1CAN099302, Forwards Relief Request from Requirements of IWB-2420(b) of ASME Boiler & Pressure Vessel Code,Section XI,1980 Edition Re Successive Insps of RCP Weld Flaw Indications

Forwards Relief Request from Requirements of IWB-2420(b) of ASME Boiler & Pressure Vessel Code,Section XI,1980 Edition Re Successive Insps of RCP Weld Flaw Indications

ML20058M530
Person / Time
Site:	Arkansas Nuclear
Issue date:	09/28/1993
From:	Yelverton J ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1CAN099302, 1CAN99302, NUDOCS 9310060165
Download: ML20058M530 (8)

Text

.  ;

Entergy Operations, Inc.

S%

9 ENTERGY Td 50144 8883 i

Jerry W. Yelverton l VccPiwdmt j 0;natms A'O '

" September 28,1993 1CAN099302 U. S. Nuclear Regulatory Commission Document Control Desk Mail Station PI-137 Washington, DC 20555

Subject:

Arkansas Nuclear One - Unit 1 Docket No. 50-313 ,

License No. DPR-51 Relief Request for Successive Inspections of RCP Weld Flaw Indications Gentlemen:

This letter is being submitted to request relief from the requirements ofIWB-2420(b) of the ASME Boiler and Pressure Vessel Code,Section XI,1980 Edition through Winter 1981

• Addenda, Rules for Inservice Impection of Nuclear Power Plant Components. The specific request is for reiief (per 10CFR50.55a(g)(5)) from the requirement to perform additional successive weld reexaminations on the Arkansas Nuclear One - Unit One (ANO-1) "A" and "B" reactor coolant pump (RCP) casing welds.

On May 4,1993, at the annual Regulatory Informatic Conference, Dr. Thomas E. Murley, Director, Oflice of Nuclear Reactor Regulation (NRR), announced a pilot program established by NRR to give special consideration to licensee requests for changes requiring Staff review that involve high cost and low safety benefit. In response to Dr. Murley's initiative, Entergy Operations met with the NRR StafTon June 8,1993, to present an initial list of cost beneficial licensing actions. As part of the Burden Redaction Program for long-term economic savings, this submittal is to request relief from performance of successive inspections on the "A" and "B" RCP casing welds. The "A" and "B" RCPs have one and two (respectively) successive i inspections remaining in accordance with IWB-2420(b). Entergy Operations estimates that approval of this r , nest will save approximately $1,100,000 and 21 person-rem radiation exposure over 6 '

five years with no reduction in safety.

Entergy Operati,. ieen performing successive inspections of the embedded inclusions in the alrected RCP cc velds since their identification in 1986. A history of the identification of the flaws and subsequent actions taken follows:

Volumetric examination of one of the RCPs (RCP "A") was attempted at the end of the 1st 10-year Interval in 1984 (IR6) pe ASME Section XI requirements. The D A 411 v 9310060165 930928 PDR ADOCK 05000313 8

j

[Of7 G PDR k lll

i 1

U. S. NRC <

j

, September 28,1993 ICAN099302 Page 2

. examination was to be performed using the MINAC, a linear accelerator developed by EPIU specifically for RCPs. The exam was intended to be a double-wall radiograph ,

that would preclude the necessity of pump disassembly. Due to equipment' malfunctions, the examination was not performed (see letter ICANI18410, dated 1 November 19,1984). j l

Entergy Operations asked the NRC for relief to allow performance of the examination l at the next scheduled refueling outage in 1986 (IR7), which was in the 2nd 10-year  !

Interval. The NRC granted relief (see letters ICAN128408, dated December 19,  !

1984, and ICNA058505, dated May 28,1885).

i The examination of RCP "A" was performed in 1986_ (IR7) using single-wall radiography, instead of double-wall, since the pump had been disassembled for other  ;

reasons. The examination revealed a flaw in the torus weld that exceeded the size  !

allowed by Section XI of the ASME Code. The flaw was determined to be a series of ,

slag inclusions that had existed since fabrication of the casing. The original  !

construction (fabrication) radiographs for the other three RCPs were reviewed for preservice flaw indications or for we ' areas of film density (which might hide a flaw).

Questionable areas of the films were computer enhanced to improve film readability.  ;

The enhanced factory films revealed an unacceptable flawed area in the "B" pump in [

the same general location as the "A" pump. An attempt was made to characterize the {

flaws using ultrasonics, however, due to the coarse-grain nature of the casting and the small size of the individual flaws, the UT was unsuccessful. The entire . area containing these small individual flaws was referred to as one large flaw in each of the t two RCPs. Fracture mechanics was then performed on these large flaws. Each flaw  ;

was found to be acceptable per the Section XI fracture mechanics criteria. The areas on both "A" and "B" pumps were examined during the next refueling outage (IR8),

which occurred in 1988, using newly developed ultrasonic techniques. The UT rever' i no evidence of a flaw, indicating that the flaws are very small and occupy littl- 9 In addition, the entire weld length of the "B" pump was also examined .

