ML20244E595
| ML20244E595 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, Zion, 05000000 |
| Issue date: | 06/16/1989 |
| From: | Richter M COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 9001K24-25, IEB-89-001, IEB-89-1, NUDOCS 8906210005 | |
| Download: ML20244E595 (10) | |
Text
l N Commonwrith Edison
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72 West Adams Strrot, Chicago, lihnnis
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/ Kddress Reply to: F5st 0Tfice 85ix~'/67~
l N/ Chicago, lihnois 60690 0767 i
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June 16, 1989 i
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U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C.
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Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 l
Zion Station Units 1 and 2 Response to NRC Bulletin 89-01 Failure of Westinghouse Steam Generator Tube Mechanical Plugs liRC_DssAgt Nos. 50-454/455, 50-456/457, and 50-295/3D.4 References (a) NRC Bulletin 89-01, dated May 15, 1989.
Dear Sire Reference (a) requests that addressees 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 pressure boundary integrity under normal operating, transient, and postulated l
accident conditions.
The attachment to this letter provides Commonwealth Edison's response to Reference (a) for Byron, Braidwood, and Zion Stations.
For Byron and Braidwood Stations, no Westinghouse steam generator tube mechanical plugs fabricated from the suspect heats were installed.
For Zion Station, plugs fabricated from suspect heats (3513 and 4523) were installed in steam generators for Unit 1 and Unit 2.
Remedial actions will be taken for the hot leg plugs, from the suspect heats, during the next scheduled refueling outage for each Zion unit.
At this time, there are no plans to implement any remedial actions during any extended outage prior to the next scheduled refueling outage for each Zion unit.
8906210005 890616 (l
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-2 Commonwealth Edison has discontinued use.of any Westinghouse steam-generator tube mechanical plugs from the suspect. heats.
Additionally, Commonwealth Edison continues to monitor industry experience and vendor recommendations concerning this issue.
P2 aase address any questions that you may have concerning this
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response to this office.
j Respectfully,
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M M.H.
Richter Generic Issues Administrator 9001k24-25 Attachment cc A.B. Davis Resident Inspectors - BY/BW/Z r
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Subfe ribed and Syy to
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befpre me this /u - day l "0FFICIAL SEAL"
- l of dll)E 1989l LELIA F. MAYO f
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'l BYRC2, IRAIDWOOD, AND ZION STATIQt RESPONSES TO ACTION ITEh 1 4
Action Item 1 Addresseec are requested to verify that information contained in i
References 1 and 2 relating specifically to their plants is correct for plugs supplied from heat numbers 3279, 3513, 3962, and 4523.
The specific
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information to be verified is the number of Westinghouse mechanical plugs j
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.
Addressees are requested to so state if their plants have not installed Westinghouse mechanical plugs from the subject heats.
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ZION STATION RESPONSE TO ITEM 1 Commonwealth Edison had Westinghouse review the procurement records for the four (4) suspect heats of plug material (3279, 3513, 3962, 4523).
Based upon the review of these records, Westinghouse has concluded that the earliest i
procurement of suspect heat material was January 1983.
Therefore, all plugs-installed prior to that date could not have been fabricated from the suspect heat material.
A review of plant documentation revealed that Zion Station had installed i
l steam generator tube mechanical plugs which were fabricated from two of the j
suspect heats (3513, 4523). Table 1 presents the heat numbers for Westinghouse mechanical plugs installed in the Zion steam generators.
1 Plant documentation for installed plugs at Zion Station has been compared j
to the information presented by Westinghouse in Bulletin References 1 and 2 for heat numbers and plug locations. There were two discrepancies between the data presented by Westinghouse (in Bulletin References 1 and 2) and the installed conditions at Zion Station. These discrepancies, shown correctly in Table 2 (marked
- ), were in stenm generator "1A",
row 6 column 25 hot leg and row 4 column 73. cold leg, where welded plugs rather than mechanical plugs were installed. Therefore, the correct number of steam generator "1A" tubes with plugs fabricated from heat 4523 is three (3), for both hot and cold legs.
