ML18153B740

Discusses Corrective Actions Re Steam Generator Tube Leak Event & Response to NRC Bulletin 89-001, Failure of Westinghouse Steam Generator Tube Mechanical Plugs. Tubes Replaced Because of Unknown Matl Heat & Leaking Tubes

ML18153B740
Person / Time
Site:	Surry, North Anna, 05000000
Issue date:	05/26/1989
From:	STEWART W L VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-373, IEB-89-001, IEB-89-1, NUDOCS 8906020254
Download: ML18153B740 (19)

Text

e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 May 26, 1989 U. S. Nuclear Regulatory Commission Attention:

Document Control Desk Washington, D.C. 20555 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 . STEAM GENERATOR TUBE LEAK EVENT CORRECTIVE ACTION AND RESPONSE TO NRC BULLETIN NO. 89-01 Serial No.89-373 NO/JBL/JDH:jmj R1 Docket Nos. 50-280 50-281 50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 On March 29, 1989, we met with you to discuss the February 25, 1989 North Anna Unit 1 steam generator tube leak event. During the meeting we discussed our future plans for North Anna Unit 1. On April 26, 1989 we submitted information concerning our assessment of procedures and training and Unit 2 tube plug corrective actions. Attachment I to this letter provides tube plug corrective action for Unit 1. In addition we have addressed the actions requested in NRC Bulletin No. 89-01, dated May 15, 1989 per Attachment II for both North Anna and Surry Power Stations.

The subject bulletin requested that licensees determine whether certain mechanical plugs supplied by Westinghouse are installed in their steam generators and if so, that an action plan be implemented to ensure that these plugs will continue to provide adequate assurance of reactor coolant system (RCS) pressure boundary integrity under normal operating, transient, and postulated accident conditions.

8906020254 890~26 ~DR AD0Ck 05000280 . F'DC e e The above information is true and accurate to the best of my knowledge.

Should you have any questions or require additional information, please do not hestitate to contact us. Attachment cc: U.S. Nuclear Regulatory Commission Region II . 101 Marietta Street, N.W. Suite 2900 Atlanta, Georgia 30323 Mr. W. E. Holland NRC Senior Resident Inspector Surry Power Station Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station COMMONWEAL TH OF VIRGINIA ) ) COUNTY OF HENRICO ) The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by W. R. Cartwright who is Vice President

-Nuclear, of Virginia Electric and Power Company: He is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief. Acknowledged before me this t& 7JI day of _..,~~~--*

19_fil. My Commission Expires: 1 ZS. tf~.g~ Notary Public *----. . . -*---. -***--****--*._

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Attachment I NORTH ANNA UNIT 1 TUBE PLUG CORRECTIVE ACTIONS The North Anna Unit 1 action plan for mechanical plugs made from material with discontinuous grain boundary carbides is comprised of the following elements:

0 The installation of a plug-in-plug (PIP) in selected plugged tube locations.

0 The replacement of a limited quantity of plugs. 0 The installation of tube plugs of optimum heats (ie, plugs of heats having continuous grain boundary carbides).

0 Water-filled tubes (sentinel plugs). 0 Remaining-life margins based on microstructure and test data. Specifically, 1251 mechanical plugs were installed in Unit 1 prior to the 1989 refueling outage. These plugs were installed in eight (8) outages prior to the current outage. In 1987, following the tube rupture event, 162 tubes were plugged by installing a solid mechanical plug in the hot leg and a mechanical plug with a drilled hole (designated "sentinel plugs") in the cold leg. Non-sentinel tubes were plugged for various reasons including primary water stress corrosion cracking (PWSCC) at the expansion transition, U-bends, and support plates; and, outside diameter attack at the top of tubesheet.

