ML20070D769
| ML20070D769 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 07/06/1994 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20070D773 | List: |
| References | |
| NUDOCS 9407120284 | |
| Download: ML20070D769 (10) | |
Text
r Stztlan Support Departmsnt a
f 10CFR50.55a PECO ENERGY
= 3 "J a,
905 Chesterbrook Boulevard Wayne, f% 19087-5691 July 6,1994 Docket Nos. 50-277 50-278 License Nos. DPR-44 DPR-56 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Subject:
Peach Bottom Atomic Power Station, Units 2 and 3 Additional Information Concerning the Request for Relief from Implier! 30 Day implementation of ASME Section > ;tepairs (Relief Request No. RR-19)
Dear Sir:
In our letter dated June 3,1994, PECO Energy Company supplied for your review and approval Relief Request No. RR-19 for the Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3, Second Ten-Year Interval inservice Inspection (ISI) Program. In that letter, PECO Energy Company requested relief from the implied implementation schedule for repairs to Class 3 pressure retaining components in the Emergency Service Water System.
As the result of further discussions between PECO Energy Company and the U.S. Nuclear Regulatory Commission regarding this requested relief, PECO Energy Company is supplying requested additional information.
If you have any questions or require additional information, please do not hesitate to contact us.
Very truly yours, bd.69..
G. A. Hunger, Jr.,
irector Ucensing Attachment cc:
T. T. Martin, Administrator, USNRC, Region I W. L. Schmidt, USNRC Senior Resident inspector, PBAPS Q
~_J'O 94o7120284 94o706 M
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ATTACHMENT PEACH BOTTOM ATOMIC POWER STATION UNITS 2 and 3 INSERVICE INSPECTION PROGRAM ADDITION INFORMATION CONCERNING RELIEF REQUEST No. RR-19 i
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PECO ENERGY COMPANY Page i of 5 PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to Request For Additional Information for ASME Section XI Relief Request RR-19 Repair and Replacement of Class 3 components The following is additional information requested by the NRC regarding the ASME Section XI Relief Request (RR-19), submitted on June 3,1994. This relief request was submitted to request relief from the implied implementation schedule for an ASME Section XI repair.
Each of the eleven (11) topics contained in the request for additional information is listed, with the PECO Energy Company response following each topic.
TOPIC 1.
A Justification for the impracticality of the Code repair.
PECO Response:
As implied in Relief Request RR-19, a Code acceptable repair is considered practical. Although the portion of the system is not readily isolable, isolation for implementing a Code acceptable repair is being pursued.
TOPIC 2.
A description of the characteristics and size of the flaw:
a.
The dats found and circumstances under which it was found, the size of the ho!e or crack, the eroded area, the number of flaws, the adjacent wall thickness, and the total area around the flaw examined.
1 PECO Response:
As documented on Action Request A/R No. A0795247, on 11/06/93; a leak was detected at a single flaw during the conduct of Modification Acceptance Test (MAT) No. 5095A. The flaw was documented as a pin hole in a pipe to elbow weld, approximately 1/16" in diameter. On 11/16/93, Nondestructive Examinations (NDE) of 33 grid areas at and around the flaw were documented in the A/R. The adjacent pipe wall thickness recorded during this examination ranged from.245" to.376".
Adjacent weld thickness was recorded aJ beheen.280" and.415". A thickness of.097" was recorded in the weld at the pin hole.
As identified in RR-19, additional indications were discovered visually, while attempting to implement the initial repair. Two indications were noted in the area prepared for the welded Code repair, adjacent to the subject flaw. As a result, the Code repair was abandoned and additional UT examinations were performed. The results of these additional examinations are discussed in the response to Topic 7.
Follow-on visual assessments of the flaw (through 7/6/94) indicate that the size of the flaw remains essentially unchanged. Leakage through the flaw is intermittent.
1 r
i PECO ENERGY COMPANY Page 2 of 5 PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to Request For Additional Information for i
i ASME Section XI Relief Request RR 19 Repair and Replacement of Class 3 components
'l b.
The location of the flaw on the pipe and its relation to the rest of the system (e.g. at the six o' clock position of the line 2 feet downstream of "x" component).
PECO Response:
The flaw is located at the intrados of a pipe to elbow weld located in the 20" diameter suction line to the "A" train Emergency Service Water (ESW) Booster Pump. This suction pipe connects to the main Emergency Service Water (ESW) System discharge pipe leading to the Susquehanna River. The attached isometric drawing (Attachment 1) depicts the location of the flaw within the piping configuration. Figure RR-19.1, attached to the Relief Request, depicts the location of the flaw with respect to the system.
c.
The examination method (e.g. UT, visual, or other).
PECO Response:
The examination method utilized was Ultrasonic Technique (UT).
TOPIC 3.
A description of the pipe and system.
a.
The name of the system....the type of fluid in the system....
i PECO Response:
The system containing the flaw is the ESW System discharge piping t
from the Emergency Core Cooling System (ECCS) room and 4
equipment coolers. The flaw is located in an attached pipe which provides suction to the ESW booster pumps. These pumps convey water into the Emergency Cooling Water (ECW) System, The fluid 4
contained within these systems is Susquehanna River water.
b.
The design and operating pressures and temperatures.
PECO Response:
The design pressure is 150 psi, the design temperature is 100 F. The nominal operating pressure of the system is 40 psi. The normal pressure at the location of the flaw, due to head pressure, is approximately 6 to 8 psi.
c.
