ML16342C195
| ML16342C195 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 12/10/1987 |
| From: | Trammell C Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8712240187 | |
| Download: ML16342C195 (66) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 DEC 10 lg87 Docket No. 50-275, 50-323 LICENSEE:
FACILITY:
SUBJECT:
Pacific Gas
& Electric Company (PG&E)
Diablo Canyon Nuclear Power Plant, Unit Nos. I and 2
SUMMARY
OF MEETING HELD ON DECEMBER 8, 1987 TO DISCUSS PROPOSED REMOVAL OF AUTOCLOSURE INTERLOCK ON RESIDUAL HEAT REMOVAL LET-DOWN VALVES On December 8, 1987, the NRC staff met with representatives of PG&E and Westinghouse Electric Corporation to discuss PG&E's proposal to remove the automatic closure for the residual heat removal system high/low pressure interface valves 8701 and 8702.
Attendees are listed in Enclosure
( I), the meeting agenda is shown in Enclosure (2), and the viewgraphs presented at the meeting are shown in Enclosure (3).
The RHR system design at Diablo Canyon has automatic closure of valves 8701 and 8702 on rising pressure.
The purpose is to assure that both valves are closed during normal operation.
Because the design is "fail-safe," these valves also close automatically on power supply transients.
This has resulted in the RHR pumps running with these suction valves closed.
In one case in
- 1983, an RHR pump ran for one hour with the suction valves shut, resulting in damage to the pump shaft and seal.
PG&E proposes to eliminate the autoclosure feature and provide an alarm on each valve instead to alert the operator to the abnormal configuration during operation (a valve not fully closed) and modify the valve position indication power supply such that indication would be available even when the circuit breakers for the valve motors are racked out.
At the conclusion of the meeting, the NRC staff stated that it was generally satisfied with the PG&E proposal, subject to additional consideration of the information presented.
We also requested PG&E to consider the following:
a.
At about 450 psig, confirm that the alarms are clear and that the status lights show the valves to be closed.
Also discuss appropriate surveillance of alarms to verify that they are operable.
b.
Remove power to the valves before conducting the leak test of both valves required by technical specification 4.4.6.2.2.
This would provide added assurance that the valves remain closed after a successful leak test.
c.
Provide additional substantiation that the valves are not capable of being opened under high differential pressure.
8712240187'71210 PDR
--ADOCK 05000275 I
PDR ,
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The NRC staff will contact the licensee in a few days to finally establish what additional information will need to be submitted to complete the review.
A Safety Evaluation issuance date of January 1988 appears to be achievable.
Charles M. Trammell, Project Manager Project Directorate V
Division of Reactor Projects - III, IV, V and Special Projects
Enclosures:
1.
Attendees 2.
Agenda 3.
Yiewgraphs cc:
See next page OFC:
DV NAME rammell DATE: 12
/87
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0ISTRIBUTION~ (Neet tag Summary)
NRC B Local PORs PD5 Reading DCrutchfield GHolahan GKnighton Et)ordan JPartlow Project Manager NRC Participants ACRS (10)
OGC-Mhite Flint Licensee Service List (see next page)
~
'C
Nr. J.
D. Shiffer Pacific Gas and Electric Company Diablo Canyon CC:
Richard F. Locke, Esq.
Pacific Gas 8 Electric Company Post Office Box 7442 San Francisco, California 94120 Janice E. Kerr, Esq.
California Public Utilities Commission 350 McAllister Street San Francisco, California 94102 Ms. Sandra A. Silver 660 Granite Creek Road Santa Cruz, California 95065 Nr.
W. C. Ganaloff Westinghouse Electric Corporation P. 0.
Box 355 Pittsburgh, Pennsylvania 15230 Managing Editor San Luis Obispo County Telegram Tribune 1321 Johnson Avenue P. 0.
Box ]12 San Luis Obispo, California 93406 Nr. Leland N. Gustafson, Manager Federal Relations Pacific Gas and Electric Company 1726 N Street, N.
