ML20010F541

Statement of Matl Facts as to Which There Is No Genuine Issue to Be Heard Re Contention 7B.Certificate of Svc Encl

ML20010F541
Person / Time
Site:	Susquehanna
Issue date:	08/31/1981
From:	Traviesodiaz ALLEGHENY ELECTRIC COOPERATIVE, INC., PENNSYLVANIA POWER & LIGHT CO., SHAW, PITTMAN, POTTS & TROWBRIDGE
To:	Atomic Safety and Licensing Board Panel
References
NUDOCS 8109100333
Download: ML20010F541 (11)

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8 August 31, 1981 UNITF3 STATES OF AMERICA NUCLEAR iEGULATORY COMMISSION

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BEFORE THE ATOMIC SAFETY AND LICENSING BOA Tn f '

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AS TO WHICH THERE IS NO GENUINE ISSUE P;.;c,;;;[h*cta IC8 TO BE HEARD (CONTENTION 7B) b T' M

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o Pursuant to 10 C.F.R. S 2.749(a) Applicants state, in support of their Motion for Summary Disposition of Contention 7B in this proceeding, that there is no genuine issue to be heard with respect to the following material facts:

1. In boiling water reactors ("BWR's ") , intergranular stress corrosion cracNing ("IGSCC") has occurred in the heat affected zones ("HAZ") adjacent to weids in the austenitic stainless steel piping systems that recirculate the reactor coolant and provide the redundant emergency cooling capacity.

Affidavit of Joseph C. Lemaire in Support of Summary Disposition of Contention 7B ("Lemaire 7B Af f. ") , paras . 6, 8. Cracking is associated with material that is highly stressed and has been weld-sensitized. Id., para. 6.

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2. Austenitic stainless steels are used extensively in the piping systems of BWR's such as the Susquehanna Steam Electric Station ("Susquehanna"). T.s this piping, the observed incidence of stress corrosion cracking has been extremely low.

Lemaire 7B Aff., para. 8. Only 267 out of approximately 34,000 austenitic stainless steel Type 304 piping weld HAZ in BWR's built by General Electric Company ("GE") have experienced IGSCC in 400 BWR reactor-years of service experience. Id., para. 11.

Nonetheless, the problem was thoroughly investigated by a GE Task Force and is well understood. Id., paras. 3, 8.

3. A study of cracking incidents for Type 304 stainless steel piping in GE BWR's indicates that the incidence of cracking decreases sharply with increasing pipe size. Cracking is generally confined to relatively low flow or intermittent flow systems, and cracks are generally located in areas immediately adjacent to welds attaching the piping to elbows or fittings.

This pattern shows that the susceptible nature of the material is caused by the welding process. Lemaire 7B Aff., paras. 12, 13.

4. For IGSCC to occur in steel in contact with pure, high temperature water such as used in Susquehanna three concurrent conditions have to exist: (1) tensile stress in excess of the local yield stress; (2) suitable environmental conditions (i.e., dissolved oxygen); and (3) a susceptible material. Stress corrosion will not occur if any one of these three conditions is absent or reduced below a critical value. Lemaire 7B Aff.,

para. 14.

i Stress State

5. A critical plastic strain is necessary for IGSCC,

and the probability of cracking increases with increasing stress above the yield stress. Lemaire 7B Aff., para. 15.

6. Occasionally, there is a combination of unanticipated stresses which particularly affect small-diameter, low-flow pipes.

Lemaire 7B Aff., paras. 15-17. The piling up of these stresses, together with unique mechanical characteristics of the welded joint, can produce pipe cracking. Id., para. 18. Cracking is only observed in very highly stressed lines. Id., para. 19.

Material Condition

7. In addition to the stress state, the material condition plays a major role in determining susceptibility to attack. Lemaire 7B Af f. , para. 21. Material susceptibility results from one or both of the following:

a. Sensitization: A change in grain boundary composition due to very high temperature exposure such as may occur during welding or through improper heat treatment, or

b. Cold Work: A high degree of plastic deformation of the material. Id., para. 27.

8. IGSCC has been found to occur in the theoretically most susceptible material, Type 304 stainless steel cold worked i from weld preparation, sensitized from welding, and subjected to welding residual stresses. Lemaire 7B Aff., para. 21. Other stainless steel materials, such as duplex (high ferrite) stainless steel and austenitic stainless alloys with low carbon content,ars

! less susceptible to sensitization and IGSCC, Id., paras. 22, 23.

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I e e Environment

9. Examination of the BWR environment has shown that chemistry excursions have not been a major factor in the observed attack, but that attack of highly stressed weld HAZ's is possible in high purity reactor water after long periods of time. Lemaire 7B Aff., para. 24. The frequency of IGSCC incidents correlates well with the number of plant start-up and shut-down cycles. Oxygen and peroxide dissolved in the water are high during part of these cycles and are substances which promote IGSCC. Id., paras. 26, 27.