4 ' nation of double-wall radiography and ultrasonics (areas tint could not I usint -

be exam,nea with RT were inspected with UT). The RT found no flaws, but the UT did find some more slag inclusions remaining from the original fabrication of the pump in the scroll weld at the pump discharge. Additional fracture mechanics and a pump  :

case stress analysis were performed on "B" pump for these new indications. These l evaluations concluded that no flaw growth would occur over the service life of the l

pump and therefore tl e purnp casing was safe for continued operation. ANO asked for relief from performing any exams on the "C" and "D" pumps since there was no insersice-induced cracking in any RCP nor any known cracking mechanism (see letter ICAN108805, dated October 27,1988).

The NRC granted relief from examining "C" and "D" pumps and from performing ,

successive RT exams on "A" and "B" pumps, which would have required disassembly l of the pumps (see letter 1CNA048906, dated April 25, 1989). However, the NRC l

k k

g U. S. NRC l

. September 28,1993 1CAN099302 Page 3 .

required an augmented inservice inspection program that consisted of the following points:

v A) "The successive inspections required by IWB-2420 on "A" and "B" RCPs are completed in the areas containing the flaw indications. External ultrasonic testing may be used as the examination method." (This is the subject of the currently proposed relief request.)

B) " Single-wall radiography is performed based on IWB-2420 and IWB 2430 in the event that any reactor coolant pumps are completely disassembled for l mainienance, repair, er examination." (This requirement would be changed

ater when Code Case N-481 was submitted, see below.)

C) "During this inspection interval the Staff will not require additional examinations based on IWB-2430 for any reactor coolant pump casing '

weld unless these examinations detect actual flaw growth or service- ,

i induced degradation."

D) "In the future, the licensee should use the most conservative published values for fracture toughness properties unless a technical justification is  !

provided for a higher value." (In the Code Case N-481 evaluation, Entergy- t Operations complied with this requirement.)

By letter ICAN049007, dated April 30,1990, Entergy Operations provided the NRC I with a schedule of future examinations for RCPs "A" and "B" The schedule stated that the "A" pump would be examined in IR10 and 1R12 and that the "B" pump would be examined in IR10, IR12, and 1R14.

During the shutdown for IR10 (March 1992), the motor bearings in RCP "D" were  !

damaged. Consequently, the pump was disassembled during the outage in order to i inspect for damage. Since the augmented ISI program required a full RT exam if any pump was disassembled, the "D" pump was required to be examined during lRIO.

However, because the disassembly of the pump was not scheduled, and since Code Case N-481 was in the NRC approval process, Entergy Operations submitted a  !

commitment change to perform the Code Case N-481 evaluation along with certain i specified visual exams (VT-1,-2, and -3) in lieu of the RT (1CANO39211, dated March 26, 1992). The visual exams on "D" were performed during IR10 and were  !

satisfactory. Supplemental ultrasonic (UT) examinations were performed on the slag inclusions in the "A" and "B" RCPs during refueling outage IR10 and indicated no flaw growth In fact, due to the improvements that had been made in UT technology since the previous examinations, the slag indications appeared to have shrunk in size.

Entergy Operations completed the Code Case N-481 evaluation for all four RCPs and submitted the report to the NRC by letters dated June 12, 1992, and June 18,1992 ,

(ICAN069201 and ICAN069207). One of the more significant findings in the j i

1

~

U. S. NRC {

.;~ September 28,1993 _l lCAN099302 Page 4 .j evaluation was that the. ANO-1 RCPs are safe to operate for the life of d e " plant utilizing the Code Case required flaws, which are much more severe than the slag .i inclusions that are actually contained.in the RCP casing welds. This Code Case .  ;

evaluation and its required visual examinations were ' performed in lieu of the: 1)- -l single-wall ' radiographic (RT) examinations required by the augmented inspection  !

program when the pumps were completely disassembled, and 2) examinations required j by Table IWB-2500-1, Examination Category B-L-1, Item No. B12.10 for the remainder of the second inspection interval.

i The attached r;!ief request further relies upon the evaluation conducted for Code Case N-481 - '

to providejustiication for discontinuance of the successive UT examinations of the "A" and j "B" RCP casing welds. The attachment includes the generic relief request justifications i required by the NRC in your letter to ANO dated June 7,1990 (2CNA069002).

i This request is not exigent; however, prompt review and approval are requested. Should you  !

have any questions regarding this submittal, please contact me. j Very truly yours,  !

