ML042670570
| ML042670570 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/23/2004 |
| From: | Hartz L Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 4-535, RR-89-52 | |
| Download: ML042670570 (13) | |
Text
Dominion Nuclear Connecticut, Inc.
hl ill\\totic Power Station I h p c I.'crry Road W/.ircrfiird, C.1. 06.385 September 23, 2004 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 b
v borninion M
Serial No.:
04-535 MPS Lic/RWM Rev 2 Docket No.:
50-423 License No.:
NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION, UNIT 3 10 CFR 50.55a REQUEST RR-89-52, TEMPORARY NON-CODE REPAIR IN SERVICE WATER SYSTEM BRAZED JOINTS TO SAFETY INJECTION PUMP COOLER (3CCI*E1 A)
Dominion Nuclear Connecticut, Inc. (DNC) requests relief from the Section XI requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, pursuant to 10 CFR 50.55a(g)(5)(iii). This request is based upon the impracticality of performing ASME Code repairs to brazed joints on service water piping associated with safety injection pump cooler (3CCI*E1 A) during plant operation. Attachment 1 to this letter describes the temporary compensatory actions taken by DNC and the basis for the proposed alternative non-Code repairs. Permanent Code repairs for these flaws will be completed during the next cold shutdown of sufficient duration to affect repair or the next refueling outage, whichever comes first.
If you should have any questions regarding this submittal, please contact Mr. Paul R. Willoughby at (804) 273-3572.
Very truly yours,
'J Leslie N. Hartz Vice President - Nuclear Engineering 1 OCFR 50.55a Request RR-89-52
Serial No.04-535 Request RR-89-52 Page 2 Commitments contained within this letter: (2)
- 1.
Compensatory Monitoring Plan:
Leakage monitoring of the 3CCI*EIA safety injection pump cooler shall be performed. The degraded joints will be observed at least once per 12-hour shift during normal operator rounds and any significant increase in leakage will be evaluated.
Periodic follow-up non-destructive examinations (NDE) for erosion rate and structural assessments will be performed within 90 days from the last examination. These periodic NDE examinations will include UT examinations of the piping at the five affected brazed joints and a visual inspection. These follow-up examinations shall continue until permanent Code compliant butt-welded replacement field welds to this cooler are performed.
Any significant changes that are observed in the condition of the degraded joints that could affect system(s) operability or structural integrity will be evaluated.
Based upon the observations from this monitoring plan, any needed evaluations will determine if further remedial measures or corrective actions are needed.
- 2.
Permanent Code repairs for the service water system brazed joint flaws in the safety injection pump cooler 3CCI*EIA will be completed during the next cold shutdown of sufficient duration to affect repair or the next refueling outage, whichever comes first.
cc: See next page
Serial No.04-535 Request RR-89-52 Page 3 cc:
U. S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Mr. V. Nerses Senior Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11 555 Rockville Pike Mail Stop 8C2 Rockville, MD 20852-2738 Mr. S. M. Schneider NRC Senior Resident Inspector Millstone Power Station
Serial No.04-535 Request RR-89-52 ATACHMENT 1 10 CFR 50.55a REQUEST RR-89-52 TEMPORARY NON-CODE REPAIR IN SERVICE WATER SYSTEM BRAZED JOINTS TO SAFETY INJECTION PUMP COOLER (3CCI"El A)
DOMINION NUCLEAR CONNECTICUT, INC. (DNC)
MILLSTONE POWER STATION, UNIT 3
Serial No.04-535 Request RR-89-52 / Page 1 of 9 10 CFR 50.55a REQUEST RR-89-52 TEMPORARY NON-CODE REPAIR IN SERVICE WATER SYSTEM BRAZED JOINTS TO SAFETY INJECTION PUMP COOLER (3CCI*E1 A)
CONTENTS 1. 0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 ASME CODE COMPONENTS AFFECTED....................................................
