ML20091E435

Requests Exemption from GDC 4 Re Application of leak-before- Break Concept to Eliminate Postulated Pipe Breaks in Pressurizer Surge Line from Plant Structural Design Basis. Safety Balance Demonstrated

ML20091E435
Person / Time
Site:	Catawba
Issue date:	05/29/1984
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML19269A197	List: ML20091E435 ML20091E446
References
NUDOCS 8406010247
Download: ML20091E435 (16)

Text

. - ..

~ '

DUKE POWER GOMPANY P.O. BOX 33189 CHARLOTTE, N.C. 28242 HAI. H. TUCKER TELEPHONE VICE PREBEDENT {yg ggg

" " " " " * * ~ "

May 29, 1984 Mr. Harold R.- Denton, Director ~ ".!

Office of Nuclear Reactor Regulation fb)M,Tf.EN] i U. S. Nuclear Regulatory Commission E- I Washington, D. C. 20555 ((}p'g* *]g Attention: Ms. E. G. Adensam, Chief g g gi g j Licensing Branch No. 4 e Re: Catawba Nuclear Station j Docket Nos. 50-413 and 50-414

References:

1) Letter from W. H. Owen-(Duke Power Company) to W. J. Dircks (NRC), dated September 19, 1983

2) Letter from H. R. Denton (NRC) to W. H. Owen (Duke Power Company), dated October 17, 1983

3) Letter from H. B. Tucker (Duke Power Company) to H. R. Denton (NRC), dated November 18, 1983

4) Letter from H. B. Tucker (Duke Power Company) to H. R. Denton (NRC), dated February 29, 1984

5) Letter from E. G. Adensam (NRC) to H. B. Tucker (Duke Power Company), dated May 8, 1984

6) Generic Letter 84-04, NRC, dated February 1, 1984.

Dear Mr. Denton:

Duke Power Company requested in Reference 4 NRC approval for application of the " leak-before-break" concept to the Catawba Nuclear Station to eliminate postulated pipe breaks in the Pressurizer surge line from the plant structural design basis. In Reference 5, the NRC requested additional information to I complete the review of this leak-before-break analysis for Catawba Nuclear Staion, Unit 2. This letter is hereby submitted to provide this information and.to request an exemption from General Design Criterion 4 (GDC-4). Additionally, a safety balance in terms of accident risk avoidance versus safety gains will be demonstrated, b

Request for Additional Information i

rg

$'k,,

e Westinghouse entitled " Technical technical report WCAP-10487 Basis for Eliminating. Pressurizer Surge(Enclosure Line RupturesAasto Reference the Structural Design Basis for Catawba Units 1 and 2" provides technical justifi-lS5 40 cation for elimination of Pressurizer surge line breaks for Catawba Nuclear A Station (the non-proprietary version, WCAP-10488, was included as Enclosure B to Reference 4). Enclosure A to-this letter provides the responses to the two items requested by the NRC in Reference 5.

i,,,g 4 ,-

fNS

~ , rw.

Mr. Harold R.' Denton, Director May 29,1984 Page 2-As Enclosure A contains informationiproprietary to Westinghouse Electric Corporation, it is supported by the attached letter (Attachment 1) and affidavit signed by Westinghouse, the owner of the infomation. The affidavit e . sets forth the basis on which the infomation may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph -(b)(4) of Section 2.790 of the~ Commission's regulations.

Accordingly, it is . respectfully requested that the infomation which is proprietary to Westinghouse be withheld from public disclosure in accordance with 10 CFR Section 2.790 of the Commission's regulations. Correspondence with respect to the proprietary aspects of the Application for Withholding or the supporting Westinghouse affidavit should reference CAW-84-47, and should be addressed to R. A. Weisemann, Manager, Regulatory and Legislative Affairs, Westinghouse Electric Corporation, P. O. Box 355, Pittsburgh, Pennsylvania,

, 15230. Because of the proprietary nature of this report, Enclosure A has been

. provided only to the addressee and Mr. James P. O'Reilly of the NRC. A non-proprietary version is included as Enclosure B and has been provided to others on the attached distribution list.