The heats of concern for North Anna Unit 1 are NX 3962, NX 3513, and NX 4523. The attached Tables I thru IV illustrate the Unit 1 mechanical plug installation history and actions taken. Tables V and VI provide a historical summary of the remaining-life margins for mechanical plugs installed in North Anna Units 1 and 2, respectively, based on microstructure and test data. Additionally, Tables VII and VIII provide a historical summary of the remaining-life margins for mechanical plugs installed in Surry Units 1 and 2, respectively, based on microstructure and test data. Because one of the elements of the action plan is based on relative time to failure from PWSCC, a long term plan must be developed to deal with those plugs that will, at some future time, experience degradation.

To develop this plan, we are evaluating several options. These include: 0

• replacement with currently available acceptable heats 0 replacement with alloy 690 plugs (the current design uses Alloy 600) 0 plug-in-plug (PIP) This long-term plan will be developed before the next refueling outage at Unit 1.

SUPPORTING INFORMATION Plug-in-Plug (PIP) Virginia Power conceived the approach of installing a plug in the existing mechanical plugs (plug-in-plug or "PIP") utilizing the threads already existing in the mechanical plug. The purpose of the design is to limit the primary-to-secondary leakage which would prevent the failure of the tube due to plug failure. The PIP is designed to be leak limiting.

By minimizing the volume of trapped primary water within the plug, the PIP minimizes the amount of stored energy available to drive a separated plug top upward, through the plugged tube. This design prevents adequate replenishment of the primary volume beneath the plug top to propel it up the tube if the plug top should become separated from the plug body. If a plug top is released it is not expected to travel beyond the expansion transition at the top of the tubesheet.

This design, therefor~.

prevents the possibility of a tube leak event occurring in a manner similar to the February 25, 1989 Unit 1 tube leak event. The PIP installation was designed to be performed robotically to minimiz~ personnel radiation exposure.

Installation of the Westinghouse PIP is a three phase process which may be accomplished by manual and/or remote (robotic) techniques.

The PIP is manufactured from the. same material as the mechanical plug shell to which it is welded (thermally treated alloy 600). The material is procured and inspected in accordance with the ASME Code or ASTM standards.

The PIP is machined and inspected in accordance with very detailed and *controlled manufacturing and inspection procedures.

Westinghouse Quality Assurance audits the manufacturing process to document compliance with the specification.

• Plug Replacement A selected number of plugs are being replaced for the following reasons: 0 leaking tube 0 circumferential indication 0 unknown heat of material 0 PIP installation problems The first two reasons are for operational concerns.

The PIP, by design, is low leakage. Should a plug located in a previously leaking tube also begin leaking, a small primary-to-secondary leak would occur. To preclude this event, we are replacing candidate hot leg plugs in these tubes. Circumferential indications at the expansion zone have been evaluated for crack growth during operation.

For North Anna Unit 1, stabilizers will be installed to mitigate the effect of tubes that have sufficiently large crack angles and may propagate and interact with other active tubes before the planned replacement of these steam generators.

In the unlikely event that a tube, currently analyzed as having adequate margin against significant crack growth, cracks through-wall, the tube would become a leaking_tube.

If the plug with a PIP then begins to leak, then a small primary-to-secondary leak would occur.

• To preclud~ this event, we are replacing hot leg plugs in tubes with circumferential indications.

The third reason, unknown heat of material, is straight forward. Two hot leg mechanical . plugs were installed in 1979. We have been unable to identify the heat of material used. Replacing these hot leg plugs is a conservative action. During the installation of PIPs, there were several instances where the installation was not possible.

These problems included PIPs that become lodged before full insertion, PIPs that would not insert fully but could be removed, and with unacceptable spot welds. The removed PIP/plug will be replaced.

Optimum Heats Several heats of material are acceptable for long term operation.

The action plan takes this fact into account. By eliminating these plugs from the population of concern, total dose from personnel radiation exposure received during the implementation of the action plan is reduced. Water-Filled Tubes Analysis demonstrates that a water-filled tube effectively mitigates the potential tor a tube penetration by a plug projectile. (The NRC Bulletin No. 89-01 permits the use of this action plan element for only one _cycle beyond this outage). Remaining-Life Margin Based on microstructure and test data, relative time to significant primary water stress corrosion cracking (PWSCC) has been determined.