Table 2 shows.the location and date of installation for all Westinghouse mechanical plugs, as well as welded plugs, installed in the Zion steam generators for heats 3513 and 4523.
Plugs fabricated from heat numbers 3279 and 3962 have not been installed in any of the Zion steam generators.
It should be noted that during the documentation review for installed plugs, Zion Station identified a total of 22 plugs installed in steam generator "1B" during May 1982 with unknown heat numbers. As indicated previously, a Westinghouse review of procurement records verified the earliest I
purchase of the suspect heat material was Januasy 1983.
Therefore, based on l
the results of the Westinghouse review, these 22 plugs were not fabricated from the suspect heats.
(1)
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1 TABLE 1 Unit 1 Unit'2 Installation Installation i
Dates Heat Numbers Installed Dates Heat Nembers Installed 3/75 none 1/76 none 3/76 none 1/77 none 9/77 none 3/78 none 9/78 none 3/79 none 2/81 1660, 85C4, 9789 9/81 85C4 5/82 1577, 1660, 1989, 2386 2387, 9357, 9739 Heats listed above were installed prior to the Westinghouse procurement of suspect heat material.
9/83 2205 3/83 2205 9/84 2387 4/84 2387 2/85 2387 9/85 2387 4/85 2387 6/87 4523 9/86 none 11/88 none j
3/88 3513, 4523 1/89 none 1
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(2) s
7ABLE 2
' Unit l1 Plug. Installation Date March 1988:
Steam Heat Numbers Steam-He at. N umbe rs Generator Row Col H/L Plug C/L Plug Generator Row Col H/L Plug C/L Plug 1A*
6 25 (Weld) 4523 IB" 32 17 4523 4523; l
-1A*
4 73 4523 (Weld)-
1B
.30-21
'4523 4523 1A 14 92 4523 4523 1B 25 22 4523
'4523 1A 4
94 4523 4523 IB 5
30 3513 4523 l
1B 26 32 4523 4523 l
-4523 1B 26 33 4523-
- 4523
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'10 45 (Weld) 4523 IB 9
55 4523' 4523 l
1C' 8
50 4523 4523
'1B 7
61 4523-4523 i
IC.
8 54 (Weld) 4523 IB 25 65 4523 4523 l'
1C 5
54 3513 4523 IB 39 71 4523 4523 1C 7
55 3513 4523
'1C 14 57 4523 4523-1D 12 2
4523 4523-IC 8
57 (Weld) 4523 1D 18 7
4523 4523 j
.9 57 3513 4523 1D-4 15' 4523
'4523 1C 8
58 (Weld) 4523 1D 2
18.
4523 4523 1C 7
62 3513 4523 1D 2
20 4523 4523 1C 8
62 (Weld) 4523 1D 34 43 4523 4523 1C 9
72 (Weld) 4523 1D 45 53 4523 4523 1D 21 86 4523 4523 1D 26 86 4523 4523 i
Unit 2 Plug Installation Date:
June 1987 Steam Heat Numbers Steam Heat Nmnbers Generator Row Col H/L Plug C/L Plug Generator Row Col H/L Plug C/L Plug.
l 2A 2
15 4523 4523 2A 2
45 4523 4523 2A 2
18 4523 4523 2A 2
47 4523 4523 2A 2
20 4523 4523 2A 41 48 4523 4523 2A 8
24 4523 4523 2A 6
49 4523 4523 2A 1
25 4523 4523 2A 5
58 4523 4523 2A 2
25 4523 4523 2A 9
58 4523 4523' 2A 5
28 4523 4523 2A 5
65 4523 4523 j
1 2A 1
34 4523 4523 2A 13 70
- 4523 4523 2A
'2 34 4523 4523 j
2A 2
35 4523 4523 2B 34 37 4523.
4523 2A 2
36 4523 4523 2B.
34 79 4523 4523 2A 7
37 4523 4523 2A 2
39 4523 4523 2C 34 51 4523 4523
' i 2A 2
41 4523 4523 2C 1
58 4523 4523
-2A 2
42 4523 4523 2D No plugs from heat numbers 3513, 4523, 3279 or 3962 installed.-
- - Information is different than that found in Bulletin References.
