ML20084K636

Forwards Gc Sih Comments on Response of Tpr & Staff & Statement to Hearing on TMI Restart Re Steam Generator Tube Repair.Certificate of Svc Encl

ML20084K636
Person / Time
Site:	Three Mile Island
Issue date:	05/09/1984
From:	Bradford L THREE MILE ISLAND ALERT
To:	Atomic Safety and Licensing Board Panel
References
OLA, NUDOCS 8405140125
Download: ML20084K636 (8)

Text

a UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION ,

Before the Atomic Safety and Licensing Board IYc In the Matter of ) 'g4 gg, y METROPOLITAN EDISON COMPANY ) Docket No. 50-289 . _ _

) (Steam Generator Repair) ' ~r ?Ic; .

(Three Mile Island Nuclear

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Station, Unit 1) ) DOCKET NUM3gry 0 0..a. U ni,,7,,1 g , ,

g STATEMENTS OF DR. GEORGE C. SIH TMIA yesterday, May 8, 1984, filed, in response to Licensing Board's Order of April 25, 1984, an Affidavit and Qualifications of Dr. George C. Sih, but inadvertently omitted attached statements of Dr. Sih.

Enclosed please_ find Comments on Resporne by TPR and the Staffs Ref pp. 27-32 and Statement to Hearing on TMI Restart: Steam Generator Tube Repair, December 16, 1983, (which were also attached to TMIA RESPONSE TO LICENSEE AND STAFF MOTIONS FOR

SUMMARY

DISPOSITION) .

Respectfully submitted,

, Three Mile Island Alert

/c l Louise Bradford

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May 9, 1984 8405140125 840509 DR ADOCK 05000 gg$

Amc Wmn+ a COMMENTS ON RESPONSE BY TPR AND THE STAFF: REF: pp. 27-32 The response of TPR and the Staff clearly indicates that their knowledge of I

fracture mechanics is limited and superficial. Fundamental misconception pre-vails throughout the above reference material. What TPR and the Staff have as-sumed in their analyses are not consistent with the damage as they claimed to have observed in reality. i l

(1) Reference to Comments on p. 27:

Line two from bottom establishes the fact that the cracks in the tube do not propagate axisymmetrically. This implies that a three-dimensional state of stress prevails around the surface flaw. The nonuniformities referred to in the second paragraph on p. 28 are not clearly defined and do not necessarily include ,

the three-dimensional effects.

(2) Reference to Line 3 from bottom of p. 28:

Unless the circumferential cracks are completely around the tube, axi-symmetry is not preserved and the stress state is locally a three-dimensional one. This j implies that even if the load is normal to the crack plane, the crack can grow in a non self-similar manner. In such a case, the analyses performed by TPR and I

! the Staff are not valid.

1 The fact that TPR and the Staff did not use the results of the axisymmetric stress analysis for the fracture mechanics fatigue or crack analysis is irrele-vant. What is relevant is the non-axisymmetry character of the local stress field that should be included in a realistic evaluation of the crack failure mode.

.i (3) Reference to Lines 2 to 4 on top of p. 29:

The statement (quote) "--- the data were developed to characterize the ma- ,

terial properties of Inconel-600, and are independent of material or loading geometry", is self-contradictory. It is well-known that all data collected from  !

specimen tests are sensitive to changes in specimen size and loading rates.

Therefore, it is necessary to si:aulate the conditions experienced in the struc-tural components when collecting material data. No justification along this line has been given by TPR and the Staff on Inconel-600.

(4) Reference to middle of p. 29: f One of the means of evaluating the adequacy of the expansion repair technique is in fact to analyze the propagation of fatigue cracks in the tubes. If the increase in hardness during repair is claimed to be beneficial, then the simul- ,

taneous decrease in fracture toughness should also be pointed out and evaluated accordingly. This relation was not discussed. In this respect, the so-called  ;

" toughness" factored into the fatigue model used by TPR and the Staff may not be valid, particularly when yielding occurs as implied on p. 30.

(5) Reference to Material on too of p. 30:

The concept of stress intensity depends on homogeneity of the crack tip stress field which prevails only when the material is predominantly in the linear elastic range. When yielding or plastic flow occurs, the local stress field becomes non-Therefore, homogeneous and the concept of a stress intensity ceases to apply.

Indeed, paragraph 3 on p. 29 confirms this and yet the statement above argues against it. Attention should be focused on the overall technical aspect of the l

problem and not whether TPR and the staff happen to discuss a particular aspect of the tube repair technique.

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.s the argument outlined on top of p. 30 is irrelevant.

e i A fundamental misconception appears in line 10 on p. 30. The fracture toughness of a material does not change when yielding occurs. The load carrying r

capacity of the specimen or structural component on the other hand does increase.

i (6) Reference to middle of p. 30:

No claims were ever made that hardness was directly associated with crack growth. Nevertheless, it is well-known that increase in hardness results in a ,

reduction *in toughness. Hence, the repair tubes with increased hardness obviously suffer a reduction in toughness and hence are no longer restored to their origi-nal state.

