ML17252A030

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Summary of Meeting Regarding BWR Feedwater Nozzle Cracking
ML17252A030
Person / Time
Site: Millstone, Hatch, Monticello, Dresden, Peach Bottom, Browns Ferry, Nine Mile Point, Oyster Creek, Cooper, Pilgrim, Brunswick, Vermont Yankee, Duane Arnold, Quad Cities, Humboldt Bay, FitzPatrick
Issue date: 03/24/1976
From: Snaider R
Office of Nuclear Reactor Regulation
To:
References
Download: ML17252A030 (6)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20665 March 24, 1976 Docket Nos. 50-133, 50-219, 50-220, 50-237. 50-245 ~

50-254, 50-259: ~60: I.

50-263, 50-265, 50-271,

_50-211, so-218, 50~293,

'50-298,.50-321, 50-325, 50-331, 50-~33, 50-336

SUMMARY

OF MEETING REGARDING BWR FEEDWATER NOZZLE CRACKING

. On February 25, 1976, represeritatives of General Electric (GE) and several

  • licensees met with members of the Regulatory staff .to discuss the latest dat_a. concerning the BWR .f eedwater nozzle cracking problem and to receive

.the GE recommended interim program for the detection and elimination of

  • the cracks.

A list of attendees, copies of the viewgraphs presented at the meeting, and GE's recommended program are attached. Significant points discussed are summarized below:

1. GE believes that the nozzle area can tolerate, without catastrophic failure, a through-wall flaw under 1000 psig pressure and l00°F
2. The cause of the cracking is still believed to be temperature fluctuations in the nozzle area. Because of leakage around the thermal sleeve, the blend radius areais*exposed'to temperature swings which range from the hot saturation temperature of core water to the relatively cold entering feedwater temperature. A frequency of 1 Hz.

can be reached during those temperature swings ..

3.
  • Although there is some uncertainty that the cracking is due.to leakage flow, the proposed "fix" is based upon the* assumption that it is the cause.
4. The maximum depth of the cracks found to date has been approximately

.5". The maximum depth of penetration into base metal has been approximately .25". Less than 50% of the cracks found to date have penetrated the base metal.

5. At Millstone I, the number of cracks found in the second examination (one year after the first cracks discovered has been ground out) was greater than the number found in the original examination. The depth of the cracks wa£ approximately the same. *'
6. The cracks are difficult to detect, even using dye penetrant examination, because they are easily plugged by oxide. Ultrasonic testing from the external nozzle circumference has not yet been shown to be a viable alternative.. However, GE mentioned investigation into a new technique which may prove successful.
7. GE's Mr. I. Kobsa explained in detail the testing program which is taking place at San Jose. Questions from the NRC staff showed concern for the studies in the thermal~hydraulic area. GE replied that such studie~ were now in progress. The staff alsq expressed concern about the thermal and pressure stress (long-term) model for crack growth.

GE answered that the long-term analysis was also in progress.

8. Mr. Kobsa discussed in detail GE's. recommended interim *examination program, which is based upon the determination of the number of cycles (N) to reach 1/10 of the miriimum metal path (MMP) between the point at which the nozzle inside diameter is tangent to the blend radius and the

.exterior surface of the reactor pressure vessel (RPV). The maximum allowable flaw size is assumed to be .1 MMP and inspections would be based upon the number of start-up/shutdown cycles (N) to reach' this ainount of crack depth, with the first scheduled refueling outage after N-20 having been selected as the starting point for annual UT irispect"ions from the outside -of the RPV. MR. Kobsa stated-that this was in conformance with the intent of ASME Code Section XI. A ur examination of all feedwater nozzle blend radii and .safe ends would be**

performed at the next scheduled 'refueling outage following N startup/

shutdown cycles. At this time a PT inspection of one nozzle ~ould be accomplished. The remaining nozzles would be inspected if cracking were found in the first. The NRG staff took exception to .several points of this. proposal. First, little,data *had* been presented to verify that UT techniques external t.o the. vessel were. acceptable.

Second, the choice of N-20 for the first inspection.was questioned, and the NRC staff members stated they required more data to justify not requiring inspections prior to that point. Mr. Kobsa mentioned that there are plants operating beyond the N-20 cutoff which have not made the initial inspection. These questions were left open, to be-resolv~d by specific questions from the NRC staff and answers from GE.

9. Mr. Kobsa mentioned that GE believes that the welded thermal sleeve and sparger, with resultant zero bypass leakage, will be the solution'to the problem. This was questioned by NRC staff members, who believe that the welds may crack under stress and who also object to the inacces'.'"

sability for inspection afforded by a welde4 sparger. Mr. Kobsa pointed out that the new design incorporates a larger (by a factor of 4).

annular space, allowing inspection.

...... -~

10. Mr. W. Zarella of GE made a presentation concerning the implementation of the various fixes (interference fit sparger/w.elded-in sparger/

blend radii indication grind-out) and broke down time, manpower, exposure, and monetary_requirements for each of the options. The data is contained in the PW Nozzle Program document (Enclosure 2).

