ML17191A820
| ML17191A820 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 08/05/1998 |
| From: | Rossbach L NRC (Affiliation Not Assigned) |
| To: | Kingsley O COMMONWEALTH EDISON CO. |
| References | |
| TAC-MA1673, TAC-MA8941, NUDOCS 9808100301 | |
| Download: ML17191A820 (5) | |
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Mr. Oliver D. Kingsley, President Nuclear Generation Group Commonwealth Edison Company Executive Towers West Ill 1400 Opus Place, Suite 500 Downers Grove, IL 60515 August 5, 1998
SUBJECT:
REQUEST FOR ADDITIONAL.INFORMATION REGARDING EVALUATION OF CORE SPRAY WELD FLAWS AT DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 (TAC NOS. MA1673 AND M98941)
Dear Mr. Kingsley:
By letters dated April 11, 1998, and June 5, 1997,. Commonwealth Edison Company (Com Ed) submitted evaluations of core spray weld flaws at Dresden.. Units 2 and 3, respectively.
In these evaluations, Com Ed concluded that sufficient m~rgin exists to operate both units for two
. cycles with the identified. flaws. The staff has performed a preliminary review of these reports in the area of flaw evaluation and has d~termined that additional information is needed. Please provide the information discussed in the enclosed request within 30 days of receipt of this letter.
Should you have any questions about this request, please contact me at (301) 415-2863.
Docket Nos. 50-237 and 50-249 Sincerely, ORIG SIGNED BY La\\Nrence W. Rossbach; Project Manager Project Directorate 111-2 Division of Reactor Projects - Ill/IV Office of Nuclear Reactor Regulation
Enclosure:
Request for Additional Information cc w/encl: See next pa~e Distribution:
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UNITED STATES NUCLEAR REGULATORY COMMISSION Mr. Oliver D. Kingsley, President.
Nuclear Generation Group Commonwealth Edison Company Executive Towers West Ill 1400 Opus Place, Suite 500 Downers Grove, IL 60515 WASHINGTON, D.C. 20555-01 August 5, 1998
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING EVALUATION OF CORE SPRAY WELD FLAWS AT DRESD!=N NUCLEAR POWER STATION, UNITS 2 AND 3 (TAC NOS. MA1673 AND M98941}
Dear Mr. Kingsley:
By letters dated April 11, 1998, and June 5, 1997, Commonwealth Edison Company (ComEd} submitted evaluations of core spray weld flaws at Dresden, Units 2 and 3, respectively.
In these evaluations, ComEd concluded that sufficient margin exists to operate both units for two cycles with the identified flaws. The staff has performed a preliminary review of these reports in the area of flaw evaluation arid has determ.ined that additional information is needed.. Please provide the information discussed in the enclosed request within 30 days of receipt of this letter.
Should you have any questions about this request, please contact me at (301} 415-2863.
Docket Nos. 50-237 and 50-249 Sincerely, c:Y~1,,_,,/(~
Lawrence W. Rossbach, Project Manager Project Directorate 111-2 Division of Reactor Projects - Ill/IV Office of Nuclear Reactor Regulation
Enclosure:
Request for Additional Information cc w/encl: See next page
1*.'.
- 0. Kingsley Commonwealth Edison Company cc:
Michael I. Miller, Esquire* -
Sidley and Austin One First National Plaza Chicago, Illinois 60603 Commonwealth Edison Company Site Vice President - Dresden 6500 N. Dresden Road Morris, Illinois 60450-9765 Commonwealth Edison Company Dresden Station Manager 6500 N. Dresden Road Morris,.Illinois 60450-9765 U.S. Nuclear Regulatory Commission Dresden Resident Inspectors Office 6500 N. Dresden Road Morris, Illinois 60450-9766 Regional Administrator U.S. NRC, Region Ill 801 Warrenville Road Lisle, Illinois 60532-4351 Illinois Department of Nuclear Safety Office of Nuclear Facility Safety 1035 Outer Park Drive Springfield, Illinois 62704 Chairman Grundy County Board Administration Building 1320 Union Street Morris, Illinois 60450 Document Control Desk-Licensing Commonwealth Edison Company 1400 Opus Place, Suite 400 Downers Grove, Illinois 60515 Commonwealth Edison Company Reg. Assurance Supervisor - Dresden 6500 N. Dresden Road Morris, Illinois 60450-9765 Dresden Nuclear Power Station Units 2 and 3 Mr. David Helwig Senior Vice President Commonwealth Edison Company Executive Towers West Ill 1400 Opus Place, Suite 900 Downers Grove, IL 60515 Mr. Gene H. Stanley PWR's \\/lee President Commonwealth Edison Company Executive Towers West Ill 1400 Opus Place, Suite 900 Downers Grove, IL 60515 Mr. Steve Perry BWR's Vice President Commonwealth Edison Company Executive Towers West_ Ill 1400 Opus Place, Suite 900 Downers Grove, IL 60515 Mr. Dennis Farrar Regulatory Services Manager Commonwealth Edison Company Executive Towers West Ill 1400 Opus Place, Suite 500 Downers Grove, IL 60515 Ms. Irene Johnson, Licensing Director Nuclear Regulatory Services Commonwealth Edison Company_