Minimization of IGSCC Potential

10. The following actions will decrease the potential for IGSCC by reducing one or more of the three factors necessary for IGSCC to occur:

1. Control of stress. If the total magnitude of stress can be controlled to an amount below yield, IGSCC is not likely to occur.

2. Solutior._ heat treatment. Solution heat-treated material is essentially immune to IGSCC.

3. Controls in cold work, heat input for welding, control of censitization, and crevice formation.

4. Controlled environment with extremely low levels of dissolved oxygen. Id., paras. 28, 32.

Solution Heat Treatment

11. Fully solution heat treated material has been shown to be immune to IGSCC in laboraivry and in-reactor surveillance testa. Therefore, a very straight forward approach to prevention of pipe cracks is to solution heat treat piping after fabrication is l 1

complete. Solution heat treatment has been qualified as a method for preventing IGSCC. Lemaire 7B Aff., paras. 33, 37.

At Susquehanna, the recirculation system riser piping shop welds have received solution heat treatment. Affidavit of Walter J.

Rhoades in Support of Summary Disposition of Contention 7B

("Rhoades Af f. ") , para. 7.

Corrosion Res,istant Cladding

12. Corrosion resistant cladding consists of an austenitic stainless steel weld metal containing more than 8% ferrite in the final fabricated condition. Corrosion resistant cladding has been qualified as an effective method for preventing IGSCC; weld metal with 8% or greater ferrite when sensitized by the welding process is not susceptible to stress corrosion. Lemaire 7B Aff., paras. 34-37. At Susquehanna, low carbon, corrosion resistant cladding was applied to that portion of the recirculation system riser piping which was field-welded. The HAZ which will come into contact with the reactor coolant also received solution heat treatment. Rhoades Aff., para. 8.

Ferrite Control

13. Weld metal with sufficient ferrite level is not susceptible to IGSCC, whereas low ferrite ((5 %) weld metal can crack by IGSCC. Lemaire 7B Aff., para. 39. All weld metal and all type 304 and type 316 castings in the reactor coolant pressure boundary at Susquehanna have at least five percent ferrite content. This level of ferrite should effectively provide immunity from the initiation of IGSCC. Rhoades Aff., para. 9.

Limited Carbon Type 304 Stainless Steel

14. A change in the basic alloy chemistry can provide a significant increase in stress corrosion resistance. In particular, the kinetics of carbide precipitation during welding can be reduced by the presence of lower carbon, such as found in Type 304 L stainless steel or limited carbon Type 304 stainless steel with .030% maximum carbon. Lemaire 7B Af f , para. 40. At Susquehanna, susceptible materials have been replaced, where practical, with materials that are substantially less susceptible to IGSCC. Specifically, the recirculation system discharge valve bypass lines, all piping in the head spray system, much of the piping in the core spray system, almost all the piping in the reactor water cleanup system, and all the piping in the instrument piping and bottom drain, were replaced with Type 304 L stainless steel or with limited carbon Type 304 stainless steel having a maximum carbon content of .03%. Rhoades Aff., para. 10. Also, the control rod drive hydraulic return line, which was Type 304 stainless steel, was removed and the design modified. Rhoades Aff., para. 12.

Residual Stress Improvement

15. During the welding process, tensile residual stress is induced in the HAZ, which can combine with other stresses to cause IGSCC. This stress can be greatly reduced by a process known as Induction Heating Stress Improvement (IHSI) , which is applied to piping after it is fully erected. Lemaire 7B Aff., para. 38.

At Susquehanna, welds in all significant piping constituting the reac'_or coolant pressure boundary not replaced by IGSCC resis-tant material will receive IHSI treatment and/or augmented .

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! in-service laspection. Rhoades Aff., para, 11.

ASME Code Compliance j 16. The original pipe components used at Susquehanna j have been designed in accordance with the ASME Code .,uich requires the design stresses to be below specified values. This limits the extent of potential cracking since high stress is required to l produce IGSCC. Lemaire 7B Aff., para. 43.

j Controlled Environment

17. The margin against IGSCC can be increased by 1

reducing the oxygen content of the water during startup and shutdown conditions, which can be achieved using continuous vacuum deaeration. Lemaire 7B Aff., para. 26. At Susquehanna, oxygen levels during start-up, hot standby and shutdown conditions will be reduced by the use of a mechanical vacuum deaerator.

1 l This deaerator is expected to maintain an oxygen content of less 1

than .25 ppm during start-up, hot standby and shutdown. Without i this deaerator, the oxygen levels would increase to about 8 ppm.

Rhoades Aff., para. 5.

18. An aqueous environment containing dissolved oxygen becomes more aggresive in a crevice. Lemaire 7B Aff., para. 27.

) At Susquehanna, the recirculation system inlet thermal sleeve and i safe-ends were redesigned to eliminate crevices. Rhoades Aff.,

para. 6.

Leak Before Break

19. Even where IGSCC does occur, it is unlikely to cause sudden, brittle-type fracture because of the high ductility of austenitic stainless steel piping. Lemaire 7B Aff., para. 9.

