ML20115A996
| ML20115A996 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 10/05/1992 |
| From: | Beck G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9210150213 | |
| Download: ML20115A996 (6) | |
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PHILADELPHIA ELECTRIC COMPANY
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NUCLEAR GROUP HEADQUARTERS 955-65 CHESTERBROOK BLVD.
WAYNE, PA 19037 5691 October 5, 1992 M""
Docket No. 50-352 License No. NPF-39 NilCLLAR S!:RVICES DLPARTMENT U.
S.
Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Subject:
L!merick Generating Station, Unit 1 Relief Request for the Corrosion Monitoring System for Residual Heat Removal Heat Exchanger
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Gentlemen:
Attacnud for review and approval is Relief Request No. RR-16 for the Limerick Generating Station (LGS), Unit 1,
American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code Section III, Class 3 Residual Heat Removal Service Water (RHRSW) System f
modification that adds a corrosion monitoring system to the "B" Residual Heat Removal (RHR) heat exchanger.
This modification is currently in place and will initiate operation during the
.7S Unit 1 fifth operating cycle.
The corrosion monitoring system was required because during the Unit 1 fourth refueling outage inspection of the "B" RHR heat exchanger, pitting on the tube inside diameter was revealed (i.e.,
the tube inside diameter is subjected to RHRSW flow).
To assure that the tubes in the heat exchanger maintain 3 mils of metal at the deepest pit, a corrosion monitoring system was installed in the RHRSW System, The installation of this system took place during the outage.
Because of the short length of time from discovery of this problem until unit restart, procurement of the material to meet ASME Code,Section III, Class 3 requirements was not possible.
Accordingly, we are requesting relief from certain provisions of the Code for portions of the corrosion monitoring system.
A detailed description of the modification is included in the attached relief request.
We would like to have an expeditious review of this relief request because, until this relief request is approved, the corrosion monitoring system will be operated in tha manual mode in order to comply with applicable requirements.
Once this relief request is
- approved, operation of this corrosion monitoring system will be char.ged to the automatic mode.
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S. Nuc. lear Regulatory Commission October 5, 1992 Document Cont.rol Desk Page 2-If you have any questions or require additional information, please do not hesitate to contact us.
Very truly yours,
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G.
J.
Beck, Manager Licensing Section Attachment cc:
T.
T.
Martin, Administrator, Region I, USNRC w/ attachment T.
J. Kenny, USNRC Senior Resident Inspector, LGS w/ attachment
Specification N E-42, LGS.1 ISI Program Appendix A 16 Page 1 of 4 RillEI' REQUEST NO. RR 16 1.
IllEFTIFICATION OF COMPONENTS limerick Generating Station (LGS), Unit 1, ASME Code Class 3 Residual lleat Removal Service W ater (RilRSW) System modification for corrosion monitoring of - the 'II" Residual llent Removal (RilR) heat exchanger.
Analysis of the results of eddy current testing performed after disassembly and hydrolazing of the Unit 1 'Ir RilR lleat Exchanger (IDE205) during the fourth Unit I refueling outage showed indications of pitting on the tube inside diameters. Identified corrective -
actions required installation of a corrosion monitoring system-for the "B* RIIR heat exchanger. 'lhis conosion monitoring system will expose specimens of 304L stainless steel tubing material to similar water chemistry and temperatures that will be experienced by the "B* RllR heat exchanger. Specimens will have pre machined defects (i.e., pits) of different depths. Actual tubes extracted from the "A" RllR heat exchanger will also be used as specimens. Periodic exarninntion oEspecimens will provide a partial means to predict the actual corrosion rate and thus assess "B" RilR heat exchanger tube integrity, to assure that at least 3 mils of metal is always present in the bottom of the deepest pit. This capability will provide information which is essential to suppmt the continued operability of the Unit 1 'B' RiiR heat exchanger, 11, CODE REQUIREMENTS FROM WillCll REIIEF IS REQUESTED ASME Code, Section X1,1986 Edition, subparagraph IWA-7210a requires replacements i
(i.e., modifications) to meet the requirements of the edition of the construction code to which the original component or part was constructed,.
LGS Updated Final Safety Analysis Report (UFSAR) Table 3.21 specifies the original construction code, for the portion of the RilRSW system in which the corrosion monitoring system is being installed, as ASME Code, Section lil, Class 3, for pipe, valves, and pumps. ASME Code, Section 111, Class 3, in turn, requires Certified Material Test Reports for all construction materials.
For the portion of the modification for the corrosion monitorina system specified in section IV of this request, which contains.RilR Service Water, relief is requested frora meeting the material requirements of ASME Code, Section Ill, Class 3.
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.CpeCibCation-
- Nf!-42, LGS 1 ISI.. Program :
Appendix A 16 Page ~ 2 of 4 -
REl.lEF REQUEST NO. Rikl6 (CONTD.)
111.
DASIS FOR ret.,lEP Since the RilRSW system at' LGS Unit I was constructed to the requirements of ASME Code Section 111, Class 3 rules; repairs, replacements or modifications connecting to this-system are required to be constmeted in accordance with the same ceastruction code.
