ML20035G792

Forwards Summary of 930421 Enforcement Conference in Arlington,Tx Re Activities Authorized by NRC License NPF-47 for Plant

ML20035G792
Person / Time
Site:	River Bend
Issue date:	04/22/1993
From:	Beach A NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:	Braham P GULF POWER CO.
References
EA-93-060, EA-93-60, NUDOCS 9304300026
Download: ML20035G792 (39)

Text

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s p RfCp UNITED STATES g

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REGloN IV 8

611 RYAN PLAZA DRIVE. SUITE 400 o

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ARLINGTON, TEXAS 760114064

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APR 2 2 ISXI3 Docket:

50-458 License: NPF-47 EA 93-60 Gulf States Utilities ATTN:

P. D. Graham Vice President (RBNG)

P.O. Box 220 St. Francisville Louisiana 70775 Gentlemen:

This refers to the enforcement conference conducted on April 21, 1993, at the Region IV office in Arlington, Texas, concerning activities authorized oy NRC License NPF-47 for the River Bend Station.

The meeting was attended by those on the attached Attendance List and was open for public observation.

The subjects discussed at this meeting are described in the enclosed meeting

summary, It is our opinion that this meeting was beneficial and has provided a better understanding of the apparent violatians identified in NRC Inspection Report 50-458/93-11 and your correctivo actions.

In accordance with Section 2.790 of the NRC's " Rules of Practice." Part 2, Title 10. Code of Federal Regulations, a copy of this let'er will be placed in the NRC's Public Document Room.

Should you have any questions concerning thi matter, we will be pleased to discuss them with you.

Sincerely, I

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us ano t)

/*ivision of Reactor Projects

. Bill Beach, Director D

Enclosure:

Meeting Summary w/ attachments cc w/ enclosure:

Gulf States Utilities ATTN:

J. E. Booker, Manager-Nuclear Industry Relations P.O. Box 2951 Beaumont, Texas 77704 9304300026 930422 j

i PDR ADOCK 05000458

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Gulf States Utilities -

P Winston & Strawn ATTN: Mark J. Wetterhahn, Esq.

1401 L Street, N.W.

Washington, D.C.

20005-3502 Gulf States Utilities ATTN:

Les England, Director

-l Nuclear Licensing l

P.O. Box 220 St. Francisville, Louisiana 70775 Mr. J. David McNeill, III William G. Davis, Esq.

l Department of Justice Attorney General's Office P.O. Box 94095 Baton Rouge, Louisiana - 70804-9095 3

i H. Anne Plettinger 3456 Villa Rose Drive Baton Rouge, Louisiana 70806 President of West Feliciana Police Jury P.O. Box 1921 St. Francisville, Louisiana 70775 i

Cajun Electric Power Coop. Inc.

ATTN:

Philip G. Harris 1

10719 Airline Highway P.O. Box 15540 Baton Rouge, Louisiana 70895 Hall Bohlinger, Administrator Radiation Protection Division P.O. Box 82135 Baton Rouge, Louisiana 70884-2135 i

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s Gulf States Utilities AJfl 221993 bcc to DMB (IE14) bcc distrib. by RIV:

J. L. Milhoan Resident Inspector DRP Section Chief (DRP/C)

Lisa Shea, RM/ALF, MS: MNBB 4503 MIS System DRSS-FIPS RSTS Operator RIV File Section Chief (DRP/TSS)

DRS Senior Resident Inspector, Cooper i

G. F. Saaborn. E0 J. Lieberman, OE, MS: 7-H-5 W. L. Brown I

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4 Gulf States Utilities APR 2 21993 bcc to DMB (IE14) bcc distrib. by RIV:

J. L. Milhoan Resident inspector DRP Section Chief (DRP/C)

Lisa Shea, RM/ALF, MS: MNBB 4503 MIS System DRSS-FIPS RSTS Operator RIV file Section Chief (DRP/TSS)