More margin exists for cold leg plugs than hot leg plugs. Using this margin approach, additional plugs may be removed from the population of concern . .. --------**-~*-----*-~--

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Attachment II RESPONSE TO NRC BULLETIN NO. 89-01 FAILURE OF WESTINGHOUSE STEAM GENERATOR TUBE MECHANICAL PLUGS Actions Requested

1. Addresses are requested to verify that information contained in References 1 and 2 relating specificially to their plants is correct for plugs supplied from heat numbers 3279, 3513, 3962, and 4523. The specific information to be verified is the number of Westinghouse mechanical plugs installed .in the hot and cold legs broken down by steam.generator number, heat number, and date of installation.

If information from these references is incorrect, appropriate corrections should be identified.

Addresses are requested to $0 state if their plants have not installed Westinghouse mechanical plugs from ~he subject heats. Response Surry 1 and 2: We have verified the number of Westinghouse mechanical plugs in the hot and cold legs per steam generator, the heat number, and date of installation.

The Surry steam generators contain only heat numbers 3962 and 2387. North Anna 1 and 2: We have verified the number of Westinghouse mechanical plugs in the hot and cold legs per steam generator, the heat number, and date of installation.

Reference 2 of this Bulletin provided the plug installation information for heat number 4523. An inaccuracy was found for Unit 1, Steam Generator "C" cold leg for the 5/87 installation activity.

Westinghouse has been notified.

Of the subject heats listed in the Bulletin, the North Anna steam generators do not contain heat number 3279. 2. Addressees are requested to take the following actions, to be implemented initially during any refueling outage or extended outage (greater than four weeks) which ends 30 days or more following receipt of this bulletin and during all future refueling outages. a) Steam generator tube plug lifetime for plugs from heats 3279, 3513, 3962, and 4523 should be estimated using the methodology from References 1 and 2 and should be based on the Millstone Unit 2 benchmark subject to any corrections per item 1 above. Lifetime estimates in Reference 2 for plugs fabricated from heat 4523 are based on the Farley Unit 2 benchmark . . . -... -.... ..,.---** ***-*----****--

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e These estimates should be adjusted to reflect the Millstone Unit 2 benchmark using the methodology described in Section 4.1.2 of Reference

1. b) Addresses should implement appropriate remedial actions (i.e., repair and/or replacement) for all plugs whose estimated life-times in 2a, above do not extend to the next refueling outage. If operation is planned beyond a refueling outage that represents the last outage before any plug exhausts the predicted lifetime, an alternative schedule with the appropriate technical justification should be submitted to the NRC at least 30 days before the end of this refueling outage. c) Prior to any plug repairs or replacement, addressees are reminded that their responsibilities under ALARA require analysis of the various plug repair or replacement methods available to determine which method will result in the lowest overall personnel radiation exposure while still remaining cost-effective.

In choosing a plug repair or replacement method, the licensee should consider the accessibility of the plugs and the dose reduction benefit of using robotic manipulators.

Prior to plug repair or replacement, the licensee should consider steam generator decontamination and/or local shielding to reduce working area dose rates. d) Installation of Westinghouse mechanical plugs from heats 3279, 3513, 3962, and 4523 should be discontinued.

e) Westinghouse mechanical plugs removed from steam generators, regardless of heat number, should be examined for PWSCC on a sample basis for each heat. Addressees should maintain a record of these examinations and the results should be provided to Westinghouse to improve the database concerning the susceptibility of plugs to PWSCC. Response Surry 1 and 2: The steam generator tube plug lifetime for plugs from the subject heats has been estimated.

The Millstone Unit 2 benchmark was used. Based on this estimated lifetime approach, the following plugs were removed from Surry: Unit 1 Hot Leg Cold Leg SG 'A' SG 'B' 2 SG'C' 2 Unit 2 Hot Leg Cold Leg SG 'A' 1 SG 'B' SG 'C' ALARA was considered.

