ML20058N055
| ML20058N055 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 08/07/1990 |
| From: | Taylor D COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-008, IEB-88-8, NUDOCS 9008130188 | |
| Download: ML20058N055 (7) | |
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Common =lth Edison -
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August 7, 1990
.U.S. Nuclear Regulatory Commission
.i ATTN: Document Control Desk Hashington, D.C.'
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Subject:
Braidwood Station Units 1 and 2 Supplemental Response to NRC Bulletin 88-08
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and 88-08, Supplements 1 and 2 HRC Docket Nos. 50-456/457
References:
(a) NRC Bulletin >88-08, dated June 22, 1988.
(b) NRC Bulletin 88-08, Supplement 1, dated June 24, 1988.
-(c) NRC Bulletin 88-08, Supplement 2, dated August 4, 1988.
(d) H. Morgan (CECO) letter to U.S. NRC, dated October 3, 1988.
Dear Sir:
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' References (a), (b), and (c) requested that licensees (1) review the
. reactor coolant-system (RCS) to identify any-connected, unisolable piping that
'could be subjected to temperature distributions which could result in i
unacceptable thermal stresses and (2) take action, where such piping is identified to ensure that the piping will not be subjected to unacceptable-thermal stresses.
Reference (d) provided Commonwealth Edison Company's (CECO) initial response to References (a), (b), and (c) for.Braidwood Station.
As reported'in Reference (d), a review of the piping systems connected to the RCS' for each Braidwood unit identified sections of piping in the Auxiliary Spray
- llne (1/2RYl8A) and the four (4) Charging Pump to Cold Leg Injection lines D
. (1/2RC30AA, 1/2RC30AB, 1/2RC30AC, 1/2RC30AD) which would be susceptible to
- thermal stresses from temperature stratification or temperature oscillations in the' event of Isolation valve leakage.
This letter reports on the actions that have been performed, and programs that will be implemented, to provide i
continuing assurance that piping integrity for both units will be maintained.
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Additionally, this letter provides the results of non-destructive examinations
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-performed on the Auxiliary Spray line for Braldwood Unit 1 during its Fall 1989 refueling outage.
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0.S; Nuclear Regulatory Commission August 7,:1990
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t In~ response to Actions 2 and 3 of Reference (a), Reference (d) indicated that the Auxiliary Spray line-for each unit would be evaluated (by'a
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stress analysis) to determine the necessity (and frequency) of future
- non-destructive examinations. Additionally, the results of the evaluation would determine if any sections of the line would be instrumented in order to detect adverse temperature distributions.
In accordance with Action 2 of Reference (a), non-destructive examinations were performed during the Fall 1989 refueling outage on the Unit 1
1 Auxiliary Spray line (1RYl8A-2) at the inspection locations identified in e
Reference-(d).
These inspection locations, which were determined by a thermal-hydraulic review, are in the vicinity of the branch connection for the
. Auxiliary Spray and Main Spray lines (shown in detail on the Figures attached
.to this letter). A surface examination (liquid penetrant) was performed on the two-inch soci'let weld at the branch connection (shown as weld ' A' on the attached figures). Additionally, the horizontal section of the Auxiliary Spray line piping upstream of the two-inch sockolet weld was ultrasonically examined (enhanced technique).
This inspection included less than one foot of piping, shown as region 'B' on Figure 1.
A portion of the Main Spray line (1RYl8-6) at the branch connection was also ultrasonically examined (enhanced technique).
The section examined spanned eight (8) inches axially and included greater than seventy-five percent (75%) of the piping cross-section (shown as region 'C' on Figures 2 and 3).
No indications were identified by the ultrasonic or surface examinations.
All documentation associated with these examinations will be retained at Braidwood Station.
To address Action 3 of Reference (a) for the Auxiliary Spray line and Main Spray line, an evaluation was performed to determine the effects of potential thermal stratification and cycling.
For this evaluation, which applies to both units, a conservative thermal transient (which considered thermal stratification and cycling) due to Auxiliary Spray line isolation valve leakage was postulated, based on the event described at Farley Station in Reference (d).
For this postulated transient, a. stress analysis and
. fatigue analysis (which used fatigue crack growth methods) was performed to determine an acceptable period of power operation.
