ML20056C481
| ML20056C481 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 06/15/1993 |
| From: | Simpkin T COMMONWEALTH EDISON CO. |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9306240248 | |
| Download: ML20056C481 (12) | |
Text
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Downers Grove, Illinois 60515 June 15,1993 Dr. Thomas E. Murley, Director Ofc. of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Zion Nuclear Station Units 1 and 2 Second Interval Inservice Inspection Program Relief Requests NRC Docket Nos. 50 295 and 50-304
Dear Dr. Murley:
The purpose of this letter is to forward the following ISI Program Relief Requests:
1.
Relief Request IWB 13, 2.
Technical Approach and Position 10, 3.
Hydro Relief #9, and 4.
Hydro Relief #10.
Relief request IWB 13 seeks relief from the Code-required volumetric examination of the Pressurizer Vessel surge nozzle inside radius section. Technical Approach and Position 10 documents Commonwealth Edison Company's (CECO's) intent to utilize Code Case N-498, which permits a system pressure test at operating pressure to be utilized in lieu of a hydrostatic pressure test for Class 1 and 2 -
Systems.
Hydro Relief #9 seeks relief from hydrostatic testing of Class 3 systems, and is consistent with proposed Code Case N-498-1, which extends the relief granted in Code Case N-498 to Class 3 systems. Hydro Relief #10 seeks relief consistent with proposed Code Case N-416-1, which would permit alternative testing in lieu of the required hydrostatic test for welded repairs or replacements in Class 1,2, or 3 systems. The basis for these reliefs and the proposed alternative examination requirements are discussed more fully in the attachments to this letter.
i Due to the impact these relief requests will have on the upcoming Dual Unit Outage, approval is requested by October 1,1993.
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Dr. Murley June 15,1993 If there are any questirms or comments regarding this matter, please direct them to this office.
Sincerely, hW N-T.W. Simpkin Nuclear Licensing Administrator Attachments cc:
C. Shiraki - NRR B. Clayton - RIII J.D. Smith - Senior Resident Inspector - Zion 4
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ZION GENERATING STATION UNITS 1 and 2 RELIEF REQUEST IHD 13 COMPONENT IDENTIFICATION: Pressurizer surge nozzle CODE CLASS:
1
REFERENCE:
Table IHB-2500-1 EXAMINATION CATEGORY:
B-D ITEM NUMBER:
83.120 DESCRIPTION: Pressurizer Vessel Surge Nozzle Inside Radius Section COMPONENT NUMBER:
IRC002, 2RC002 CODE REQUIREMENT:
Volumetric examination of the code required volume shall be performed on the inside radius section in accordance with Table IHB-2500-1.
BASIS FOR RELIEF:
Relief is requested on the basis that compliance with the code requirements would result in hardship or unusual difficulty without a compensating increase in the level of plant quality and safety.
Insulation on the lower head of the pressurizer prohibits access needed to The perform the examination of the surge nozzle inside radius section.
removal of the insulation covering the lower pressurizer head will result in high radiation exposure to plant parsonnel.
A 1987 radiological survey performed in the area of the Unit 2 lower pressurizer head found dose rates of 2.25 R/hr on contact with the surge The dose rates nozzle, 1.2 R/hr at 18", and 70n mP/hr in the general area.
would increase if the mirror insniation was removed.
The pressurizer has a singic sorgo nozzle in the lower vessel head.
In order to perform exams on the pressurizar surge nozzle inside radius, the
" blend region" (reference Zion figurc 013), which is the optimal scanning surf ace, must be accessible foi in voor surface penetration and ultrasonic scanning.
1 i
ZCORRTS-391 (1)
BAS!S FOR RELIEF (Continued)
The blend region is not accessible since it is covered by the lower Zion Station pressurizer head insulation that was not designed for removal.
investigated the impact of removing the lower head insulation, as well as, the possibility of conducting a limited exam by removing the surge nozzle insulation and scanning on the nozzle surface.
