1CAN039211, Provides Info to Change Util Commitment to Perform single-wall Radiography in Pump Casing & to Instead Conduct Reactor Coolant Pump Casing Structural Integrity Exams & Evaluations Using Methodology Contained in Listed ASME Case

Provides Info to Change Util Commitment to Perform single-wall Radiography in Pump Casing & to Instead Conduct Reactor Coolant Pump Casing Structural Integrity Exams & Evaluations Using Methodology Contained in Listed ASME Case

ML20141M070
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/26/1992
From:	James Fisicaro ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1CAN039211, 1CAN39211, NUDOCS 9203310279
Download: ML20141M070 (5)

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&.~; Ent:rgy y gor-- u Operations j ,

March 26 1992 3 1CANO39211

• 1 S. Nuclear Regulatory Commission Document Control Desk Mail Station PI-137 Washington, DC 20555

Subject:

Arkansc.s Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Revision to Reactor Coolant Pump. Augmented Inservice Inspectior. Commitment Gentlemen:

The NRC's Safety Evaluation (dated April 25, 1989) granted relief concerning additional examination of the reactor coolant pumps (RCPs) of Arkansas Nuclear one, Unit _1 (ANO-1). Entergy Operations committed to conduct an augmented RCP inspection plan. As part of this augmented

- plan, Entergy Operations was to perform single-wall radiography of the pump casing welds in the event of a pump is completely disassembled for maintenance, repair, or examination. This submittal provides information to change Entergy Operations' commitment to perform single-wall radiography of the pump casing and inctead conduct RCP casing structural integrity examinations and evaluations using the methodology contained in ASME Code Case N-481.

0+) February 29, 1992,-during the shutdown of ANO-1 to commence the IR10 refueling outage, a series of flow coastdown tests of the RCPs was performed. After testing of the "D" RCP had been completed, the "D" RCP was testarted to allow flow testing of another RCP. Approximately thirty minutes after restarting the pump, an alarm occurred due to high temperature on the controlled bleedoff for the "D" RCP. In accordance with operating procedures, the pump was tripped.

Subsequent evaluation of the availabic instrumentation indicated that the motor thrust bearing may have failed and that the motor / pump rotating element was stuck in an "up" position. The pump and motor were decoupled on March 20, 1992, and the RCP seal removed. Dimensional information and visual inspection indicated that the pump rotating assembly was still in the "up" position. Subsequent attempts to move the shaft were unsuccessful. A decision was made on March 21, 1992, to remove the motor and disassemble the RCP to inspect for potential damage.

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920331527E520326 '

l PDR ADOCK 05000313 P PDR l

O. S. NKC March 26, 1992 page 2

. Activities are currently underway to remove the KCP rover anu rot at ing assembly. A remoto inspection of these components will occur during removal, llowever, a detailed exsmination will be deferred until af tet the outage. The results of this examination will be made available on

= complellon of the detailed examinat ion. A detailed root enese evnination for the pu..ip/ motor f ailure is pending.

Sinco the current teardown of the "D" RCP was ncs a planned ouuge evolution, s(ngle-wall radiography cannot bo practically performed without excessive outage and eun-rem impact. Previous pump casing eneminat ionn of the "A" and "B" RCPs , as described lu Attachment 1 of 3 this letter, have been performed. These previous RCP ex2minations htwo 3 tot tiet ected s ay flaw growth or ident ified any service induced defects.

In lieu of performing sing)e-wall radiography for the casitig welds of the "D" RCP dor tug the curreat IR10 out.nge, Entergy Operations plans to conduct RCp ca$ltig r,t rutt ural integrity examinations and evaluat ions us ing t he nothodNgy contained in ASHC Code Case N-481. The use of the i..ethodology described in the Codo CSne represents a change in commituent to t.hn AN > l augmented inspection nian and is not a change to the AS:1E Code ren,nimi it.spections, The spproach nplied by thn Code Dane requires that a VT-1 visual exar;instfor of the ext ernal nurf aces of the wcld of the pump enning and a V'i + ;: ,isuetl aramination of the internal surfaces whenever a pump is .

dinctsambled So perfe> mul. The results of these examinat ions for the "D" RCP will oe eenmunicaL+.3 to thn Staf f at the concluulon of tho oxon hattona. A VU2 v1wal examination of the exterior of all pumps durina o hs.trostatic piensure tout in also requirtsd by the Code Cass.

i!.~to,ty Operwtic*9 will por /ca m thin examinat ion prior t o returning the un it to power operetions.

