ML18057A228

Discusses Low Upper Shelf Energy Matl in Reactor Vessel Beltlines.Nrc Intends to Issue Guidance Re Credibility of J-R Curves Representative of Vessel Matl Toughness & Will Define What Conservative Bound to J Delta Data Means

ML18057A228
Person / Time
Site:	Palisades
Issue date:	05/14/1990
From:	De Agazio A Office of Nuclear Reactor Regulation
To:	Berry K CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
References
PAL-90-029, PAL-90-29, NUDOCS 9005170072
Download: ML18057A228 (6)

Text

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 May 14, 1990 Docket No. 50-255 Serial No. PAL-90-029 Mr. Kenneth w*. Berry Director, Nuclear Licensing Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201

SUBJECT:

LOW UPPER SHELF ENERGY MATERIAL IN REACTOR VESSEL BELTLINES Appendix G to 10 CFR Part 50 requires that the Charpy upper shelf energy (USE) throughout the l"ife of the vessel be no less than 50 ft.-lb. unless it is demonstrated that lower USE values will provide margins of safety against failure equivalent to those provided by Appendix G of the ASME code.

Specifically, Paragraph IV. A. 1. of Appendix G states, in part:

"Reactor vessel beltline materials must... maintain upper-shelf energy throughout the life of the vessel of no less than 50 ft.-lb. (68 J),

unless it is demonstrated... that lower values of upper-shelf energy will provide margins of safety against fracture equivalent to those required by Appendix G of the ASME Code.

11 For the Palisades Plant, the USE is projected to fall below 50 ft.-lb. before the end of plant life.

However, reactor vessels may continue to be operated if the 50 ft.-lb. minimum requirement is not met provided all three requirements identified in Paragraph V. C. of Appendix G are satisfied.

Two of these requirements relate to 100% volumetric examination of the beltline materials that do not meet the 50 ft.-lb. requirement and supplemental fracture toughness testing of the beltline materials, while the third relates to an analytical demonstration of the existence of an equivalent margin of safety for continued o~eration. It is this third requirement to which the attachment to this letter relates.

Paragraph V. C. provides, in part, that:

11 *** reactor vessels may continue to be operated provided.... an analysis is performed that conservatively demonstrates, making appropriate allowances for all uncertainties, the existence of equivalent margins of safety for continue<:! operation." (cf. Paragraph V. C. 3.)

9005170072 900514 PDR ADOCK 05000255 p

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2 -

NUREG 0744, issued by Generic Letter 82-26 as part of the resolution to Unresolved Safety issue A-11, provided a method for evaluating reactor vessel materials when their Charpy USE is predicted to fall below 50 ft.-lb.

The successful analytical demonstration, however, required by Paragraph V. C. 3.

has been dependent upon advances in elastic plastic fracture mechanics.

The technology has now advanced to the point where the criteria being written for the ASME Code are acceptable for regulatory use.

The criteria contained in the attachment to this letter are those we believe will appear in the ASME Code, with one modification.

The pressures are given in terms of accumulated pressure, P-acc.

This term comes from ASME Code Paragraphs NB 7311 and NB 7410.

These paragraphs require that the set pressure for expected system transient pressure conditions shall be such that the total accumulated pressure shall not exceed the design pressure by more than 10%.

Basing the criteria on P-acc takes advantage of reduced operating pressure, provided the pressure relief devices are set at correspondingly lower pressures.

For a nominal case where:

P-design = 2500 psig P-operating = 2250 psig P-acc ~ 2750 psig.

Then, for the conditions of Criteria 1 and 2 respectively of 1.15 and 1.25 times P-acc the two criteria would call for maximum pressures of 3162 and 3437 psig respectively.

The actual values will deperid upon the value of P-acc.

given in the Overpressure Report of Paragraph NB 7200.

The staff intends to issue guidance regarding the credibility of J-R* curves that are representative of the vessel material toughness, and will define what is meant by a conservative bound to J-A a data.

You are urged to consult with the staff as you proceed with your analyses until that guidance is available.

You are advised also that some SA302 Grade B plate material has poor upper shelf properties in the transverse direction, therefore, you should plan to address this issue with your submittal.

You are invited to discuss the issue of low USE reactor vessel materials with the staff prior to initiating your program for compliance with Paragraph V. C.

3. of Appendix G.

Please submit, within 60 days of receipt of this letter, your plan for completing the required analysis and the additional testing and examination requirements of Paragraph V. C. of Appendix G.

ATTACHMENT LOW UPPER-SHELF CRITERIA Level A and 8 Conditions For a postulated semi-elliptical surface flaw with a/t = 0.25 and with an aspect ratio of 6 to 1 surface length to flaw depth, and oriented along the weld of concern, two criteria must be satisfied as described below.

Smaller flaw sizes may be used on an individual case basis if a smaller size of the above postulated flaw can be justified.

1.

The crack driving force must be shown to be less than the material toughness as given below:

J applied < J 0.1 (1) where J

1. d is the J-integral value calculated for the postulated flaw unde¥PBr~~sure and thermal loading where the assumed pressure is 1.15 times accumulated pressure, and thermal loading using the plant specified heatup and cooldown conditions.

The parameter J is the J-integral characteristic of the material resistance to duc21le tearing (J

t

. 1), as usually denoted by the J I-R curve test, at crack ma eria extension of 0.1 inch.

2.

The flaw must be stable under ductile crack growth as given below:

dJ applied dJ material da da (2) at J applied = J

~aterial where J

1. d is calculated for the postulated flaw under pressure and thermal T8Ra~~g for all service level A and B conditions where the assumed pressure is 1.25 times accumulated pressure, and thermal loading, as defined above.

The J~integral resistance versus crack growth curve shall reflect a conservative bound to J-6 a data representative of the vessel material under evaluation.

3 -

The reporting and/or recordkeeping requirements of this letter affect fewer than ten respondents; therefore, OMB clearance under PL 96-511 is not required.

cc:

w/attachment:

See next page Sincerely, Albert W.

e Agazio, Sr. P.

Project irectorate III-1 Division of Reactor Projects - III, IV, V & Special Projects Office of Nuclear Reactor Regulation

~ Mr. Kenneth W. Berry Consumers Power Company cc:

M. I. Miller, Esquire Sidley & Austin 54th Floor One First National Plaza Chicago, Illinois 60603 Mr. Thomas A. McNish, Secretary Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201 Judd L. Bacon, Esquire Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201 Regional Administrator, Region III U.S. Nuclear Regulatory Co1T111ission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Jerry Sarno Township Supervisor Covert Township 36197 M-140 Highway Covert, Michigan 49043 Offic~ of the Governor Room 1 - Capitol Building Lansing, Michigan 48913 Mr. Gerald B. Slade Plant General Manager Palisades Plant 27780 Blue Star Memorial Hwy.

Covert, Michigan 49043 Resident Inspector c/o U.S. Nuclear Regulatory Corrmission Pa 1 i sades Pl ant 27782 Blue Star Memorial Hwy.

Covert, Michigan 49043 Palisades Plant Nuclear Facilities and Environmental Monitoring Section Office Division of Radiological Health P.O. Box 30035 Lansing, Michigan 48909

'.* The reporting and/or recordkeeping requirements of this letter affect fewer than ten respondents; therefore, OMB clearance under PL 96-511 is not required.

Sincerely, Original signed by Albert W. De Agazio, Sr. Project Manager Project Directorate III-1 Division of Reactor Projects - III, IV, V & Special Projects Office of Nuclear Reactor Regulation cc:

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