The results of the evaluation, which were available subsequent to the inspections during the Fall 1989 refueling outage, indicated that it_would i
take a minimum of forty (40) months of power operation for a crack to propagate to an unacceptable size.
Therefore, if non-destructive examinations of the inspection locations (identified by the evaluation) are performed during-a refueling outage and no cracks are identified, the structural integrity of'the Auxiliary Spray and Main Spray lines would be maintained for at least two (2) fuel cycles, and no temperature monitoring would be l
required.
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O.S. Nuclear Regulatory Commtsslon ~
Augurt.7,~ 1990'.
The evaluation updated the inspection locations for the Auxiliary Spray and Main = Spray lines (in the vicinity of the branch connection).
These
.inspectiLn'~ locations, which will receive ultrasonic examinations (enhanced-technique)..are shown as regions 'X' and 'Y' on figure 2, and weld 'Z' on.
Figure 1.
Region 'X' - a 360 degree circumferential region located in the Auxiliary Spray line beneath the sockolet weld (weld
'A').
j Region 'Y' - a 360 degree circumferential region. located in the Main Spray line around the branch connection.
Held 'Z' - located in the Main Spray line, downstream of the branch connection.
These locations will be inspected during the next refueling outage for Unit 1 i
(the unit's second refueling outage), presently scheduled for January 1991.
Additionally, the Inservice Inspection (ISI) program is being revised.to
. include the inspection of these locations at a frequency of every other-refueling outage.
The evaluation performed, coupled with the commitment to a long-term inspection' program, provides the continued assurance of Auxillary Spray line and Main Spray line integrity and fulfills Bulletin Action 3.
In response'to Actions 2 and 3 of Reference (a) for the Charging Pump to Cold leg. Injection lines (1/2RC30AA, 1/2RC30AB, 1/2RC30AC, 1/2RC30AD),
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Reference (d) reported that there was assurance that the isolation valves (1/2SI8801A and 1/2SI8801B) for these lines had not leaked based on the 0
results of previous surveillance testing (RCS back leakage tests) for the Cold Leg Injection-Check Valves-1/2SI8815.
Since there was no indication that the i
Charging Pump to Cold Leg Injection lines had not been subjected to excessive thermal stresses, these lines were not scheduled to be examined (non-destructive examinations).
In order to assure that these lines would not be' subjected to long-term thermal cycling, surveillance procedures were to be developed or revised to ensure that leakage testing is specifically performsd on'the isolation valves (1/2SI8801A and 1/2SI88018) for the Charging Pump to Cold Leg Injection lines, c
The appropriate station survelliance procedures (1/2BwVS 4.6.2.2-1, Reactor Coolant System Pressure Isolation Valve Leakage Surveillance) have been revised to include leak testing of 'he Cold Leg Injection isolation valves (1/2SI8801A and 1/2SI88018). As indicated in Reference (d), leak j
testing on the isolation valves will be performed:
- at least once per 18 months,
- prior to entering Mode 2 whenever the plant has been Cold Shutdown for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or more and if Icakage testing has not been performed in the previous 9 months, l
O O.S.NuclearRegulatoryCommission. August 7, 1990
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prior to returning the valves to service following maintenance which 4
impacts the valves seat tightness, and'
- within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following valve actuation due to automatic or normal action or flow through the valve.
Surveillance testing performed during the refueling outage revealed no leakage, thus, providing assurance that the Charging Pump to Cold Leg Injection lines would not be subjected to excessive thermal stresses.
Please direct any questions that you may have concerning this response to this office.
Respectfully, L
D. L. Tay or Generic Issues Administrator Attachments:
Figure 1 - Isometric of Auxiliary Spray - Main Spray Branch Connection Figure 2 - Auxiliary Spray - Main Spray Branch Connection Figure 3 - Side View of Main Spray Line at Auxiliary Spray
- Main Spray Branch Connection, cc: A.B. Davis - Regional Administrator, Region III Senior Resident Inspector - Braidwood Station S. Sands - NRR Project Manager
/Imw/ID91' Subscribed and (' worn to before me this l h day Ount u4 A, 9
KMA i
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Notary Public '
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