ML20140G076

Summary of 860124 Meeting W/Consultants to Discuss Adequacy of Downcomer Design in Context of Reanalysis Performed by Util.Design Marginal.Recommends Granting OL W/Listed Condition.List of Attendees Encl

ML20140G076
Person / Time
Site:	Nine Mile Point
Issue date:	01/31/1986
From:	Liaw B Office of Nuclear Reactor Regulation
To:	Bernero R Office of Nuclear Reactor Regulation
Shared Package
ML17055B282	List: ML20140G076
References
TAC-63425, NUDOCS 8602050231
Download: ML20140G076 (4)

Text

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1. UNITED STATES 8 'o,A NUCLEAR REGULATORY COMMISSION

• E 3 WASHINGTON. D. C. 20565

(.....,/ .

JAN 311986 Docket No.: 50-410  ;

MEMORANDUM FOR: R. M. Bernero, Director Division of BWR Licensing THRU:

G. C. Lainas, Assistant Director for BWR Division of BWR Licenisng i

FROM: B. D. Liaw, Chief Engineering Branch Division of BWR Licensing

SUBJECT:

DOWNCOMER DESIGN FOR NINE MILE POINT NUCLEAR STATION, UNIT 2 (NMP-2)

REFERENCE:

Letter from C. V. Mangan to E. Adensam, dated 1/23/86,regardingabovesubject.

On January 24, 1986, the NRC staff met with its consultants to discuss the adequacy of NMP-2 downcomer design in the context of a reanalysis performed by the applicant, Niagara Mohawk Power Corporation, and transmitted by the letter referenced above. The list of attendees is attached. The discussion focused on the acceptability of the design of the downcomers for NMP-2 and on corrective actions that might be required if the current design is found unacceptable.

On the basis of a review of the applicant's reanalysis and assuming that; -

there are no significant errors in the new calculations; and the way that the applicant applies the 800-series chugging loads is acceptable, the staff and the consultants (the Group) conclude that the unbraced downcomer design at NMP-2 is marginal. The Group also concludes that the NMP-2 design meets the licensing criteria for upset and emergency conditions; however, the applicant has not adequately demonstrated the design adequacy for the faulted condition. 51ecifically the downcomer may lose geometrical stabilitybeforereac11ngthecalculatedstresslevelsforthefaulted condition.

, 1

Contact:

R. Li

• X-24417 I g(ooaosOK5s)@yg. l

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. R. M. Bernero JAN 311555 In reaching these conclusions, the Group discussed technical areas where excessive design conservatisms may be reduced in order to justi,fy the adequacy of the downcomer design; e.g.,

higher structural dampir.g; load combination methodology; use of cert.ified material data (yield strengths) instead of Code-specified minimum; and load definitions.

1 Other than the use of certified material data, the applicant has already taken credit for the relaxed criteria that the NRC staff has accepted. The

, Group was informed that the downtomer pipes are rolled-and-welded, not seamless pipes. Attual material yield strengths would be higher for the latter. For welded pipes, some geometrical imperfections (out-of-i roundn'ess, non uniformities in seam welds, etc.) and the residual stresses j are present; therefore, it may not be appropriate to provide relief in this area unless one can quantify the effect of these imperfections and residual j stresses to properly allow for the use of certified material data, i In spite of the conclusions stated above, the Group recommends that the staff proceed with granting an operational license on the condition that by the first refueling, the design adequacy with respect to the faulted condition be demonstrated, e.g., out-of plant testing which simulates the downcomer installation for NMP-2, or hardware modifications to the downcomers be made during the first refueling outage. The bases for this recommendation are as follows: .

Themateria]usedfortheNMP-2recirculationpipingsystemis316NG which is cohsidered much less susceptible to intergranular stress i

corrosion ended pipecracking; therefore,ll.theprobabilityofhavingamajordouble-break is rather sma The probability of the simultaneous occurrence of a LOCA and SSE is small for the life of the plant and is even smaller during the first fuel cycle.

The existing design is adequate to meet either SSE or LOCA loads in combi-nation with other normal loads, but not both.

R. M. Bernero JAN 31 1935 Therefore, the Group concludes that the oleration of the plant to the first refueling outage poses no significant risi to the public healtd and safety.

iq..:':-t *;  :

C. :;. D::t B. D. Liaw, Chief Engineering Branch i Division of BWR Licensing i

Attachment:

As stated i

, cc: H. R. Denton l

D. G. Eisenhut R. W. Houston G. C. Lainas 1 E. Adensam M. Haughy R. LaGrange W. Hazelton R. Hermann E. Rodabaugh G. Wilkowski B. Saffell .

R. Mesloh M. Hartzman K. Wichman C. P. Tan Y. Li -

DISTRIBUTION:

umb - Docket Files BWEB Reading Files BWEB NMP-2 Files BWEB Li Chron. Files l

l 3 1

• SEE PREVIOUS SHEET FOR CONCURRENCE. s~

• *' / ,

j i k Otc : BWEB  : BWEB  : 5 ]  : WD0  :  :  ;

........__....__.......____.......$.4(.M..:...[A ........... __ .__......__.........__.......

NAME :R. Li: jar :R.LaGrange : BOLibw  : G. (nas  : R.B ro :

DATE : 1/28/86 :1/ /86 : 1/qi /86 : 1/ g\ /86  : / /8 :  :

0FFICIAL RECORD COPY,. .

_ ~ . - . _ _ _ . - - _ . -

ATTACHMENT

LIST OF ATTENDEES MEETING ON DOWNCOMERS NMP-2 JANUARY 24, 1986 NRC Staff:

R. Bernero - Director, DBL (part-time)

G. Lainas - Assistant Director, DBL (part-time)

B. D. Liaw - Chief, EB, DBL Y. C. Li - Mechanical Engineer, EB, DBL C. P. Tan - Structural Engineer, EB, DBL M. Hartzman - Sr. Mechanical Engineer, EB, DPL-B K. Wichman - Sr. Materials Engineer, EB, DPL-B Consultants:

E. C. Rodabaugh (E. C. Rodabaugh & Associates)

G. Wilkowski (BCL)

B. Saffell (BCL)

R. Mesloh (BCL) c h*-

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