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NUCLEAR REGULATORY COMMISSION E
WASHINGTON, D C. 20555
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M RAN U FOR:
for Licensing Division of Licensing FROM:
Robert J. Bosnak, Acting Assistant Director Components & Structures Engineering Division of Engineering
SUBJECT:
SER FOR DIABLO CANYON 2 ON CONTAINMENT ISOLATION DEPENDABILITY BY DEMONSTRATION 0F CONTAINMENT PURGE AND VENT VALVE OPERABILITY NUREG 0737, ITEM II.E.4.2(6) (DOCKET N0. 50-323)
Plant Name:
Diablo Canyon Unit 2 Docket No.:
50-323 Licensing Stage: OL Responsible Branch: Licensing Branch No. 3 Responsible Project Manager:
H. Schierling Review Status: Complete This Safety Evaluation Report (SER) was prepared by DE:C&SE, Equipment Qualification Branch. The SER addresses containment isolation dependability by demonstration of containment purge and vent valve operability. The EQB has the responsibility for reviewing and evaluating the containment purge and vent valve program for Near Team Operating License (NT0L) plants. Demonstration of operability of the containment purge and vent valves, particularly the ability of these valves to close during a design basis accident, is necessary to assure containment isolation. This demonstration of operability is required by Standard Review Plan (SRP) 6.2.4, Branch Technical Position (BTP)
CSB 6-4, and SRP 3.10 for containment purge and vent valves which are not sealed closed during operational conditions 1, 2, 3, and 4.
In Sections 6.2.3 and II.E.4.2 of supplements numbers 9 and 14, respectively, to the Diablo Canyon Safety Evalustion Report, the staff required the 12-inch vacuum / overpressure relief valves ue limited to opening angles of 509 or less 0\\
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until their operability has been demonstrated. PG&E has not provided information to demonstrate valve operability. Therefore, the following condition should be included in the Diablo Canyon Unit 2 Operating License:
"PG&E shall limit the 12-inch vacuum / overpressure relief valve opening to less than or equal to 50 degrees."
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. Bosnak, Acting Assistant Director Components & Structures Engineering Division of Engineering
Enclosure:
As stated cc:
J.P. Knight V. Noonan G. Bagchi R. Wright E. Reeves G. Knighton H. Schierling R. Perch
Contact:
R. Wright Ext. 28209 l
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HEMORANDUM FOR:
T. A. Rehm Assistant for Operations Office of the Executive Director for Operations FROM:
Jesse L. Funches Director Planning.and Program Analysis Staff Office of Nuclear Reactor Regulation
SUBJECT:
COMMENT RE PRE-HEARING QUESTION FOR 2/28/85 UDALL AUTHORIZATION HEARIhGS Englosed is our revision to Udall Question 3 to respond to Henry Myers' coir.cnt.
If you have any questions, please cont'act ne or Lars Solander on extension 24516.
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Jesse L. Funches, Director Planning and Progran Analysis Staff Office of Nuclear Reactor Regulation
Enclosure:
As stated
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H. Denton
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CLESTION 3.
EFFECT OF EARTHQUAKES ON EMERGENCY PLANS:
IN AE HORIZING FULL POWER OPERATION AT DIABLO CANYON, THE ComISSION ADOPTED THE POSITION THAT AN EARTHQUAKE WITH MAGNITUDE LESS THAN THE SAFE l
SHJTDOWN EARTHQUAKE-(SSE) WAS UNLIKELY TO CAUSE A REACTOR ACCIDENT REQUIRING IMPLEMENATION OF THE EMERGENCY PLAN. THIS POSITION WAS AN ESSEMIAL ELEENT IN THE C0 MISSION'S DECIDItiG THAT, IN THE D.IABLO CANYON PROCEEDING, THERE WAS NO NEED TO CONSIDER THE IMPACT OF AN EARTHQUAKE UPON THE WORKABILITY OF THE EMERGENCY PLAN.
(A) MiAT ANALYSIS WAS CONDlbTED TO ESTIMATE THE PROBABILITY THAT AN EARTHQUAKE, SMALLER THAN
- w-THE SSE, WOULD INITIATE AN ACCIDENT THAT MIGHT REQUIRE IMPLEE NTATION OF THE DIABLO CANYON EERGENCY PLAN?