W.
Washington, DC 20036-4502 Dian N. Grueneich Marcia Preston Lavi Office of Dian N. Grueneich 380 Hayes Street, Suite 4
San Francisco, California 94102 NRC Resident Inspector Diablo Canyon Nuclear Power Plant c/o U.S. Nuclear Regulatory Commissior P. 0.
Box 369 Avila Beach, California 93424 Nr. Dick Blakenturg Editor E Co-Publisher South County Publishing Company P. 0.
Box 460 Arroyo Grande, California 93420 Bruce Norton, Esq.
c/o Richard F. Locke, Esq.
Pacific Gas and Electric Company Post Office Box 7442 San Francisco, California 94120 Dr. R. B. Ferguson Sierra Club - Santa Lucia Chapter Rocky Canyon Star Route Creston, California 93432 Chairman San Luis Obispo County Board of Supervisors Room 220 County Courthouse Annex San Luis Obispo, California 93<01 Director Energy Facilities Siting Division Energy Resources Conservation ard Development Commission ibl6 9th Street Sacramento, Ca'ifornia 9:F14 Ps.
Jacquelyn Wheeler 3033 Barranca Court San Luis Obispo, California 93401
Pacific Gas
- 8. Electric Company 2 -
Diablo Canyon CC:
Hs. Laurie Hc0emott, Coordinator Consumers Organized for Defense of Environmental Safety 731 Pacific Street, Suite 42 San Luis Obispo, California 9"401 Hr. Joseph 0.
Ward, Chief Radiological Hea'lth Branch State Department of Health Services 714 P Street, Office Building P8 Sacramento, California 95814 Regional Aomini s tra tor, Region V
U.S. Nuclear Regulatory Commission 1450 Haria Lane Suite 210 Walnut Creek, California 94596 Hs.
Nancy Culver 192 Luneta Street San Luis Obispo, California 93401 President California Public Utilities Commission California State Building 350.HcAllister Street San Francisco, California 94102 H>chael H. Strum:asser, Eso.
Special Assistant Attorney General State of California Department of Justice 3580 Wilshire Boulevard, Room 800 Los Angeles, California 90010
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AGENDA FOR PG&E/NRC/WESTINGHOUSE MEETING DECEMBER 8, 1987 REMOVAL OF RHR AUTOCLOSURE INTERLOCKS I.
INTRODUCTION
- THE PURPOSE OF ACI REMOVAL
- RESULTS OF ANALYSES Lsv PG&El II. LOSS OF RESIDUAL HEAT REMOVAL ATTRIBUTED TO SPURIOUS ACI ACTUATION (ITEM 1 OF NRC LIST)
Lsv PG&El A.
PROBLEMS AT DIABLO CANYON B.
POTENTIAL REMEDIES (I~m 2 ot= NRC Lzs~)
III. ASSESSMENT OF EFFECT OF REMOVAL OF ACI ON PLANT SAFETY (Ivm 4 ot=
NRC Lxs~)
[BY WESTINGHOUSEl A.
SUMMARY
OF RESULTS B.
OVERVIEM OF WCAP-11117 C. DETAILS OF PROBABILISTIC ANALYSES (ZNctuoING ITEM 3 QF NRC LIST) 1V.
CLOSING REMARKS Lsv PG&El sLxoEs 11
SS OF RHR EVENTS DUE TO ACI ACTUATION from isolation elieving onsiders ACI ction valve closed during work on the solid state "tion system during pre-core loading startup testing 004 -
RHR pump ran for about 5 minutes with the RHR on valves shut with no damage.
ents 004 -
RHR pump seal damage and a slightly bowed occurred after one hour of pump operation with the RHR on valves shut.
stal 1 ed CI.
ld be applied w flow alarm 005 -
RHR flow was lost for approximately six es.
.-85-006 -
RHR flow was lost for approximately two
,'es.
require that GEE requested removed to emove power
!-86-002 RHR flow was lost for approximately 13
- es.
