (4) N-16 monitoring may provide better diagnostics and should be evaluated.
ABB-CE's presention included discussions of single and multiple tube rupture transients with graphs reflecting anticipated plant response over time, a survcj of anticipated plant response to design basis transients, and the bases for the evaluation.
The staff asked ABB-CE to describe what the plant operators would have to do to isolate a faulted steam generator. The staff also described four main options to resolve the issue. The options include: (1) a passive cooler on the secondary side (Swiss have adopted), (2) increase setpoints of secondary safety valves (French have adopted), (3) main steam N-16 automatic protection, and (4) secondary safety valve discharge back into containment.
The staff also summarized the additional concerns on this issue. The staff stated that it is difficult to believe the probabilistic risk assessment (PRA) l numbers presented by ABB-CE (10-8 4- 10 ), especially 4 since it is widely I accepted that the probability of a SGTR is about 10 per reactor year, and j this event requires significant operator action. It was stated that the staff I
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August 19, 1993 believes that the uncertainties in the SGTR PRA event tree are very large.
The staff would like ABB-CE to do a systematic assessment of the event and to look at all challenges to MSSVs, not just those recommended by the NRC.
The staff asked ABB-CE how long it would take to challenge MSSVs if the plant responded as designed and no operators took any action. The staff added that event mitigation places too puch reliance on operator action, combined with the fact that there is a 10~ probability of a bypass event (although there is no source term to cause a concern).
ABB-CE acknowledged the staff's concerns and c.,mmitted to perform the following PRA analyses for a five tube SGTR event: (1) assume the plant responds as designed, but operators take no action, (2) assume the plant responds as designed, but operator decisions are incorrect, and (3) determine how long there is for operator action at each decision point. They also committed to perform a thorough review of all potential design changes. All parties agreed to hold another meeting on August 16, 1993, to attempt to resolve the issue.
(Original signed by)
Stewart L. Magruder, Project Manager Standardization Project Directorate Associate Directorate for Advanced Reactors and License Renewal Office of Nuclear Reactor Regulation
Enclosures:
As stated cc w/ enclosures:
See next page DISTRIBUTION w/ enclosures:
Docket File PDST R/F DCrutchfield PShea PDR MFranovich TWambach GBagchi, 7H15 SMagruder TEssig Dis 1ribution w/o enclosures:
TMurley/FMiraglia RBorchardt JMoore, 15B1.8 WBeckner, 10E4 RJones, 8E23 AThadani, 8E2 SAli, 7H15 MRubin, 8E23 JStrosnider, 7D4 ACRS (11) GGrant, 17G21 g/w 0FC: LA:PDST:ADAR / PiPDST:ADAR SC:PDST:ADAR NAME: PSheapjJ DATE:
fSMagruder:tz TEssig ^I$
08/qf93 08//f/93 08//'t /93 f 0FFICIAL RECORD COPY: DOCUMENT NAME: MSUM0805.SLM I
I ABB-Combustion Engineering, Inc. Docket No.52-002 cc: Mr. C. B. Brinkman, Acting Director Nuclear Systems Licensing ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Windsor, Connecticut 06095-0500 Mr. C. B. Brinkman, Manager Washington Nuclear Operations ABB-Combustion Engineering, Inc.
12300 Twinbrook Parkway, Suite 330 Rockville, Maryland 20852 Mr. Stan Ritterbusch Nuclear Systems Licensing ABB-Combustion Engineering, Inc. i 1000 Prospect Hill Road Post Office Box 500 -
Windsor, Connecticut 06095-0500 Mr. Sterling Franks U.S. Department of Energy NE-42 Washington, D.C. 20585 Mr. Steve Goldberg Budget Examiner 725 17th Street, N.W.
Washington, D.C. 20503 Mr. Raymond Ng 1776 Eye Street, N.W.
Suite 300
- - Washington, D.C. 20006 Joseph R. Egan, Esquire Shaw, Pittman, Pott: & Trowbridge 2300 N Street, N.W.
Washington, D.C. 20037-1128 Mr. Regis A. Matzie, Vice President Nuclear Systems Development ABB-Combustion Engineering, Inc.