The pipe material (ASTM classification), diameter, schedule, liner material, l
and thickness.
i PECO Response:
The piping is fabricated from ASTM 106 Grade B carbon steel material, 20" diameter, schedule 40, with a nominal.375" wall thicknes0. The piping does n]ol utilize a fining material.
d.
A copy of the appropriate sections of the piping diagram.
' PECO Response:
See Figure RR-19.1 of the Relief Request.
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.f PECO ENERGY COMPANY Page 3 of 5 PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to Request For AdditionalInformation for ASME Section XI Relief Request RR-19 Repair and Replacement of Class 3 components TOPIC 4.
A description of the root cause (Indicate whether it is based on previous similar failures, metallurgical examination, other cause, or uncertain cause).
PECO Response:
Without removal of the flawed piping, as is planned for the repair, the root cause of the degradation cannot be confirmed. Based on previous indications found in this system, the expected cause is "under deposit general corrosion". However, until the piping can be removed and examined, this is only an assumption.
TOPIC 5.
A description of the safety significance of a postulated failure related to:
a.
Flooding b.
Spray c.
Loss of flow d.
Other interactions e.
System fallure consequences f.
The effect on safe shutdown capability PECO Response:
a & b. The room / area has been analyzed for both flooding and spraying scenarios, and has been found acceptable.
- c. Loss of flow is not significant since the flaw is located downstream of all cooling loads.
- d. No other interactions have been identified.
e & f. System failure would have an effect on safe shutdown capability since the failure would eventually render the ECCS pumps and Emergency Diesel Generators inoperable due to loss of cooling.
However, system failure is not a factor in this situation, because the flaw is located downstream of these cooling loads.
TOPlc6.
The implications of the root cause for other systems that could be affected by the same degrading mechanism.
PECO Response:
As identified in item 4, the root cause has not been determined at this time. When the pipe spool is removed for repair / replacement, the root cause will be determined. In the interim, examinations of components similar to the subject components are being conducted. These examinations are in accordance with Generic Letter (GL) 89-13.
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b PECO ENERGY COMPANY Page 4 of 5 PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to Request For Additional Information for ASME Section XI Relief Request RR 19 Repair and Replacement of Class 3 components TOPIC 7.
A description of the augmented Inspections...
a.
An assessment of the overall degradation of the affected system.
PECO Response:
Currently, routine examinations are performed on the service water system in response to GL 89-13. The GL 89-13 examinations have identified some areas of localized pitting, but not the advanced degradation observed at the leaking weld. A further assessment of the GL 89-13 examinations, with regard to examination locations, will be performed following the removal of the degraded portion of piping and its subsequent metallurgical analysis.
b.
A discussion of any additional examinations required (based on root cause). Specify number of Inspection locations and frequency of Inspections. A minimum of five other locations is suggested.
c.
A description of the areas selected for augmented inspection and the basis of the selection.
PECO Response:
Five other welds were selected for augmented examination. Two welds-were selected on either side of the leaking weld, due to their close proximity to the leak. The other three weld locations were selected from-the parallel train (train "B") because of their similarity to the subject
- weld, d.
A discussion of the results of the augmented inspections.
e.
A discussion of the requirements and results of the expanded augmented Inspections,if available.
PECO Response:
The results of the augmented examint.tions showed the leaking weld to exhibit the most advanced degradation occolry around the entire weld circumference. The upstream and downstrearo welds examined exhibited some localized pitting, and therefore are within the repair.
plan. The three welds on the "B" train exhibited r o indications which '
require repair, however some localized pitting wt.s recorded. Follow-up -
UT surveillance will be performed on these wdds initially on a six (6) month frequency to establish a corrosion rate.
~
TOPIC 8.
Specify whether a leak-mitigating measure is used or not.
- PECO Response:
To date, a leak mitigating measure has not been used.'
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i PECO ENERGY COMPANY Page S of 5 PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to Request For Additional Information for ASME Section XI Relief Request RR 19 Repair and Replacement of Class 3 components
- TOPIC 9.
The Code repair schedule.
PECO Response:
As indicated in Relief Request RR-19, two attempts at implementing a code acceptable repair have been unsuccessful. Attempts at a third Code repair or use of an alternate repair mechanism are being studied, and a decision will be communicated on or before July 15,1994.
t TOPIC 10.
The flaw evaluation calculations.
a.
The inputs (material properties, stresses) b.
A copy of the operability assessment calculations....
i PECO Response:
See Attachment 2.
c.
The end of cycle flaw evaluation calculations....
)
PECO Response:
A specific end-of-cycle calculation was not developed since a code repair has been, and continues to be the intended resolution of the situation. Accordingly, there is no intended cycle to evaluate.
Additionally, the flaw is being monitored on a regular basis until the
-l code repair is implemented.
TOPIC 11.
The flaw monitoring measures taken, including:
a.
The frequency of walk down Inspections (for monitoring leaks).
b.
The frequency of follow up NDE....
PECO Response; The leak is visually monitored on a weekly basis, and follow-up NDE will be performed every 90 days until the repairs are performed.
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t PECO ENERGY COMPANY PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to request for additional information for ASME Section XI Relief Request RR 19 Repair and Replacement of Class 3 components ATTACHMENT 1 1
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i PECO ENERGY COMPANY PEACH BOTTOM ATOMIC POWER STATION UNITS 2 & 3 Response to request for additional Information for ASME Section XI Rellef Request RR 19 Repair and Replacement of Class 3 components ATTACHMENT 2 Operability Assessment Calculation 1
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