ML20203L408
| ML20203L408 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/20/1986 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| 5211-86-2132, NUDOCS 8608260175 | |
| Download: ML20203L408 (11) | |
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GPU Nuclear Corporation NggIg{
Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057-0191 717 944-7621 TELEX 84 2386 Writer's Direct Dial Nurnber:
i August 20, 1986 5211-86-2132 Office of Nuclear Reactor Regulation Attn:
J. F. Stolz, Director PWR Projects Directorate No. 6 U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Stolz:
Three Mile Island Nuclear Station Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Inservice Inspection (ISI) Requests for Additional Relief from Code Requirements GPUN has determined that conformance with certain ASME Code Section XI requirements which are part of the ISI program for TMI-1 are impractical.
Therefore, in accordance with 10 CFR 50.55 a(g), it is necessary that we notify the Commission and submit information to support our determinations.
Pursuant to the provisions of 10 CFR 170.21, a check for $150.00 is enclosed.
The current ISI program for TMI-1 is based upon the ASME Boiler and Pressure Yessel Code Section XI,1974 Edition through Summer 1975 Addenda.
Additionally, GPUN has adopted certain portions of the Section XI 1977 Edition through Summer 1978 Addenda (specifically, IWA-2200, IWA-2300, and IWA-3000) as described in our letter of July 6,1981.
Included in Attachment 1, items 1 through 7 are requests for specific relief from the ASME Code Section XI,1974 Edition through Summer 1975 Addenda and GPUN's proposed alternate examinations.
Item 8 is provided in order to document an interpretation.
Please note that items 1 and 2 deal with inspections which are required for Outage 6R while the remainder of the items must be completed by the end of the 10 year interval.
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11 GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation
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5211-86-2132 August 20, 1986 As discussed with Mr. John Thoma on July 16, 1986, we would appreciate NRC review of these items such that we can get them resolved prior to the 6R Outage in November.
Sincerely, J
H. D.
ukill Vice President & Director, TMI-1 HDH/MRK/spb:0635A cc:
J. Thoma R. Conte Attachments
ATTACINENT 1 1.
GPUNC requests relief from full volumetric examination of 10% of the length of the letdown cooler (MU-C1 A and MU-C1B) manifold longitudinal seam welds (Category B-B, Item B3.1).
Basis - The letdown cooler manifolds are approximately 31" long and contain two longitudinal weld seams.
This manifold is an integral part of the heat exchanger and only approximately 1 1/4" of the inlet and 2 3/4" of the outlet welds are accessible for examination.Section XI of the ASME B&PV Code requires 10% or 3.1" of these welds be volumetrically examined each interval but, in this case, less than 3.1" of the welds are accessible (see Drawing NU-D-1092-1, items C and D).*
Proposed Alternate Examination - Volumetrically examine the accessible portion of these welds as design permits.
2.
GPUNC requests relief from volumetric examination of Class 2 valve body welds on valves AH-V1 A, AH-V1B, AH-V1C, and AH-V1D (Category C-G, Item C4.1).
Basis - The 1974 Edition with Addenda through Summer 1975 requires volumetric examination of pressure retaining valve body welds.
The welds on these valves are of. such a configuration that meaningful volumetric examination results cannot be obtained whereas meaningful surface examination results are obtainable. This was recognized for Class 2 valve body welds in general, as later NRC approved versions of Section XI (Summer 1978 and later) changed the examination method required from volumetric to surface.
Proposed Alternate Examination - Perform surface examination in lieu of volumetric examination on these valve body welds.
3.
GPUNC requests relief from surface and visual examination of vessel clad patches (Items Bl.13, Bl.14, B2.9, and B3.8; Examination categories B-I-l and B-I-2) as required by ASME Section XI 1974 Edition with Addenda through Summer 1975.
Basis - The examination of vessel cladding patches requires examination personnel to enter high radiation areas and accumulate a large amount of Person-Rem.
Based on radiation levels obtained during the 1979 TMI-1 refueling outage, personnel would be entering radiation fields from 3 to 5 R/hr.
It is estimated that this examination would expend 1.5 - 3.0 Person-Rem.
- A legible full size print of this drawing has been provided to the NRC Licensing Project Manager, John Thoma, and is not a par t of this submittal.
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To date four 36 sq. in. patches have been surface and visually examined in the Reactor Vessel Head and four 36 sq. in. patches have been visually examined in the Reactor Vessel. These examinations revealed no degradation, which is consistent with other B&W plants of similar design and provides a basis for assuring the structural integrity of the cladding. Further examinations would provide minimal information to be gained for the amount of radiation expenditure involved.
Later NRC accepted Editions of ASME Section XI (1977 with Addenda through Summer 1978) do not require cladding examinations.