1000 Prospect Hill Road Post Office Box 500 Windsor, Connecticut 06095-0500
ABB-CE SYSTEM 80+
SGTR/ CONTAINMENT BYPASS MEETING ATTENDEES August 5, 1993 Name Orqanization NRC Mail Stoo R. Matzie ABB-CE J. Longo ABB-CE F. Carpentino ABB-CE W. Beckner NRC 10E4 R. Jones NRC 8E23 A. Thadani NRC 8E2 '
S. Ali fMC 7H15 M. Rubin NRC 8E23 J. Strosnider NRC 704 S. Magruder NRC 11H3 39 #
Enclosure 1
SGTR/ CONTAINMENT BYPASS AUGUST 5, 1993
+. .
Enclosure 2
l PURPOSE OF MEETING DISCUSS STAFFS CONTAINMENT BYPASS CONCERNS AND TO ARRIVE AT A CONSENSUS FOR CLOSURE THAT HAS CLEAR AND ACHIEVABLE ACCEPTANCE CRITERIA A FOCUSED DIRECTION LEADING TO ,
RAPID CLOSURE WITH MINIMUM EXPENDITURE OF RESOURCES k
SUMMARY
ABB-CE EVALUATION SHOWS THAT o WITH REACTOR CUTBACK AND STEAM BYPASS SYSTEMS OPERATING, THE SAFETY VALVES ARE NOT CHALLENGED EXCEPT FOR LOCV AND MSIV CLOSURE.
o FOR SEVERE ACCIDENT SCENARIOS WITH SGTR OCCURRING ALONG WITH SEVERE CORE DAMAGE; THE PROBABILITY OF CONTAINMENT BYPASS IS QUITE LOW
< 10^8 AND ALMOST INDEPENDENT OF SECONDARY SIDE FIXES.
o FOR PRIMARY SIDE FIXES (AUTOMATIC DEPRESSURIZATION BY N-16 SIGNAL), OPERATOR ACTION IS ALWAYS NECESSARY TO PREVENT CONTAINMENT BYPASS. ,*, AUTOMATIC ACTUATION DOES NOT PROVIDE ANY BENEFIT BUT DOES INTRODUCE SOME CONCERNS.
o N-16 MONITORING MAY PROVIDE BETT5R DIAGNOSTICS AND SHOULD BE LOOKED AT.
OUTLINE I. SINGLE & MULTIPLE TUBE RUPTURE TRANSIENTS II. SURVEY OF DESIGN BASIS TRANSIENTS MSSV ACTUATIONS IN CHAPTER 15 MSSV ACTUATIONS BASED ON REALISTIC CONDITIONS SEQUENCE FREQUENCIES FOR EVENTS +
MSSV FAILURES + CORE DAMAGE WITH -
ASSUMED TUBE RUPTURES STEAM LINE BREAK AND ATWS WITH ASSUMED TUBE RUPTURES SEVERE ACCIDENT SCENARIOS WITH POTENTIAL CREEP FAILURE OF TUBES III. BASES FOR EVALUATION CURRENT FEATURES POTENTIAL ADVANCED FEATURES:
ADVANTAGES VS. DISADVANTAGES -
I. CHAPTER 15
- SINGLE SGTR ANALYSIS RESULTS -
ASSUMES:
LOSS OF OFFSITE POWER NO NSSS CONTROLS OPERATE ATMOSPHERIC DUMP STICKS OPEN (FOR 30 MINUTES)
NO PRESSURIZER SPRAYS
I i
I l
2500 j ; ; ,
j OPERATOR TAKES CONTROL OF PLANT OPENS ONE ADV IN EACH SG St FLOW INITIATED TO RCS !
2000 -
EMERGENCY FEEDWATER FLOW TO AFFECTED SG -
ISOLATED, OPERATOR ATTEMPTS TO CLOSE ADV OPERATOR CLOSES BLOCK VALVE ON STUCK OPEN ADV ,
5 '
y OPERATOR INITIATES PRES 3URIZER VENT FLOW i
. 1500 -
4
\
h o OPERATOR CONTROLS PRESSURIZER VENT FLOW, BACKUP PRESSURIZER
$ HEATER OUTPUT, AND St FLOW IN t j( ORDER TO KEEP THE RCS 20*F SUBCOOLED l
g 1000 -
I 500 - -
1 i
)
l RCS REACHES SHUTDOWN _
COOLING ENTRY CONDITIONS-.