2 APPLICABLE CODE EDITION AND ADDENDA............................................
2 APPLICABLE CODE REQUIREMENTS.........................................................
2 IMPRACTICALITY OF COMPLIANCE............................................................
3 BURDEN CAUSED BY COMPLIANCE..........................................................
3 PROPOSED ALTERNATIVE AND BASIS FOR USE.....................................
3 DURATION OF PROPOSED ALTERNATIVE................................................
7 PRECEDENTS............................................................................................... 7 FIGURE 1:
FIGURE 2:
SAFETY INJECTION PUMP COOLER (3CCI*EIA) ASSEMBLY..... 8 3CCI*EIA ASSEMBLY WITH TEMPORARY SUPPORTS............... 9
Serial No.04-535 Request RR-89-52 / Page 2 of 9 10 CFR 50.55a REQUEST RR-89-52 TEMPORARY NON-CODE REPAIR IN SERVICE WATER SYSTEM BRAZED JOINTS TO SAFETY INJECTION PUMP COOLER (3CCI*E1 A)
Relief Request In Accordance with 10 CFR 50.55a(g)(S)(iii)
-Inservice Inspection Impracticality -
1.O ASME CODE COMPONENTS AFFECTED:
The affected components include ASME Code Class 3 service water brazed joints, Cu-Ni SB-465 piping, and associated bronze SB-62 socket fittings, for 2-inch and 1.5-inch nominal piping. The affected joints leak service water and are located in the piping associated with the 'A' safety injection pump cooler (3CCI*ElA). There are five (5) affected joints, identified as FW-50, FW-53, FW-55, FW-63 and FW-66, as shown in Figure 1.
Four (4) of the leaks are at 2-inch joints within the boundary of the heat exchanger and one (1) leak is at a 1.5-inch joint immediately downstream of the heat exchanger.
The 'A' safety injection pump cooler (CCI) is a heat exchanger composed of a series of four pipe-within-a-pipe segments that are connected by brazed fittings.
System:
Design Code:
Safety Code Class:
Piping size:
Nominal Thickness:
Material (pipe / fitting):
Design Pressure:
Temperature:
Code Minimum Wall:
Service Water ASME Ill 1971 Class 3 2-inch and 1.5-inch 0.1 56 inches / 0.150 inches Cu-Ni SB 466 / Bronze SB 62 100 psi design / 63 psi max. operating 75 eF design max. / 33 eF min.
0.01 inches (thickness) 2.0 APPLICABLE CODE EDITION AND ADDENDA:
Millstone Unit 3 is currently in the second 10-year lnservice Inspection (ISI) interval, which started on April 23, 1999. The 1989 Edition of Section XI with No Addenda applies to the IS1 program and the 1998 Edition of Section XI with No Addenda is used as the primary ASME Code Edition for the SectionXI Repair/Replacement program activities.
3.0 APPLICABLE CODE REQUIREMENTS:
Applicable ASME Code requirements are those contained in ASME Section XI, 1 989 Edition, IWA-4000, Repair and Replacement.
NRC approved analysis
Serial No.04-535 Request RR-89-52 / Page 3 of 9 methods are those contained in Generic Letter (GL) 90-05, "Guidance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2 and 3 Piping,"
dated June 15, 1990 and 10 CFR 50.55a. GL 90-05 also provides guidance for performing temporary non-Code repairs of ASME Code Class 1, 2 and 3 piping.
4.0 IMPRACTICALITY OF COMPLIANCE:
There is no acceptable method for analyzing leaking brazed socket joints in Generic Letter 90-05 or permitted by ASME Section XI, 1989 Edition, IWA-4000.
Additionally, NRC approved Code Cases, such as N-513, "Evaluation Criteria for Temporary Acceptance of Flaws in Class Three Piping,Section XI, Division 1," are not applicable to these brazed socket joints.
Consistent with the Millstone Unit 3 long-term service water brazed joint remediation plan, the repair planned in this instance is to replace the brazed joints with butt-welded fittings. Isolation of the affected piping results in loss of cooling to the 'A' train safety injection pump and unavailability of this safety injection pump.