DRS Senior Resident Inspector, Cooper G. F. Sanborn, EO J. Lieberman, OE, MS: 7-H-5 W. L. Brown RIV:PD/DSPfC C:DRP/Cl D$RP Eldffns$df JEGag[N/So AMach 4/fjf93 4 /'Lf/9:b 4/1)/93 I

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MEETING

SUMMARY

fi Licensee:

Gulf States Utilities (GSU)

)

i Facility:

River Bend Station (RBS)

License No.: NPF-47 Docket No.:

50-458 l

Subject:

Enforcement Conference (50-458/93-11)

On April 21, 1993, representatives of Gulf States Utilities met with Region IV-personnel in Arlington, Texas, to discuss the apparent violations identified in NRC Inspection Report 50-458/93-11. The conference was held at the request of Region IV and was open for public observation.

The licensee presented a summary of the causes for the apparent violations and their corrective actions.

The attendance list and licensee presentation are attached to this summary.

Attachments:

1.

Attendance List 2.

Agenda and NRC Presentation 3.

Licensee Presentation (NRC distribution only)

ATTACHMENT 2 AGENDA OPEN ENFORCEMENT CONFERENCE CULF STATES UTILITIES River Bend Station April 21, 1993 I.

OPENING REMARKS - Mr. Ja:es Milhoan., Regicnal Administrator, Region IV II.

INTRODUCTION OF NRC AND LICENSEE REPRESENTATIVES - Mr. Milhoan III. DESCRIPTION OF ENFORCEMENT PROCESS - Mr. Gary Sanborn, Enforcement Officer IV.

DESCRIPTION OF APPARENT 7IOLATIONS & REGULATORY CONCERNS -

- Mr. Bill Beach Division Director V.

LICENSEE PRESENTATION & NRC QUESTIONS - Mr. Phil Graham Vice President VI.

BPIAK TO PEPEIT CAUCUS I? NRC & LICENSEE STAFFS VII.

NRC QUESTIONS - Mr. MiIhoan and Regional Staff VIII. CLOSING REMARKS - Mr. Graham IX.

CLOSING REMAEKS - Mr. MiIhoan

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'I RIVER BEND ENFORCEMENT CONFERENCE APRIL 21,1993

SUMMARY

1990 PROBLEMS WITH ELECTRICAL INTERLOCKS REVIEW (OCTOBER 25. 1991) CONCLUDED ABSENCE OF ELECTRICAL

=

INTERLOCKS NOT A CHANGE TO USAR - VENDOR'S GUIDANCE CHANGE PROCESS SUBSTANTIALLY REVISED FEBRUARY 25, 1993. TWO EREACHES OF PRIMARY CONTAINMENT OPERABILITY DETERMINATICN (MARCH 2,1993) CONCLUDED ONLY L

MECHANICAL INTERLOCK NEEDED NRC INSPECTORS CONCLUDED ABSENCE OF ELECTRICAL INTERLOCK e

t CONSTITUTED CHANGE TO USAR AND TECHNICAL SPECIFICATION LICENSEE IMPLEMENTED ACTION STATEMENT RE0VIREMENTS - ELECTRICAL INTERLOCK RESTORED MARCH 29: HOWEVER. WE UNDERSTAND THAT RIVER BEND STATION MAINTAINS THAT ELECTRICAL INTERLOCK NOT REQUIRED i

APPARENT VIOLATIONS CHANGED FACILITY W/0 WRITTEN SAFETY EVALUATION OPERATED PLANT WITHOUT "EETING TECHNICAL SPECIFICATION ACTION

=

STATEMENT 3.6.1.*

INADEQUATE SURVEILLANCE TESTING (TECHNICAL SPECIFICATION 5.S.I.d)

ISSUES PREVIOUS CHANGE REVIEWS *AY HAVE BEEN INADEQUATE HOW 0FTEN HAD CONTAINMENT AIRLOCK DOORS BEEN MISOPERATED The apparent violations discussea in this enforcement conference are subject to further review ana 2ay be subject to change prior to any resulting enforcement action.