O I I ! ! !
O 5,000 10,000 15,000 20,000 25,000 ~30,000 l 1
TifAE, SECONDS
- THIS PRESSURE DOES NOT INCLUDE THE PRESSURE DIFFERENCE BETWEEN THE COLD LEG AT RCP DISCHARGE AND THE SURGE LINE i
i w STEAfA GENERATO11 TUBE RUPTURE WITH LOSS OF d b f[ / OFFSITE POWER AND A STUCK OPEN ADV REACTOR COOLANT SYSTEfd PRESSURE vs T!!aE l-I I
1*-**he~ ,
m e*-
65 l 1 I l 1 600 -
'\
550 HOT LEG f
t uI 5
ti a 500 -
2 N
! \
8 450 -
O 8
y \1 400 -
350 -
300 !
O 5,000 10,000 15,000 20,000 25,000 30,000 TIME, SECONDS l w CTEAM GENERATOR TUBE RUPTURE WITH LOSS OF I
OFFSITE POWER AND A STUCK OPEN ADV
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REACTOR COOLANT TEMPERATURES vs TIME '
- ~ . _. - . - _ _ _ _ . . . . . . _ . . __ ___ .. .... _ .,___ ,._, _
1400 -- -- -
1200 -
g -
r l
1000- -
S E
N
$ 800-- -
\
f .FFECTED f
= \
P i I
E ! L 5 'O Z 600l-
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w 0 \<
2 U
u) ,.
400 -
\ -
A'\ /
h Uf4AFFECTED
/ ~ - -
0 ! ! ! I O 5,000 10,000 15,000 20,000 25,000 30,000 TIME, SECOf40S
- v. STEAM GEf4ERATOR TUBE RUPTURE WITH LOSS OF l
/ 1 OFFSITE POWER Af40 A STUCK OPEf4 ADV NNN[ / '
STEAM GENERATOR PRESSURES vs TIME
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REALISTIC ANALYSIS OF FIVE SG TUBES RUPTURED ASSUMES:
NORMAL AC POWER NSSS CONTROLS OPERATE (STEAM BYPASS)
RCPs MANUALLY TRIPPED (ELIMINATES MAIN PZR SPRAY)
AUXILIARY PZR SPRAY OPERATES d
SYS~~E V 80 V L'LT PLE SGTR 5 TUBES IN ONE SG - NONE IN OTHER 2500
\
2000 4 REACTOR TRIP TURBINE TRIP
^
( 'N 'SBCS ACTUATED H
Z 1500 N h M
p I w
w N
h 1000 -
% v w
U
~
500 -
I I ! I ' ' ' I 0 I I 0 1 2 3 4 5 6 7 8 9 10 11 Thousands TIME (SEC)
. i SYSTEM 00 V JLTIPLE SGTR :
' 5 TUBES IN ONE SG - NONE IN OTHER f 650 h
m :
~
O i
600 - i NSECS ACTUATED b/ ,
N M
p 550 - ;
b - '
N 3 !
N \
j h 4 500 -
i m ,
H i I
C 450 -
i
-l j
.. A -
400 -
U3 U .'
t M -i 350 I ' I I ' I I I I ' i 0 1 2 3 4 5 6 7 8 9 10. 11 Thousands i TIME (SEC) I 1
l
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. SYSTEM 80+ MULTIPLE SGTR S TUBES IN ONE SG - NONE IN OTHER 1200 SBCS ACTUATED 1000
\/
TURBINE TRIP REACTOR TRIP n 900 -
W 800 v . . -
700 -
v i
Q t]
1 !
w g 600 -
\
500 4 -
400 -
~'
- l. .