Plant Technical Specification 3.5.2 requires that two independent Emergency Core Cooling System (ECCS) subsystems be operable. Each subsystem requires one operable safety injection pump. Plant Technical Specification 3.5.2 requires that any inoperable ECCS subsystem be made operable within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or commence shutdown to hot standby. The estimated repair time, with reasonable allowance for contingencies exceeds the 72-hour allowance of the Technical Specification.
5.0 BURDEN CAUSED BY COMPLIANCE:
The permanent repair for this condition could potentially require an unnecessary shutdown of the unit without a commensurate safety benefit. The structural analysis of the current piping configuration using this temporary non-Code repair indicates that all required functions would be maintained for postulated design basis accidents and transients.
6.0 PROPOSED ALTERNATIVE AND BASIS FOR USE:
For the purpose of analyzing structural capacity, the total loss of the braze material within the leaking pipe joints has been assumed. Therefore, additional supports were added to prevent pipe separation from the affected brazed socket fittings. If braze material failure occurs, the added supports maintain structural continuity of the degraded configuration and will restrict the potential for leakage to annular clearances between the affected socket fittings and piping. This use of temporary supports is shown in Figure 2 and will ensure 3CCI*EIA service water piping is structurally adequate for all design loading conditions.
An operability determination (OD) has been completed. The OD will remain applicable until the permanent butt-welded replacements of joints for this cooler can be installed, and the piping fully qualified.
Based on the evaluations, examinations and monitoring procedures associated with this temporary repair, the
Serial No.04-535 Request RR-89-52 I Page 4 of 9 proposed actions provide reasonable assurance that the joints will maintain the structural integrity and functional performance of the line. Specific considerations associated with the basis of this request are discussed in the balance of this section.
6.1 Flaw Characterizations and Mechanism of Degradation:
Non-destructive examination included ultrasonic testing (UT) on the affected piping, elbow and union sockets.
Visual examination (VT-1) on flaws, adjacent components and augmented inspections were performed.
The extent of the braze disruption is very small and not distinguishable by visual examination. The resulting leakage is slow and can be characterized as weeping (less than 1 drop per minute). Adjacent pipe material and fittings have no cracking or wastage. UT examination showed no deterioration in the piping or the fittings and, consequently, erosion rate estimates are not applicable to this condition.
The degradation mechanism appears to be limited to the adequacy of the braze material fill in the affected joints which have resulted in through-braze leaks and assumed braze material failures. Fitting and piping are intact.
Therefore, any potential leakage area is limited to the annular area (derived from nominally 0.005 inches of gap within the joint) between pipe and sockets.
6.2 Augmented Inspections:
There are four service water system coolers that have the same brazed piping and fittings with a pipe-within-pipe configuration like the 'A' safety injection pump cooler (3CCI*ElA). The other three coolers are the 'B' safety injection pump cooler (3CCI*ElB), and the 'A' and 'B' charging pump coolers (3CCE*E1 A and 3CCE*E1 B). A visual inspection was performed of the other three coolers, which included a total of 81 separate field joints, and no additional brazed joint leaks were identified.
Additional examinations of similar pipe designs and adjacent piping was performed to provide assurance that other brazed joints were not leaking and that no damage had occurred due to leaking service water.
6.3 Structural Assessment:
The flaws are located in brazed joints and therefore previously approved methodologies to show structural integrity are not applicable. The operability determination conservatively assumes a potential for total loss of the braze material in joints FW-50, 54, 55, 63 and 66. The affected joints are shown in Figure 1. The structural integrity of the service water system is adequate based on the joint design and the location of new supports as shown in
Serial No.04-535 Request RR-89-52 I Page 5 of 9 Figure 2, (i.e., the affected piping will remain within the fitting sockets even if braze material were to totally fail). The 3CCI"ElA service water piping is subject to deadweight, thermal, seismic inertial, and fluid pressure thrust loading. The new supports from this temporary non-Code repair ensure affected piping is structurally intact for all design loading conditions for this application.