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ATTENDANCE. LIST 3

GSU P. Graham. Vice President, River Bend Nuclear Group J. Schippert,' Plant Manager i

J. Booker, Manager, Safety Assurance and Quality Verification i

J. Hamilton, Manager, Engineering M. Stein, Director, Design Engineering D. Derbonne, Assistant Plant Manager, Operations L. Woods, Shift Supervisor i

D. Lorfing, Supervisor, Nuclear Licensing J. Gallagher, Civil / Structural Engineer i

NRC J. Milhoan, Regional Administrator, Region IV A. Beach, Director, Division of Reactor Projects (DRP)

S. Collins, Director, Division of Reactor Safety (DRS)

J. Gagliardo, Chief, Project Section C, DRP W. Smith, Senior Resident Inspector, River Bend Station E. Baker, Project Manager, Office of Nuclear Reactor Regulation D. Loveless, Resident Inspector, River Bend Station G. Sanborn, Enforcement Officer, Region IV i

W. Brown. Regional Counsel J. Gilliland, Public Affairs Officer t

E. Collins, Project Engineer, DRP Other R. Bainbridge, Baton Rouge Advocate, Reporter I

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ATTACHMENT 3 i

e GULF STATES UTILITIES COMPANY i

PRESENTATION ENFORCEMENT COhFERENCE i

NRC INSPECTION REPORT 93-11 i

APRIL 21,1993 i

AGENDA ENFORCEMENT CONFERENCE APRIL 21,1993 OPENING REMARKS PIHL GRAHAM MANAGEMENT OVERVIEW JOE SCHIPPERT AIRLOCK DESIGN MIKE STEIN TIMELINE OF EVENTS ON DON DERBONNE FEBRUARY 25,1993 AIRLOCK DESIGN AND OPERATIONAL MIKE STEIN HISTORY ROOT CAUSE AND CORRECTIVE JOIIN HAMILTON /

ACTIONS JOE SCHIPPERT CONCLUSIONS PHIL GRAHAM i

i

6 MANAGEMElNT OVERVIEW p

4 NRC VIOLATIONS THE RIVER BEND STAFF FAILED TO IDENTIFY A CHANGE TO THE AIRLOCK MECHANISM AS AN UNREVIEWED SAFETY QUESTION THE AIRLOCKS WERE OPERATED FOR OVER TWO r

YEARS IN A CONDITION PROHIBITED BY TECHNICAL SPECIFICATIONS THE SURVEILLANCE PROCEDURE ASSOCIATED WITH THE AIRLOCK INTERLOCK WAS INADEQUATE i

G ADDITIONAL GSU CONCERNS i

THE RIVER BEND STAFF DEMONSTRATED INADEQUATE UNDERSTANDING OF THE DESIGN BASIS OF AIRLOCK INTERLOCK EXERCISE - OF THE 50.59 PROCESS REVEALED WEAKNESS f

MAINTENANCE

~ ISSUES ASSOCIATED WITH DEGRADED PLANT EQUIPMENT INFLUENCED MANAGEMENT DECISIONS i

1

S CORRECTIVE ACTIONS SURVEILLANCE TEST PROCEDURES HAVE BEEN CHANGED TO INCORPORATE THE AIRLOCK ELECTRICAL INTERLOCK THE 10CFR50.59 IMPLEMENTATION PROCESS HAS BEEN EXAMINED AND WILL BE STRENGTHENED A MULTI-DISCIPLINE TEAM HAS BEGUN A REVIEW OF ALL BACKLOG MAINTENANCE WORK ORDERS WITH POTENTIAL SAFETY SIGNIFICANCE AN UPGRADED WORK CONTROL PROGRAM WILL IDENTIFY AND FOCUS CORRECTIVE MAINTENANCE ON DEGRADED EQUIPMENT l