The-informatio'n on this. Table is correct.
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(3) i i
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BYRON STATION RESPONSE TO ITEM 1 Plant documentation for' installed steam generator plugs has been reviewed for heat numbers end plug locations.
It has been determined that there are no Westinghouse mechanical tube plugs, fabricated from the suspect heats.(3279, 3513, 3962, 4523) installed in Byron Units 1 and 2.
The data review has shown that all Westinghouse mechanical plugs are of heat NX1989 or NX2386.
Westinghouse has stated that the microstructure of these heats (NX1989, NK2386) provide enhanced primary water stress corrosion cracking (PWSCC) resistance.
BRAIDWOOD STATICM RESPCMSE TO ITEM 1 Plant documentation for installed steam generator plugs has been reviewed for heat numbers and plug locations.
It has been determined that there are no Westinghouse mechanical-tube plugs fabricated from the suspect heats (3279,.
3513, 3962, 4523)- installed in Braidwood Units 1 and 2.
The data review has shown that all Westinghouse mechanical plugs are either of heat NX2387 or NX1989. Westinghouse has stated that the microstructure of these heats (NX2387, NX1989) provide enhanced PWSCC resistance.
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(4) l
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BYRCM, BRAIDWOOD, AND ZICQ STATION
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RESPONSES TO ACTION ITEMS 2, 3, AND 4 Actisn_Ltem_2 l
Addressees are requested to take the following actions, to be implemented l
I 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 j
based on the Farley Unit 2 benchmark. 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)
Addressees should_ implement appropriate remedial actions (i.e.,
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l repair and/or replacement) for all plugs whose estimated lifetimes 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)
Inata11ation 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.
A6dressees 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 I
PHSCC.
l Action _ Item _3 Remedial actions at plants where the steam generator tubes are partially-I depth-expanded within the tubesheet as described above may be deferred on a l
one time basis to the next scheduled refueling outage if the outage that l
Immediately follows receipt of this bulletin ends before October 1, 1989.
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(5)
ACLipILItem 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 o.utage that immediately follows. receipt of this' bulletin ends before October 1,1989.
ZION STATION RESPCHSE TO ITEMS 2, 3, 4 f
Remedial actions will be taken for.the: Zion Station hot leg plugs fabricated from the two. identified suspect; heats.. Implementation of remedial actions for Unit 1 will be performed, for the 5 hot leg plugs f rom heat 3513 and the 23 hot leg' plugs from heat 4523, during the next refueling' outage, scheduled to begin in September 1989.
Remedial actions for Unit 2 (27 hot leg plugs from heat 4523) will be performed during the next refueling outage -
scheduled to begin in March 1990.
No immediate remedial actions are planned for tne identified cold leg.
plugs of suspect heats. Remaining plug lifetimes have been evaluated-for the cold leg plugs using Bulletin Reference 1.
The projected life is beyond the year 2000. Remedial action will be taken prior to the estimated lifetime of
.j the plugs is' exceeded.
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It should be noted that Commonwealth Edison will continue to monitor industry results regarding projected PWSCC of Westinghouse steam generator.
tube plugs and will take corrective actions as required.
Items 2a and 2b The shortest calculated lifetime (based on the Millstone Unit 2 d
benchmark) for the Unit I hot leg plugs is May 1990, and for'the Unit 2. hot leg plugs is December 1989. These estimated lifetimes expire.beyond the next scheduled refueling outage for Unit 1, and approximately 80 days. prior to the i
scheduled refueling outage for Unit 2.
Commonwealth Edison does not plan to implement any remedial actions during extended outages prior to the next scheduled refueling outage on each unit. The technical justification for operation of Unit 2 until the March 1990 refuel outage is based upon the j
information in Section 3 of WCAP-12244, and the fact that the Zion steam generators (for both units) have partial depth enpanded: tubes'in the tubesheet
(<
3 inches). This precludes a failed plug from becoming'a high energy missile.
i ltem_.2.C Consideration is given to the items listed in Item-2c of the Bulletin.
These are essentially standard considerations during all steam generator work,-
whether for planned or unplanned outages.