The results of these investigations are presented below.
The lower head of the pressurizer is covered by 4 inch thick multi-layered stainless steel mirror insulation which was not designed for removal.
In order to remove the insulation, the 78 pressurizer heater cables would have to be disconnected (reference Zion floures BIZ and 813).
In addition, each of the 78 convection stops which are riveted to the insulation would have to be cut and removed so that the insulation could be removed over the pressurizer heaters (reference Zion figure Blo.
The radiation exposure to plant personnel for insulation removal, surface preparation, and inspection is estimated to be 53 person-rem (based on a dose rate of 1.2 R/hr).
Insulation covering the pressurizer surge nozzle can be removed. However, the " blend region" will still not be accessible to allow for adequate surface preparation and inspection.
A limited exam is possible if ultrasonic scanning is conducted from the nozzle. Ilowever, due to the complex geometry of the nozzle, the resulting coverage would provide very limited data from which to assess the condition of the pres:an izer surge nozzle inside radius.
The estimated radiation exposure for insulation removal, surface preparation, and to perform the scan from the nozzle would be 2.5 person-rem (based on a dose rate of 1.2 R/hr).
Tho limited riata nhtained from this inspection does not provide a compensatory increase in quality and safety to justify the hazards of personnel radiation exposuto ic'.elvad to obtain the data.
The radiological conditions for the required surge nozzle inspections would result in significant individual and cumulative radiation exposure conflicts with Zion Station's ALARA objectives.
The basis of this relief requer.t is consistent with that of relief request IHB-11, which requested relief from performing the volumetric examination of the Unit 2 pressurizer surge nozzle tu vessel weld.
IHB-ll was approved in the Safety Evaluation Report dated October 3!, 1991 provided that a visual examination of the weld surface be pet for med.
ZCOP.RTS-391 (2)
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PROPOSED A1.TERNATIVE EXAMINATf0N:
Visual examinations (VT-2) will be performed after each refueling outage in accordance with the requirements of IHB Category B-P and Code Case N-498.
Zion Station has evaluated the possibility of performing a remote visual inspection of the pressurizer surge nozzle inside radius from the inside of the pressurizer. A det'ris screen exists that covers the surge nozzle orifice from the inside of the pressurizer A debris screen exists that covers the surge nozzle orifice from the inside of the bottom head (reference figure B13).
This screen may limit the remote visual inspection since it is not known if the inspection surface can be seen through the debris screen.
An attempt will be made to conduct a remote visual inspection (VT-3) on the surge nozzle inside radius from the inside of the pressurizer. Since it is not known if the inspection surface is visible, a best effort will be made to conduct a visual exam on accessible portions of the inside radius.
Examination limitations will be noted on the examiner's data sheet and in the outage summary report.
The VT-2 exams performed aftei cach refueling outage will verify integrity of the pressurizer surge nozzlo.
The intogrity of the pressurizer has been demonstrated by satisfactory plant eperation since the mid-1970's. No leakage ovoi tho operating history of the plant.
has been found during these exam:
RELIEF REQUEST STATUS This relief request was originally submitted as part of relief request IHB-2 and was reviewed by the NRC in the Safety Evaluation Report (SER) dated February 11, 1986.
The original relief was granted provided that a volumetric examination was performed to the extent practical.
Zion Station intends to comply with the terms of the relief request reviewed as IHB-2 as granted in the SER dated February 11. 1986 for the pressurizer safety and spray nozzles, reactor vessel nozzles, and the stoam generator primary nozzles. However, due to the high radiation exposure to plant personnel that would result by performing this exam, relief is requested from performing volumetric examination on the pressurizer surge nozzle inside radius section.