200 - 1 100 O 1 2 3 4 5 6 7 8 9 10 11 Thousands l TIME (SEC) l
_ _ - - - - - - - _ - - - - _ - - - - - - - _ - - - - - - _ - - _ - - - - - - - - - - - - - - - - - - - - - - - - -- u
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SEQUENCE OF EVENTS FOR SGTR EVENT CASE #1 CASE #2 i CHAPTER 15 REALISTIC ONE TUBE FIVE 'IUBES EVENT / TIMING (SECONDS) RUPTURED RUPTURED i TUBE RUPTURES 0 0 :
REACTOR TRIPS 0.44 154 TURBINE TRIPS 0.55 155 i LOSS OF OFFSITE POWER 3.55 NONE MSSVs OPEN 5.4 NONE STEAM BYPASS OPENS NONE 170 ;
SAFETY INJECTION ACTUATED 1455 175 ,
~~
AUXILIARY FEEDWATER 1527 185 l ACTUATED !
OPERATOR INITIATES PLANT 1800 1200 i COOLDOWN l SHUTDOWN COOLING ENTRY 28800 12000 CONDIT7 1S REACHED :
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RESULTS OF MULTIPLE SGTR h
REALISTIC ANALYSES SHOW MSSVs ARE NOT ACTUATED :
WHEN MORE THAN 5 SG TUBES ARE RUPTURED. IT IS ,
l ESTIMATED THAT APPROXIMATELY 200 TUBES CAN RUPTURE WITHOUT OPENING THE MSSVs.
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- n. DESIGN BASIS TRANSIENTS AND ACCIDENTS THAT RESULT IN MSSV OPENING TRANSIENT SINGLE FAILURES LOSS OF CONDENSER VACUUM (No Cutback, No Bypass)
TURBINE TRIP (Loss of Offsite Power, LOOP)
LOOP -
(No TG Runback to House Load)
SGTR (LOOP, No Aux Spray) t LOSS OF FEEDWATER (LOOP)
LOCKED RCP ROTOR (LOOP, No TG Runback)
~ ~
PLCS MALFUNCTION (LOOP) _. _
CLOSURE OF ALL MSIVs --
I
4 TRANSIENTS FOR WHICH THE MSSVs OPEN UNDER REALISTIC
- CONDITIONS e LOSS OF CONDENSER VACUUM b
Occurrence Frequency = 0.027 per year
- SPURIOUS CLOSURE OF ALL MSIVs Occurrence Frequency = 0.006 per year Credits NSSS Control System Operation (Auto Steam Bypass and Rx Power Cutback) i e
i 0
- v. -,-,.-- --n.. r,. e ,, .-n-,-m .--n---, v w ,.,w~ , .,. . - +e , v --- --- , - - - - - . . - . -- - ----+ -- - -- - - - - - . . - - - - - -
CONTAINMENT BYPASS SCENARIOS INVOLVING ASSUMED TUBE RUPTURES & SIGNIFICANT CORE DAMAGE -
e S = (Transient)(MSSVs Lift)(Assumed SG Tube Rupture)(Safety injection Fails)(Aggressive Secondary Cooldown or SCS Injection Fails)(MSSV Fails to Rescat)
- ELEMENT OCCURRENCE FREQUENCIES:
(Assumed SG Tube Rupture) = 0.01 per demand (Safety Injection Fails)(Aggressive Secondary Cooldown or SCS Injection Fails)
= 6.4E-05 { Based on SGTR-16 and SGTR-17}
(MSSV Fails to Rescat) = 6.0E-02 per demand { Based on Failure to Isolate Ruptured SG (MSSVs Open) = 1.0 for specified initiators
- SEQUENCE FREQUENCIES St ocy = 1.0E-09 per year Susiv, = 2.3E-10 per year i
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_------_---._-_--s. - = . _ - - . -a - - -+ -. . . . - .- -- - , - - - -- - . _ - - - , , - - - - -- - -- - w _- - - _ ---- _ _ , -- - - - _ _ _ --- .-----a
i OTHER CONTAINMENT BYPASS SEQUENCES INVOLVING ASSUMED STEAM GENERATOR TUBE RUPTURES &
SIGNIFICANT CORE DAMAGE e S = (Steam Line Break)(Assumed Tube Rupture)(High Pressure Injection Fails)(Aggressive Secondary Cooldown or SCS Injection Fails)(Failure To Isolate Bad SG)
I e ADDITIONAL ELEMENT FREQUENCIES (Steam Line Break) = 1.5E-03 per year (Failure to Isolate Bad SG) = 1.0 per demand
- conservative assumption ,
- encompasses SLB upstream of MSIVs and failure of MSSVs or ADVs to rescat.