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SAFETY PERSPECTIVE LOW ACTUAL SAFETY SIGNIFICANCE

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1 PRIMARY CONTAINMENT AIRLOCKS OVERVIEW OF DESIGN L

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PRIMARY CONTAINMENT BOUNDARY CYLINDRICAL STEEL BARREL WITII FLAT BULKHEADS AT EACII END i

A DOOR IN EACII BULKIIEAD TIIAT SWINGS IN TOWARDS THE CONTAINMENT VESSEL TWO INFLATABLE SEALS ON EACII DOOR l

9 AUTOMATIC OPERATION O

ELECTRICALLY COUPLED AND MECIIANICALLY INTERLOCKED MECIIANICAL INTERLOCK ACTUATED BY HANDWHEEL POSITION i

ELECTRICAL HANDWHEEL LOCKING SOLENOID i

ACTUATED BY DOOR POSITION CONCLUSION:

WITH AIRLOCK INFLATABLE SEALS, TIIE MECHANICAL INTERLOCK AND THE ELECTRICAL HANDWHEEL LOCKING SOLENOID FUNCTIONING, PRIMARY CONTAINMENT IS PROTECTED.

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's H ANDWHEEL LOCKING MECH ANISM a

UPPER CONTAINMENT AIRLOCK IJRB*DRA1 EVENTS i

9 1350 HOURS, FEBRUARY 25,1993 SEALS ON ONE AIRLOCK DOOR WERE PARTIALLY DEFLATED WIIILE OTHER AIRLOCK DOOR WAS NOT COMPLETELY CLOSED AIRLOCK TAKEN OUT OF SERVICE STP-057-0401

" PRIMARY CONTAINMENT AIRLOCK DOOR INTERLOCK TEST" PERFORMED IMMEDIATELY

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1937 HOURS, FEBRUARY 25,1993 WITH ONE AIRLOCK DOOR CLOSED BUT SEALS NOT INFLATED THE OTHER DOOR HANDWHEEL WAS MOVED TO TIIE EQUALIZE POSITION LCO NO.93-069 INITIATED (TECH SPEC 3.6.1.4)

MAINTENANCE WORK ORDER R174728 GENERATED TO INSPECT AND CORRECT THE INTERLOCK MALFUNCTION CONDITION REPORT 93-0105 INITIATED TO HAVE ENGINEERING EVALUATE OPERABILITY OF AIRL.OCK INITIAL EVALUATION 2/26/93 AIRLOCK INOPERABLE REVISED EVALUATION 3/2/93 AIRLOCK OPERABLE

'l STP-057-0401 COMPLETED SATISFACTORY 3/2/93 LCO CLEARED 3/2/93

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3/11/93 PLANT MANAGER DIRECTED THAT AIRLOCK BE ADMINISTRATIVELY CONTROLLED IN ACCORDANCE WITH TECH SPEC 3.6.1.4 AIRLOCK NOT LOCKED PROPERLY l

IMPROVED AIRLOCK LOCKING DEVICE i

G SAFETY PERSPECTIVE j

LOW ACTUAL SAFETY SIGNIFICANCE

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i PRIMARY CONTAINMENT AIRLOCKS DESIGN AND OPERATIONAL HISTORY ORIGINAL DESIGN 9

FULLY AUTOMATIC OPERATION l

4 DESIGN = 2000 CYCLES PER YEAR t

RIVER BEND STATION (RBS) = 3000 CYCLES PER MONTH e

LIMIT SWITCH FOR ELECTRICAL HANDWHEEL LOCKING SOLENOID LOCATED ON DOOR HINGE

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INTENDED FOR PERSONNEL AND EQUIPMENT PROTECTION r

.i ALLOWED DOOR TO OPEN SLIGHTLY PRIOR TO l

ACTUATING SOLENOID r

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FINAL SAFETY ANALYSIS REPORT AUTOMATIC OPERATION DESCRIBED IN GENERAL INTERLOCK VAGUELY DESCRIBED l

MANUAL OPERATION DESCRIBED WITH LOSS OF l

POWER i

CONCLUSION:

ORIGINAL DESIGN OF AIRLOCK DOOR WAS INADEQUATE.