.-86-012 RHR flow was lost for approximately two
- es.
equirement to with power
?-87-011 -
RHR flow'as lost for approximately 5 minutes.
ider removal ie analysis and ACI.
.ion requested ect to ation
ALTERNATIVES TO REMOVAL OF THE RHR ACI FUNCTION
- Removal of power from the RHR hot leg suction valves.
- Remove the failsafe feature from the RHR autoclosure interlock.
Other hardware modifications
RESIDUAL HEAT REtviQVAL SYSTEM (SIMPLIFIED)
Cont ainmen t Recirc Sump CCW Spray CCP RWST RHR Pump A RHR Pump B Heat Ex CVCS L
t wn CW RCS Hot Legs 1 and 2 Heat Ex Containment Recirc Sump Spray SIP
MR S't(@TEM ~ line damager gP Q2 CP le 0$3$
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- SYSTEM, CCM beeon.Heat TaAaneer T1-12T HCT-133 TCT 130 TE-130 IIC li9 I
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TCT-II9 8117 4152 a
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1-2 Oo~lns Alterna to Char9Inb Lacy 3 Noreel Charblny Loop I PIA Ana Sbray bill blli 81IS
~li8 8181
~IIN TT II2 FT-I28 f
I TCT LT-112 LCT-II24 LCT-112C Cation baaalns N-li2 FCT 128
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8148 bCT Seal Injection FIC-9I9 Col ~ Le9 1nJec tIon 880 IA bnf 0A 88108 4IT FT-917 f
1-2 Seel Heter Heat Igshenber Io2 beberetlnb Oenlns 88014 491 I 8104 blOS frcaa 4A Trans fertuaers Seal Return
r w
M ARY F
E THE RESULTS OF THE ANALYSIS OF THE REMOVAL OF THE ACI PLUS THE ADDITION OF A VALVE-NOT-FULL-CLOSED SIGNAL IN CONDUCTION MITH A HIGH RCS PRESSURE SIGNAL ARE THE FOLLOWING:
1)
RHR SYSTEM UNAVAILABILITYIS ED ED:
RHR INITIATION -
NO CHANGES SHORT TERM COOLING - 62%
IMPROVEMENT LONG TERM COOLING - 31<
IMPROVEMENT 2)
INTERFACING SYSTEM LOCA (V-SEQUENCE LOCA)
FREQUENCY IS REDUCED 7~0 3)
OVERPRESSURE FREQUENCIES ARE INCREASED BUT REMAIN E L I (ABOUT 1.0E-12 /YR)
THE RESULTS CLEARLY SHOW THE PROPOSED MODIFICATION IS AN IMPROVEMENT TO PLANT SAFETY.
SLIDES 1
OVERVIEW OF MCAP-11117 PURPO E A D OBJECTIVES THE REPORT PROVIDES A QUANTITATIVE BASIS FOR THE MODIFICATION OF THE DIABLO CANYON UNITS 1 AND 2 RHR SUCTION ISOLATION VALVES TO REMOVE THE ACI FEATURE.
THE REASON FOR REMOVING THE ACI IS TO PREVENT THE LOSS OF DECAY HEAT REMOVAL CAPABILITY DURING SHUTDOWN AND REFUELING OPERATIONS CAUSED BY FALSE SIGNALS, DEENERGIZATION OF POWER BUSES AND VARIOUS TESTING ERRORS THAT RESULT IN ACI ACTUATION.
IN ADDITION TO THE ORIGINAL CONFIGURATION, TMO MODIFICATIONS TO THE RHR SUCTION ISOLATION VALVES WERE EVALUATED AND REPORTED IN THE MCAP:
1)
ACI REMOVED AND ALARMS FOR HIGH RCS PRESSURE AND VALVE-NOT-FULL-CLOSED ADDED.
2)
ACI REMOVED AND A SINGLE SWITCH TO CLOSE BOTH VALVES ADDED (BASED ON NRC SUGGESTIONS).