- SEQUENCE FREQUENCY FOR STEAM LINE BREAK Sstu = 8.2-10 per year
- ATWS WITII ASSUMED STEAM GENERATOR TUBE RUPTURE ATWS Sequences ATWS-13 through ATWS-24 Core Damage Frequency Contribution = 4.6E-10 per year With Failure to Isolate, Total Sequence Frequency Becomes 2.7E-11 per year 4
SEVERE ACCIDENT SCENARIOS WITH POTENTIAL CREEP FAILURE OF STEAM GENERATOR TUBES
- SEVERE ACCIDENT SCENARIO RCS Pressure at PSV Setpoint at Onset of Core Damage RCS not Depressurized by Rapid Depressurization Valves RCS Hot Legs and Surge Line Remain Intact One or More SG Tubes Fail Due to High Temperature Creep Rupture EIGHT HIGH PRESSURE SEQUENCES Total Core Damage Frequency Contribution = 5.4E-07 ELEMENT FREQUENCIES (RCS not Depressurized by RDVs) = 0.2 per demand (RCS Hot Legs and Surge Line Remain Intact) = 0.35 per demand (One or More SG Tubes Fail due to Iligh Temperature Creep Rupture) = 0.014 TOTAL SCENARIO FREQUENCY = 5.3E-10 per year e
-. m _ . . _ , _ _ _ . , - - - - ._ _ ._ _ . . _. _ - . _ _ _ .-- _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _
BASES FOR EVA_L_UATION
- 1. USE OF NON-SAFETY SYSTEMS (includes AC power &
controlsystems)
- 2. USE OF PROBABILITY TO LIMIT SCENARIOS (scenarios greater than 10-8)
- 3. BEST ESTIMATE ANALYSES (includes use of design codes &
initial conditions)
- 4. EVENTS CAUSING DIFFERENTIAL PRESSURE EQUAL TO OR GREATER THAN THE DIFFERENCE OF PRIMARY SYSTEM DESIGN PRESSURE AND NORMAL OPERA'fING SECONDARY PRESSURE 1
1
,, ~ , -
n-- - , ~ -- -- -, __ _. _ . - - .
SECONDARY STEAM RELIEF TYPE: SAFETY VALVES ATMOSPHERIC TURBINE DUMP VALVES BYPASS VALVES QUANTITY: 10 PER SG 2 PER SG 8 TOTAL MINIMUM 107.7% 5.4% 55% TOTAL CAPACITY: MSR MSR PER VALVE MSR DISCHARGE: ATMOSPHERE ATMOSPHERE CONDENSER ISOLATION MOTOR OPERATED MSIV VALVE TYPE: NONE GATE VALVE i
- MSR - MAIN STEAM RATE (17,64 x 10' lbm/hr) .
0
.m_ -__.__ _ _ _ _ _ _ _ _ _ _ _ ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ----. _ _ ._ _ _ . , _ _____________s_ - m -_ _ . _ _ _ _ ____ _ _ . _ _ _ _- _______ _______ ____.______ _ __.