An evaluatien will aisc be performed to confirm the safety and nerviceshilf t y of the pump casing as di-cussed in the Code Case. This ualuaturi in c ;rrent ly being performed, llownver, the evaluation will net bn complote.4 until May 22, 1992. A t eport of this ovnluation wi?1 be se na P t.ed to th. Staff by June 5, 1992. Fracture mechanics and stress analynia ovaluat: ions were performed in 1086 and 1988 for the AND-1 "A" a nd 'B" FCPn. It was concluded. based on those evaluations, that s ynj fica nt flew growth will Ubt occur over the life of thn purp. Based on these evaluationa, E m ergy Operations expects that thn current evaluation will donmst rate tun : Integrity of thn casing undet postulated flawed condiu m.

Using the mntnod;1ony conta:lned .in Code Case N-481 in lieu of ningle-wall radiography, Entbrry )pernt.f orts helleves that the intent of the av2mented itnervice insipoetion plan described in the NRC opril 15, 1989, Safety 1;rduation will be met without increasing the radiatica exposure (20-25 nm n- r 20 '. :h. a to this unexpected RCP we,rk. Ent ergy Operat ions is perf o nning f.bn it rm; tdng por tions of the augment ed pinn described in the April 25, IM9, Sofety Evaluation.

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i U. S.'NRC I; Harch 26, 1092 Page 3

. This revision to the Aho-1 augmes;t,ed inspection plan was discussed with

s. mernbers of thr. Region IV and NRR Staf f on Hrach 24, 1992. Should you i

[ have any questaens reg.arding this issue, plus.e contact tne.

Very t ruly' yours.

1

\. t e- .

, t ny i: James J. Fisicato /- d l l

Director Licensing i l' .!

o JJF/kWC/sjf At t achtnent s  :

I 6

~_ cci 'Mr. Robert Martin '

[ .d ~ U. 5. Nuclear Regulatory Congnission L Region.IV '

611 Ryan Plaza Drive, Suite 400  ;

Arlingt on. TX 76011-8064  ;

I l

KitC Senior Resident ---Inspect or i Arkansas Nuclear One - ANO-1 6 2 {

L Number 1, Nuclear Plant Road ,

Russellville.-AR 72801 l Mr.-Thomas V. Alexion  ;

NRR Project Manager, Region IV/ANO-1  :

L s U. 3. Nucicar Regulat ory Conunission j NRR Mall Stop 13-11-3 l One White Flint North  ;

11555-Rockvflic Pike Rockville. M&ryla d 20852 ,

t Ms. Sherl Peterson '

K'AR Project Menager, Regicn IV/ ANO-2 U. .S. Nuclear Regulatory Cocunission .

NR A Hall Stop 13-11 '

one Whito: Flint North l

11555 Rockville t'lke l- Rvekville Maryland 20852 i

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ATTACl!HENT 1 l 1

lilSTORY ol' RCp CASING VELD l l FLAW INDICATIONS AT AN0-1 1 During IR7 (1986 refueling outnge) Arkansas Nuclu r One. Unit 1 (ANO-1) conducted an insetylce Itapestion of the "A" Reactor Coolarit ptutip (HCp) casing weld usitig conventional radiography (RT). The RT indicated the presence of a flaw which exceeded the ASME Code acceptance statidards for ati allowable ilaw sire. The Indicatlon was described as a setlos of shg inclusions located in the vertical weld which connects the upper cod lower scroll wolds of the pump casing. Supplemental ultrasonic testing (01) in the region of the flaw ludication was petformed.