Because of the small number, manual removal was determined to be the most effective process. Surry will not use the subject heats for future plugging.

Plugs were removed by drilling.

Only a remnant resulted from this process. The samples from North Anna that were analyzed are a worst case representative of the Surry plugs. One of the elements of the Surry plug action plan is based on relative time to primary water stress cor:rosion cracking.

A long term plan must be developed to deal with those plugs that will, at some future time, experience degradation.

This long term plan will be developed before the next refueling outage of each unit. North Anna .1 and 2: The steam generator tube plug lifetime for plugs from the subject heats has been estimated.

The Millstone Unit 2 benchmark was used. Based on this estimated lifetime approach, repair strategies were developed for each unit. The plug-in-plug (PIP) was not available for Unit 2 at the time of its scheduled outage. Virginia Power elected to replace 51 hot leg plugs. A robotic manipulator was used where possible.

More information is available in our letter to you dated April 26, 1989. For North Anna Unit 1, 430 hot leg plugs and 7 cold leg plugs required action. A robotic manipulator was used where possible.

North Anna will not use the subject heats for future plugging.

Several plugs were removed from Unit 1 for laboratory examination.

This information will improve the database on plug failure history. One of the elements of the North Anna plug action plan is based on relative time to primary water stress corrosion cracking.

A long term plan must be developed to deal with those plugs that will, at some future time experience degradation.

This long term plan will be developed before the next refueling outage of each unit.

3. Remedial actions at plants where the steam generator tubes are expanded within the tubesheet as described.

above may be deferred on a one time basis to the next scheduled refueling outage if the outage that immediately follows receipt of this bulletin ends before October 1 , 1989. Response Surry 1 and 2: Neither Surry unit has partially-depth-expanded tubes within the tubesheet.

The tubes are hydraulically expanded full-depth of the tubesheet.

North Anna 1 and 2: Neither North Anna unit has partially-depth-expanded tubes within the tubesheet.

The tubes were hard-rolled at the primary face of the tubesheet and were later, before operation, explosively expanded full-depth of the tubesheet.

4. Remedial actions for "sentinel related" mechanical plugs described above may be deferred on a one time basis to the next refueling outage if the outage that immediately follows receipt of this bulletin ends before October 1 , 1989. Response Surry 1 and 2: Neither unit at Surry uses sentinel plugs. North Ann_a 1 and 2: Both North Anna units have sentinel plugs installed.

The use of water-filled tubes (sentinel strategy) was employed when the action plan for each unit was developed.

Virginia Power has re-evaluated antivibration bar insertion and fatigue usage in both units. We will shortly submit those reports. They support the removal of many of the sentinel plugs in both units. Our long term plan will deal with the sentinel plugs at the next refueling outage of each unit. -,--**-*-. -----**----. ---*****-~-**--. .---. --**--.--, **----... --, -.--.*. *------* --.. *----------.-

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PLUG CORRECTIVE ACTION

SUMMARY

UNIT 1 SUMMATION TOTAL PLUGS: 1822 Plug T~~es HOT LEG COLD LEG Number of Plugs Action Taken Number of Plugs Action Taken Explosive Plugs: 199 NONE 279 -NONE We I ded PI ug s: 92 NONE NONE Mechanical Plugs: 9/79 Outage Unknown Microstructure 2 2-Replaced 4 1-P IP 3-Replaced 12/80 Outage Heat NX 9789 0 NONE 1/84 Outage Heats NX 1989 and 8 3-PIP NX 2205 1-Replaced NONE Heat NX 2205 only 9 NONE z 5/84 Outage 0 B&W fleats 12 NONE 16 NONE t; NX 3624, and NX 3531 ::>" 8/85 Outage > Hec1t NX 2387 13 NONE 13 NONE = = > . 11/85 Outage PJ t:rl t"'4 ijeat NX 3962 71 56-PIP 73 72-NONE q tz:I 15-Replaced 1-Replaced

