ML20064A018
| ML20064A018 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 08/16/1990 |
| From: | Taylor D COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-008, IEB-88-8, NUDOCS 9008240172 | |
| Download: ML20064A018 (7) | |
Text
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'y Commonwealth Edison
\\"~ f-l1400 Opus Pl c3 n
Downers Grove, Illinois 60515.
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August 16, 1990 m
U.S. Nuclear Regulatory Commission-m I'
-ATTN:
Document Control Desk Hashington, D.C.
2.0555 t
Subject:
Byron-Station Units 1 and 2 Supplemental Response to NRC Bulletin 88-08' and 88-08, Supplements 1 and 2 NRC_DaChet Nos; 50-454/455
References:
(a) NRC Bulletin 88-08, dated June 22, 1988.
o (b) NRC Bulletin 88-08, Supplement 1, dated June 24, 1988.
l (c) NRC Bulletin 88-08, Supplement 2, dated i
August 4, 1988.
<(d) H. Morgan (CECO). letter to U.S. NRC, dated October 3, 1988.
i
Dear Str:
^
. References'(a), (b), and (c) requested that'llcensees (1) review the reactor coolant system (RCS) to identify any connected, unisolable piping-that -
.could be. subjected to temperature distributions which could result in 1
unacceptable thermal stresses and (2) take action, where such piping is identified, to ensure that the piping will not beisubjected to unacceptable thermal stresses. ' Reference (d) provided Commonwealth Edison Company's-(CECO) linitial-response to References (a),-(b), and-(c) for Byron Station. -As s
reported in: Reference (d), a review of the piping-systems connected to the RCS for each. Byron unit.identifled sections of piping in-the Auxiliary _ Spray line (1/2RYl8A) and the four (4) Charging Pump to Cold Leg Injection lines
,(1/2RC30AAL l/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 N,
.Lthat have been performed, and programs that will be implemented. to provide
.ff continuing assurance that piping integrity for-both units will be maintained.
^
Additionally, this letter provides the results of non-destructive examinations
' performed on the Auxil'iary Spray line for Byron Unit I and Byron Unit 2.
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D U.S'.-. Nuclear Regulatory. Commission August 16, 1990 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 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 accordsnce with Action 2 of Reference (a), non-destructive examinations were performed during the Unit 1 Fall 1988 and Unit 2 Spring 1989 refueling outages on the Auxiliary Spray lines (1/2RY18A-2) at the inspection locations identified in Reference (d).
These inspection locations, which were determined by a thermal-hydraulle 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 sockolet 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 (1/2RYl8-6).at the branch connection was also ultrasonical'y examined (enhanced technique).
The section examined spanned eight (8) inches axially and included greater than seventy-five percent (751.) 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 Byron Station.
To address Action 3 of Reference (a) for the Auxillary Spray line and Hain 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 Indicated that it would 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)
I fuel cycles, and no temperature monitoring would be required.
IN
^
..U.S. Nuclear Regulatory Commtssion August 16, 1990
,x The evaluation updated the inspection locations for the Auxiliary Spray _and Main Spray lines (in the vicinity of the branch connection).
These inspection 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').
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 were inspected at Unit i during the Spring 1990 refueling outage and no indications were identified..The Unit 2 locations will be inspected during the fall 1990 refueling outage.
Additionally, the Inservice Inspection (ISI) program has been 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 -f Auxiliary 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 Lq Injection lines (1/2RC30AA, 1/2RC30AB, 1/2RC30AC, 1/2RC30AD),
Reference (d) reported that there was assurance that the isolation valves (1/2318801A and 1/2SI8801B) for these lines had'not leaked based on the 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 Charging Pump to Cold Ler 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 revised to ensure that leakage testing is specifically performed on the isolation valves (1/2SI8801A and 1/2SI88010) for the Charging Pump to Cold Leg Injection lines.
The appropriate station surveillance procedures (1/2BVS 4.6.2.2-1, Reactor Coolant System Pressure Isolation Valve Leakage Surveillance) have been revised to include leak testing of the Cold Leg Injection isolation valves (1/2SI8801A and 1/2518801B).
As indicated in Reference (d), leak 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 leakage testing has not been performed in the previous 9 months,
,..U.S. Nuclear' Regulatory Commission August 16,_1990
~
- prior to returning the valves to service following maintenance which 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, j
i Please direct any questions that you may have concerning this response to this office.
i Respectfully, D. L. Taylor i
Generic Issues Administrator l
Attachments:
Figure 1 - Isometric of Auxiliary Spray - Main Spray Bran:h Connection-Figure 2 - Auxiliary Spray - Main Spray Branch Connection Figure 3 -' Side View cf Main Spray Line at Auxiliary Spray
- Main' Spray Branch Connection.
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-cc: A.B.l Davis - Regional Administrator, Region III l;
Senior Resident Inspector - Byron Station i
T. Boyce - NRR Project Manager l
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Subscribed and Srprn to
.befor me this~,Lp day of _
_,44f
, 1990
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Notary Publ'ic
LYNN M. WLODARSKI NOTARY PUBLic. STATE OF ILLINOIS MY COMMIS$!ON EXPIRES 6/25/94
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