Exemption Request Pursuant to 10 CFR 50.12(a), Duke Power Company hereby applies in connection with the Catawba Nuclear Scation license for an exemption from the provisions to 10 CFR Part 50, Appendix A, authorizing alternative pipe break analyses for the Catawba Nuclear Station Pressurizer surge line. The requested exemption i is based upon the application of advanced fracture mechanics technology as evaluated in the Westinghouse technical report WCAP 10487 (Enclosure A of Reference 4).

Specifically, we request the elimination of postulated circumferential and longitudinal pipe breaks in the Pressurizer surge line from consideration in the structural design basis of Catawba Nuclear Station. 'The impact on important design aspects of implementing leak-before-break on Catawba Nuclear Station has been evaluated by Duke Power and is summarized in Attachment 2. A detailed list of previously postulated pipe breaks and associated rupture devices is provided in Attachment 3.

The bases for .the requested exemption are as follow:

1. In-shop, pre-service, and in-service. inspections performed on piping for

'; the Catawba Nuclear Station' minimize the possibility of flaws existing in such piping. The application of advanced fracture mechanics has demonstrated that if such flaws exist they will not grow to a leakage crack when subjected to.the worst case loading ' condition over the life of the plant.

( If.one postulated a through-wall crack, large margins against unstable p

2. . . crack extension exist for certain stainless steel piping when subjected to,the. worst ca:,e loading conditions over the life of the plant".

7_

. . , ,m. ,mx

Mr. Harold R. Denton, Director May 29,1984 Page 3 The application of advanced fracture mechanics technology has demonstrated that small tiaws or leakage cracks (postulated or real) will remain stable and will be detected either by in-service inspection or by leakage monitoring systems long before such flaws can grow to critical sizes which otherwise could lead to large break areas such as a double-ended rupture of the surge line. To date, use of this advanced fracture mechanics technology has been limited by the definition of a LOCA in Appendix A to 10 CFR Part 50 as including postulated double-ended ruptures of piping regardless of the associated prob-ability. Application of the LOCA definition without regard to this advanced technology to large diameter thick-walled piping such as the Pressurizer surge line of a PWR imposes a severe penalty in terms of cost and occupational exposure because of the massive pipe whip restraints it requires which must be removed for in-service inspections. This penalty is unreasonable because these pipes do not have a history of failing or cracking and are conservatively designed.

Accordingly, for design purposes associated with protection against dynamic effects, we request this exemption from the regulations to eliminate the need to postulate circumferential and longitudinal pipe breaks. This exemption request does not extend to specifying design bases for containment, the emergency core cooling system, or environmental effects.

We request that the exemption authorize, with respect to the plant structural design basis, the elimination of pipe breaks in the Pressurizer surge line.

Thus, the use of advanced fracture mechanics permits a detenninistic evaluation of the stability of postulated flaws / leakage cracks in piping as an alternative to the current mandate of overly conservative pcstulations of piping ruptures.

I This exemption request is consistent with the provisions of footnote 1 to l 10 CFR Part 50, Appendix A, which refers to the development of "further details relating to the type, size and orientation of postulated breaks in specific components of the reactor coolant pressure boundary." The Pressurizer surge line is a part of this boundary.

As support for this request, in addition to the previously specified information, we would request consideration of the following:

1. Letter from Darrell G. Eisenhut (NRC) to E. P. Rahe (Westinghouse) dated February 1,.1984.

2. Memorandum from Darrell G. Eisenhut (NRC) to All Operating PWR Licensees, Construction Permit Holders and Applicants for Construction Pennits dated February 1, 1984 -

Subject:

Safety Evaluation of Westinghouse Topical

< Reports Dealing with Elimination of. Postulated Pipe Breaks in PWR Primary Main Loops (Generic Letter 84-04).

3. -CRGR resolution of generic issue A-2.

4. ACRS letter dated June 14, 1983, re: " Fracture Mechanics Approach to Pipe Failure."

1 Mr. Harold R.~ Denton, Director i LMay-29, 1984 Page 4

! 5. Memoranden from William J. Dircks, EDO, to ACRS dated July 29, 1983, re:

" Fracture Mechanics Approach to Postulated Pipe Failure."

