ML20086G312
| ML20086G312 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 11/27/1991 |
| From: | Vaughn G CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20086G317 | List: |
| References | |
| IEB-80-13, NLS-91-303, NUDOCS 9112050038 | |
| Download: ML20086G312 (6) | |
Text
=
Carolina Power & Light Company P o Don is51 e Raleigh. N C 21602 BOY,37199}
G. E. VAUGHN SERIAL: NLS 91303 Vge President Nucleat $ermes oepartment United States Nuclear Regulatory Commission j
ATT ENTION: Document Control Desk 1
Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50 324/ LICENSE NO. DPR 62 RESPONSF TO BULLETIN 80-13 EXAMINATION OF CORE SPRAY SYSTEM SPARGERS Gentlemen The purpose of this letter in to submit the results of visual examinations of the invessel core spray piping and spargers for the Drunswick Steam Electric Plant, Unit 2. These examinations, which were performed during the Brunswick Unit 2 Relord 9 outage, are being submitted in accordance with NRC Bulletin 8013 dated May 12,1980. provides the results of the invessel examinations and basis for the continued operation of the Brunswick Plant, Unit 2 until the next refueling outage.
The crack indication previously identified on the north core spray line has been repaired by reinforcing the piping using a bracket. The method of repair was previously outlined in CP&L's letter dated September 13,1991 (Serial: NLS-91-223). Enclosure 2 provides a detailed description of the repair method used for the north core spray line.
Please refer any questions regarding this submittal to Mr. W. R. Murray at (919) 540 4661.
Yours very truly,
~yh/du G. E. Vaughn WRM/wrm (b2r9-es.wpf)
Enclosures cc:
Mr. S. D. Ebneter Mr. N. B. Le Mr. R. L. Prevatte l
ma mar t
t o
I ENCLOSURE 1 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 n.
NRC DOCKET NOS. 50 325 & 50 324 a
OPERATING LICENSE NOS. DPR 71 & DPR 02 RESPONSE TO BULLETIN 8013 EXAMINATION OF CORE SPRAY SYSTEM SPARGERS RESULTS OF REMOTE VISUAL EXAMINATIQN (PERIODIC TEST F F 90.11 In accordance with NRC Bulletin 8013, a visual examination of the core spray spargers and in-vessel core spray piping of the Brunswick Steam Electric Plant, Unit 2 was performed during the Relosd 9 outage. Other than the previously identified indication on the north loop of the core spray piping, no other relevant indications were noted.
The crack indication previously identitified on the north core Spray line was repaired by reinforcing the piping using welded brackets. The bracket modification is shown on Figure 2 of the General Electric report provided in Enclosure 3 of this letter. The bracket attachment welds were visually examined for pre service requirements. These bracket attachment welds are being added to thc scope of examinations that are being performed each refueling outage as part of the Brunswick Plant's response to NRC Bulletin 8013.
Since. Carolina Power and Light Company is adding the bracket attachment welds to the examination scope and will visually examine them every outage as part of the response to NRC Bulletin 8013, CP&L does not intend to perform liquio penetrant (LP) examination of the crack on the north loop piping in future outages to monitar crack growth. The brackets provide full structuralintegrity of the piping, even if the crack grows to 3600 of the pipe circumference.
Carolina Power & Lig',t Company believes that crack growth monitoring for this indication is no longer necessary and, therefore, requests NRC concurrence with this action.
Based on the visual exan'ination results and the installation of the brackets on the north loop of the invessel core spray piping, CP&L believes that start up and continued operation of the Brunswick Plant, Unit 2 until the next refueling outage, currently scheduled for to begin March 1993, is
- justified and wil not adversely affect the health and safety of the public. Therefore, Carolina
. Power and Light Company intends to proceed with the start up of Brunswick Unit 2 as currently scheduled.
REFERENCES 1.
lE Bulletin 8013, " Cracking in Cors Spray Spargers," dated May 12,1980, 2;
Letter from L,1. Loflin (CP&L) to NRC Document Control Desk, " Response to IE Bulletin 80-13 Examination of Core Spray System Spargers," February 23,1990 (Serial:
El 1
. - = - - -
1
. i 3.
Letter from N. 0, Le (NRC) to L. W. Eury (CP&L), ' Review of the Carolina Power & Light l
Company's Report on Growth of Crack Indications on the North Core Spray Lines -
t Brunswick Steam Electric Plant, Unit 2 (TAC No. 70068),' Juno 5,1991.
t 4.
