ML20044H345
| ML20044H345 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/28/1993 |
| From: | George Thomas DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-90-05, GL-90-5, NUDOCS 9306080210 | |
| Download: ML20044H345 (10) | |
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[ eaver Valley Power Station Shippingport. PA 15077-0004 (412l 393-5206 (412) 643-8069 FAX May 28,1993 GEORGE S THOMAS Division Vice President Nuclear Services Nuclear Power Dms on U.
S.
Nuclear Regulatory Commission Attn:
Document Control Desk Washington, DC 20555
Subject:
Beaver Valley Power Station, Unit No. 2 Docket No. 50-412, License No. NPF-73 Request for Relief for a Non-Code Repair on 2-SWS-EJM-237A Attached for NRC review and approval, is a request for relief for a
temporary non-code repair on Unit 2 Service Water System metal expansion joint (MEJ) 2-SWS-EJM-237A.
The MEJ cannot be isolated and repaired or replaced during the time permitted (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) by Tech Spec 3.7.4.1 and the performance of an ASME Code repair would necessitate a plant shutdown.
Based on the above and guidance provided by Generic Letter 90-05, an ASME Code repair during power operation is impractical.
Therefore, pursuant to 10 CFR 50.55a(g) (6) (i), it is requested that the NRC grant relief for a
temporary non-code repair to be used until the next scheduled outage exceeding 30 days, but no later than the next refueling outage which is scheduled to begin in September, 1993.
This request was discussed with the NRC staff during telecons on 5/25/93 and 5/26/93.
Based on these discussions, the NRC staff provided verbal approval of this request on 5/26/93, contingent on their review and approval of the formal submittal.
If there are any questions concerning this matter, please contact Mr. N. R. Tonet at (412) 393-5210.
Sincerely, 10 3 eor e S.
Thomas Attachment cc:
Mr.
L. W.
Rossbach, Sr. Resident Inspector Mr.
T. T.
Martin, NRC Region I Administrator Mr.
G.
E.
Edison, Project Manager Mr. M.
L. Bowling (VEPCO) 40 9306080210 930528
)
1 PDR ADOCK 05000412 pi J
P PDR
I DUQUESNE LIGHT COMPANY Nuclear Power Division
]
Beaver Valley Power Station, Unit 2 Request for Relief for a Non-Code Repair on 2-SWS-EJM-237A A
small leak was discovered on a Class 3 metal expansion joint (MEJ).
on Train B
of the Unit 2 Service Water System.
The maximum leakage rate observed since discovery is estimated to be less than one gallon per hour.
The leak is believed to be on the weld between the stainless steel bellows and the carbon steel flange (see Figure 1).
The leak is suspected to be caused by corrosion / pitting in the region of the weld joint which is a
dissimilar weld between a stainless steel bellows and carbon steel flange (a stainless steel weld filler material was used).
A failure analysis will be performed on the expansion joint' following its removal in the upcoming refueling outage.
This leak was discovered during power operation on a Class 3 piping section of the Service Water System.
This system is moderate energy (temperature 200*F, pressure < 275 psig) that supplies river water to various safety related heat exchangers for cooling purposes.
The i
MEJ cannot be isolated and repaired or replaced during the time permitted (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) by Tech Spec 3.7.4.1 and the performance of an ASME Code repair would necessitate a plant shutdown.
Based on the above and guidance provided by Generic Letter 90-05, an ASME Code repair during power operation is impractical.
Therefore, pursuant to 10 CFR 50. 55a (g) (6) (i), it is requested that the NRC grant relief for a
temporary non-code repair to be used until the next scheduled outage exceeding 30 days, but no later than the next refueling outage which is scheduled to begin in September, 1993.
k Evaluation of Flaw The leak is on an MEJ and the configuration of the joint (see Figure 1) does not permit the flaw to be evaluated by either the "Through-Wall Flaw" or
" Wall Thinning" approaches provided by Enclosure 1
Therefore, the following alternative evaluation is provided for NRC staff review and approval.
A seismic evaluation was performed on the subject piping when decoupling the piping system at the metal expansion.
The expansion joint was decoupled to conservatively evaluate the piping system when the expansion joint weld is leaking.
~
Request for Relief for a Non-Code Repair on 2-SWS-EJM-237A Page 2 The loading conditions evaluated were for
- pressure, deadweight,
- thermal, pressure thrust and seismic.
The evaluation included a Nupipe Computer Study Run on the subject piping when decoupled, and a review of the piping stress levels, pipe supports, flanges, piping displacements and valve accelerations connections for any adverse affect to their integrity while the piping is decoupled.