- ANSER,
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THE SAFE SHUTDOWN EARTHQUAKE, OR SSE, FOR A NUCLEAR PLANT IS BASED UPON AN EVALUATION OF THE MAXI M EARTHQUAKE POTENTIAL FOR THE SPECIFIC SITE. THE SSE IS EVALUATED AS THAT EAR E QUAKE WHICH
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PRODUCES THE MAXI M VIBRATORY GROUND MOTION FOR WHICH CERTAIN l
1 STRUCTURES, SYSTEMS AND COMPOWENTS MJST BE DESIGNED AND CON-STRUCTED TO REF%IN FUNCTIONAL. ALL STRUCTURES, SYSTEMS AND i
UDALL/NRR 4/16/85
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Q.ESTAN 3.A. (CONTINUED).
COPPONENTS NECESSARY TO ACHIEVE A SAFE SHUTDOWN ARE SEISMICALLY r
WALIFIED IOR THE SSE AND ARE EXPECTED, WITH HIGH CONFIDENCE, TO FUNCTION TO BRING THE PLAIR TO A SAFE SHUTDOWN.
PROBABILISTIC ESTIM TES FOR THE OCCURRENCE OF AN SSE ARE TYPICALLY ON THE ORDER OF ONE IN A THOUSAND TO ONE IN TEN THOUSAND PER YEAR.
BECAUSE OF THE SHORT EARTHQUAKE HISTORY IN THE U.S., IN COMPARISON TO THE PITURN PERIOD OF LARGE EARTHQUAKES, AMONG OTHER FACTORS, THESE ESTIMATES MAY HAVE'LARGE UNCERTAINTIES.
ONLY IN.THE EVENT OF MJLTIPLE UNRELATED FAILURES OF SAFETY RELATED SYSTEMS DUE TO SOME UNDISCOVERED C0ftiON CAUSE FAILURE MECHANISM -
(SUCH AS A MAJOR DESIGN ERROR), COINCIDENT WITH A SEVERE EARTH-QUAKE SUCH AS AN SSE, WOULD THERE BE A CHANCE OF AN ACCIDENT WHICH WOULD REQUIRE OFFSITE EMERGENCY RESPONSE. THE PROBABILITY OF THESE TWO EVENTS OCCURRING PROXIMATELY IN TIME IS VERY MJCH LOWER THAN THE PROBABILITY OF EITHER INDIVIDUAL EVENT.
l IHE NECESSARY STRUCTURES, SYSTEMS AND C0tPONENTS OF THE DIABLO CANYON PLANT WERE DESIGNED AND CONSTRUCTED IN ACCORDANCE WITH THE APPROPRIATE NRC REQUIREENTS TO PERFORM THEIR INTENDED FUNCTION DURING AND FOLLOWING AN EARTHQUAKE OF A M GNITUDE UP TO THESSE.,
UDALUNRR 4/16/85
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d QUESTION'3.
(B) 44AT IS THE BASIS FOR CONCLUDING THAT SUCH AN EARTHQUAKE IS SIGNIFICA U LY LESS LIKELY TO INITIATE AN ACCIDENT REQUIRING IMPLEE NTATION
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0F THE EMERGENCY PLAN THAN OTHER ACCIDENT INITIATORS WHICH ARE IMPLICIT IN THE IMPOSITION OF EMERGENCY PLANNING REQUIREMENTS?
ANSWER THE OBJECTIVE OF EMERGENCY PLANNING IS TO ASSURE SUITABLE EMERG RESPONSE CAPABILITY FOR A WIDE SPECTRlE OF ACCIDENTS, IRRESPECTIVE 0F ANY PARTICULAR INITIATING EVENT. THUS,..NO PARTICULAR ACCIDENT IS USED FOR PLANNING PURPOSES; RATHER, POTE TIAL CONSEQUENCE SEQUENCES ARE USED TO DEVELOP AN APPROPRIAK. PLANNING. BASE WITH0ls w
REGARD FOR THE INITIATING EVENT.
THE PARTICULAR ELEN NTS OF AN ACCIDENT SEQUENCE (E.G., INITIATION OF EMERGENCY C)RE COOLING, OCCURRENCE OF FIRES, ETC.) ARE CCNSIDERED AS INITIATING CONDITIONS FOR VARIOUS EMERGENCY ACTION LEVELS, AS IS THE OCCURRENCE, OR PROJECTED OCCURRT.NCE, OF NATURAL PHENOMENA SUCH AS HURRICANES, TORNADOS, FLOODS, AND EARTHQUAKES.
