ML20212M356

Safety Evaluation Rejecting Util Schedule for Completion of Mark I Containment Program Re Vacuum Breaker Integrity. Required Vacuum Breaker Parts Should Be Replaced Prior to Startup from Cycle 12 Refueling Outage

ML20212M356
Person / Time
Site:	Oyster Creek
Issue date:	03/03/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20212C077	List: ML20212C072 ML20212M326 ML20212M356
References
GL-83-08, GL-83-8, NUDOCS 8703110383
Download: ML20212M356 (3)

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-- . n* , ..,'g,- UNITEb' STATES E 3 h. NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20655 -

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULAT10t!

3ATING TO W.ARV E CONTkTNMENT PROGRAM - VACUlfY P

- CPP NUCLEAP'CORPORATTOM J$RSEY CENTRAL P0k'ER AND LIGHT COMPANY f- ,

l (0YSTEPCREEKNilCLEARGENERATINGSTATION r L. - ',

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DOCKET NO.: 50-219 1

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4;.E ] .0 INTRODUCTION fn addition to the staff's Safety Evaluation (SE) dated January 13, 1984, of

,'tne suppression chamber, torus attached piping, pressure relieving lines, etc.,

s unde" the newly defined loadings, the Mark I containment program required the r assurance of the structural integrity of torus-to-drywell vacuum breakers q during operation in all Mark I plants. This requirement on these vacuum breakers was categorized as a separate effort because the adequacy of other comoinents was already discussed in the SE dated January 13, 1984 This

separate effort was Generic letter 83-08.

The staff's .:ontractor, Franklin Research Center (FRC), has performed an evaluation cf the structural integrity of vacuum breakers in the Oyster Creek Nuclear Generatino Station (Oyster Creeki for the NRC staff. Results of the review are reported in the attached :ocument, TER-C5506-319, " Structural

'- Evaluation of the Vacuum Breakers (Mark I Containment Program), General Public h (Utilities,OysterCreekPlant." FRC has concluded that actions taken by p Oystec Creek are adequate to restore the original design margin of safety for Li its vscuum breakers under the revised loadings in the Mark i Containment.

NRC staff reviewed the attached document and concurred with the FRC findings, t .

/f', '. , JPU Nuclear has submitted its responses to Generic letter 83-08. These are its analyses of thecintegrity of the vacuum breakers during the loss-of-coclant accident (LOCA) in its submittals dated August 14, 1985, and May 23, 1986.

Tnese submittals Were reviewed by the contractor. They were based on the

!' staff's approved nethodology for use in the analysis anc' cualification of the 4

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• breakers which was issued in the staff's SE dated December ?4, 198f, to GeneN1 Electric.

2.0 DISCUSSION During steam condensation tests on PWR Mark I containments, the wetwell-to-drywell vacuum breakers cycled repeatedly during the transient phase of steam bl adown. This load was not included in the original load combinations used in the design of the vacuum breakers. Consequently, the repeated impact of the pallet on the valve seat and body created stresses that may impair its capebility to remin functional.

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. A vacuum tbeaker is a check valve. installed between. the wetwell, or torus, ard the.drywell. Its ' primary function is to prevent the formation' of a negative -

pressure on the drywell containment duringfrapid condensation of steam in th -

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f drywell. and in the final stages of a LOCA. The vacuum breaker maintains a>

.wetvell' pressure less' than oreeoual .to the drywell pressure. by. permitting air -

flow from the wetwell =to the drywell whe.n the wetwel1~.is prese"rized and the r

~ drywell is depressurized slowly,

, '3.0'EVALUATINE(

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' n g- In the Oyster Creek Mark I containment, there are 14 external: type. vacuum

' ' breakers,made by Atwood and Morrill. There are two vacuum breakers mounted on p 'each of seven' external lines codnecting the drywell and the wetwell or torus. ,

L'o dings on the Park I structures and vacuum breakers are based on the General

~g ETectrfcN Company Report, NED0-21888, " Mark I Containment Program Load v Definition Report," Revision 2, dated November 1981. For vacuum breakers,