Proposed Alternate Examination - The reactor vessel interior only will undergo remote visual examination at or near the inspection interval in conjunction with the inspection requirements for the removable core support structure.
This examination will include the reactor vessel cladding and any degradation would be noted at that time.
4.
GPUNC requests relief from surface examination of the two reactor vessel core flood safe-end welds (Examination Category B-F, Item B.l.6).
Basis - The reactor vessel core flood safe-end welds are located inside the reactor vessel primary shield wall and would require removal of sand plugs and insulation to gain access into this high radiation area.
The reactor vessel is of such a design that ID ultrasonic examination of these welds is possible when the core barrel is removed.
Present techniques indicate ultrasonic examination has a high degree of sensitivity to degradation at the opposite surface from which the examination is performed.
The ASME Section XI Code 1977 Edition with Addenda through Summer 1978, Section IWB-3514.2, Paragraph (b) and IWB-3514.3, Paragraph (b) state: "Where indications on the outer surface of piping as detected by the surface examination method during an inservice examination exceed the allowable standards, the indications may be examined by the volumetric method. The acceptance of these indications shall be governed by the allowable indication standards for the volumetric examination method in Table IWB-3514-2".
The conclusion made from this quote is that volunetric examination results may be used to disposition surface indications and are adequate to detect unacceptable surface flaws.
The GPUNC ISI program examinations have not revealed any degradation on bi-metallic welds to date and all other Section XI required bi-metallic weld examinations will have both a surface and volumetric examination.
Therefore, surface examination of the reactor vessel core flood safe-end welds would provide minimal information gain in return for the radiation exposure estimated to be 43 Person-Rem.
Proposed Alternate Examination - Perform full volumetric examination only of the core flood safe-end welds.
5.
GPUNC requests relief from volumetric examination of the RC-RV2 valve body to flange and valve body to operator welds (Category B-M-1, l
Item B6.6).
Basis - The valve is of such a design that meaningful volumetric examination results cannot be obtained (see Figure 1).
The valve does not have sufficient area to apply angle beam ultrasonic transducers for scanning.
Radiographs of the areas of interest cannot be made without inclusion of unfavorable images from other parts of the valve.
Proposed Alternate Examination - Perform surface examination of the valve body to flange and valve body to operator welds.
6.
GPUNC requests relief from volumetric examination of integrally welded support attachments (Categories B-H and B-K-1, Items B1.12, B2.8, B3.7, B4.9 and B6.4).
Basis - The expected service failure mode for integrally welded support attachments would involve an outside surface flaw.
The configuration of these attachments are also seldom simple (see drawing NU-D-1092-1, detail A-A', item 281, for a typical example *).
The results of volumetric examination would be less sensitive to the detection of surface flaws than a surface examir.ation method, particularly where the configuration of the welded attachment is more complex and ccessibility is a problem.
Later NRC accepted editions of the Section XI Code (Summer 1978 and later) allow surface examination of welded attachments.
Proposed Alternate Examination - Perform surface examination in lieu of volumetric examination on Class 1 integrally welded attachments.
7.
GPUNC requests relief from volumetric examination of Class 2 pipe branch connection weld joints (Categories C-F and C-G, Item C2.3).
Basis - Pipe branch connection weld joints are of configurations which make volumetric examination difficult and may produce less than optimum results (see Figure 3 for a typical example). This was recognized in later editions of the Section XI Code (Summer 1978 and later) which changed the examination method required from volumetric to surface.
GPUNC recognizes that 10 CFR 50 has not given blanket approval of codes other than the 1974 edition through Summer 1975 Addenda for Class 2 piping but has noted that Regulatory Guide 1.147, Revision 4 approves Code Case N-408 (Alternate Rules for Examination of Class 2 Piping,Section XI, Division 1). Code Case N-408 does require surface examination only of branch connection welds as recognized in later editions of the Code.
- A legible full size print of this drawing has been provided to the NRC Licensing Project Manager, John Thoma, and is not a part of this submittal.
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Proposed Alternate Examination - Perform surface examination in lieu of volumetric examination on Class 2 pipe branch connection weld joints.
8.
Section XI,1980 Edition with Addenda through Winter 1980 clarified the examination boundaries for integrally welded attachments (see Figures 2A, 28 and 2C). The attached figures show that if the attachment weld distance from the pressure boundary is greater than the pressure boundary thickness, it is not in the IWB-Boundary.
Section XI 1974 Edition with Addenda through Summer 1975 does not address this configuration.
Therefore, it is the position of GPUNC that the 1980 Edition of Section XI contained a clarification to examination of welded attachments and this clarification was the intent of the Section XI 1974 Edition with Addenda through Summer 1975.
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