Because of pitting found m the Unit i RilR heat exchanger tubes, installation of the -
corrosion monitoring system is required to support operation of LGS Unit
.t. over the next fuel cycle. Since the pitting was dciermined to result. from the deposition of '
manganece on the heat cxchanger tubing which it a function of' operating history, installation of this corrosion monitor was required in a very short time frame due to the startup of Unit 1 on July 9,
1992, Given a very chort time-period - for design / construction (approximately 10 weeks), material availability has precluded the ability l to procure all construction materials and components to ASME Code, Section Ill, Class 3 requirements. Therefore an alternate design / construction approach is requiud.
I IV.
Al> TERNATE PROVISIONS This modification is designed to operate for only the next fuel cycle, or approximately 24 months.
The only safety related function which this modincation must perfonn is to maintain an intact pressure boundary as part of the RIIRSW System.
s ACME Code required - material will be used for the portions of the inlet and outlet piping of the corrosion monitoring system directly connected to the RilRSW system, extending to single valves capable of automatic closure. Material a' ; ability precluded the ability to purchase a second ASME Code, Sc. tion 111, Class 3,alve for the inlet and outlet-lines.
l The inlet isolation valves will automatically close when the pressure inside the monitoring system exceeds a predetermined value based on a postulated RilR heat exchanger tube.
Itipturc, or on loss of air and/or power to the valve operators. The outlet lines are provided with check valves whichill also close as a result of reverse diflerential pressure
- between the corrosion monitor and the RilR heat exchanger.
The high pressure actuation signal, however, will not be Class -lE qualified, since the pressure separation function served by these valves is not safety-related. Additionally, commercial grade manual isolation valves will be provided to allow for isolation between high and low pressure piping classes. Also the low pressure piping will be provided with a safety relief valve sized to handle the design basis RIIR heat exchanger tube leakage.
Specification N E-42, LGS 1 ISI l'rogram Appendix A-16 Page 3 of 4 RillEl' ItEQUINI' NO. Ril-16 (CONTD.)
Additionally the specimen holder will be constructed in accordance with the ASME Code Section Vill, using ASME Code requiicd materials.
Commercial grade materials will be used in place of ASME Code materials for the remanider of the RilRSW corrosion monitoring system.
The commercial grade portion of the corrosion monitoring system connected to the RilRSW system will be designed in accordance with ANSI Standard B311 for conditions which bound all cperating modes of the RilRSW system with the exception of a postulated failure of an RilR lleat Exchanger tube for which autornatic isolation and overpressure protection is provided as described above.
The commercial grade portion of the system is designed to isolate under Iass of Coolant Accident (l OCA) conditions with single valve isolation provided by fail-closed air operated valves. Ilowever, this isolation function is not required, since the design of the co:amercial grade portion of the system would accommodate post LOCA conditions and the portion of the RilRSW System Dow bypassing the RilR heat eabanger thrt. gh the conosion monitoring system is sulTiciently small that the operation of the RilR heat exchanger will not be degraded.
Additionalb, the commercial grade portion of the corrosion monitoring system will be subjected to material requirements similar to the requirements of the ASME Code,Section III, Class 3 portions of the system.
Chemical and hardness tests will be performed on all materials where Certified Material Test Reports are not available and Certificates of Compliance will be prepared to the appropriate ASTM material specification. Where practicable, tensile tests will also be performed on mateiial ;amples and Certified Material Test Reports will be prepared.
All ficid wehls in the R11RSW portion of the corrosion monitoring system will be subjected to the same Nondestructive Examination (NDE) requirements as similar welds in the ASME Code, Section 111, Class 3 portion of the RHRSW eystem. All ik'd welding will use qualified filler metal and be subjected to the same quality requir..acnts as the ASME Code Section 111, Class 3 welds in the RHRSW system. All piping and components in the RllRSW portion of the corrosion monitoring system will also be mbjected to hydrostatic testing in accordance with ASME Code, Section 111 Class 3.
Additionally, all RilR5W piping and components will be required to meet the reduced ASME Code specified stress allowables for Seism.ic Category I piping, and will be supported to Seismic Category I requirements.
Specification z..
NE 42, LGSl'-
~ ' ~
. ISI Program Append;x A 16
.Page 4 of 4 RELIEF REQUEST NO. RR-16 (CONTD.)
Finally, all design considerations for safety related piping and components (i.e., liigh Energy Line Break / Moderate Er.crgy Line Break, flooding protection, missile protection, fire protection, etc.) will be addressed for the' RilRSW portion of the corrosion monitoring system as required, and plant operating procedures will be revised accordingly.
Schematic Diagram Of Corrosion Monitoring System. I,oop 'B'
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SPECIMEN CHAMBER l
HC0 u
3" sc'o ELEC HTR t
3"-
L x
~7 H80 GBD.'
A 3,
x
=
s o
2a 2a m
O I
g W X-XX t
2*
2' o
n t
20' 20" u
NOTES:
GBC,GBD(HBD-SEISMIC CATEGORY I HCD-SEISMIC CATEGORY IIA
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