SLIDES 2
OVERVIEW OF MCAP-11117 RP E
D BE INFORMATION REQUESTED BY NRC TO COMPLETE ACI REMOVAL EVALUATION (NRC LETTER DATED 1/23/85, KNIGHTON TO SHIFFER):
1.
MEANS AVAILABLETO MINIMIZEA LOCA OUTSIDE CONTAINMENT.
- INTERFACING SYSTEMS LOCA PROBABILITY REDUCED.
2.
ALARMS TO ALERT THE OPERATOR OF AN IMPROPERLY POSITIONED RHR ISOLATION VALVE.
- VALVE-NOT-FULL-CLOSEDALARM WITH HIGH RCS PRESSURE ALARM.
3.
VERIFICATION OF THE ADEQUACY OF RHR RELIEF VALVE CAPACITY.
- VERIFICATION PROVIDED.
.4.
MEANS OTHER THAN ACI TO ENSURE BOTH ISOLATION VALVES ARE CLOSED
- ENHANCED OPERATING PROCEDURES, REDUNDANT VALVE POSITION INDICATION AND ALARMS.
SLIDES 3
OVERVIEW OF WCAP-11117 PURPOSE A D OBJECTIVE c
=5.
ASSURANCE THAT THE OPEN PERMISSIVE CIRCUITRY IS NEITHER REMOVED OR AFFECTED BY THE PROPOSED CHANGE.
- THE OPEN PERMISSIVE CIRCUIT REMAINS INTACT.
6.
ASSURANCE THAT ISOLATION VALVE POSITION INDICATION WILL REMAIN AVAILABLEIN THE CONTROL ROOM REGARDLESS OF THE PROPOSED CHANGE.
- THE VALVE POSITION INDICATION REMAINS INTACT.
7.
ASSESSMENT OF THE EFFECT OF THE PROPOSED CHANGE ON RHRS AVAILABILITY,AS WELL AS LOW TEMPERATURE OVERPRESSURE PROTECTION.
RHRS AVAILABILITYIMPROVES
- LTOP EFFECTS ARE NEGLIGIBLE SLXOES 4
OVERVIEW OF WCAP-11117 HISTORICAL REVIEW OF LOS OF DECAY HEAT PROBLEMS THE AEOD REPORT (AEOD/C503, DATED 12/85)
AND NSAC/EPRI REPORT (NSAC/52, DATED 1/83)
PROVIDE ANALYSIS AND
SUMMARY
INFORMATION OF DOMESTIC PWR LOSS OF DECAY HEAT REMOVAL (DHR)
EVENTS BETWEEN 1976 AND 1981.
OF 130 LOSS OF DHR EVENTS EXAMINED BY AEOD, 37 OF THEM (THE MOST OF ANY SINGLE CATEGORY)
WERE CAUSED BY INADVERTANT ACI ACTUATION DUE TO PROCEDURAL INADEQUACIES AND/OR HUMAN ERROR.
MOST ERRORS WERE COMMITTED WHILE PERFORMING MAINTENANCE, TESTING OR REPAIR OPERATIONS DURING RHR OPERATION.
THE AEOD REPORT AND A REPORT BY SANDIA LABS (NUREG/CR-4335)
ANALYZED THE OPERATIONAL DATA AND PERFORMED A RISK ASSESSMENT, RESPECTIVELY, EXAMINING THE ISOLATION VALVE CLOSURES AND CAME TO THE SAME CONCLUSION RECOGNIZING REMOVAL OF THE ACI AS A SAFE, EFFECTIVE METHOD FOR PREVENTING SPURIOUS RHR ISOLATION.
stzoes 5
OVERVIEW OF MCAP-11117 LICENSI G BASI F ACI SECTION 3 OF WCAP-11117 GIVES A DETAILED ACCOUNT OF THE GENESIS AND EVOLUTION OF THE REGULATORY REQUIREMENTS FOR ACI ON THE RHR SUCTION ISOLATION VALVES.