Executive Towers West Ill 1400 Opus Place, Suite 500 Downers Grove, IL 60515 Mr. Michael J. Wallace Senior Vice President Commonwealth Edison Company Executive Towers West Ill 1400 Opus Place, Suite 900 Downers Grove, IL 60515
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REQUEST FOR ADDITIONAL INFORMATION REGAROING EVALUATION OF CORE SPRAY WELP FLAWS AT PRESOEN. UNITS 2 & 3 Dresden Untt 3 (1)
In your flaw evaluation report,.the flaws in the Loop A upper sparger 800 downcomer shroud pipe to collar weld (1 P8a) were determined to be so extensive after crack growth
. and that the subject weld is assumed not to carry any load. The staff has concerns regarding the functionability of the core spray Loop A because the hidden weld pg, c0nnecting the shroud penetration pipe to the sparger tee box, is not accessible for inspection. Therefore, the structural* integrity of weld pg can not be assured.
(a) Provide a comprehensive discussion on a plant specific basis. regarding the susceptibility of the weld pg (adjacent to weld 1 P8a) to IGSCC; and its impact to the structural integrity of weld pg, The discussion should include the effect due to the presence of a crevice condition (annulu~ between the collar and the pipe) and the grinding of the weld root in accelerating the crack initiation and growth in the subject weld.
- (b) Discuss the safety consequences including its impact to the peak cladding temperature (PCT) for the-most bounding case of LOCA, when both weld pg and its adjacent weld 1 PSa are assumed to be completely failed due to extensive through-wall cracking.
(c) Discuss the industry-wide effort in developing the techniques to inspect P9 welds and the feasibility of inspecting P9 welds during the upcoming refueling outage.
- (d) In the staff's safety evaluation of BWRVIP-18, usWR Core Spray Internals Inspection and Flaw Evaluation Guidelines," which was issued on June 8, 1998, the staff requires
- that the inspection of P9 welds should be performed when extensive cracking of the
- corresponding PSa welds was found. What is your plari to meet that requirement?
(e) Discuss your contingent repair/replacement plan in the event that the structural integrity of weld 1 Paa or its adjacent weld P9 ean not be assured?
(2)
In the staff's safety evaluation of BWRVIP-18 which was issued on June 8, 1998, the staff requires that the inspection uncertainties in measuring the flaw length by UT or VT should be considered in flaw evaluation. Therefore, the licensee should perform additional flaw evaluations by incorporating the inspection uncertainties in the crack growth calculations and discuss the results of load margin factors.
(3)
The staff notes that, for the five cracked welds, both VT and UT were performed. Describe
- the crack indications that were observed by visual examinations and compared to that reported by UT.
ENCLOSURE
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2 (4)
For the two cracked lower.elbow welds (P4C), cracking was originally found during the previous refueling outage (D3R 13) and were reinspected during the following refueling outage D3R14. Discuss the inspection techniques used in each refueling outage and estimate the crack growth rate.based on the flaw sizes measured at the two refueling outages.
Presden Unit 2 (5)
In the staff's safety evaluation of BWRVIP-18 which was issued on June 8; 1998, the staff does not agree with the BwRVIP provided guidelines regarding the flaw evaluation of the inaccessible region by assuming that "2Xn percent of the inaccessible length is cracked, where "X" is the percent cracking in the accessible area. Instead, the staff requires that the inaccessible region should be assumed to be completely cracked for flaw evaluation.
Therefore, the licensee should perform an additional flaw evaluation of the (loop B) 110 ° shroud penetration thermal sleeve collar weld (2P8a) by assuming the inaccessible region to be completely cracked, ahd discuss the results of load margin factors (safety factors).
Presden Units 2 and 3 (6)
For the Tables reporting the results of flaw evaluation or stress values, identify the bounding conditions (normal/upset or emergency/faulted conditions) for.each reported evaluation result.
(7)
Provide the information on reactor water chemistry (conductivity, chloride, sulfate and oxygen content) for the last three operating cycles..
'(8)
Provide a brief discussion of the methodologies used in your flaw*evaluation including load calculations and combinations, piping modeling and stress analysis, and crack growth calculations that deviate from the guidelines provided in BWRVIP-:18.