Letter from S. D, Floyd (CP&L) to NRC Document Control Desk 'In vessel Core Spray l
Piping Repair,' September 13,1991 (Serial: NLS 91-2231, t
I k
i k
t i
I El 2 w-,w-rv y -
,,--w sri,y-y v-w, ey-t y 3 - u m -wh m,- ene %W tyvW y,sr-www yaup-a----
.e-t-g-c= ce,
,w-++eee<-,&we+e a e-eEw
.g.irg-w = w,cew veem.--.wmwer s-ywvse, em r w - ww--mwr*w ew w wr rie -, ev v v w e -d
ENCLOSURE 2 BRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKET NOS, 50 325 & 50 324 OPERATING LICENSE NOS. DPR 71 & DPR 02 RESPONSE TO BULLETIN 8013 EXAMINATION OF CORE SPRAY SYSTEM SPARGERS PESCRIPTION OF REPAIR TECHNIQUE The north (*A") loop of the invessel core spray piping was repaired using underwater welding techniques to weld two brackets across the tee box and adjacen' piping on both sides of the 100.
The two brackets are designed to maintain full structural integrity of the invessel piping, even if cracks propagate through the entire pipe cross section on both sides of the tee box. The leakage through four 300' long cracks Ithe hydraulic evaluation addresses leakage through all four tee box to piping weld joints, i.e., both north and south loops) was evaluated and is within the design margin of the core spray system. The analytical results are summarized in a report prepared by General Electric Nuclear Energy entitled ' Core Spray Crack Analysis Update for Brunswick Steam Electric Plant Unit 2 Safety Evaluation, July 1991," RDE-410791. A copy of this report is provided as Enclosure 3.
The brackets were fit up and welded underwater with fit up venfication and final non-destructive (visual) examination (NDE) performed remotely by quality control techricians on the refuel floor.
The diver positioned the camera and held go-no-go gages for the verification of fit up, final weld sire, and final NDE. The bracket material and weld filler metal are both resistant to intergranular stress corrosion cracking (IGSCC). The use of underwater welding minimizes the base metal susceptibility to IGSCC due to the quick cooling following the welding.
Due to delays caused by the fit up of the brackets and the higher than anticipated dose rates, only the north I'A*) loop had brackets installed. Only the north loop of the invessel core spray piping has a flawed weldment. The brackets were to be installed on the 'B' (270*) loop since the installation contractor was already mobilized on site for the "A" (90') loop mandatory repair.
FINAL NDE AND BRACKET SEAL WELDS DEFERRAL The final weld NDE performed during this outage was a remote visual examination which assures welds of acceptable quality for at least one cycle of operation. Although the invessel core spray piping modification is not under the jurisdiction of ASME Code, this repair was implemented as a Section XI repair /replacernent. The ASME Code,Section XI, paragraph IWA 7210 states that
" replacement for parts or components originally constructed without Code requirenients shall be in accordance with the original design, fabrication, and inspection requirements for the part or component being replaced". The original piping welds were LP examined; therefore, conservatively an LP examination of the bracket attachment welds should be performed since the brackets serve the same structural function as the piping circumferential welds. As previously noted, the final weld NDE performed this outage was a remote visual examination; liquid penetrant examination of the bracket welds was not performed because a vessel drain down was not performed following E2-1
\\
l
4 a
the repair. The bracket attachment welds are scheduled to be LP examined during the next refueling outage (Reload 10 outage) when vessel drain down is planned for feedwater sparger i
examinations pursuant to NUREG 0019.
In order to eliminate the potential for crevice corrosion cracking developing under the brackets, seal welds across the open ends of the brackets will be added durmg the next refueling outage. It was not possible to apply the seal welds underwater since the area under the brackets could not be dried'out. The sealing of the ends of the brackets does not add any strength to the bracket attachment welds; it is oni', being applied to preclude the possibility of future cracking of the welds due to water filled crevice corrosion. Therefore, not installing the seal welds this outage does not in any way affect the function of the brackets to provide full structuralintegrity of the core spray piping for operation until the next refueling (Reload 10) outage.
SAFETY EVALUATION
SUMMARY
Carolina Power and Light Company believes that the start up and continued operation of the Brunswick Plant, Unit 2 until the next refueling outage, currently scheduled to begin March 1993, is justified and will not adversely affect the health and safety of the public. Therefore, Carohna Power and Light Company intends to proceed with the start up of Brunswick Unit 2 as currently scheduled.
L E2 2 pngy pm-+y-----ew-megi-ygn=--
w g-vevw
't' yu-*we-iyy--e v-y--ey9-&T'Ttn'9 T T PTT'T9 W-W*'sW**"9rT-"FP"'W'*MeY7WTWMOfW'P'***W 4 e *-DF E'TE*Y'TM*WemT"'TT"pe'*iM'awWwTr' a 3
-m e m W T't#N w svr e-'TF'W4*1FWrM'*FN WMi r w mar Wv'
e ENCLOSURE 3 DRUNSWICK STEAM ELECTRIC PLANT, UNITS 1 AND 2 NRC DOCKET NOS. 50-325 & 50 324 JPERATING LICENSE NOS. DPR 71 & DPR 02 RESPONSE TO BULLETIN 8013 EXAMINATION OF CORE SPRAY SYSTEM SPARGERS GENERAL ELECTRIC REPORT RDE 41-0791 CORE SPRAY LINE CRACK ANALYSIS UPDATE FOR BRUNSWICK STEAM El.ECTRIC PLANT UNIT 2
.