6.4 System Interactions:
Specific considerations from system interactions such as consequences of flooding and spraying water on equipment, and potential for loss of flow from leakage, are discussed in the balance of this section.
Floodinq:
Currently, only weeping has been observed at the affected brazed joints.
Catastrophic failure of the joints is not expected from this condition.
However, a conservative assumption of a total loss of braze material in affected joints has been considered. Any potential leakage area is limited to the annular area (derived from nominally 0.005 inches of gap within the affected joints) between pipe and sockets.
The greatest leakage postulated to result from such an assumption is estimated at a cumulative 20 gpm from the combined contribution to leakage from all 5 affected joints, and 4 gpm per affected joint.
Any leakage that occurs at the 3CCI*ElA cooler travels through floor drains to a sump that is located in the 'A residual heat removal pump cubicle below. Review of the Engineered Safety Features building flood calculation indicates that safety related equipment is located in this area.
However, the available volume for flooding without affecting safety related components is significant and corresponds to a fill time estimate of 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br />, from a 20 gpm leak rate. Considering that the assumptions of this leakage estimate are conservative and that operator rounds observe the degraded joints at least once per 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> shift, any increased leakage would be identified and isolated well before any safety related components could become affected. Note also that a review of the predicted dose rates in this area show it to be accessible and an adequate response time would be achieved.
Serial No.04-535 Request RR-89-52 / Page 6 of 9 Jet sway:
If further degradation of the affected joints were to take place, spray or jet impingement upon adjacent components is not a concern. No safety related targets vulnerable to spray are within close proximity to the affected joints.
The nearest spray target is motor operated valve 3SIH*MV8923AI a suction valve to the safety injection pump. This valve is approximately five feet from any potential leak point, and is environmentally qualified for inside containment, post-accident atmospheres, including spray.
Loss of flow:
In modeling this condition, the analysis shows that in the unlikely event of a simultaneous maximum leakage from all five affected joints, the service water flow to the 3CCI*EIA cooler remains adequate. After accounting for the assumed leakage, the final flow rate at the outlet of the heat exchanger still exceeds the minimum required flow rate for the postulated accident condition. Other service water heat exchangers on the same branch line with 3CCI*ElA also maintain adequate required flow rates by this analysis, and the worst case loss of flow from 3CCI*EIA cooler is negligible with respect to the service water system header flow margins.
6.5 Compensatory Monitoring Plan:
Leakage monitoring shall be performed. The degraded joints will be observed at least once per 12-hour shift during normal operator rounds and any significant increase in leakage will be evaluated.
Periodic follow-up non-destructive examinations (NDE) for erosion rate and structural assessments will be performed within 90 days from the last examination. These periodic NDE examinations will include UT examinations of the piping at the five affected brazed joints and a visual inspection. These follow-up examinations shall continue until permanent Code compliant butt-welded replacement field welds to this cooler are performed.
Any significant changes that are observed in the condition of the degraded joints that could affect system(s) operability or structural integrity will be evaluated. Based upon the observations from this monitoring plan, any needed evaluations will determine if further remedial measures or corrective actions are needed.
Serial No.04-535 Request RR-89-52 / Page 7 of 9 7.0 DURATION OF PROPOSED ALTERNATIVE:
Permanent Code repairs for these flaws will be completed during the next cold shutdown of sufficient duration to affect repair or the next refueling outage (fall 2005), whichever comes first.
8.0 PRECEDENTS
The NRC Staff's review and approval of a similar temporary non-Code repair of a brazed joint leak at Millstone Unit 3 is in a letter dated May 21, 2004, "Request for Relief From ASME Code Class 3 Piping, (TAC No. MB9996)." This request is at ADAMS Accession No. ML032040024.
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FIGURE 2:
3CCI*EIA ASSEMBLY WITH TEMPORARY SUPPORTS Serial No.04-535 Request RR-89-52 1 Page 9 of 9