LICENSING i

DOCUMENTATION AMBIGUOUS

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PRIMARY CONTAINMENT AIRLOCKS DESIGN AND OPERATIONAL HISTORY t

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AUGUST 1986: CR 86-1296, DATED 8/27/86 PRBIARY CONTAINMENT BREACH WHILE DOOR BEING USED IN MANUAL OPERATION j

9 SEPTEMBER 1986: MR 86-1438, INITIATED 9/3/86, DESIGN APPROVED 9/15/86, INSTALLATION COMPLETE ON 11/23/86 f

RELOCATES LIMIT SWITCH FOR SOLENOID FROM HINGE TO DOOR FRAME REQUIRES SOLENOID TESTING BE INCLUDED IN STP-I 057-0401 O

JULY 1988: CR 86-1296 ROOT CAUSE ANALYSIS RECOGNIZES MR 86-1438 AS PROVIDING MORE RELIABLE OPERATION OF AIRLOCK DOORS CONCLUSION:

INADEQUACY OF AIRLOCK DESIGN RECOGNIZED IN 1986.

DESIGN AND

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LICENSING BASES WERE NOT RECOGNIZED AS BEING INADEQUATE AT THIS TIME.

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PRIMARY CONTAINMENT AIRLOCKS DESIGN AND OPERATIONAL HISTORY 8

OCTOBER 1990 l

CR 90-0834, DATED 10/1/90, INITIATED DUE TO REPEATED PROBLEMS WITII DRYWELL AIRLOCK DOORS CR 90-0934, DATED 10/17/90, INITIATED DUE TO FAILURE OF ELECTRICAL SOLENOID ON CONTAINMENT AIRLOCK C

POWER REMOVED FROM CONTAINMENT AIRLOCK i

DOORS i

9 MARCH 1991 FINAL CLOSURE REVIEW OF MR 86-1438 SIIOWS TIIAT t

STP-057-0401 IIAD NOT BEEN REVISED 9

OCTOBER 1991 CR 90-0834 AND CR 90-0934 FINAL DISPOSITION RECOMMENDS CONTINUED MANUAL OPERATION WITHOUT POWER.

i CONCLUSION:

INAPPROPRIATE CIIANGE TO STP Al@

INADEQUATE 10CFR50.59 SCREENING FOR INTERLOCK OPERATION.

13 i

PRIMARY CONTAINMENT AIRLOCKS DESIGN AND OPERATIONAL HISTORY i

e FEBRUARY 1993: CR 93-0105, DATED 2/26/93 PRIMARY CONTAINMENT BREACH t

S MARCH 1993: PMR 93-0009, DATED 3/22/93 ENERGIZES ELECTRICAL HANDWIIEEL LOCKING SOLENOID.

COMMITS TO MAINTAIN ELECTRICAL SOLENOID AS PART OF AIRLOCK DOOR INTERLOCK i

CONCLUSION:

ELECTRICAL HANDWHEEL LOCKING SOLENOID AND MECHANICAL INTERLOCK

-l ARE REQUIRED TO MAINTAIN INTERLOCK l

SYSTEM OPERABLE.

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PRIMARY CONTAINMENT AIRLOCKS DESIGN AND OPERATIONAL HISTOR.Y

SUMMARY

S NUMEROUS MAINTENANCE AND OPERATIONAL PROBLEMS DUE TO ORIGINAL DESIGN.

S DESIGN PROBLEMS RECOGNIZED IN 1986.

DESIGN AND LICENSING BASES WERE NOT RECOGNIZED AS BEING INADEQUATE AT TIIIS TIME.

9 INAPPROPRIATE DIRECTION GIVEN TO OPERATIONS CONCERNING TIIE STP.

I 9

INADEQUATE 10CFR50.59 SCREENING PERMITTED CONTINUED MANUAL OPERATION OF TIIE AIRLOCK DOORS WITHOUT POWER.