AS. DESCRIBED IN THE " CRITERIA FOR PREPARATION-AND EVALUATION RADIOLOGICAL BiERGENCY RESPONSE PLANS AND PREPAREDNESS IN SU OF NUCLEAR POWER PLANTS" (NUREG-%54/FD%-R9-1, REV.1, APPENDIX 1),
EARTHOUAKES UP TO THE SSE ARE INITIATING CONDITIONS FOR THE " UNUSUA EVENT" AND " ALERT" LEVELS.
UDALL/NRR l
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CUESTiON3.B.(CONTINUED) 2-THIS DESIGNATION DOES NOT IMPLY, HOWEVER, THAT THE OCCURRENCE OF r
SUCH AN EARTHQUAKE WOULD CAUSE AN ACCIDENT WITH OFFSITE RADIOLOGICAL IffLICATI0hS. RATHER, THESE EERGENCY ACTION LEVELS DESIGNATE GENERAL PREPAREDNESS CONDITIONS TO ASSURE THAT, AT THE " UNUSUAL EVENT" LEVEL, THE FIRST STEP IN ANY RESPONSE LATER FOUND TO BE
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NECESSARY HAS BEEN CARRIED0UT AND THE OPERATING STAFF IS IN A STATE OF READINESS TO SYSTEMATICALLY HANDLE THE INFORMATION AND DECISION-t% KING ASSOCIATED WITH THE EVENT AND, AT THE " ALERT" J
LEVEL, THE EMERGENCY PERSONNEL ARE READ:LY AVAILABLE TO RESPOND IF THE SITUATION BECOMES MORE SERIOUS AND TO PROVIDE CURRENT STATUS.INFORMATIONTOAPPROPRIATEOFFSITEA)THORITIES. THESE-FUNCTIONS ARE INTENDED TO ASSURE THAT ALL RESPONSE ORGANIZATIONS-1 L
THAT COULD BE POTENTIALLY IfNOLVED RECOGNIZE THE EVENTUALITIES THAT MIGHT HAVE TO PE DEALT WITH IF ANY EE RGENCY RESPONSE BECAME NECESSARY.
THE CamISS10ti'S DECISION IN DIABLO CANYON, FOR THESE PURPOSESs DOES NOT DETRACT FROM THE FUNDAMENTAL REQUIREMENT THAT SUFFICIENT t
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FLEXIBILITY BE PROVIDED IN THE EERGENCY PLAN TO ACCom0DATE A WIDE SPECTRLN OF ACCIDENTS IRRESPECTIVE OF THEIR CAUSE. THIS DECISION PROPERLY RECOGNIZES THAT POTENTIAL IMPEDIENTS TO EERGENCY RESPONSE CAUSED BY MORE FREQUENT NATURAL PHENDENA (WHICH HAVE BEEN EXPLICITLY. CONSIDERED IN THE PLANNINGb ARE UDALL/NRR 4/9/85
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QUESTION 3.B'. (CONTINUED) i SUFFICIENTLY SIMILAR TO PERilT Ni EFFECTIVE RESPONSE EVEN IN THE EVEffT OF N EARTHOUAKE WHICH HAS NOT BEEN EXPLICITLY PLANNED FOR BECAUSE OF ITS LOh' PROBABILITY, FOR THE REASONS ~ DESCRIBED IN THE RESPONSE TO QUESTION 3(A). WE COMPAPE THE EMERGENCY PLANN!tE AND PREPAREDNESS PROVISIONS APPLICABLE TO EARTHQUAKES WITH OTHER NATURAL PHEf0MENA BECAUSE THEY HAVE IN C0ft10N THE COMPLICATIONS ASSOCIATED WITH THE NATURAL EVENT; FOR EXNFLE, IMPASSABLE ROADS, SEVERED C0ftUNICATION LINES, AND POOR WORKING CONDITIONS. ON THE OTHER HAND, ACCIDEllTS CAUSED BY SIPPLE HLf1AN ERRORS OR EQUIP-MENT FAILURES DO NOT HAVE SUCH COMPLICATIONS AND, THEREFORE, ARE NOT AS. SEVERE WITH RESPECT TO EFERGENCY PLANNITE REQUIREENTS -
IN THIS SENSE, THEN, THE LIKELIHOOD OF AN EARTHQ' AKE UP TO THE --
J w-SSE IS t0T A SIGNIFICANT FACTOR WITH RESPECT'TO THE EFFECTIVENESS.
OF THE EMERGENCY PLAN.
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UDALL/NRR 4/9/85 p, -
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