ML20134H466
| ML20134H466 | |
| Person / Time | |
|---|---|
| Issue date: | 02/06/1997 |
| From: | Craig C NRC (Affiliation Not Assigned) |
| To: | Matthews D NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9702110315 | |
| Download: ML20134H466 (28) | |
Text
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WASHINGTON, D.C. 20555-0001 p
February 5, 1997 MEMORANDUM T0:
David B. Matthews, Chief Generic Issues and Environmental Projects Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation FROM:
Claudia M. Craig, Senior Project Manager Q}
b Generic Issues and Environmental Projects Branch
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Division of Reactor Program Management Office of Nuclear Reactor Regulation
SUBJECT:
SUMMARY
OF MEETING WITH WESTINGHOUSE TO DISCUSS FUEL CORR 0SION MODEL The subject meeting was held at the Nuclear Regulatory Commission (NRC) office in Rockville, Maryland on December 12, 1996, between representatives of Westinghouse and the NRC staff. The purpose of the meeting was for Westinghouse to discuss the reasons for developing a revised fuel corrosion model, the model and its application, and future plans for use of the revised model. Attachment 1 is the list of meeting participants.
Westinghouse provided proprietary and non-proprietary versions of the presentation material in an application for withholding proprietary information dated January 17, 1997 (AW-97-1063). Attachment 2 is a copy of the non-proprietary presentation material.
The Westinghouse presentation discussed the background of the issue, the data and trends concerning corrosion, the revised model development and schedule, the preliminary assessment of impacts on design features, and the plans for implementation of the revised code.
Westinghouse discussed the differences in composition of fuel cladding for conventional Zircaloy-4, improved Zircaloy-4, and the new ZIRLO. The data from the mid 1980s indicated an increase in corrosion as burnup increases.
This led Westinghouse to take actions including:
development of corrosion surveillance programs to expand the database in support of a revised model, introduction of improved Zircaloy-4, which is lower in tin than conventional Zircaloy-4 and therefore has a lower cor osion rate, and modification of the G'V/
corrosion design model.
Even though the improved Zircaloy-4 provides greater corrosion resistance, the improvements in operational efficiency that have also occurred over the past several years, such as longer fuel cycles, higher f2 coolant temperatures, higher power levels, and more aggressive coolant eV chemistry, have overtaken the extra corrosion margin provided by the improved Zircaloy-4. A comparison of the current model with the data indicated that the model underpredicts corrosion for both conventional and improved Zircaloy-4, particularly at end of life for the improved Zircaloy-4.
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i D. Matthews February 6, 1997 Therefore, Westinghouse developed a revised model for predicting corrosion rates. Westinghouse compiled a list of potential correlating variables and then selected the ones that gave the best improvements in correlation. These variables were then inserted into the model.
The revised model is currently complete, however, is considered preliminary until final signoff.
Westinghouse plans to implement the'model in standard!
designs in April 1997 and plans to extend the model to fuel assembly ~
a~
l structural components in August 1997.
In addition to the use of the rev~ised model to predict corrosion, Westinghouse plans to use ZIRLO in high' corrosion, plants that have long cycles.
ZIRLO is, considered much more resistant to corrosion and will be used as the basis for high burnup programs.
x Westinghouse estimated that next year 80% of, fuel'they provide will have ZIRLO' cladding.
i Westinghouse and the staff discussed the regulatory implications of the implementing the revised model. Westinghouse will' keep the staff informed 'f o
their progress.
Attachments: As stated cc w/atts:
Mr. Nicholas J. Liparulo Westinghouse Electric Corporation Mail Stop ECE 4-15 P.O. Box 355 Pittsburgh, PA 15230-0355 Mr. Hank A. Sepp Westinghouse Electric Corporation Mail Stop ECE 4-07A P.O. Box 355 Pittsburgh, PA 15230-0355 Mr. Andrew P. Drake, Project Manager Westinghouse Owners Group Westinghouse Electric Corporation Mail Stop ECE 5-16 P.O. Box 355 Pittsburgh, PA 15230-0355 i
s t
t D. Matthews February 6. 1997 Therefore, Westinghouse developed a revised model for predicting corrosion rates. Westinghouse compiled a list of potential correlating variables and then selected the ones that gave the best improvements in correlation.
These variables were then inserted into the model.
The revised model is currently complete, however, is' considered preliminary until final signoff. Westinghouse plans to implement the model in standard designs in April 1997 and plans to extend the model to fuel assembly structural components in August 1997.
In addition to the use of the revised model to predict corrosion, Westinghouse plans to use ZIRLO in high corrosion plants that have long cycles. ZIRLO is considered much more resistant to corrosion and will be used as the basis for high burnup programs.
Westinghouse estimated that next year 80% of fuel they provide will have ZIRLO cladding.
Westinghouse and the staff discussed the regulatory implications of the implementing the revised model. Westinghouse will keep the staff informed of their progress.