4 9

ELECTRICAL IIANDWIIEEL LOCKING SOLENOID IS REQUIRED FOR OPERABILITY-OF AIRLOCK IN1TRLOCK SYSTEM.

1

ROOT CAUSE SYMPTOM CLASSIFICATION METHOD i

I ORIGINAL DESIGN NOT ADEQUATE e

INADEQUATE DESCRIPTION OF INTERLOCK f

SAFETY FUNCTIONS IN FSAR

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ROOT CAUSE CONTRIBUTING FACTORS e

USAR AND DESIGN DOCUAENTS NOT RECOGNIZED AS INADEQUATE IN MR 86-1438 e

AIRLOCK EQUIPhENT PROBLEMS NOT CORRECTED DUE TO BACKLOG AND WORK AROUND ATTITUDE e

DISABLED ELECTRICAL INTERLOCK NOT RECOGNIZED AS A DEGRADED CONDITION j

t i

e INSUFFICIENT DEPTH IN CR 90-934 50.59 SCREENING i

- INSUFFICIENT QUESTIONING ATTITUDE

- PROCEDURAL GUIDANCE NOT USED

- RELIANCE ON STP BASIS MEMO f

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i EXTENT OF PROBLEM PREVIOUS ACTIONS TO IMPROVE DESIGN DOCUMENTATION CONTINUAL IMPROVEMENT OF DESIGN DOCUMENTS EXISTING 50.59 PROCEDURE AND GUIDANCE JUDGED ADEQUATE

- IF EXISTING GUIDANCE IS USED

- IF A QUESTIONING ArnTUDE IS MAINTAINED SELF ASSESSMENT OF A SAMPLE OF PAST 50.59 SCREENING EVALUATIONS WAS SATISFACTORY ADDITIONAL REVIEWS IN PROGRESS i

CORRECTIVE ACTION e

MANAGEMENT ACTION TO REDUCE AIRLOCK USAGE e

ADMINISTRATIVE CONTROLS AND TEMPORARY MODIFICATION TO ACIIIEVE TECII SPEC COMPLIANCE e

USAR CIIANGED TO CLARIFY SAFETY FUNCTION OF INTERLOCK t

e INTERIM ACTIONS TO IMPROVE RELIABILITY OF MECIIANICAL PORTION

{

OF INTERLOCK' UPGRADED INTERLOCK DESIGN ADEQUATE -

e FOR SERVICE BY RF-5 e

CASE STUDY TRAINING TO CORRECT EQUIPMENT PROBLEMS AND ENIIANCE SAFETY CULTURE j

e ADDED 50.59 TRAINING AND PROCEDURAL l

GUIDANCE-RECOGNIZE DEGRADED CONDITIONS REINFORCE USE OF PROCEDURAL GUIDANCE AND QUESTIONING ArnTUDE 1

ADDITIONAL QUALIFICATION 1

FOR 50.59 REVIEWERS 19

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t CORRECTIVE ACTIONS l

9 SURVEILLANCE TEST PROCEDURE REVIEW INITIATIVES ARE UNDERWAY OR PLANNED TO INSURE TECHNICAL.

SPECIFICATION REQUIREMENTS. FUNCTIONAL AREAS:

l LOGIC SYSTEM FUNCTIONAL TESTS CONTAINMENT LOCAL AND INTEGRATED LEAK RATE TESTS i

PUMP AND VALVE IN SERVICE TESTS INTEGRATED EMERGENCY CORE COOLING TESTS I

INSTRUMENTATION AND CONTROL CHANNEL l

FUNCTIONAL AND CHANNEL CALIBRATION TESTS 9

ONGOING AND BACKFIT REVIEW OF PLANT MAINTENANCE WILL PROVIDE AN ADDITIONAL BARRIER AGAINST DEGRADED OPERATION 9

CONTINUED SAFETY IMPROVEMENT IS ACHIEVED WITH CRITICAL, ONGOING AND OPEN SELF-ASSESSMENT l

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i SAFETY CONCLUSIONS l

O CONTAINMENT OPERABILITY REQUIREMENTS ARE SCRUPULOUSLY OBSERVED S

SAFETY IMPACT DUE TO ACTUAL AIRLOCK BREACH IS LOW i

O AIRLOCK BREACH OCCURRED ON THREE INSTANCES FOR A TOTAL OF APPROXIMATELY FIVE MINUTES, SINCE OCTOBER 1985 9

PROPER OPERATION IN CONJUNCTION WITH AN OPERABLE MECHANICAL INTERLOCK AND AIRLOC,K MAINTAINED CONTAINMENT EFFECTIVENESS O

PLANT PERSONNEL ~ RECOGNIZED AND PROMPTLY CORRECTED THE THREE INTERLOCK OPERATIONAL ERRORS f

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9 SUPPLEMENTAL INFORMATION 1

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LOCKING AIRLOCK DOORS i

9 3/24/93 RESIDENT INSPECTOR OBSERVED THAT AIRLOCK WAS NOT LOCKED PROPERLY l

CR 93-0143 INITIATED BY CONTROL OPERATING I

FOREMAN SIIIFT TECHNICAL ADVISOR, NUCLEAR EQUIPMENT OPERATOR DISPATCHED TO AIRLOCK TO SECURE IN PROPER MANNER OPERATOR AID 93-I-020' INITIATED AND POSTED IN THE AIRLOCK i

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3/31/93 APM-OUTAGE AND SR. RESIDENT INSPECTOR OBSERVED THAT AIRLOCK WAS NOT LOCKED PROPERLY SR.

RESIDENT INSPECTOR NOTIFIED CONTROL ROOM CR 93-0160 INITIATED BY APM-OUTAGE AIRLOCK OPERATOR ACQUIRED LONGER CHAIN TO PROPERLY SECURE AIRLOCK OPERATOR AID 93-I-024 AND 93-I-025 INITIATED a

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2_7 _ _ _

MEMORANDUM TO:

T. Hoffman April 16, 1993 FROM:

J. Burton NE-FM-93-0577

SUBJECT:

Safety Assessment Regarding Two Airlock Doors Open

- Breech Of Containment

REFERENCES:

1)

TWR 93-046 2)

CR 93-0105 3)

G13.18.14.0*129-0 Per your request (Ref. 1) we have performed a safety assessment of the condition reported in CR 93-0105.

The Condition Report identifies two incidents that occurred on 2/29/93 in which the containment airlock on the 171' elevation was operated improperly.

The misoperation resulted in the deflation of the seals on one door with the other door not completed closed.

Consequently, a containment breech occurred.

In our analysis we have used a PRA approach as well as a mechanistic approach to assess the safety significance of the condition reported.

Both of these approaches are presented in detail below.

In summary, the condition reported is not safety significant from either a PnA or a mechanistic basis.

PRA ADoroach Based on Security computer records for the card reader at the airlock cage, there are approximately 40768 entries I

into the containment or exits from the containment per year via the airlock on the 171' level.

We have conservatively assumed that it would take 45 seconds to open and close each door of.the airlock.

In other words, it takes 90 seconds to make one entry or exit through the 171' airlock.

We also assumed.that there were only two mis-operations of the containment airlock in the last year.

This was determined by reviewing past condition reports for similar events.

Consequently, there have been 2 mis-operations per 40768 entries or exits on a per year basis.

As a result the probability of mis-operating an airlock door is:

2 mis-ocerations 2.5E-5

=

(2 x 40768) door operations i

28

i Therefore, if the frequency of a large LOCA is 1.0E-4 l

per year (or 3.17E-12 per second) then the probability of a large LOCA occurring when an airlock door is mis-operated l

is:

l 3.17E-12 x 45 sec x (2 x 40768) door ons x 2.5E-5 = 2.9E-10 l

sec door ops year 1

year If we compare this to the NRC's Safety Goal for large releases (1.0E-6 per year), thEn it is clear chat the probability of a large LOCA concurrent with the mis-operation of the airlock doors is 3000 times less than the safety goal.