Note:
The axial pressure thrust loading considered is 111,846.
lbs.
This value of 111,846 lbs.
was applied in the north direction on the embedded wall anchor PSA829T and buried piping and applied in the south direction on the embedded wall PSA828T and buried piping.
Conclusions /Results The piping stress values are acceptable.
The piping deflection values are acceptable.
The pipe supports are acceptable.
The pipe flanges are acceptable.
The valve acceleration levels are acceptable.
There were no significant changes to stress levels.
Ron-Code Repair The proposed non-code repair will consist of:
1.
A fiberglass reinforced epoxy resin material wrapped completely around the joint between the bellows and the flange.
This material is pressure rated and will seal the joint and prevent gross leakage or water spray.
2.
In order to prcvent the possibility of the bellows from disengaging from the flange, six (6) dogs (see Figures 2 and 3) will be bolted to the flange joint.
These dogs will hold.the.
first bellows convolution in place.
In the unlikely event of a-complete weld
This modification will not prevent the bellows from performing its normal function.
~
In the event of a complete weld failure, the repairs described above will prevent the joint from coming apart and minimize leakage or l
water spray.
Request for Relief for a Non-Code Repair on 2-SWS-EJM-237A Page 3 Examination of Flaw Limited ultrasonic examinations have been performed on the leaking Train "B"
MEJ (2-SWS-EJM-237A) and also the Train "A"
MEJ (2-SWS-EJM-237B) as shown in the attached report WP-93-111.
Further ultrasonic (UT) examination of Unit 2 SWS metal expansion joint 237A pressure-retaining weld is impractical for the following reasons:
1.
Weld joint design is incompatible with conventional THC Code techniques.
The weld joint illustrated in Pathwt Bellows Drawing D-3-3213 Rev A-1 is essentially a dissimilar Jal seal weld set within a counterbore in the carbon steel flange surface.
2.
The taper angle and flat surface of the 150# weld neck flange creates geometrical limitations with regard to examination beam angles and examination surface access.
3.
There are no reference standards or readily available mockups available to allow development of UT techniques and/or reference sensitivity determination, j
System Interactions The following is an evaluation of possible system interactions-from I
flooding, spraying water on equipment and loss of flow:
Floodina:
The MEJ is located in the west side ("B" header) service water valve pit and is physically separated from. the east ("A" header) side.
This valve pit is located in the yard area and is separate from any other structure.
Any leakage from a complete weld failure will be minimal due to design of non-code repair seal.
- However, if any leakage would occur, it would be collected in the valve pit sump which has a
high level alarm (at 9" level) in the control room and is equipped with an automatic sump pump rated at 28 gpm.
- However, in the event of catastrophic failure of the MEJ, all of the equipment located in the west side of the valve pit is associated with the Train B
header, therefore, the Train A header will be unaffected.
Loss of a complete Service Water train has been previously analyzed in UFSAR Section 9.2.
Therefore, this failure-would not create an unanalyzed condition.
Water Spray:
The design of the non-code repair should eliminate-any concern due to water spray.
However, if water spray should occur, it would only affect a
limited amount of Train B equipment located in the west side of the valve pit.
Again, loss of one train of service water has been previously analyzed.
. ~.
Request for Relief for a Non-Code Repair on 2-SWS-EJM-237A Page 4 Loss of Flow:
Loss of flow to the "B" service water header could only be caused by catastrophic failure of the MEJ.
The design of the non-code repair should minimize the possibility of a catastrophic failure of the MEJ due to a complete weld failure.
However should this failure occur, it would result in a low header pressure alarm in the control room.
Alarm response Procedure 20M-30.4.AAB directs the operators to OM-2.53C.4 Abnormal Operating Procedure (AOP) 2.30.1
" Severe Water / Normal.
Intake Structure Loss."
This failure mode is analyzed by UFSAR Section 9.2.
The loss of the Train B header will not affect the ability of the Train A header to fulfill its safety function.
Periodic Assessment of Structural Intecrity The leaking MEJ is in a confined space.
It will be inspected once per day by plant operators during walkdowns.
A temporary log will be initiated to assess the leakage rate.
Any significant increase in the leakage rate will require notification of the Nuclear Shift Supervisor and Nuclear Engineering.
Augmented inspections of other MEJs in the Unit 2 Service Water i
System will be performed within 15 days.
These MEJs will be VT-2 visually inspected by certified examiners.
As discussed above, further ultrasonic examinations of other MEJs are impractical due to the configuration of the joint.
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