/ h i Q, ,/ to 4(& ~ZP 1

/ / t

/ JWY/JJD 'l r

Attachment l r

'l I

i 1

h p

i t

4- .,

I

U. S. NRC September 23,1993 ICAN099302 Page 5 cc: Mr. James L. Milhoan Regional Administrator U. S. Nuclear Regulatory Commission Region IV  ;

611 Ryan Plaza Drive, Suite 400 l Arlington, TX 76011-8064 i NRC Senior Resident Inspector Arkansas Nuclear One - ANO-1 & 2 Number 1, Nuclear Plant Road Russellville, AR 72801 Mr. Roby B. Bevan, Jr.

NRR Project Manager Ryon IV/ANO-1 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Thomas W. Alexion NRR Project Manager, Region IV/ANO-2 U. S. Nuclear Regulatory Commission NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Paul W. O' Conner NRR Project Manager, Region II/ Grand Gulf U. S. Nuclear Regulatory Commission s NRR Mail Stop 13-H-3 One White Flint North 11555 Rockville Pike Rockville, MD 20852  ;

i

Attachment to ICAN099302 Page 1 of 3 .

'l A NO-1 Inservice Inspection 6 Relief Request 93-001 i Aprilicable Interval:

Second ,

Applicable Edition and Addenda of ASNIE Section XI:

1980 Edition with Addenda through Winter '81 l Code Class:

1 y Code Examination Category:

B-L-1 .

t Code Item No.:

B 12.10  !

Code Itenuired Examination:

Volumetric Examination ofPressure-Retaining Welds in Pump Casings t

Compont at(s) or Relief Area (s):

Reactor Coolant Dump Casing Welds i

ISI Exam Nom Examination Area Description Component No. l"43-001 Upper Scroll Weld RCP P32A 43-001 A Torus Weld between 001 and 002 RCP P32A

• 43-002 Lower Scroll Weld RCP P32A 44-001 Upper Scrol! Weld RCP P32B ,44-001 A Torus Weld between 001 and 002 RCP P32B 44-002 Lower Scroll Weld RCP P32B  !

i 5

. -i Attachment to ICAN099302 Page 2 of 3

' Requirement from which Reliefis Reospsted: IWB-2420(b), requires that the areas of  !

components that contain flaws evaluated in accordance with IWB-3122.4 and found acceptable for continued service must be reexamined during the next three inspection .

periods to monitor flaw growth.

Ilasis for Relief: [

The flaws in the RCP Casing Welds are sub-surface fabrication flaws (slag inclusions) that' l

have existed since the pumps were originally manufactured in the early 1970s. As'such, they are not service-induced and do not pose any threat to the structural integrity of the pressure-retaining boundary of the pumps. Entergy Operations has performed extensive non-destructive examinatien on these fabrication flaws and has determined that they -

existed pre-service and are not growing in size. Entergy Operations has also performed a rigorous fracture mechanics evaluation, per ASME Code Case N-481, which' has 't demonstrated that flaws which are actually.more severe than those which exist for these  ;

welds will not grow significantly during the remaining service lifetime of the plant. This  ;

evaluation was previously submitted to the NRC by letters dated June 12,1992, and June l 18,1992 (IC.AN069201 and ICAN069207).

Additionally, ASME is developing a Code Case (ISI 93-06, Code Case N-XXX,

" Alternate Rules for Successive Inspections IWB-2420, IWC-2420") that provides increased guidance on the subject of successive examinations if the flaws are not likely to propagate with time. The draft Code Case is in the ASME approval process and approval j is expected soon. The draft Code Case basically states that a flaw may bc exempted from l future successive examinations if the flaw meets the following three basic criteria:

1) The flaw is " subsurface"; i.e., buried within the component.

2) The flaw existed pre-service, which means that the flaw is a result of the fabrication process rather than being service-induced. +

3) The flaw is demonstrated by fracture mechanics to be acceptable until the next  !

scheduled inspection or until the end of service lifetime of the component. i The slag inclusions in the ANO-1 "A" and "B" RCP casing welds meet all three of the '

above criteria as discussed previously.

Entergy Operations estimates, based on experience performing these examinations in the ,

recent past, that the remaining successive examinations will cost approximately $1.1 j million and will expose plant personnel to approximately 21 person-rem. Continued -l examination of these indications places an undue economic and radiation-exposure j hardship on the plant without any compensating increase in the level of plant safety.

]

Attachment to

. 1CAN099302

~

Page 3 of 3 .

' Alternative Examinations: >

i Entergy Operations has performed visual examinations (VT-1 and VT-3) on the "D" RCP while disassembled in 1992 (IR10). A VT-2 examination was also performed on all four

' RCPs (P32A, B, C, and D) during 1R10. These examinations were done to satisfy ASME ,

Code Case N-481.

Entergy Operations will continue to perform visual examinations (VT-2, and VT-3) on all four RCPs as required and delineated by ASME Code Case N-481.

I

?

I P

l

, , , .