From a PRA perspective, this event.is not safety significant.

Mechanistic Acoroach l

The containment airlocks constitute potential annulus l

bypass leakage paths between primary and secondary l

containments and are included as such in TABLE 3.6.1.3-1 of the Technical Specifications.

Also included in this table are the 36" primary containment purge isolation valves, which provide analogous communication paths between primary and secondary containment.

According to Technical Specification 3.6.1.9, each of the 36" primary purge isolation valves may be opened.for purge system operation.

However, purge system operation is limited to a total of 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> per 365 days.

The rationale behind the 1000-hours-per-365-days limit is that the probability of a LOCA occurring any time during any one purge system operation is very small.

(Note that this argument is similar to the PRA approach discussed above.)

It is reasonable to use this rationale to cover any combination of annulus bypars pathways, since the net impact is the same.

If it can be shown that during any 365-day period,.the total number of hours during which the purge valves and the airlocks were open comes to a total of s 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, then we can consider that the intent of the Technical Specifications has been met with regard to open pathways between the primary and secondary containments during normal plant operation.

To do this we compare the number of times either airlock door is open (N) to the number of times they are allowed to be open.

The allowed time either door can be opened is based upon the time the 36" purge valves are estimated opened for a given year.

Based on the recorded times for purge valve openings in STP-000-001 from January 1, 1992 through March 18, 1993, the estimated open time is 784 hours0.00907 days <br />0.218 hours <br />0.0013 weeks <br />2.98312e-4 months <br /> per year.

l

n-r

'i The basis for the Technical Specification value of 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> is the NRC's calculated probability of a LOCA and the dose released.

The dose released is related to the leakage flowrate and the length of time the leak occurs.

In our particular case that length of time is built into the number e

of times the airlock doors are opened a year.

To find the leak rate, calculation G13.18.14.0*129-0 was performed.

It consisted of two parts, one part determined the leakage through the 36" purge valves and the i

other part determined the leakage through deflated seals on one airlock door while the other door is opened.

DBA-LOCA conditions were assumed in both parts of the calculation.

For the purge valves, the DBA-LOCA flow rate was found to be 2.54E5 scfm, or 14 times the airlock leakage rate of 1.77E4 sefm.

P Since one airlock door operation is assumed to take 45 t

seconds, then 80 door operations are possible per hour.

Also, since purge valves were estimated to be open for 784 r

hours per year, then the airlocks could leak for 216 hours0.0025 days <br />0.06 hours <br />3.571429e-4 weeks <br />8.2188e-5 months <br /> (1000 hrs - 784 hrs).

Since the purge valve flow rate is 14 times greater than the airlock leak rate,'then 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> with the purge valves open is equal to 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> of airlock door operations.

Therefore, the equivalent time for airlock door operations is 3024 hours0.035 days <br />0.84 hours <br />0.005 weeks <br />0.00115 months <br /> (216 hours0.0025 days <br />0.06 hours <br />3.571429e-4 weeks <br />8.2188e-5 months <br /> x 14).

Then, the number of airlock door operations could be lus high as 241920-(3024 x 80) without exceeding the 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> of annulus bypass leakage presumed-in T/S 3.6.1.9.

Because the estimated number of airlock door operations

{

(81536 per year) was 1/3 the allowed number of operations we were bounded by the Technical Specification limit of 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> for annulus bypass leakage.

Therefore, the safety significance of this condition is low from a mechanistic perspective.

b.'B'urton Supervisor PRA JLB/TLH/tlh cc:

J. Miller

]

M. Stein D.

Lorfing I

J. Gallagher i

l 2)C)

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