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No piping severance has ever resulted from IGSCC. All instances

, of ICSCC in operating BWR's have resulted in small detectable leakage or nondestructive detection prior to leakage. Id.

Susquehanna has a continuous on-line leak detection system capable of sensing small leaks and small leak changes. Rhoades Aff.,

para. 13. The leak before break principle has been verified in operating plant experience and detailed laboratory analyses.

Lemaire 7B Aff., para. 10.

20. The extensive program at Susquehanna to eliminate stainless steel pipe cracking has been developed and implemented since 1975, is based on a full understanding of the causes of cracking, and is directed towards minimizing each of the major factors contributing to IGSCC. Lemaire Aff., para. 44; Rhoades Aff.,

para. 4. Because of the implementation of this program, the possibility of stainless steel cracking at Susquehanna should be effectively eliminated. Rhoades Aff., para. 14. The empirical observa cion of leak before pipe breck and the installation of a leak detection system at Susquehanna assure that any cracking that may occur will be detected and corrected before pipe rupture can take place. Lemaire 7B Aff., para. 45.

Dated: August 31, 1981.

Respectfully submitted,

, SHAW, PITTMAN, POTTS & TROWBRIDGE By M M " Mr7 Jay E. Silberd ,'

, Matias F. Travieso-Diaz

, Counsel for Applicants 1800 M Street, N.W.

Washington, D. C. 20036 (202) 822-1000

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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of )

)

PENNSYLVANIA POWER & LIGHT COMPANY )

)

and ) Docket Nos. 50-387

) 50-388 ALLEGHENY ELECTRIC COOPERATIVE, INC. )

)

(Susquehanna Steam Electric Station, )

Units 1 and 2) )

CERTIFICATE OF SERVICE This is to certify that copies of the foregoing " Applicants' Motion for Partial Summary Disposition of Contention 7B", " Appli': ants ' '

Statement of Material Facts As To Which There Is No Genuine Issue To Be Heard (Contention 7B)"," Affidavit of Joseph C. Lemaire in Support of Summary L5.sposition of Contention 7B" and " Affidavit of Walter J.

Rhoades in Support of Summary Disposition of Contention 7B", were served by deposit in the U. S. Mail First Class, postage prepaid, this 31st day of August, 1981 to all those on the attached Service List.

M' D Matias F. Travieso-Diaz Dated: August 31, 1981.

- UNITED STATES OF AMERICA .

NUCLEAR REGULATORY COMMISSION 1

3EFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of )

)

PENNSYLVANIA POWER & LIGHT COMPANY )

)

AND ) Docket Nos. 50-387 l'

) 50-388 ALLEGHINY ELECTRIC COOPERATIVE, INC. )

)

(Susquehanna Steam Electric Station, )

Units 1 and 2)

)

SERVICE LIST acrotary of the Commission Dr. Judith H. Johnsrud S. Nuclear Regulatory Commission Co-Director

>shington , D. C . 20555 Environmental Coalition on Nuclear Power (ministrative Judge James P. Gleason 433 Orlando Avenue 1 Gilmoure Drive State College, Pennsylvania 16801

,1 var Sp' ring, Maryland 20901 Susquehanna Environmental Advocates

. GlGnn O. Bright c/o Gerald Schultz, Esquire omic Safety and Licensing Post Office Box 1560 Soard Panel Wilkes-Barre, Pennsylvania 18703 S. Nuclear Regulatory Commission ishington, D. C. 205.55 Mr. Thomas J. Halligan, Correspondag

,,,, The Citizens Against Nuclear Dangerc

. Paul W. Purdom Post Office Box 5 5 Gulph Hills Road Scranton, Pennsylvania 18501 fnor, Pennsylvania 19087 Ms. Colleen Marsh

,:mic Safety and Licensing Box 558 A, R. D. j4 Scard Panel Mt. Top, Pennsylvania 18707 S. Nuclear Regulatory Commission Ishington, D. C. 20555 Jessica H. Laverty, Esquire Office of the Executive Legal

-koting and Service Section Director I'ica of the Secretary

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U' S: Nuclear Regulatog Commission S. Nuclear Regulatory Commission Washington, D. C. 20ssa shington, D. C. 20555 i

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shor W. M'er, Esquire Mr. Thomas M. Gerusky, Director spartmenc of Environmental Resources Bureau of Radiation Protection

=onwaalth of Pennsylvania De, car cent of E".vironmental 25 Executive Ecuse Resources as: Office Box 2357 Cor..monwealth of Pennsylvania Errisburg, Pennsylvania 17120 Post Office Box 2063 ames 10. Cucchin, IV, Esquire ffico of the Encutive Legal Atomic Safety and L' censing Appeal Director Board Panel e S. Nuclear Regulatory Cor: mission U. S. Nuclear Regulatory Commissi@

ashington, D. C. 2'0555 Washington, D. C. 20555

@Witt C. Smith irector ennsylvania Emergency Management A'gency acasportation and Safety Building gr:-isburg, ' Pennsylvania 17120 l

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