?P the Toadings included in the analysis are gravity, seismic, and hydrodynamic loads. The., hydrodynamic forcing functions were developed by Continuum Dynamics, Inc. usino a dynamic model of.a Park I pressure suppression system and the full,'sca7e test facility data. The system model was capable of predictina pressureLtransients at specific locati.ons in the vent system. Loading across

'the vacuum breaker disc caused by pressure differentials based ori test data was thus quantified as a. function of time. This' issue was reviewed and approved by NRC on December 2a, 1984. Loadings were combined according to the Oyster Creek Updated Final Safety Analysis Report (FSAR1 comitments.

To detennine the structural integrity of the vacuum breakers, the licensee compared results from a finite element model and ANSYS program analyses with i p .g design limits specified in-the ASME Boiler and Pressure Vessel Code, Section

!: :III, Division 1,, Subsection NC,1977 Edition and addenda up to Sumer'1977. It

' concluded-that 'several vacuum breaker parts, namely the counterweight arms, the disc arms and disc arm keys, the valve shaft, and the counterweight hubs and arm hub' keysc could be overstressed under the revised loading. The licensee proposed to replace these parts with parts made of higher strength p . material durine the next two refueling outages (Cycle 12 and Cycle 13 outages).

4 By letter dated December 3, 1986, the licensee provided its justification for the above replacement schedule. The staff has reviewed that information and concludes that there is. insufficient justification for deferring the replacements lfor two refueling outages, a.0 CONCLUSION The action proposed by the licensee to restore the original design margin of safety under the revised loadings is acceptable. However, the licensee's schedule for completion of those actions is not justified. Therefore, the vacuum breaker parts required to be replaced should be replaced prior to r

startup from the next refueling outace (Cycle 12).

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5.0 REFERENCES

1. NUREG-0661, " Safety Evaluation Deport, Mark I containment Long-Term Proaran Pesolution of Generic Technical Activity A-7," Off. ice of Nuclear Reactor Regulatior, USNRC, dated July 1980,

2. "USNRC Generic Letter 83-08, Modification of Vacuum Breakers on Mark T Containment", dated February 2,1983.

3. NE00-24583-1, " Mark i Centainment Program Structural Acceptance Criteria Plant Unioue Analysis Application Guide," General Electric Co., San .tose, CA, dated October 197P.

4 American-Eociety of Mechanical Engineers, Boiler and Pressure Vessel Code,Section II', Division 1, " Nuclear Power Plant Components," New York,1977-Edition and Addenda up to Summer 1977.

5. NE00-?l888 Revision 2, " Mark I Containment Program Load Definition Report,"

General Electric Co., San Jose, CA, dated November 1081.

6. P. B. Vassallo, NRC, Letter with Attachment to H. C. Pfefferlen, RWP Licensing Programs, GE, " Evaluation of Model for Predicting Drywell to Wetwell Vacuum Breaker Valve Dynamics", dated December 74, 1984 7.- General Electric Company, letter MFN-159-87 to NRC dated October 20, 1982.

8. P. B. Fiedler (GPUN), letter to D. G. Eisenhut (NRC), Mark I Containment Torus-To-Drywell Vacuum Breakers, dated May 11, 1983.

9. J. A. Zwolinski (NRC), letter to P. B. Fiedler (GPUNi, Wetwell-To-Drywell Vacuum Breakers, dated April 11, 1985.

10. P. B. Fiedler (GPUN), Letter to J. A. Zwolinski (NRC), Mark I Containment Torus-To-Drywell Vacuum Preakers, dated August 14, 1985.

11. P. B. Fiedler (GPUN), Letter with attachment to J. A. Zwolinski (NRC),

Mark I Containment Torus-to-Drywell Vacuum Breakers, dated May 23, 1986.

1?. P. B. Fiedler (GPUN), Letter to J. A. Zwolinski (NPC), Mark I Containment Torus-To-Drywell Vacuum Breakers, dated December 3, 1986.

Principal Contributor: H. Shaw Dated: March 3, 1987

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