-6. Memorandum from Harold Denton (NRC) to Murray Edelman (AIF), dated May 2,1983.

j Safety Balance i

Further, pursuant to 10 CFR 50.12(a), we believe the requested exemption will not endanger life or property or the common defense and security and is in the 4

public interest. The total increase in public and occupational accident exposure associated with omitting the Pressurizer surge line whip' restraints and jet

, deflectors is estimated to be less than .5 man-rem for the nominal case with i 40-year plant life. This estimate is based on an analysis similar to that for i the primary loop in the " Leak-before-Break Value-Impact Analysis" of Enclosure 2

to Reference 6, but perfonned specifically for the Pressurizer surge line. The major difference in the analysis is that a surge line break will not contribute to asymmetric blowdown; therefore, no LOCA is assumed to occur in the reactor

i. cavity for the surge line break. A reactor cavi:y LOCA leads to a majority of l the potential accident risk for the primary loop; thus, a. surge line break would

!. result in a lower risk than a primary loop break.

The benefits in avoidance of exposures for Catawba Unit 2 associated with the requested exemption are estimated to be 216 man-rem of occupational exposure over plant life, based on Duke Power studies. This eliminated radiation exposure is related to pipe whip restraint inspection tasks, restraint disassembly /

i reassembly for pipe weld inspections, and improved personnel access for operation and maintenance. Consequently, the. savings in exposure by granting the exemption far_ exceed the potentially small increase in public risk and occupational accident exposure associated with deleting restraint devices. Duke Power Company estimates cost savings 'for Catawba Nuclear Station, Unit 2 of at least 1.7 million dollars as given in Attachment 4. Benefits with regard to plant safety, operation, and.

j design are given in Attachment 4.

With these benefits and with a net reduction of radiation exposure of 216 man-rem,

a net safety gain has been demonstrated for. Catawba Unit 2. Also, a cost savings of at least 1.7 million dollars has been shown, and a technical basis for elimina-tion of Pressurizer surge line. breaks has been demonstrated. Implementation _of the leak-before-break. concept will thus be cost-effective as well as technically' justifiable while resulting in improved overall plant safety. Therefore, Duke Power Company hereby requests NRC approval of an exemption to GDC-4 in order to i apply the leak-before-break concept to Catawba Nuclear Station.to eliminate postulated pipe breaks in the Pressurizer. surge line from the plant structural

[ design basis.

Enclosure C of' Reference 4 consists of the revised Catawba FSAR pages associated with the elimination of pressurizer surge line breaks, and it will be included in a; future revision to the FSAR. This current request is for implementation on Unit 2 only; Duke Power will submit additional information prior.to implementation

, on Unit 1.-

i 4:

___.---s _ . - - . .~~ s.. .. .-...-. . . . . . ~ _ _ _ ~ . . , . _ . . . - , - - . . , _ _ . _ _ _

. = . . . . . . . . . - - -..

. Mr. Harold R. Denton, Director

- May 29, 1984 Page 5

~ Construction ' completion of the Pressurizer surge.line devices at Catawba

- Unit 2 is on hold pending an NRC ruling on this proposal. We request a resolution concerning this matter prior to June 25, 1984.

If'I'can-be of further assistance, or if a meeting with the staff is deemed beneficial for a final resolution of this matter, please contact me.

' Very truly yours, kpASTadnw Hal B. Tucker-ROS/KWH/php

! Attachments cc: (w/proprietaryattachments)

[ Mr. James P. O'Reilly, Regional Administrator j.~ U. S. Nuclear Regulatory Commission Region II' 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 i

i (w/o proprietary attachments)

NRC Resident Inspector

. Catawba Nuclear Station f Mr.' Robert Guild, Esq. '

Attorney-at-Law

P. O. Box 12097

! Charleston, South Carolina 29412 Palmetto Alliance 21351 Devine Street 1 .

Columbia, South Carolina 29205 l-Mr. -Jesse L. ' Riley .. .

! Carolina Environmental Study-Group 854 Henley~P1 ace

. Charlotte, North _. Carolina 28207 -

t m . - ,.

'% y T l'

., p.1 ., , . , , - .u--y y- ,, ,. y e, w x - -, , , , - - .- 6

Attachment 2 Impact of Elimination of Postulated Circumferential-and Longitudinal Pipe _ Breaks in the Pressurizer Surge Lines Structures, Systems, Components.