Note the various assumptions which were made.

  • As mentioned above, several.items remain outstanding a,nd wilLrequire communication between the staffs of the NRC and GE. GE has promised to
  • provide mor.e information as it becomes available; arid more meetings may be set for the future ..

7 ' .

~ti .

Ric rd P. naider, Project Manager Operating Reactors Branch #2 Division of Operating Reactors

Enclosures:

1. List .of Attendees
2. Viewgraph copies -

"PW Nozzle Program"

3. GE paper entitled "Peedwater Nozzle Interim Exaniination Recommendation" cc: Se~ next pige

cc' Pacific Gas and Electric Company Yankee Atomic Electric Company ATTN: Mr. John C. Morrisey ATTN: Mr. Robert H. Groce Vi~e President and General Licensing Engineer' Counsel 20 Turnpike Road

. Philadelphia Elec.tric Company Jersey Central Power & Light Company . ATTN: Mr. Edward G~ Bauer, Jr.

ATTN: Mr .. I~ R. Finfrock . . Vice President and General Vice President - Gerieration -

  • Counsel Madison Avenue at Punch Bowl Road 2301 Market Street Morristown, New Jersey 07960 Philadelphia, Pennsylvania 19101 Niagara Mohawk Power Corporation Boston Edison Company ATTN: Mr. Gerald K. Rhode M/C NUCLEAR Vice President - Engineering ATTN: Mr. J. E. Larson 300 Erie Boulevard West Nuclear Licensing Syracuse, New York 13202 Administrator - Operations 800 Boylston.Street Commonwealth Edison Company Boston, Massachusetts
  • 02199 ATTN: Mr. R. L. Bolger .

Assistant Vice President Nebraska.Public Power District P. 0. Box 767 ATTN: Mr. J. M. Pilant, Manager .

Chicago, Illinois 60690 Licensing and Quality Assurance P. O. Box 499 Northeast Nuclear Energy Company Columbus, Nebraska , 68601.

ATTN: Mr. Donald c. Switzer

  • President Georgia Power Company and Oglethorpe P. 0. Box 270 *
  • Electric Memt:tership Corporation .

Hartford, Connecticut 06101 A1TN: I. S. *Mitchell, III Vice President and S~cretary Tennessee Valley Authority Georgia Power Company ATTN: Mr. Godwin Williams, Jr *. Atlanta, Georgia 30302 '.

Manager of Power 818 Power Building Carolina Power & Light Company Chattanooga, Tennessee* 37401 AT'IN: Mr. J. A. Jones Executive Vice President .*

Northern States Power Company Engineering, Construction ATTN: Mr. L. 0. Mayer, Manager and Operations Nuclear Support Services 336 Fayetteville Street 414 Nicollet Mall - 8th Floor Raleigh, North Carolina 27602*

Minneapolis, Minnesota 55401 Iowa Electric Light & Power Company PowerAuthority of the State of New York ATTN: Mr *. Duane Arnold, President ATTN: Mr. George T. Berry Security Building General Manager &Chief Engineer P. o. Bax 351 10 Columbus Circle Cedar Rapids, Iowa 52406 New York, New York 10019

/

/

~-

/

J

  • ATTENDANCE LIST NAME ORGANIZATION .

R. P. Snaider NRC - DOR B. C. Buckley NRC *- DOR H. T. Watanabe GE Licensing W. T. Zarella GE - Product*Service I. R. Kobsa GE - BWRSD R. Gamble NRC - DOR:

B. D. Liaw NRC - DOR*.*

R. K. Mattu. NRC - NSS/MEB K. N. Jabbour NRC - DOR/EB W. S. Hazleton NRC DOR/EB P. N. Randall NRC - 0$D/DOR Pei-Ying Chen NRC - DSS/MEB W. J. Coll ins . NRC - OI&E/RTAB L. C. Shao NRC - DOR G. K. Hussak Niagara Mohawk C. E. Cantrell 'TVA E. A. DeBarba Northeast titilities T. J. Perkins Niagara Mohawk C. S. .Bohanan Carolina Power & Light Comp.any W. R. Schmidt MPR Associates B. Biava JerseyCentral Power & Light T. Madden* Jersey Central.Power & Light.

J. Guibert NRC - DOR R. T. DeMuth Boston Edison Company D. Ziemann NRO - DOR

  • K. D. Desai NRC - MEB V. S. Noonan NRC - DOR/EB C. Y. Cheng NRC - DOR/EB J. M. Pilant Nebraska Public Power District

\ _____

\

MEETING

SUMMARY

DISTRIBtrrION:

~-(22)

NRG PDR (22)

Local PDR (22) .

ORB 112 Reading NRR Reading B. Rusche E. Case V. Stello K. R. Goller

o. Eisonh(it T. J. Carter

~* A. Purple G. E. Lear R. W. Reid L. c .. Shao*

R. L. Baer A. Schwencer B. K. Grimes Project Manager OELD. ..

O_I&E. (3)

RMDiggs R. Fraley, ACRS (16)

T. B. Abernathy '.

J. R. Buchanan NRG

Participants:

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