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(7) Reference to Material on top of p. 31:

The propagation of small and/or large cracks in a thermal environment is im-l portant to the kinetic expansion repair technique since the restoration of the system to-its original state is at. issue. Hence, it would be relevant to estab-lish the life discrepancy of the repaired tubes as compared with those used in

-the original design.

(8)' Reference to Lines 11 and 12 on p. 31: t The stress intensity approach used by TpR and the Staff cannot accurately determine the state of affairs for partial through-wall cracks. In fact, the l stress intensity factors as defined in the linear elastic fracture mechanics  !

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theory are zero at the intersection of the crack and free surface. However, j dansge does occur near the surface.

1 (9) Reference to Material at bottom of p. 31 and top of p. 32: l TPR and the Staff have apparently failed to understand that the stress inten-l sity, when it can be applied, may not be a monotonic function of the crack length  ;

I under thermal environments. Global instability can occur for cracks that are much smaller than those estimated by approximated and invalid analyses. The point-is that the true nature of the thermal crack behavior may.not be reflected by the analysis made by TPR and the Staff.

To conclude, the relevant issue is the validity of the technical evaluation made by TPR and the Staff on the repaired tubes. The problem must be viewed in its entirety based on consistency and validity of the technical approach .

f Disposal of the issue on legal grounds at the sacrifice of technical understanding -

and safe control can further lead to unexpected shutdowns and further repairs, l imposing additional burden on an already economically-illed nuclear industry. l i

It is not justifiable to claim as the state-of-the-art which is irrelevant to the safe evaluation of nuclear reactor components. Other means and approaches for evaluating the damage caused by surface flaw have been available in the open lit-erature for many years.

The fracture mechanics discipline is not limited to the views and definitions as conceived by TPR and the Staff.

hkhrnehb STATEMENT TO HEARING ON TMI RESTART: STEAM GENERATOR TUBE REPAIR j December 16, 1983 i

( With regard to the technical aspects of steam generator  ;

i tube repair, there arises the following concern:

(1) It is questionable that the kinetic expansion repair process could restore the. tubes to their original condition.

Should the hardness of the tube be increased then the resistan.ce of the material to cracking measured by the fracture toughness is likely to drop.

(2) The fatigue life of tubes depends on the sequence and magnitude of the combined' thermal and mechanical loading. Predictions based on LEFM' (linear elas. tic fracture mechanics) may not be reliable since the methodology does not address accumulative damage.

In my opinion, there is not suffucient technical evidence {

to reach any conclusion on the safety of the repaired steam -

generator tubes of TMI. .

G. C. Sih  :

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• Application of LEFM cannot be justified on the ground that it is still the state-of-the art of twenty years ago.

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOURD 00tKETED

' tim c In the Matter of j *d4 gy J j g

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METROPOLITAN EDISON COMPANY ) Docket Wag 50.-289

) 00CXE T,Isa~d lygf/,3 (Three Mile Island Nuclear )  : RANCH  ;

Station, Unit No. 1) ) i CERTIFICATE OF SERVICE I hereby certify that copies of the attached STATEMENTS of Dr. George C. Sih dated May 9, 1984, were served this '

9th day of May, 1984, by deposit in the U.S. Mail, first class, postage prepaid to thise on the attached service i list.

I 67 W Pc Louise Bradford

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May 9, 1984

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,s UNITED STATES OF AMERICA l NUCLEAR REGULATORY COMMISSION f Before the Atomic Safety and Licensing Board In the Matter of ) ~

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METROPOLITAN EDISON COMPANY, ET AL. ) Docket No. 50-289-OLA I

) ASLBP 83-491-04-OLA (Three Mile Island Nuclear ) (Steam Generator Repair)

Station, Unit No. 1) )

SERVICE LIST [

Sheldon J. Wolfe> -  :. ,

Administrative Judge Chairman, Atomic Safety and .

Licensing Board l U.S. Nuclear Regulatory l Commission Docketing and Service Section Washington, D.C. 20555 Office of the Secretary l U.S. Nuclear Regulatory Commission Dr. David L. Hetrick washington, D.C. 20555 Administrative Judge Atomic Safety and Licensing Board t Professor of Nuclear Engineering George F. Trowbridge, Esq. ,

University of Arizcna Shaw, Pittman, Potts & Trowbridge  !

Tucson, Arizona 85271 1900 M St., N.W. 3 l Washington, D.C. 20036 l l Dr. James C. Lamb, III Administrative Judge Jane Lee Atomic Safety and Licensing Board 183 Valley Road 313 Woodhaven Road Etters, Pennsylvania 17319 j Chapel Hill, North Carolina 27514  ;

i Norman Aamodt l Richard J. Rawson, Esq. R. D. 5, Box 428 I Mary E. Wagner, Esq. Coatesville, Pennsylvania 19320 l Office of Executive Legal Director  ;

j U.S. Nuclear Regulatory Commission i

! Washington, D.C. 20555  ;

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