Programs Considered for Impact Impact Pressurizer Surge Line Pipe Whip Deleted from Design Restraints and Jet Barriers Primary Shield Wall / Crane Wall / Reduction in pressurization loading Operating Floor RCS Pressure Boundary Leakage No change Detection Systems Environmental Qualification Program No change o

k e

i mi e

- I Attachment 3 1

Postulated Pressurizer Surge Line Pipe Breaks

+

and Associated Rupture Devices 1

. Erection Status Postulated Break Location Devices Associated with Break

• Catawba Unit 2

.l.. Terminal end at- 21 pipe whip restraints Not installed

. Pressurizer Nozzle L

2. Teminal end.at 21 pipe whip restraints Not installed hot leg connection and 2 jet deflectors

, 3. Intermediate break 21 pipe whip restraints Not installed i

at Node 2AA

.c

4. Intermediate break 21 pipe whip restraints Not installed

< at Nodes 98, 9ABA, & and 1 jet deflector 9AB 4

i

• All 21 Pressurizer Surge Line pipe whip restraints are loaded by each of

this line's breaks. Thus, the total number of devices being deleted is

, 21 pipe whip restraints and 3 jet deflectors.

4 h

[

L

i. .

l

.. . s.,,, m., w., , , - . . . . -% .- - - . , ,- - . - ._ .. , ~ . , , , , , - . - . . ~ , , _ _ . - - - , _

s ,

w l

Attachment 4 Summary of Benefits from the Elimination of Pressurizer Surge Line Pipe Breaks on Catawba Nuclear Station Unit 2 Category Benefit

1. Design, material and erection costs $1.1 million*

associated with 24 rupture devices. .

2. Plant design Simplifies overall plant design by elimination of potential inter-ferences with piping, hangers, impulse tubing, etc.

3. Relief of congestion, improving 216 man-rem reduction in radiation access for operation and maintenance. exposure over life of Unit 2

($595,000)

4. Reduction in piping heat loss at ' Not quantitatively assessed.

whip restraint locations. Insulation can be installed on piping at current locations.of-Pressurizer Surge Line pipe whip-restrai.nts.

5. Improvement in overall plant Improvement in ISI quality.

safety (NUREG/CR-2136). Elimination of potential for restricted thermal or seismic movement.

• Current (1984) dollars.

-ENCLOSURE B

. +" .

ADDITIONAL INFORMATION CATAWBA SURGE LINE Ouestion 1 Paragraph 5.2 on page 5-2 of Reference (a)*below states that the pipe is subjected to internal pressure And. an axial load (underlining added).

Similar statements.aopear elsewhere in the report, however, other in-fonnation presented indicates that the axial force due to pressure is included in the axial load. Please clarify. '

Resoonse:

d a,c.e !

The surge line under investigation is ].subjected to a-pressure of a,c,e [In a 4

The pressure is subjected causes to other axialan axial forces of load of ((

.] Thus, the. pipe is subjected _a,c,e to' a total axial load of.[ ] kips. a,c e i Since the [ ] an axial force does not result a,c.e by applying the pressure of [ ] surfaces. - Therefore, to. a,c.e

simulate the actual pipe loading an axial force of [

has to be ao311ed to the a,c.e

[ ] in the axial direction in addition to tne] pressure of [' ] applied a,c.e <

to [ ] a,c.e Ouestion 2 The Paragraph at the top of pa weld connection between the [ ge 3-2 of Reference (a)*below identifies thea,c,e

] as being the Ifmiting location to be analyzed. Figure 7-2, page 7-12, is a schematic i drawing of this location. Provide the materials properties for the weldment as well as for the base metal, preferably in the fann of a J-resistance plot.

State the maximum value of J-material to be considered in your analyses and your basis for it.

Resoonse:

, The fracture toughness JI c .used for the 304 forged pipe was obtained from the compilation cf test results for this material reported in Reference 1.

The table of toughness results presented in this reference-is reproduced in the attachment. It is easily seen that the value of-[ ] used in a,c e the report is the minimum of the three sets of test results reported. The J integral R curves for each of the three sets of tests at 600F are also pro-vided in the attachment, and are the. original figures from Reference 1.

The fracture toughness of stainless steel welds has been found to range from L

] to over [ ] in recent studies. The weld J about

.va l ue o [f ' c l able for s[tainless steel welds used in commercial fabrication, a , c .e an tained directly.from Reference 2 and also published in Reference 3.

Reference:

a. WCAP-10487, ' 2/10/84 c .