= I-'* H 4/87 Outage Heats NX 3962, 261 211-PIP 263 262-NONE NX 3513 and NX 4523 50-Replaced 1-Rep I aced I-' 7/87 Outage Non-Sentinel Mated ( H/L) 91 81-PIP Heats NX 3962 and NX 4523 10-Rep I aced Non-Sentinel (C/L) 90 NONE e Heat NX 4523 ' Sentinel Mated (H/L) 162 161-NONE Heats NX 3962 and NX 4523 1-Replaced Sentinels (C/L) 162 161-NONE Heats NX 3962 and NX 4523 1-Replaced I .1 j, Ii ! I i ! .,

• 1 I: i j .I PLUG CORRECTIVE ACTION

SUMMARY

UAIT 1 SUMMATION TOTAL PLUGS: 1622 Plug Types HOT LEG Number of Plugs Action Taken TOTALS: Hot Leg : 9 11 p I ug s 199 -Explosive, No action taken 92 -Welded, No action taken 620 -Mechanical 351 -PIPs installed . 79 Replaced with acceptable microstructure per ~estinghouse 190 -No action taken 161 -Sentinel Mated *17 -Acceptable for service per Westinghouse 12 -Acceptable for service per Babcock and Wilcock Cold Leg: 911 plugs 279 -Explosive, No action taken 1 -Welded, No action taken 631 -Mechanical 1 -PIP Installed 6 -Replaced with acceptable microstructure per Westinghouse 624 -No action taken 447 Acceptable for service per Westinghouse 16 Acceptable for service per Babcock and Wilcox 161 -Sentinel_

plugs COLD LEG Number of Plugs Action Taken -z 0 t-3 11 CT :i:,, ::,' b:l t-4 :i:,, tz:I = 1-1 = II.I -c:::l (') = 0 I-'* z CT t-3 . t:I -e

-, I TOTAL PLUGS: 628 Plug Types PLUG CORRECTIVE ACTION

SUMMARY

STEAM GENERATOR A UNIT 1 HOT LEG Number of Plugs Action Taken* Explosive Plugs: Welded Plugs: Mechanical Plugs: 5/84 Outage B&:W Heats NX 3624 and NX 3531 8/85 Outage Heat NX 2387 11/85* Outage Heat NX 3962 4/87 Outage Heats NX 3962, NX 3513, NX 4523 Heat NX 4523 7/87 Outage TOTALS: Non-Sentinel Mated (H/L) Heat NX 4523 Non-Sentinel (C/L) Heat NX 4523 Sentinel Mated (H/L) Heat NX 4523 Sentinels (C/L) Heats NX 3962 and NX 4523 Hot Leg: 314 plugs 77 -Explosive, No action taken 21 -Welded, No action taken 216 -Mechanical 99 -PIPs installed 77 NONE 21 NONE 8 N_QNE 13 NONE 9 8-PIP 1-Replaced 81 67-PIP 14-Replaced 25 24-PIP 1-Replaced 80 NONE 16 -Replaced with acceptable microstructure per Westinghouse 101 -No action taken 80 -Sentinel Mated 13 -Acceptable for service per Westinghouse 8 -Acceptable for service per Babcock and Wilcock Cold Leg: 314 plugs 94 -Explosive, No action taken 220 -Mechanical, No action taken .. 130 -Acceptable for service per Westinghouse 10 -Acceptable for service per Babcock and Wilcock 80 -Sentinel plugs Number of Plugs 94 0 10 13 9 83 25 80 COLD LEG Act-ion Ta ken NONE NONE NONE NONE NONE NONE NONE :z: 0 l'1. ct" =" > = = Ill c::: = I-'* ct" .... e t:D t-1 l:z:I H H ' e .I ,,