1971 AEC REQUIRES INTERLOCK FOR AUTOMATIC CLOSURE ON PRESSURE.
74-76 IN SUPPORT OF RESAR-3 AND -41, WESTINGHOUSE PERFORMS ANALYSES THAT DEMONSTRATE ADEQUATELY SIZED RELIEF VALVES PROTECT RHR FROM OVERPRESSURE AND ACI IS NOT NEEDED.
1975 NRC PUBLISHES BTP ICSB-3 WHICH REQUIRES AUTOMATIC CLOSURE OF RHR ISOLATION VALVES WHEN PRIMARY PRESSURE EXCEEDS RHR DESIGN PRESSURE.
1977 WESTINGHOUSE TECH BULLETIN RECOMMENDS REMOVAL OF POWER FROM ISOLATION VALVE DURING REFUELING TO PREVENT SPURIOUS CLOSURE.
1977 ANS-56.3 PERMITS A CHOICE BETWEEN ACI OR ADEQUATE RELIEVING CAPABILITY.
sLEDEs 6
I
OVERVI84 OF WCAP-11117 I E I A I F
1981 NRC ISSUES SRP INCLUDING RSB 5-1 WHICH CONTAINS RHR PRESSURE RELIEF REQUIREMENTS AND REQUIRES ACI.
1984 NRC MEMO (DUNNING TO MATTSON, DATED 4/17/84)
RECSMNDS ACTION BE TAKEN TO PREVENT LOSS OF RHR FOLLOWING LOSS OF INSTRUMENT BUS AND NOTES THAT THE PURPOSE OF THE ACI NEEDS TO BE CLARIFIED.
1985 RSB RECNNENDS CAREFUL CONSIDERATION OF ANY RHR ISOLATION VALVE CONTROL CHANGES AND NOTES THAT EACH REQUEST SHOULD BE REVIEWED ON A CASE-BY-CASE BASIS WITH ACI REMOVAL ASSESSED AGAINST THE SEVEN ITEMS.
sLIDEs 7
OVERVIEW OF MCAP-11117 RHR SY TEM DESIGN A D OPERATION SECTION 4 OF L4CAP-11117 PROVIDES A DETAILED DISCUSSION OF THE DIABLO CANYON RHR SYSTEM.
A SYSTEM DESCRIPTION IS GIVEN ALONG WITH A SCHEMATIC FLOW DIAGRAM.
SYSTEM OPERATION IS DISCUSSED FOR STARTUP, POWER OPERATION, SHUTDOWN AND REFUELING MODES OF OPERATION.
COMPONENT DESCRIPTIONS ARE PROVIDED FOR THE PUMPS, HEAT EXCHANGERS, VALVES AND INTERLOCKS.
4 TWO PUMPS, TMO HEAT EXCHANGERS SINGLE DROP LINE (FROM LOOP 4)
FOUR DISCHARGE LINES (ONE PER LOOP)
SLIDES 8
OYERYIEM OF MCAP-11117 PROPOSED MODIFICATIO S SECTION 5 OF WCAP-11117 DEFINES FUNCTIONAL REQUIREMENTS FOR CHANGES THAT WILL NEED TO SE MADE TO THE ELECTRICAL DESIGN AND OPERATING PROCEDURES IN ORDER TO IMPLEMENT ACI REMOVAL.
FUNCTIONAL DIAGRAMS OF THE PROPOSED NEW INTERLOCK CONFIGURATION AND OPERATOR ALARM ARE PROVIDED IN ADDITION TO FUNCTIONAL DIAGRAMS OF THE CURRENT INTERLOCK.
A MARKED-UP ELEMENTARY WIRING DIAGRAM IS PROVIDED SHOWING THE PROPOSED MODIFICATION.
ALSO DISCUSSED IS THE NRC-PROPOSED SINGLE SWITCH ALTERNATIVE MODIFICATION.