Zion Station also requires i
I experienced personnel, proven techniques and tested equipment for all steam generator work as a means of reducing. exposure and cost.
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lteRL2d Zion Station has discontinued use of Westinghouse mechanical plugs from the suspect heats (3279, 3513, 3962, 4523).
Zion Station will also-discontinue use of any mandrel expanded steam generator. tube plugs fabricated j
.from Inconel-600 material.
i (6)
= _ _ _ - - - - _ _ _ - _ _ - _ - _ _ _ _ _ _ _ -
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- ' Commonwealth Edison is working with, steam generator tube plug' vendors to review plug designs using thermally treated Inconel-690 material for future applications.
Item 2e Westinghouse mechanical plugs removed from the steam generators, regardless of heat number, will be examined for PWSCC on a sample basis for each heat.
It should be noted that if the plug is removed.by drilling or some
~j other method that destroys the plug, the plug examination may not be-Kj l
possible. A record of these examinations will be maintained and the results -
provided to Westinghouse.
Item 3 The remedial actions for Units 1 and 2 have been scheduled for.the next' refueling outage, therefore, this deferral will not.be exercised.
Item 4 This item is not applicable to Zion Station.
Sentinel plugs are not installed in any Zion steam generator.
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BYRON STATION RESPONSE TO ITEMS 2, 3, 4 l
Items 2a, 2b, and 2c Since Byron Station does not have Westinghouse mechanical plugs of the suspect heats, there are no app 11 cable actions or commitments required.
However, Commonwealth Edison will continue to monitor industry results regarding projected PWSCC of Westinghouse steam generator tube plugs and will take corrective actions as required.
In addition, tube plugs from other vendors installed at Byron Station ~will be reviewed for the potential of PWSCC. Again, corrective actions will be taken based upon this review.
It211L2_d In the future, Byron Station will not install Westinghouse mechanical plugs fabricated from the suspect heats (3279, 3513, 3962,.4523).
Byron Station will also discontinue use of any m,andrel expanded steam generator tube plugs fabricated from Inconel-600 material.
Commonwealth Edison is working with steam generator tube plug. vendors to review plug designs using thermally treated Inconel-690 material for future applications.
ItenL2n Westinghouse mechanical plugs removed f rom the steam generators, regardless of heat number, will be examined for PWSCC on a sample basis for.
each heat.
It should be noted that if the plug is. removed by drilling or some other method that destroys the plug, the plug examination may not be possible.
A record of these examinations will be maintained and the results-provided to Westinghouse.
(7)
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- f Dsk_1' i-Remedial action is not required at Byron Station, therefore this deferral will not be exercised.
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Item 4 This item is rot applicable to Byron Station.
Sentinel plugs are not l
installed in any Byron steam generator.
BRAIDWOOD STATION RESPONSE TO ITEMS 2, 3, 4 hems 2a, 2b, and 2c Since Braidwood Station does not have Westinghouse mechanical. plugs of the suspect heats, there are no applicable actions or commitments required.
However, Commonwealth Edison will. continue to monitor industry results regarding projected PWSCC of Westinghouse steam generator tube plugs and will.
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take corrective actions as required.
Item.2.d In the future, Braidwood' Station will not install Westinghouse mechanical plugs fabricated from the suspect heats (3279, 3513, 3962, 4523). Braidwood Station will also discontinue use of any mandrel expanded steam generator tube plugs fabricated from Inconel-600 material.
Commonwealth Edison is working with steam generator tube plug vendors to review plug designs using thermally treated Inconel-690 Material for future applications.
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Esm 2e Westinghouse mechanical plugs removed from the steam <3.nerators, regardless of heat number, will be examined for PWSCC r.. O ce.aple basis for-q each heat.
It should be noted that if the plug is A wwnd 'er tirilling' or some other method that destroys the plug, the plug'examic tio^.
, not be possible. A record of these examinations will be maintained and the resulto provided to Westinghouse.
Hem _1 Remedial action is not' required at Braidwood Station, therefore this' deferral will not be exercised.
Rem _A This item is not applicable to Braidwood Station.
Sentinel plugs are not installed in any Braidwood steam generator.
0140k (8) 1
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