i
- 1 e
POTENTIAL ADVANCED DESIGN FEATURES
- 1. PASSIVE COOLER ON SECONDARY SIDE
- 2. INCREASE SETPOINTS OF SECONDARY SAFETY VALVES
- 3. MAIN STEAM N-16 AUTOMATIC PROTECTION
- 4. SECONDARY SAFETY VALVE DISCHARGE INTO CONTAINMENT i
1 e
_____-_______.___.___________.-______________u____._ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ . _ _ _ _ m e _ _ --_ _ - . __ _-- _. _ -.,4
.c PASSIVE CO_O_L_ER Q_N SECONDARY SIDE ADVANTAGES DIEADVANTAGES MINIMIZES RELEASE BECOMES FIRST OF A KIND IN TO ATMOSPHERE DESIGN AND OPERATION ADDS COMPLEXITY TO THE DESIGN AND MAINTENANCE REQUIRES INCREASED BUILDING SPACE INCREASES CONTAINMENT HEAT REMOVAL REQUIREMENTS (NORMAL &
ACCIDENT) i INCREASES STEAM LEAKAGE DOES NOT REDUCE RISK OF OFF-SITE DOSE VIA SGTR
., _.r 1..,_.... ..- _ . - . . _ . ,_-.._-...-m._. -
e INCREASE SETPOINTS OF SECONDARY SAFET_IES ADVANTAGES DISADVANTAGES DELAYS OR MINIMIZES INCREASES SECONDARY RELEASE TO ATMOSPHERE DESIGN PRESSURE INCREASES SG WEIGHT BY OVER 100 TONS IF DESIGNED TO 1500 PSI ADDS COMPLEXITY TO SG SUPPORT SYSTEM INCREASES STORED ENERGY TO CONTRIBUTION IN PRIMARY HEAT REMOVAL EVENTS i
INCREASES TURBINE & RELATED SYSTEMS DESIGN PRESSURE INCREASES FW & RELATED SYSTEMS DESIGN PRESSURE
- - ~ _ . - - . - .- . _ _ _ _ _ _
INCREASE SETPOINTS OF SECONDARY SAFETIES (Cont ' d)_ '
ADVANTAGES DISADVANTAGES _
BECOMES A FIRST OF KIND IN DESIGN & OPERATION REDUCES SMALL LOCA PERFORMANCE CHALLENGES PRIMARY SYSTEM SAFETIES (LOCV)
DOES NOT REDUCE RISK OF OFF-SITE DOSE VIA SGTR i
e i
--____.---_--_._.-------.---------x - - . - - - - - e--a-,+--, -, ,r- , -- , - - -
i -
MAIN STEAM N-16 AUTOM_ATIC PRO _TECTION ADVANTAGES DISADVANTAGES _
LESS CONTAINMENT INCREASES THE FREQUENCY OF BYPASS INADVERTENT PRIMARY SYSTEM DEPRESSURIZATION AND INITIATION OF THE SAFEGUARD SYSTEMS MINIMIZE RELEASE REDUCES SUBCOOL MARGIN TO ATMOSPHERE INTRODUCES DESIGN COMPLEXITY N-16 MONITORING EXPOSES COMPONENTS AND FACILITATES STRUCTURES TO ADDITIONAL IDENTIFICATION i TEMPERATURE TRANSIENTS OF SG WITH RUPTURED TUBE INCREASES POTENTIAL FOR DNBR VIOLATIONS FOLLOWING SGTR 4
_ _ . _ _ _ _ _ _ _ . _ . _ _ _ _ _ _ _ . . . _ _ . _ . - _ _ . . . _ . . _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _._.___m.___._ _- _ _ _ _ _ _ . ,_ _ . , - . . . e>. --
MAIN STEAM N-16 AUTOMATIC _ PROTECTION (Cont'dl ADVANTAGES DISADVANTAGES INCREASES LOCA PROBABILITY IF THE RAPID DEPRESSURIZATION SYSTEM IS USED INCREASES RISK FOR BORON DILUTION DOES NOT REDUCE RISK OF OFF-SITE i
DOSE VIA SGTR i
k
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.~
S_ECONDARY SAFETY VALVE D_I_SCHARGE INTO CONTAINMENT ADVANTAGES DISADVANTAGE _S MINIMIZES RELEASE ADDITIONAL CONTAINMENT TO ATMOSPHERE PENETRATIONS DILUTION OF IRWST BORON CONCENTRATION AND INCREASE OF IRWST LOADING POTENTIAL INCREASE TO POST ACCIDENT CONTAINMENT P/T TRANSIENTS REQUIRES SAFETY VALVE OF AN i
UNPROVEN DESIGN INCREASES HVAC LOADING INSIDE CONTAINMENT DOES NOT REDUCE RISK OF OFF-SITE DOES VIA SGTR
.-w., _ ,a- - .-- ,-. -,~.- - . - . . - - - , . . - - . . . . . . , . ~ - - . - . , - - , - ~ . - . _ . . - - - - . . - - - . , . -- , . - _ - - - . . _ _ . . _ . - - . . . .