SLEDES 9
4
~
OVERVIEW OF WCAP-11117 PROBABILISTIC ANALY IS SECTION 6 AND APPENDICES A THROUGH D OF WCAP-11117 DESCRIBE IN DETAIL THE PROBABILISTIC ANALYSES THAT WERE PERFORMED IN ORDER TO JUSTIFY REMOVAL OF THE ACI.
THERE WERE THREE MAIN AREAS OF ANALYSIS FOR THE EFFECT OF THE MODIFICATION:
1.
EFFECT ON RHR SYSTEM AVAILABILITY 2.
EFFECT ON INTERFACING SYSTEM LOCA 3.
EFFECT ON OVERPRESSURIZATION TRANSIENTS stzom 10
ra RVlXUIOVATXR SllSAtZ TANK LEGEND ILIL SNJT N
- ILC, IKIDWU.T CLD5Q fSL fAILKCol UL UXXO lFQ Q
<<<<<<<<w<<<<<<
MJKF VILK RZTDfl.T VN.K
ILUK VN.VC
~ KININ. aATC VN.VC RESIDUAL HEAT REMOVAL SYSTEM
PROBABILISTIC ANALY ES PURPOSE:
TO QUANTITATIVELYDETERMINE THE IMPACT ON THE FOLLOWING AREAS OF REMOVAL OF THE RHR AUTOCLOSURE INTERLOCK RHR AVAILABILITY-BENEFITS OBTAINED, AVAILABILITYINCREASES 2)
INTERFACING SYSTEM LOCA - BENEFITS OBTAINED, FREQUENCY DECREASES 3)
COLD OVERPRESSURIZATION - ACI AND SLOW ACTING SUCTION VALVES ARE NOT DESIGNED TO PROTECT AGAINST OYERPRESSURE, RHR RELIEF VALVE WOULD OPERATE
HR AVAILABILITY AVAILABILITYOF RHR SYSTEM TO PERFORM ITS FUNCTION DURING COLD SHUTDOMN IS IMPROVED THREE DIFFERENT SCENARIOS 1)
FAILURE DURING RHR XNITIATION 2)
FAILURE DURING FIRST 72 HOURS 3)
FAILURE DURING LONG TERM ( 6 WEEKS)
RHR INITIATION MARMUP PERIOD TO MINIMIZE THERMAL SHOCK BASED ON OPERATING PROCEDURE SHORT TERM COOLING (72 HOURS)
HIGH DECAY HEAT TWO TRAINS OF RHR REQUIRED NO TEST OR MAINTENANCE OF RHR OCCURS LONG TERM COOLING (6 MEEKS)
ONE TRAIN OF RHR REQUIRED TEST AND MAINTENANCE CAN OCCUR
HR ILAB CASE PRESENT PROPOSED NRC CONFIGURATION MODIFICATION MODIFICATION MOV 8701 OR 8702 SPURIOUSLY CLOSE T=72 HRS MOV 8701 OR 8702 SPURIOUSLY CLOSE T=1008 HRS 6.64E-05 9.29E-04 2.22E-05
(-66:)
3.11E-04
(-66:)
2.22E-05
(-66:)
3.11E-04
(-66:)
RHRS FAILS DURING 2.07E-02 INITIATION 2.07E-02 2.07E-02 RHR FAILS DURING SHORT TERM RHR FAILS DURING LONG TERM 7.11E-05 2.01E-03 2.69E-05
(-62:)
1.39E-03
(-31.4) 2.69E-05
(-62:)
1.39E-03
(-31
'o)
INTERFACING SYSTEM LOCA BREACH OF THE HIGH PRESSURE REACTOR COOLANT SYSTEM BOUNDARY AT INTERFACE WITH THE LOW PRESSURE PIPING INTERFACE AFFECTED BY REMOVAL OF THE AUTOCLOSURE INTERLOCK RHR SUCTION FROM RCS FREQUENCY OF INTERFACING SYSTEM LOCA CALCULATED FOR THREE CASES:
1)
PRESENT INTERLOCK CONFIGURATION 2)
PROPOSED MODIFICATION 3)
NRC PROPOSED MODIFICATION (SINGLE SWITCH)
OVERALL, REMOVAL OF ACI RESULTS IN DECREASE IN INTERFACING SYSTEM LOCA FREQUENCY
INTERFACING SYSTEM LOCA FORMULA TO CALCULATE FREQUENCY:
F(VSEQ)
= ~2 Q(Vl) + ~1 (V2) + ~2 Q(V1R)
WHERE
'A 2 =
RUPTURE FAILURE RATE FOR MOV 8702
),1 = RUPTURE FAILURE RATE FOR MOV 8701 Q(V1)
= PROBABILITY THAT MOV 8701 IS OPEN Q(V2)
= PROBABILITY THAT MOV 8702 IS OPEN Q(V1R)
= PROBABILITY THAT MOV 8701 RUPTURES
~2
=
Xl = 1.0E-7/HOUR Q(V1R)
=
6.57E-04 PRESENT PROPOSED NRC CONFIGURATION MODIFICATION PROPOSED Q(V1)
Q(V2) 2.39E-05 2.39E-05 1.27E-08 1.27E-08 1.19E-08 1.19E-08 F(VSEQ) 6.17E-07/YR 5.76E-07/YR 5.76E-07/YR
\\
Ol
COLD OVERPRESSURIZATION IMPACT OF REMOVAL OF THE AUTOCLOSURE INTERLOCK ON COLD OVERPRESSURE PROTECTION IS NEGLIGIBLE METHODOLOGY 1)
EXAMINE TRANSIENTS THAT COULD BE IMPACTED 2)
CALCULATE FREQUENCIES FOR TRANSIENTS 3)
DEVELOP AND QUANTIFY MODELS TO DETERMINE IMPACT OF REMOVAL OF ACI
INITIATING EVENT
SUMMARY
OF OVERPRESSURIZATION ANALYSIS INITIATING EVENT FREQUENCY (PER YR)
EFFECT OF REMOVAL OF AUTOCLOSURE INTERLOCK 1.
PREMATURE OPENING oF RHRS (NONE TO DATE)
NO EFFECT.
THE PREVENT-OPEN INTERLOCK IS OF IMPORTANCE IN THIS CASEt NOT THE AUTOCLOSE INTERLOCK.
2.
ROD WITHDRAWAL (NONE TO DATE)
NO EFFECT.
A SMALL INCREASE IN TEMPERATURE IS EXPECTED BUT THIS INCREASE WOULD NOT AFFECT THE RHRS.
3.
FAILURE TO ISOLATE NOT ANALYZED RHRS DURING STARTUP THIS TRANSIENT IS DESCRIBED IN SECTION 6. 3.
HOWEVERS THE RHRS RELIEF VALVE S OPERATION WOULD STOP FURTHER INCREASES IN PRESSURE.
4.
PRESSURIZER HEATERS ACTUATION 5.
STARTUP OF AN INACTIVE LOOP 6.
Loss OF RHR COOLING TRAIN
THE RELIEF VALVES ARE AVAILABLETO MITIGATE THE TRANSIENT.
PRESSURIZER HEATERS WOULD AUTOMATICALLYSHUTOFF.
NO EFFECT.
NO EFFECT.
THE RISE IN PRESSURE IS TOO QUICK FOR THE SLOW CLOSING ISOLATION VALVES.
NO EFFECT.
THE RISE IN PRESSURE FROM DECAY HEAT IS SLOW WHICH WOULD GIVE THE OPERATOR MORE TIME TO REACT.
7.
OPENING OF 1.89E-2 ACCUMULATOR DISCHARGE ISOLATION VALVES NO EFFECT.
MASS WOULD BE INPUT FROM THE ACCUMULATOR UNTIL THE RCS AND ACCUMULATOR PRESSURE EQUAL.
ACCUMULATOR PRESSURE WOULD NOT EXCEED 700 PSIG.
