ML20197A734
| ML20197A734 | |
| Person / Time | |
|---|---|
| Issue date: | 02/26/1998 |
| From: | Essig T NRC (Affiliation Not Assigned) |
| To: | Modeen D NUCLEAR ENERGY INSTITUTE (FORMERLY NUCLEAR MGMT & |
| References | |
| PROJECT-689 NUDOCS 9803090364 | |
| Download: ML20197A734 (7) | |
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pa aseg y- A UNITED STATES s* NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30eeH001
'g..... February 26, 1998 David J. Modeen, Director Engineering, Nuclear Energy Institute 1776 l Street, NW Suite 400 Washington, DC 20006 3708
SUBJECT:
PROPOSED DATA EXCLUSION CRITERIA AND ADJUSTMENT OF MEASURED LEAK RATE FOR TUBE R28C41 (PLANT S)
Dear Mr. Modeen:
Appendix C to " Steam Generator Tubing Outside Diameter Stress Corrosion Cracking at i
Tube Support Plates Database for Alternate Repair Limits" (NP 7480 L V2 R2), Volume 2, dated November 1997, from the Electric Power Research Institute (EPRI) proposed additionai data exclusion criteria to address measured steam line break pressure leak rates l that appeared to be outliers with respect to other data in the 3/4 inch tube database. Two criterion are proposed to address leak rete data that appear to be significantly lower than the expected leak rates. The industry proposed similar exclusbn criteria prior to issuance of Generic Letter (GL) 95 05, " Voltage Based Repair Criteria for ' Westinghouse Steam Generator Tubes Affocted By Outside Diameter Stress Corrosion Cracking," but they were rejected by the NRC. In addition to the proposed exclusion criteria, Appendix C also provided 'he bases to reduce the assigned leak rate for tube R28C41 (Plant S) from 24V y to 1250 t/hr. %ls proposalis based on a reanalysis of the calculated crack leak rate using input parameters more representative of the crack morphology prior to testing.
The motivation for developing additional exclusion criteria is to cddress leak rate data that appear to have been affected by pluggNg of the crack during testin0 fiGm impurities in the water, in the field, this effect is conservatte with respect to the leakage and offsite dose consequences. However, the inclusion of outtler data in the leak rate database leads to unrMistically high accident leak rate results because of the statistical models used in the calculation. As indicated in the staff's origlaal assessme;nt of similar criteria proposed prior to issuance of GL 95-05, the leak rate correlutions are entirely empirical, and it is not statistically valid under these ub:umstances to dvete data simply because the data values do not conform to expectations. Ab proposed, Criterion 3b would exclude (lata on the basis of a single parameter, the measured leak rate. This criterion does not consider other factors which may have contributed to e lower than expected leak rate. Therefore, the staff concludes that proposed Criterion 3b as specified on page C 5 of the above referenced report is not acceptable for the exclusion of leak rate data. Criterion 3a considers both the crack morphology (i.e., crack length) and the leak rate relative to statistical prediction interva!= for the entire data set. However, sines this criterion is primarily statistically based and significant scatter is expected in leak rate correlations, the staff recommsnds that the proposed interval (95%) be increased to a one sided 99%
prediction interval to provide a higher level of assurance that the outlying data are 17,C, (l RC =
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D. Mod:cn 2-inconsistent with other leak rate data in the datthess. A one sided 99% prediction interval should crack be applied to the correlations for leak rate as a function of bobbin coil voltage and length.
At this time, the staff requires additionalinformation to complete its evaluation of data exclusion Criterion 3a, in addition, information is required in order to conclude whether a reduction in the leak rate for tube R28C41 is appropriate. Unreanived questions related to these proposals are included in Encicture 1 to this letter. Please provide the NRC with a response to these quentlans so that the staff can complete its review of data exclusion Criterion Sa and the proposed reduction in leak rate for the one tube noted above. If y have any questions, please contact Ted Sullivan at (301) 415 2795.
Sincerely, 44 w& -
.Ahemos H. ssig, Acting Chie -y l Generic Issess and Environme5 al Pro,lects Branch Division of Reactor Program Ntnagement Office of Nuclear Reactor Regulation Project No.: 689
Enclosure:
As stated cc: C. Ct:laway, NEl I
l N
D. Modeon - 2-i i inconsistent with other leak rate data in the database. A one sided 99% prediction interval shouM M applied to the correlationt for leak rate as a function of bobbin coil voltage and crack length.
4 j At this time, the staff requires additionallnformation to complete its evaluation of data exclusion Criterion 3a. In addition, information is required in order to conclude whether a reduction in the leak rate for tube R28C41 is appropriate. Unresolved questions related to these proposals are included in Enclosure 1 to this letter. Please provide the NRC with a j response to these questions so that the staff can complete its review of dat.a. exclusion .
Criterion 3ri and the proposed reductiot,in leak rate for the one tube noted above. If you have any ouestions, please contact Ted Sullivan at (301) 415 2795.
Sincerely, f
(original signed by:]
Thomas H. Essig, Acting Chief Generic Issues and Environmental Projects Branch 4 Division of Reactor Program Management
! Office of Nuclear Reactor Regulation Project No.: 689
Enclosure:
As stated cc; C. Callaway, NEl Distribution: ,
EMCB RF BSheren E His CenterO PWen PUBUC EDebec Mathet
> CBeardslee SCoffin AKeim 5:
i
. DOCUMENT NAME: G:\ RUSH \NEl-RAl.WPD
' Gee previous concurrence f
To receNo e copy of this documerit. Indeste in the boat *C' = Copy gut ettechmerit'orelosure "t* = Cev with attachment'entsure 'N' = No copy 3
OFFICE DE:EMCB lE DOE:EMCB lE (A)BC:EMCB:Dt1 E PERB:dRF]p d 1 NAME PRush' JTsao* E$uilivan' TEsstgM1%
O2/10/98 02/10/98 02/19/98 DATE 02/, # /98
- OFFICIAL RECORD COPY
- D. Modeen 2-inconsistent with other leak rate data in the database. A one sided 99% prediction interval sh'..J be applied to the correlations for leak rate as a function of bobbin coil voltage and
- crack length.