Attachments: As stated cc w/atts:
Mr. Nicholas J. Liparulo Westinghouse Electric Corporation Mail Stop ECE 4-15 P.O. Box 355 Pittsburgh, PA 15230-0355 Mr. Hank A. Sepp Westinghouse Electric Corporation Mail Stop ECE 4-07A P.O. Box 355 Pittsburgh, PA 15230-0355 Mr. Andrew P. Drake, Project Manager Westinghouse Owners Group Westinghouse Electric Corporation Mail Stop ECE 5-16 P.O. Box 355 Pittsburgh, PA 15230-0355 i
DISTRIBUTION:
See attached page DOCUMENT NAME:
12_12MTG. MIN To,eceive a copy of thle document,indcate in the box: 'C' = Copy without attachment /snelosure "E" = Cogs with attachment / enclosure
- N" = No copy j
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OFFICE PGEB/4 O SRXk{t)BC PGEB:SC yt v PGEBL M'i NAME CCrailg?sW " JLyotis RArchitzel DMattb6ws DATE l/J\\/97 A/3 /97 l /A /97 t / 6 /97 i
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DISTRIBUTION w/ attachments: Summary of December 12 1996, with Westinghouse dated ebruary 6, 1 gf l
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WESTINGHOUSE / NRC MEETING FUEL CORROSION MODEL DECEMBER 12, 1996 AT ROCKVILLE, MD MEETING PARTICIPANTS 4
H8ME ORGANIZATION Claudia Craig NRC/NRR/PGEB Francis Grubelich NRC/NRR/EMEB H.F. Conrad.
NRC/NRR/EMCB Shi-Liang Wu' NRC/NRR/SRXB Sumit Ray.
Westinghouse CNFD George Sabol Westinghouse CNFD Robert Weiner
., Westinghouse CNFD t
Vincent J..Esposito Westinghouse CNFD John Galembush:
Westinghouse NSD Steve King.
> Westinghouse CNFD 4..
. Howard Menke Westinghouse CNFD
- Larry Phillips NRC/NRR/SRXP Muffet Chatterton NRC/NRR/SRXB Jack Rosenthal NRC/AE0D Eric Weiss NRC/NRR/SRXB t
ATTACHMENT 1
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In-Reactor Corrosion of Zircaloy-4 in Westinghouse PWRs i
Presentation to NRC December 12,1996 k
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i Westmghause Propneug Class 2 Westinghouse / NRC meeting to discuss fuel rod corrosion model Purpose of meeting
- To present the revised Westinghouse fuel rod corrosion model and discuss implementation plans with the NRC Reasons for development j
Discussion of model and preliminary application j
Future plans i
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WestmgkrJse Propnetary Class 2 Agenda Background - Fuel Cladding Corrosion Data acquisition and trends in corrosion Revised corrosion model development Schedule for completion l
Preliminary assessment of impact on design Plans for Implementation I
Corrosion margin restoration prc1212a ppt i
wesunghose Propetary Class 2 W Fuel Cladding and Structural Materials Nominal Composition %
Sn Nb Fe Cr Conventional 1.5 0.2 0.1 Zircalov-4 improved 1.3 0.2 0.1 l
Zircaloy-4 Im ZlRLO 1
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Mid '80s Database and First Indications I
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Wettinghouse Propnetary Class 2 Response to Observations of High Corrosion Institute corrosion surveillance programs in multiple plants to expand database Introduction of Improved Zircaloy-4
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- Tighter control of C, N, Si Modification of Corrosion Design Model nrc1212a ppt
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- Modified chemistry higher Li/B Combined corrosion severity rapidly used margin provided by Improved Zr-4 l
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Cladding Model Development Status
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Intermediate Design Review May 10, '96 Final Design Review July 17, '96 Action Item Completion in-progress
- Model is complete and not expected to change, but being considered " preliminary" until sign off.
- Being used to support fuel design i
Design Review Closeout Jan. 31, '97 Design Code Development, Validation Feb. 28, '97 Formal Code implementation March 31, '97 l
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Assessment of Impact of Model on i
Design Criteria No significant effect on the following criteria (a.c) i Criteria more sensitive to corrosion (a,c) i neciziza.ppi
Westinghose Propnetary Clasa 2 l
Preparation for Implementation of Revised 4
Cladding Corrosion Model (a,c) i l
Assessments indicate no immediate safety concerns for operating plants I
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I Plan for Implementation of Revised Corrosion Model Operating plant evaluations Feb - May '97
" Preliminary" model being used for future core designs Model implemented in standard design April '97 Design with Revised Model will ensure acceptable corrosion margin with Zircaloy-4 cladding f
Assessment for extending new corrosion August '97 l
model to fuel assembly structural ZlRLO usage ensures margin for high duty fuel components nre1212a ppt
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Westinghcuse Propnetary Class 2 Summary - Fuel Cladding Corrosion Current Model found to underpredict corrosion for Conventional Zircaloy-4 Benefit with improved Zircaloy-4 but model still l
underpredicts end-of-life corrosion I
Revised corrosion model developed for both conventional and Improved Zircaloy-4 cladding 4
Revised model will be implemented 1st Q'97 ZlRLO cladding is being rapidly introduced for high j
corrosion duty applications i
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