SUMMARY
OF OVERPRESSURIZATION ANALYSIS INITIATING EVEN~
INITIATING EVENT FREQUENCY (PER YR)
EFFECT OF REMOVAL OF AUTOCLOSURE INTERLOCK 8.
LETDOWN ISOLATION RHRS OPERABLE
- l. 01E-1 INCREASES FREQUENCY OF HIGH OVERPRESSURE INTERFACING SYSTEMS LOCA FROM 6.5E-15/YR TO 2.28E-12/YR.
DECREASES OTHER TYPES OF CONSEQUENCES.
9.
LETDOWN ISOLATION RHRS ISOLATED 2.34E-1 (PRESENT)
DECREASES FREQUENCY OF ALL CONSEQUENCES DUE TO
- 1. 17E-1 (MODIFI-DECREASE IN LETDOWN ISOLATION FROM INADVERTENT CATION)
CLOSURE OF ISOLATION VALVES.
10.
CHARGING/SAFETY INJECTION PUMP ACTUATION
- 1. 01E-1 INCREASES FREQUENCY OF HIGH OVERPRESSURE INTERFACING SYSTEMS LOCA FROM 5.89E-15/YR TO 2.05E-12/YR.
DECREASES OTHER TYPES OF CONSEQUENCES.
Al
RT RHR AVAILABILITY AVAILABILITYDEGRADED BY 30 - 60 PERCENT.
ALARM DOES NOT PRECLUDE THE VALVES SPURIOUSLY CLOSING DUE TO FAILURE OF THE ACI DURING RHR OPERATION.
FREQUENCY OF INTERFACING SYSTEM LOCA F(VSEQ)
= 5.76E-07/YR REMAINS THE SAME AS PROPOSED MODIFICATION CASE BECAUSE THE DOMINANT FAILURE MODE XS THE RUPTURE OF TWO VALVES IN SERIES LTOP CONCERNS SLOW ACTING SUCTION VALVES ARE NOT DESIGNED TO PROTECT AGAINST OVERPRESSURE, RHR RELIEF VALVE WOULD OPERATE CONCLUSION THIS MODIFICATION IS NOT DESIRABLE BECAUSE THE AVAILABILITYOF THE RHR SYSTEM IS NOT INCREASED.
f
DOCKETNO.
5P 275/323 December 9, 1987 Rules and Procedures Branch MEMORANDUMFOR:
~
Division of Rules and Records Office of Administration FROM:
Office of Nuclear Reactor Regulation
SUBJECT:
PACIPIC GAS AND ELECTRIC C01IPANY DIABLO CANYON NUCLEAR POWER ZLANTs UNITS 1 IlI 2 One signed original of the Federal Register Notice identified below is enclosed for your transmittal to the Office of the. Federal Register for publication. Additional conformed copies (
5
) of the Notice are enclosed for your use.
~
f Notice of Receipt of Application for Construction Permit(s) and Operating License(s).
Notice of Receipt of Partial Application for,Construction Permit(s) and Facility License(s): Time for Submission of Views on Antitrust Matters.
Notice of consideration of Issuance of Amendment to Facility operating License.
and Prior Hearing Notice of Receipt of Application for Facility License(s); Notice of Availability of Applicant's Environmental Report; and Notice of Consideration of Issuance of Facility License(s) and Notice of Opportunity for Hearing.
Notice of Availabilityof NRC Draft/Final Environmental Statement.
Notice of Limited Work Authorization.
Notice of Availabilityof Safety Evaluation Report.
Notice of Issuance of Construction Permit(s).
Notice of Issuance of Facility Operating License(s) or Amendment(s).
0 Order.
Exemption.
Notice of Granting Exemption.
Environmental Assessment.
Notice of Preparation of Environmental Assessment..
Other:
Office of Nuclear Reactor Regulation
Enclosure:
As stated
Contact:
Je+> Lee Phone:
OFFICE>
SURNAME>
OATE>
1 PD5 87 NRC FORM 318 <IO/80> NRCM 0240 OFFlCIAL RECORD COPY
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