,, ; I ! fOTAL PLUGS: 43q Plug Types PLUG CORRECTIVE ACTION

SUMMARY

STEAM GENERATOR B UNIT 1 HOT LEG Number of Plugs Action Taken Exp Io s i ve PI ug s: We I ded PI ug s: Mechanical Plugs: 1/84 Outage Heat NX 2205 5/84 Outage. B&W Heats NX 362L1 and 3531 11/85 Outage Heat NX 3962 4/87 Outage Heats NX 3513; HX 4523 Heat NX 4523 7/87 Outage TOTALS: Non-Sentinel Mated (H/L) Heat NX 4523 Non-Sentinel (C/L) Heat NX 4523 Sentinel Mated (H/L) Heat NX 4523 Sentinels (C/L) Heats NX 4523 and NX 3962 Hot Leg: 217 plugs 58 -Explosive, No* action taken 36 -Welded, No action taken 123 -Mechanical 97 -PIPs installed 58 NONE 36 NONE 4 1 17 62 27 12 NONE NONE 15-PIP 2-Replaced 59-PIP 3-Replacet 23-PIP 4-Replaced 11-NONE 1-Replaced 10 -Replaced with acceptable microstructure per Westinghouse 16 -No action taken 11 -Sentinel Mated 4 -Acceptable for service per Westinghouse 1 -Acceptable for service per Babcock and Wilcock Cold Leg: 217 plugs 94 -Explosive, No action taken 123 -Mechanical Number of PI ugs 94 0 4 17 62 27 12 COLD LEG Act.ion Ta ken NONE NONE NONE NONE NONE NONE NONE 11-NONE 1-Replaced 1 -Replaced with acceptable microstructure per Westinghouse because of dampener installation.

122 -No action taken 110 -Acceptable for service per Westinghouse 1 -Acceptable for service per Babcock and Wi I cock 11 -Sentinel plugs H H H TOTAL PLUGS: 760 Plug Types PLUG CORRECTIVE ACTION

SUMMARY

STEAM GENERATOR C UNIT 1 HOT LEG Number of Plugs Action Taken Exp I o s i ve P I ug s: Welded Plugs: Mechanical Plugs: 9/79 Outage Unknown Microstructure 12/80 Outage Heat NX. 9789 1/84 Outage Heats NX 1989 and NX 2205 Heat NX 2205 only 5/84 Outage B&:W Heats NX 3624 and NX 3531 11/85 Outage Heat NX 3962 4/87 Outage Heats NX 3962, NX 3513 and N~ 4523 7/87 Outage TOTALS: Non-Sentinel Mated (H/L) Heat NX 4523 and NX 3962 Non-Sentinel (C/L) Hec1t NX 4523 Sentinel Mated (H/L) Heats NX 3962 and NX 4523 Sentinels (C/L) Heats NX 3962 and NX 4523 Hot Leg: 380 plugs 64 -Explosive, *No action taken 35 -Welded, No action.taken 281 -Mechanical 155 -PIPs installed 64 NONE 35 2 0 4 3 45 118 39 70 NONE 2-Replaced NONE 3-PIP 1-Replaced NONE 33-PLP 12-Replaced 85-PIP 33-Replaced 34-PIP 5-Replaced NONE 53 -Replaced with acceptable microstructure per Westinghouse 73 -No action taken 70 -Sentinel Mated 3 -Acceptable for service per Babcock and Wilcox Cold Leg: 380 plugs 91 -Explosive, No action taken 1 -Welded, No action taken 288 -Mechanical 1 -PIP Installed 5 -Replaced 282 -No action taken 207 -Acceptable for service per Westinghouse 5 -Acceptable for service per Babcock and Wi !cock 70 -Sentinel plugs Number of Plugs 91 1 4 1 5 5 47 118 38 70 COLD LEG Action Taken NONE NONE 1-PIP 3-Replaced NONE NONE NONE 46-NONE 1-Replaced 117-NONE

• 1-Replaced NONE NONE z 0 t-1 CT ::s' t-3 > > = tJ:j = t"' Ill tr.I c::: H = < I-'* CT .....