At this time, the staff requires additionalinformation to complete its evaluation of data exclusion Criterion 3a. In addition, information is required in order to conclude whether a reduction in the leak rate f or tube R28C41 is appropriate. Unresolved questions related to these proposals are included in Enclosure 1 to this letter. Please provide the NRC with a response to these questions so that the staff can complete its review of data exclusion Criterlon 3a and the -roposed reduction in leak rate for the one tube noted above. If you !
have any questions, please contact me at (301) 415 2795.
Sincerely, Edmund J. Sullivan, Acting Chief Materials and Chemical Engineering Branch Division of Engineering Office of Nuclear Reactor Regulation Project No.: 689
Enclosure:
As stated I
cc: C. Callaway, NEl Qistribution:
EMCB RF BSheron File Center SMagruder PUBLIC EDebec Mathet CBeardslee SCoffin AKeim DOCUMENT NAME: G:\ RUSH \NEl-RAl.WPD
'See previous concurrence -
1 Tag Wwe e copy of tNo document, indcote in the box: "C" = Copy without ettschmentlenclosure "E" = Copy with attachmery ',Mosure *N' = No copy OFFICE DE:EMCB E DE:EMCB E (A)BC:EMCB:DE E. PERE % M NAM 2 PRush' JTsao* ESullivan fd4\ TEs%g jDATE 02/10/98 02/10/98 O 02/f)/98 O2Olg98 -
OFFICIAL RECORD COPY
David Modeen At this time, the staff has yet to fully evaluate data exclusion Criterion 3a. In addition, further information is required in order to c >nclude whether a reduction in the leak rate for tube R28C41 is appropriete. Unresolved questions related to these proposals are included in Enclosure 1 to this letter. Please provide the NRC with a response to these questions in order so that the staff can complete its review of data exclusion Criterion 3b and the proposed reduction in leak rate for the one tube noteJ above. If you have any questions, please contact me at (301) 415 2795.
Sincerely, Edmund J. Sullivan, Acting Chief Materials and Chemical Engineering Branch Division of Engineering Office of Nuclear Reactor Regulation Project No.: 689
Enclosure:
As stated cc: C. Callaway, NEl l Dnitibution EMCB RF BSheron File Center SMagruder PUBLIC EDebec-Mathet CBeardslee SCoffin AKeim DOCUMENT NAME: G:\ RUSH \NEl RAl.WPD he To recolve a cony of this document, indicate in the bou *C' = Copy without attachment' enclosure *E* = Cor r with attachment! enclosure *N* = No copy OFFICE DE:EMCB lE DE:FMCB 6 (A)BC:EMCB:DE PERB:DRPM NAME PRush M g JTsao @ f ESullivan TEssig DATE O2//0/98' 02//cV98 02/ /98 02/ /98 OFFICIAL RECORD COPY
I Nuclear Energy Institute Project No. 689 cc: Mr, Ralph Beedle Ms. Lynnette Hendricks, Director Senior Vice President Plant Support and Chief Nuclear omcer Nuclear Energy Instituto j Nuclear Energy institute Suite 400 Suite 400 1776 i Street, NW 1776 i Street, NW Washington, DC 20006 3708 !
Washington, CC 20006-3708 i4r. Alex Marion, Director Programs Nuclear Energy Institute Suite 400 1776 l Street, NW Washington, DC 20006-3708 Mr. David Modoen, Directc,'
Engineering Nuclear Energy lnetitute Suite 400 1776 i Street, NW Washington, DC 20006-3708 Mr. Anthony Pietrangelo, Director Licensing '
Nuclear Energy Institute Suite 400 1776 l Street, NW Washington, DC 20006 3708 Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Activities Nuclear and Advanced Technology Division Westinghouse Electric Corporation P.O. Box 355 Pittsburgh, Pennsylvania 15230 Mr, Jim Davis, Director Operations Nuclear Encrgy Institute Suite 400 1776 l Street, NW Washington, DC 20006-3768 N' '
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s e
4 QUESTIONS RELATED TO PROPOSED EXCLUSION CRITERION 3b AND REDUCTION IN LEAK RATE FOR STEAM GENERATOR TU8E R28C41 FOa PLANT S
- 1. Discuss whether the proposed exclusion criteria be applied to leak rate data for 7/8 inch diameter tubing. In addition, specify what data, if any, would be affected.
2.
Proposed Criterion 3a excludes data based, in part, on a calculated leak rate from a measured crack length. As demonstrated for tube R28C41, such calculations are highly sensitive to the input crack length. Describe the process and criteria established to determine the appropriate crack length for input into the leak rate calculations. Also discuss what crack length will be assumed in the situation where multiple flaws tocated at a tube support plate intersection leak at steam line break pressures.
3.
It was indicated in the text that CRACKFLO accounts for crack tip tearing. Describe how the CRACKFLO code determines the extent uf crack tearing fcr steam generator tube flaws. If the g;verning fracture parameter of CRACKFLO is the J integral, describe any benchmarking done of the code since J controlled crack growth is not applicable to steam generator tube flaws. For tube 828C41, provide the overall crack length that was calculated by CRACKFLO in order to determine the tube leak rate.
ENCLOSURE 1
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