ZCORRTS-391 (3)
f RELIEF REQUEST NUMBER:
INB 13 FIGURE B12 BOTTOM VIEW OF PRESSURIZER
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RELIEF REQUEST IWB-13 FIGURE B13 SIDE VIEW OF UNIT 2 PRESSURIZER HEAD CONFIGURATION WITH INSTALLED INSULATION AND SUPPORT SKIRT 1; Pressurizer v'W
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119997 814 SIDE AND BC1 TON VIEWS _OF A TYPICAL CONVECTION STOP FOR A PRESSURIBER HEATER
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ZION GENERATING STATION, UNITS 1 AND 2 TECHNICAL APPROACH AND POSITION 10 COMPONENT IDENTIFICATION:
Class 1 and 2 piping and vessels.
CODE CLASSES: 1 and 2
REFERENCES:
Table IHB-2500-1 Table IHC-2500-1 EXAMINATION CATEGORY:
B-P, C-H ITEM NUMBERS: B15.11, B15.21. B15.31, B15.41, B15.51 B15.61, B15.71, C7.20, C7.40, C7.60, C7.80.
DESCRIPTION:
Adoption of Code Case N-498 for Class 1 and 2 hydrostatic pressure tests.
CODE REQUIREMENT:
Table IHB-2500-1 Category B-P and Table IHC-2500-1 Category C-H require a system hydrostatic pressure test once each inspection interval.
POSITION:
It is the position of the station that the alternative rules stated in Code Case N-498, " Alternative Rules for 10 Year Hydrostatic Pressure Testing for Class 1 and 2 Systems,Section XI, Division I," will be used in lieu of the 10 year hydrostatic pressure test requirements stated in Table IHB-2500-1 Category B-P, and Table IHC-2500-1 Category C-H.
Zion will also apply the alternative rules stated in Code Case N-498 for Interval 2, Class 1 and 2 relief requests which make reference to the 10 year hydrostatic test as an alternate examination.
In these instances, VT-2 examinations will be conducted in accordance with Code Case N-498.
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ZOSR-303(5)
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HYDRO RELIEF #9
.i COMPONENT IDENTIFICATION: Class 3 piping and vessels.
CODE CLASS: 3
REFERENCES:
Table IWD-2500-1 EXAMINATION CATEGORY: D-A, D-B, D-C ITEM NUMBERS: D1.10, D2.10, D3.10 DESCRIPTION:
Alternative rules for Hydrostatic Testing of Class 3 components.
BASIS FOR RELIEF:
Recent ASME Code Committee activities have included the development of Code Case N-498 " Alternative Rules for 10-Year Hydrostatic Pressure Testing for Class.1 -
and Class 2 systems", which allows a system pressure test at operating pressure to be performed in lieu of the Section XI required hydrostatic test, which is performed at higher pressures. It has been demonstrated by research conducted by the'ASME Special Working Group on Pressure Testing that an elevated pressure test, as.
required by ASME Section XI, will neither challenge the structural integrity of the system or increase the chances of detecting leakage. Leakage signaling potential' component defects were readily noticed at the operating. system pressure. Code Case N-498 has been approved for use in ISI Programs in Regulatory Guide 1.147.
The ASME Boiler and Pressure Vessel Code is currently developing Code Case N-498-1 to provide alternative rules for pressure testing for Class '3 systems as a logical extension of Code Case N-498. Zion Station proposes the following alternative rules, based on proposed Code Case N-498-1, as stated below, t
These requirements will provide reasonable assurance that the safety and integrity.
of Class 3 components will be maintained.
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ZION STATION HYDRO RELIEF #9 ALTER, NATIVE EXAMINATION:
Zion Station will adopt the following rules in lieu of the 10-year system hydrostatic pressure test required by Table IWD-2500-1 Categories D-A, D-B, and D-C:
1.
A system pressure test shall be conducted at or near the end of each inspection interval or during the same inspection period of each inspection interval of Inspection Program B.
2.
The boundary subject to pressurization during the system pressure test shall extend up to and including the first normally closed valve capable of automatic closure as required to perform the safety system function.
3.