! . NORTH ANNA 1 MECHANICAL PLUG REMAININQ MARGIN Remaining Fuel C;:t:cles Descri[!tion SG A SG B SG C 1. NONE {Note 2) 11/85 Outage-Heat NX 3962 9(HL) 17( HL) 1t5( HL) 2. tjONE (Note 2) 4/87 Outage 81(HL) 62(HL) 118(HL) Heats NX 3962/3513/4523

3. NONE (Note 2) 7/87 Outage-Possible 25(HL) 27(HL) 39(HL) Heats NX 3962/4523

4. UNKNOWN 9/79 Outage-unknown 2(HL) Mic rost ructu re 4(CL) 5. 5 11/85 Outage-Heat NX 3962 9(CL) 17 (CL) 47(CL) 6. 5+ 4/87 Outage Heats 83(CL) 62(CL) 118(CL) NX 3962/3513/4523

7. 6 7/87 Outage-Non Sentinel 25(CL) 27(CL) 38(CL) Plugs Heat NX 4523 8. 12+ 1/84 Outage-Heats 4(HL) 4(HL) NX 2205/1989

9. 13+ 8/85 Outage Heat NX 2387 13(HL) 10. 110+ 12/80 Outage Heat NX 9789 1 ( CL) 11. hO+ 1/84 Outage Heat NX 2205 4(CL) 5(CL) 12. /10+ 8/85 Outage Heat NX 2387 13(CL) 13. Not Applicable Sentinel Mated Plugs 80(HL) 12(HL) 70(HL) Sentinel Plugs 80(CL) 12(CL) 70(CL) 14. Note 1 5/84 Outage-B & W Plugs 8(HL) 1 ( HL) 3(HL) Note 1: Heats NX 3624/3531 lO(CL) 1 ( CL) 5(CL) TOTALS: 216(HL) 123(HL) 281(HL) 220( CL) 123( CL) 288( CL) Steam Gen Totals: 436 246 569 Plant Tota I; 1221 Awaiting results of additional B&W testing. Previous B&W testing implies plugs are good for rema1n1ng life of plant. Westinghouse testing of similar microstructures would indicate a remaining hot leg I ife of 12 plus fuel cycles and a cold leg I ife of 40 plus ~uel cycles. Note 2: These plugs will be replaced or a PIP installed prior to restart. -z 0 I; CT ::,' 1-3 > > = c::I = t"'4 '1J t::l d < = .... CT f--,1 Remaining Fuel Cycles None* None* None* 5 6 12 120 .e TABLE VI NORTH ANNA UNIT 2 MECHANICAL PLUG REMAINING MARGIN Steam Generator Description A 8 C 8/87 Outage -Hot Leg Heat NX 3962/ 9 6 22 3513/4523 w/o Cold Leg Sentinel 8/87 Outage -Hot Leg Heat NX 3962/ 2 i 2 3513/4523 w/ Cold Leg Sentinel (Fatigue Susceptible) 2/86 Outage -Hot Leg Heat NX 3962 2 1 6 2/86 Outage -Cold Leg Heat NX 3962 2 1 6 8/87 Outage -Cold Leg Heat NX 3962/ 9 6 22 4523 (Non-Sentinel) 8/84 Outage -Hot Leg Heat NX 2387 1 2 8/84 Outage -Cold Leg Heat NX 2387 1 2

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TABLE VII SURRY UNIT 1 MECHANICAL PLUG REMAINING MARGIN Remaining Steam Generator Fuel Cycles Description A 8 None* 5/86 Outage -Hot Leg Heat NX 3962 2 2 8 5/86 Outage -Cold Leg Heat NX 3962 2 2 12 9/84 Outage -Hot Leg Heat NX 2387 3 1 120 9/84 Outage -Cold Leg Heat NX 2387 3 1

• Plugs have been replaced

• . TABLE VIII SURRY UNIT 2 MECHANICAL PLUG REMAINING MARGIN Remaining Fuel Cycles None* 8 Description 6/86 Outage -Hot Leg Heat NX 3962 6/86 Outage -Cold Leg Heat NX 3962

• Plug has been replaced Steam Generator A 8 C. 1 1