The original radiographs taken at the time of fabricat.lon were reviewed to determine whether the flaw existed priot to sotvice, rive small inclusions that were part of the ' arrent Indica *.lon were found- lloweve r , I these five inclusions were accept able por the ASME Codo during the i preservice examinatlons. The original consttuctlon radiographs-for the )

remaining three pumps voto also reviewed for preservice flaw indications i or weak areas in film density. Toese ateas were computer-enhanced in an  ;

attempt to identif y any unacceptable flaws that ware not identified  !

previously, i From this review, "C" and "D" piunp casings wr e determined to have nn - l unacceptable prariervice flaw Indications. Ilowever, the computer  !

enhancement of "11" pump revealed an unacceptable flaw Indication in t.he l same general weld area as the "A" pump. The original construct.lon radiograph showed a flaw that was acceptable per the ASM" Code. UT i techniques were used in an att empt to bet ter characterize the finw. Duo

to the material of the casing and the small size of the flaw, UT was

-unable to $pecifically site tha flaw.- Fracture mechanics analyses and_a  ;

pump case stress analysis were perf ormed assuming conservative values for i the sju of the indication, and demonst rated compilance with the accept ace criter!r of the Code. As a esult, the NRC granted rollet -

f rom the Code to ai4ow examination of the "!!" RCp during 1RH, using 3 advanced state-of-the-art external surf ace volumet ric techulques without pump disassembly.

UT examinations of the "A" and "11" RCPs in the areas of the provinus. RT ludications were perfotw d during IRN (1988 refueling outage). These examinations utilized a Babcock and Wilcox automated ultrasonic data

,-- acquir.stion and imaging system (ACCUSONEX). The previous. slag ,

! indications were not detectable with this UT technologyt therefore, it was determ_tned that t.ho indicotions were vety small, occupy very little l volume, and are below the limit of detection for present-day UT technology.-

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in accordence with the ASME Code, Entergy also conducted a complete 4

volumetric external surf ace examination of the "li" RCP tasing weld during i 1RS. This examination was performed using double-wall RT and advanced  !

UT. The areas of the casing weld examined by RT showed no rejectable  !

Indications. Sections of the upper and lower scroll welds near the j

' discharge end of. the pump. wbleh could not be successfully examined by RT. along with the remainder of thi vertical weld were examined by UT. ,

in the lower scroll wuld several indications were detected (using ACCUSONi@ . These indications were considered *.o be slag inclusions. l The upper scroll weld could not be rxamined with ACCUSONEX- due to i Insufficient access for the robot; however, a manual scan was performed  ;

which identified three Indicatlons. These Indications were considered to  :

consist of slag inclusions result.ing from the original construction welding process and not a service induced condition. The "B" RCp factory [

radiographs for the areas of the indications and t.he low density radiographs taken during 1R8 were computer enhanced. The analysis of i these enhanced radiogr @ s showed no rejectable indications in the welds. l A f racture mechanics :r,raysis and a pump case st ress nnalysis wera also  !

performed for the "B" RCP. These evaluations concluded that no ,

significant flaw growth would occur over the life of the pump and the  !

pump casing is capable of maintaining its pressure retaining capability with t he flaws that were sized for the life of the ptunp.  ;

y Since' flaw indications woro initially identified for tho "A" RCP. the #

Code requires an examination tf the remaining components ("C" and "D" RCPs). If flaw Indications are valuated in accordance with the Code and the component qualifies as acceptable for continued service, the Code l requires that these areas shall be examined during throo inspection 6 periods. Entergy Operations requested relief from these requirements for the RCPs for ANO-1 in letter dated October 27, 1988 (1CAN108805). Tho .

ANO-1 Inservice Inspection Program was revised to schedule-augmented examinations of the "A" RCP during 1R10 and 1R12 and thc "B" RCP. during -

IK10, 1R12, and 1R14. These augmented examinations are being performed

- with enhanced UT techniques.

In their Safety _ Evaluation report dated April 25, 1989, the NRC granted the relief request with the provision that ANO-1 conduct an augmented i inservice inspection program that consisted of 1) performing successive inspections required by the Code on "A" and "B" RCP in the areas ,

containing the flaw indications { external UT may be used); 2) single-wall >

radiography be performed in the event that any RCP is completely disassembled for maintenance, repair or examination; 3) additional examinations are not required during this inspection interval unless these examinations detect actual-flaw growth or service induced ,

y degradation; and 4) in the future, use the most conservative published values Cor fracture toughness properties. ANO-1 ogreed to perform the augmented inspections.

The enhanced UT of.the "B" RCP during the_ current outage (1R10) has'not-detected any flaw growth or-identified any service induced flaws. The- ,

- examination of the "A" RCP is currently being performed.

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