The syst.em shall be pressurized to nominal operating pressure for at least 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for insulated systems and 10 minutes for noninsulated systems. The system shall be maintained at normal operating pressure during the performance of the VT-2 examination.
4.
The VT-2 examination shall include'all components within the boundary identified in (2) above.
5.
Test instrumentation requirements for system hydrostatic pressure test are not required.
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i ZION GENERATING STATION, UNITS 1 AND 2 HYDRO RELIEF #10 COMPONENT IDENTIFICATION: All piping and vessel welds.
CODE CLASS: 1, 2, and 3.
REFERENCES:
IWA-5214, IWA-4400, IWA-4600 DESCRIPTION:
IWA-4400(a), Pressure T< st, states "after repairs by welding on the pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA 5000."
IWA-5214, Repairs and Replacements, states "a component repair or replacement shall be pressure tested prior to resumption of service if required by IWA-4400 and IWA-4600."
Test pressure and temperature for a system hydrostatic test subsequent to the component repair or replacement shall comply with the system test pressure and temperature specified in IWB-5222, IWC-5222, and IWD-5223, as applicable to the system which contains the repaired or replaced component.
CODE REQUIREMENT:
Hydrostatic pressure tests are required after repairs by welding or after installation of replacement items by welding.
BASIS FOR RELIEF:
Recent ASME Boiler and Pressure Vessel Code Committee activities have included the development of Code Case N-498," Alternative Rules for 10-year Hydrostatic Pressure Testing for Class 1 and 2 Systems", which allows -
a system leakage test (IWB-5221) for Class 1 systems and a system pressure test (IWC-5210) for Class 2 components at operating pressure to he performed in lieu of the Section XI hydrostatic test. It has been demonstrated by research conducted by the ASME Special Working Group on Pressure Testing that an elevated pressure test, as required by Section XI, will neither challenge the structural integrity of the system or increase the chances of detecting leakage. Leakage signaling potential component defects were readily noticed at the operating system pressure. _ Code Case N-498 has been approved for use in ISI Programs by Regulatory Guide L147.
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ZION STATION HYDRO RELIEF #10 BASIS FOR RELIEF (continued)l Proposed Code Case N-416-1 " Alternative Pressure Test Requirements for Welded Repairs of Installation of Replacement Items by Welding," is under consideration for publication in the ASME Boiler and Pressure Vessel Code.
Code Case N-416-1 applies to Division 1, Class 1,2, and 3 components.. The -
basis for Code Case 1
N-416-1 is similar to Code Case N-498.
Zion Station requests relief from the current Section XI rules for hydrostatic testing of Repairs, Replacements, and Modifications for Class 1,2, and 3 components and proposes to apply the alternative requirements derived from proposed Code Case N-416-1 as stated below.
These alternative examinations are sufficient to assure the safety and reliability of ASME Code piping and vessels and will not adversely affect the safety or integrity of the plant.
ALTERNATIVE EXAMINATION:
Zion Station will follow the alternative requirements stated below, based on -
proposed Code Case N-416-1, in lieu of the hydrostatic pressure test requirements stated in IWA-4000.
1.
NDE shall be performed in accordance with the Original Code of Construction.
2.
Additional NDE shall be performed in accordance with the methods and acceptance criteria of the 1989 Edition of Section III in instimces where the 1989 Edition of Section III states methods and acceptance' criteria beyond those stated in the Original Code of Construction. In addition, UT will be performed on Class 1 full penetration corner welded nozzles, branch, and piping connections.
3.
Prior to or immediately upon return to service, a VT-2 examination shall be performed in conjunction with a system leakage test at nominal operating pressure. The system shall be pressurized at nominal operating pressure for at least four hours for insulated systems and 10 minutes for noninsulated systems.
4.
The use of this relief request will be documented for specific repairs, replacements, or modifications on the Repair / Replacement section of the NIS-1 form.
In cases where use of this relief request is not practicable, Zion Station will perform hydrostatic exams per IWA-4000.
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