MSSV(5) l f ATMOS ATMOS l ADV jg-,SOCS
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f s y3;y3 TURBlitE *- -
Q 4
l z BYPASS ATMOS ATMOS , . VALVES STEAM ! t, GEN l ': ADV
-* i
\ / l MSSV(5)
SBCS-@ -*
TURB CONDENSER
-~*
MSSV(5) SBCS --@
sL6 : 9 Q A- ,SBCS l zfATMOS ATMOS TURBINE RV 'u l ADV O BYPASS
--l- X VALVES PZR IOF -SBCS l
' n -
/ N I
% MAIN MSIVs v l z SEAM
(/ STEAM l s ATMOS ATMOS EQUALIZATION GEN ; Q ADV HEADER MSSV(5)
INSIDE l OUTSIDE CONT ' CONT M i SYSTEM 80+ TURBINE BYPASS SYSTEM ,
TURBINE BYPASS SYSTEM DESCRIPTION: TURBINE BYPASS VALVES - MIN. CAPACITY 55 PERCENT MSR STEAM BYPASS CONTROL SYSTEM FUNCTIONS:
- ACCOMMODATE ANY LOAD REJECTION WITHOUT TRIPPING REACTOR OR LIFTING PRIMARY OR SECONDARY SAFETY VALVES (IN CONJUNCTION WITH REACTOR POWER CUTBACK SYSTEM)
- CONTROL NSSS THERMAL CONDITIONS TO PREVENT OPENING SAFETY VALVES FOLLOWING A UNIT TRIP
- MAINTAIN NSSS AT' HOT ZERO POWER CONDITIONS
, - - . . . - - --.-n,--s -,-,n-------s - - - - --se-,v-~v.--<- ~--*,~e~- - --,v-s.- . . - - - ~ - -e n ~---- -------~~-v - - ~ ~ - -- - - - - - - - - - - - - - - - - - - - - - - - - - -
r.
MEASURED MAIN '
STEAM HEADER // AIR SUPPLY PRESSURE (ACTUAL)
ATMOSPHERE STEAM V A R*
MAIN STEAM 1+ .
MODULA T10N l H R
> p E
> ONEOLLB - E 9_I S - - - _ ^ + ! W
R PROGRAM A + NOTE 1 (EXPECTED) S S i ,
PRESSURIZER !'
PRESSURE !' -
STEAM FLOW BIAS QUICK OPENING SIGNAL l -FC
~"""~~~~~~~~~""~"~" l
__ ) CHANGE DETECTOR
- - - - > - TO REACTOR POWER l A CUTBACK SYSTEM l (TWCAL)
THRESHOLD SETTINGS STEAM FLOW VALVE PE ', MISSIVE )'
& SIGNAL STEAM PRESSURE = VALVE PERMISSIVE _______________________j PZR PRESSURE r SIGNALS LOGIC (NOTE 2)
SYSTEM 80+ STEAM BYPASS CONTROL SYSTEM (SIMPLIFIED)
DESCRIPT10N: CONTROLS TURBINE BYPASS VALVES.
MODULATION:
- MEASURE STEAM FLOW, CAlpVLATE EXPECTED STEAM HEADER PRESSURE THRESHOLD
- COMPARE EXPECTED AND MEASURED STEAM PRESSURE
- IF MEASURED > EXPECTED PRESSURE THRESHOLD, MODULATE OPEN ONE OR MORE TBVs
- BIAS FOR PRESSURIZER PRESSURE (DEVIATION FROM 2250 PSIA)
OUICK OPENING .
- MEASURE STEAM FLOW RATE OF CHANGE
- COMPARE WITH THRESHOLD
- IF THRESHOLD EXCEEDED, QUICK OPEN TBVs IN TWO GROUPS OF FOUR NOTES: 1. SOLEN 0ID OPERATED VALVES SHOWN IN DE-ENERGlZED POSITION.
- 2. SIMILAR TO LOGIC ABOVE. SEPARATE, PARALLEL CONTROLAND PERMISSIVE SIGNAL PATHS ARE PROVIDED FOR INADVERTANT OPENING CONCERNS.
-- . , . - - . . . .. - ,. . . - . - . . - .. - _ _.____ - _ . _ . _ _ - _ . - - _ _ - . _ - _ _ _ - _ - _ - _ - _ _ _ _ .