- . . , s.- ,.-,- _ - - - _ _ _

• Fage 2 The highest value of applied J used in the analyses of WCAP 10487 is [ ] a,c.e in-lb/in2, as demonstrated in the report. The maximum applied J in the weld metal ' sill be lower, bactuse of the higher yield strength of the weld metal.

The maximum value of J obtained in the fracture tests is in excess of 25000 as may be seen from examining the plots attached for base metal tests.

The

[ maximum value2cf J obtained in the weld metal tests was in excess of ] in-lb/in . a,c,e s

O G

e ,

REFERENC$5 a ti P ast Fr ctu , AS S 68, A r can So i of T s and Materials 1979, pp. 553-557.

2. Slama, G., et.al., Effect of Aging on Mechanical Properties of Austenitic Stainless Steel Casting and Welds, presented at SMiRT Post Conference Seminar 6 - Assuring Structural Integrity of Steel Reactor Pressure Boundary Components, August 1983, Monterey, Calif.

3. Bamford, W. H., et.al. , "The Effects of Thermal Aging on the Structural

. Integrity of Cast Stainless Steel Piping for Westinghouse Nuclear Steam

, Supply Systems, Westinghouse Electric Corp. WCAP 10456, Nov.1983.

(W Proprietary Class 2).

t i

TAR.E3 J

IC N N SS N TS IhERIAL ORIB(TATION SPECIMEN IOPERATURE JIC

• (IN L.B/IN )

D RE==u STAINL.ESS AXIAL 1 2T-CT RT 4449 (CISPECIMENS)

CIRCLNERefTIE[

CIRCLNERENTIAL 3 PT BEND RT >4000

'AxIn 7 2T-CT 31@C 2569 CIRCLNERENTIAll CIRCLNERerTIAL 3PTBEND 31@c 2737 RADIAL IT-CT 31@C 2308 316 CAST STAINUISS AxIn  ? 2T-CT RT 4293 (SWSPECINENS) CIRCLNERefr1AL I CIRCINERENTIAL 3 FT BEND RT >4000 CIRCLNER9(TIAL CE p CRACKED RT 4568 AXIAL 7, 2T-CT 316 C 1933 CIRCLNERB(TIAL)

CIRCLNERENTIAL 3PTBEND 31@C 2908 304 PLATE 1T-CI 31@C 1500 (J SPECIMENS)

Note: All results here were obtained from multiple specimen tests

• To convert from in lb/in2 to NJ/m2 multiply by 0.0001751 heieie i e am -

ii . im

J (In.-Lb./in!)

4 22000 - LEGEND:

E IT Compact Specimens 20000 - -

18 @ =

Blunting 16000 -

J 14000 -

E 12000 -

10000 -

8000 -

E i

l 6000 -

E 4000 -

2000 -

E O g g g ,

0 0.10 0.20 0.30 0.40 0.50 l Aa (Inches) i Figure 11. JIC Determination - 304 Forged Stainless Steel -

Radial Orientation Compact Specimens b

t J (In.-Lb./in2)

LEGEND: l 22000 -

9 Circumferential Orientation, RT l o Circumferential orientation, soo*F 20000 -

A Axial Orientation,.RT

1. ' 0 " " " "'

• E 18000 -

16000 -

Blunting Line (Rwm Temp.) Blunting Line 14000 -

(600*F) 12000 -

10000 -

e 8000 -

6000 - G O

400g G 2000 - O g

O l l 1 1 1 0 0.10 0.20 0.30 0.40 0.50 Aa (Inches)

Figure 10. JIC Determination 304 Forged Stainless Steel - Compact Specimens

O ,

' J (In.-Lb./in!)

28000 - (Blundng Une Room Temp.)

2'4000 X

20000 - I""

flne (600*F) 16000 -

12000 -

Legend:

8000 -

e RT.

E 600*F 4000 -

X RT-Precrackedin Compression 0 =

l 1 l l l' O 0.10 0.20 0.30 0.40 0.50 0.60 Aa (Inches)

Figure 14. JIC Determination - 304 Forged Stainless Steel -

Three Point Bend Specimens

I l

i t.

I i

L

- +a,c.e l

l l

.\.

s Figure 2.4-8: [ a,c.e 3

1 a

e e

t 1

m

, - *